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PostPosted: Mon Jan 01, 2007 9:33 pm 
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andrewk wrote:
Small 2 cycle maintence

First off, in the OPE world there are 3 types of engines. There are the 4 strokes, the 2 strokes and the hybrids. Hybrids (like the Sthil 4180 series, like the FS 100, 110, etc) are 2 strokes that operate as 4 strokes. Sthil is the only maker I know if making these. You get the weight and simplicity of a 2 stroke with the torque of a 4 stroke. To do this they actually use a cam and valves, but that is a whole other post. I will be focusing on the handheld, port style 2 strokes here, but the same principles apply.

The most important things to 2 strokes are fuel mix, and not having any air leaks. Air leaks will lean out the mixture and cause scoring. Air leaks will also allow debris to enter the cylinder, causing dirt gut. Fuel mix is vital to keeping everything lubed, but not gummed up.

To properly tune up one of these pieces of equipment, you need 3 things. A new air filter, a new spark plug, and a new fuel filter. Replace these components, and you should be set, if the unit was in good running condition previously. However, if the unit wont start...

First off, do a compression and ignition check. If the engine has less than 100 pounds of compression, round file it and get a new one. If it has more than 170, do the following. Pull the muffler, and look at the exaust side of the piston. Any vertical scoring or marring indicates a lean condition and the unit is more than likely not worth repairing. Look at the intake side of the cylinder by moving the piston up or down the cylinder. Any scoring here indicates dirt gut. If all is fine, pull the carb, or find the intake port, and look at the piston and cylinder here. Any scoring on the lower exaust side indicates dirt gut, as does a nice and shiny piston. Pistons will have machine marks in them, and if you cant seem those, its junk. Scoring of the intake side of the piston also indicates dirt gut.

If the piston and cylinder check out fine, pull the inlet side of the carb and check it out. If there is alot of corrosion or dirt in the carb, it will need replaced. Newer carbs have 4 or 5 non seriviceable check valves in them, and these can be destroyed by soaking the carb in solvent. It is almost impossible to get dirt or gummy fuel out of these carbs.

If the carb and cylinder are fine, and you have ignition, the next step is a pressure and vaccum test of the crankcase. This is too far for most guys, and I will go into this part later, if needed.

I talked alot about dirt gut, and some may wonder, "How do we prevent dirt gut??" The answer is simple. Keep the unit clean, and clean it the right way. Make sure the air filter always seals, and stays clean, but blow out through the clean side. I have seen alot of chainsaws that are junk because the owner thought they were taking excellent care of the saw, by blowing off the filter, when they are actually blowing dirt through the filter into the intake or cylinder to be a nice abrasive into the cylinder.

Also, carburators, at least the newer ones, are very sensitive and non adjustable, at least with out the right tools... The EPA has this stuff running very lean, and the smallest thing can plug it. It is important to not lean out the high side too much (if you can even adjust it) and it is vital to make adjustments only after the saw is warm. Base adjustments are 1 turn for both high and low.

If I missed anything, I will add it later... this is a complex subject, but hopefully it helps someone out.

Andrew


One thing I forgot to mention that is extremely vital is fuel quality. Bad fuel is the number one killer of 2 stroke machinery.

Engine manufacturers say you can run E-10 (thats a ten percent ethanol blend) but I would stick with the straight stuff. The alcohol does not bind with the oil well, and this creates an emulsion instead of a mixture. If the equipment is older, the rubber in the carb and the fuel lines will turn to a soft mush, and could cause a lean condition. If the mixture has seperated, the oil will sink to the bottom, and it will be like running on straight gas. No lubrication.

If you must use an ethanol blend, shake up the gas can everytime you use it. If there is fuel in the unit, shake it up, and prime the heck out of it if it is a closed prime circut. (A closed prime circut will pull fuel from the tank, and push it back in through the carb. An open prime system just pushes fuel to the carb.) This will ensure that you have adequate lubrication.

Also remember that water and oil dont mix. If there is water in the fuel, or alot of moisture, you can suck it throught the engine, where it will have no lubrication properties, resulting in engine damage.

When you go to mix your fuel, put the oil in first, followed by the gas, it will blend fairly well and a gentle shake should be all that is needed.

So if you use a good fuel, with a good oil, mixed and stored properly, you can effectively eliminate about 90 percent of all 2 cycle problems. I bet most of my 2 cycle work is fuel related, and could have been prevented by just taking a little extra time to enusre that the engine is getting its fuel/oil requirements.

Andrew



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PostPosted: Mon Jan 01, 2007 10:23 pm 
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How to pick what OPE you need, and where to buy it.

Well, believe it or not, its time to start thinking about mowing that yard again. If your local OPE dealer has an off-season service special, be sure to take advantage of it. Not only will you save money, but it helps them too.

I was thinking that alot of people begin shopping for mowers soon. (not like tomorrow, but we usually start getting them in about a month)

If you can afford it, go to an OPE dealer. The prices will be a little steeper than the local big box, but you will be getting a premium product and premium service. Most places only sell equipment set up, ready to go, and go over all the controls and features with you. Most dealers also offer shop priority to equipment serviced from them.

You are building a realtionship with the dealer. Believe it or not, alot of them will remember you!

You should also consider a new mower (or chain saw, or snowblower, etc) an investment. Sure, you can get a mower for 99 bucks, but how long will it last, and what kind of support does the product have?

For 400 bucks, you can get a 10-15 year mower, and it will be a good mower, that has good product support.

However, not everyone can afford 400 bucks in the short term. My advice is to do what you have to in order to get by. Check the dealer for used mowers, and you might find a killer deal. Most places will haggle about 10-15 percent on used equipment, but you will be hard pressed to haggle on a new mower. For a base line mower, my shop makes about 20 bucks on the mower. Less if you figure the cost to pay someone to set it up, polish it if it gets dusty, then fill it with gas and oil when it sells. New equipment is set by the MSRP, but if you buy alot of equipment, or buy in quantity, you might get a little bit of a deal. Just remember that margins are tight, and we have to eat too. It's irritating when I get the question "Can I get a better price than that?" on a mower that we make 20 bucks on.

The other thing to remember is that since margins are tight, a dealership is unlikely to have an "end of season special". Equipment is floorplaned through a finace company, so it is more cost effective for us to hold on to it than to lose money on it. I wish we could do it, but there is no room in the margin to do it. When a manufacturer advertises it in the paper, they actually reimburse us the difference, depending on whether or not it is actually any different than MSRP.

But I am digressing. I believe that there is a point to which people should make the investment to buy certain pieces of equipment. If you prune your trees once a year, you really have no use for a gas powered chain saw. If you dont want to use an electric, just rent one. You will spend more storing it and then fixing it b/c it sits so much than you will renting.

My rule of thumb that I reccommend to people is that if you use it more than three times a year or more than 10 hours, then you should buy it.

There are exceptions obviously, like multi purpose units that can function as many things. Like a split boom trimmer. Its well worth the investment for the chain saw attachment if you use the string trimmer attachment all summer.

The other rule of thumb is how avid one is about caring for their yard. If yard care is a hobby, make the best investment you can. If it is a burden to you, still make the best investment you can, but dont spend the money on all the added features. Pick something that will last, perform well, but doesnt have lots of useless frills.

I have stressed buying at a dealership, and here's why. When you buy at a dealership, sure the prices may be a little higher, but you are spending local, which helps your town, and you will get service that is unmatched to that of a big box store. An MTD or Craftsman mower will do the job, and there is nothing wrong with them, but doing your business with a dealer will make the whole experience eaiser, and more enjoyable. Just my 2 cents.

Andrew

EDIT- Should add here... Not only are you getting the premium service at a dealer, when it comes to any warranty work, you have someone that will go to bat for you with the manufacturer. When you buy at the big box, and you have warranty issues, it will most likely be that same dealer that does that warranty, and most dealers dont get too excited by this type of warranty. They also wont put up a fight if the OEM says 'no warranty'. Just food for thought.


Last edited by andrewk on Sat Jan 06, 2007 10:26 am, edited 1 time in total.


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PostPosted: Tue Jan 02, 2007 2:33 am 
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I have a question...My Honda mower(OHV)4 stroke sometimes has water in the bowl below the carb(usually quite full)and when I clean it out it has a film on the bottom. I store this in my garage when not in use. My garage does not leak! How does it accumulate this much water?


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PostPosted: Tue Jan 02, 2007 8:30 am 
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Erroneous Restrictionism! wrote:
I have a question...My Honda mower(OHV)4 stroke sometimes has water in the bowl below the carb(usually quite full)and when I clean it out it has a film on the bottom. I store this in my garage when not in use. My garage does not leak! How does it accumulate this much water?


It must be either coming from the air, or your fuel supply. If you use a metal gas can, you are more prone to water collecting in your fuel than if you use a plastic one.

Is the film varnish? Otherwise it is something in the fuel supply. You could try a new gas cap on the mower, but that seems unlikely to me.

Hope this helps,

Andrew



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PostPosted: Tue Jan 02, 2007 1:40 pm 
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I use a plastic can...we dont have metel ones in Canada, too much static from them...now that I think of it this mower was rebuilt before given to us. It was mentioned that it "Varnished" in the cylinder. Thanks for the info I'll look into a new cap..Can I use water/gas antifreeze(separator) in a 4 stroke?


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PostPosted: Tue Jan 02, 2007 6:43 pm 
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Erroneous Restrictionism! wrote:
I use a plastic can...we dont have metel ones in Canada, too much static from them...now that I think of it this mower was rebuilt before given to us. It was mentioned that it "Varnished" in the cylinder. Thanks for the info I'll look into a new cap..Can I use water/gas antifreeze(separator) in a 4 stroke?


In the cylinder? Seems unlikely. Unless the Carb is leaking, the fuel has no open path to the cylinder in a non running condition. Sure you don't mean the carb?

Or do you mean the engine was rebuilt because the cylinder was worn and glazed?

What do you mean by a water gas antifreeze? Like Sta-bil or something? Or Heet?

The best way to avoid the problem is to get good, clean, fresh fuel to use.

Sorry for more questions, but I want to be accurate.

Andrew



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PostPosted: Wed Jan 03, 2007 1:37 am 
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It may have been "Worn and Glazed"...Sorry it was awhile back!.
Yes..Sta-bil.. I don't cut my grass for winter, its been sitting for about a month and a half. I never drained the gas, so I wanted to know what i could use to stop the water in gas so it'll start nice in the spring.

Sorry, I should have said that the first time....!


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PostPosted: Wed Jan 03, 2007 8:28 am 
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Erroneous Restrictionism! wrote:
Yes..Sta-bil.. I don't cut my grass for winter, its been sitting for about a month and a half. I never drained the gas, so I wanted to know what i could use to stop the water in gas so it'll start nice in the spring.


Here's what I wrote earlier... should help.

Quote:
Proper Storage of Equipment.

There are many theories revolving around OPE storage, mostly revolving on whether or not to drain the fuel. Here is my field tested opinion.

If it is going to sit in your garage, fill it completely full with fuel, and then run it to get the fresh fuel into the carb. The more fuel you have in the system, the less room there is for moisture. Come spring, dump the gas out of the equipment and put it in your car. Your car will run this minute parcel of semi stale fuel through with no problem, however, you could also dispose of it properly.

If the equipment will be indoors, completely drain the system. Drop the carb and wipe out whatever remains, and you will be fine.

Other than that, if your seasonal equipment sits where mice and rodents can get at it, protect it accordingly, like with moth balls and mouse killer. Mice can cause all sorts of headaches.

By following this simple procedure, your equipment should be ready for the following season, or at least ready for its seasonal tuneup, which wont be a headache, since it was stored properly!



Regards,

Andrew



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PostPosted: Wed Jan 03, 2007 10:27 am 
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thanks


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PostPosted: Sat Jan 06, 2007 10:33 am 
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Warranty: What it is, and what it covers.

Hi all,

We have had alot of warranty problems here at work, so I thought I would touch on what OEM warrantys typically cover.

The only thing a warranty covers is defects in parts and workmanship. That it. If you hit a rock with a mower, not warranty. If you break the handle off of it, not warranty, unless you can prove that it wasnt correct to begin with. Consumables arent warrantied, so that eliminates the blade and cables and such, unless again, they are messed up from the factory. Water and gunk in the fuel system and carb is not warranty. It isnt factory installed, it is a consequence of using crap fuel. Read the owners manual, and follow all reccommended maintence. Just like my maintence article, there are things you are supposed to do to your mower to maintain it. Failure to do it means increased chance of having problems.

Some big boxes offer an extended or premium warranty. Sometimes they cover stuff that isnt warranty, but its few and far between. For the most part, these extra warranty programs are a waste of time and money.

Just some insight on warranty policy for you all-

Andrew



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PostPosted: Mon Jan 15, 2007 11:46 am 
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Hi all,

With the recent midwestern winter storm, I thought I should post up some basic troubleshooting for snowblowers to help avoid headaches.

What to do when the snowblower just wont start.

I am assuming you have primed it, turned the key on, and pulled the crap out of it.

#1 problem is fuel. We are recommending no more than 30 day storage time on fuel. For some reason the fuel we have seen lately is much less volitle that what it used to be. Also keep in mind, if you get gas at a station with one nozzle for all of the selections, you could be getting up to a half gallon of a fuel type you didnt want, like E85.

You have probably flooded it, and most people assume the plug is bad. Plugs rarely go bad. Clean and dry it, and put it back in. Smell the fuel, if its real skunky, you are looking at more work than a drain and refill. Otherwise, pull the fuel line, drain the gas, drop the carb bowl, and drain and clean that out. Spray down the carb internals with some carb spray, reassemble using new gaskets if need be. Prime it, choke it, and pull. If this doesnt work, then try a new plug. If that doesnt work, take it in, unless you have more advanced skills, in which case you probably would have stopped reading long ago.

If you have to take it in- Realize that there are probably a dozen other people that did the same thing as you and now need repair. Don't go in with the expectation that you are going to get instant service. OPE dealerships are not McDonalds, but we try to do the best we can. At my shop, I offer same day service if someone wants to pay double. It's worth my time to stay late if I am getting 100 bucks for a fuel drain/flush. You need to realize that you had all winter to get the thing going, and the fact that you waited until last minute is your problem, not the dealers. There's always the exception, like if its new and under warranty, or you just had it tuned up. ('just' means within 30 days, not 6 months or 2 years)

Dont try to save a few pennies and run ethanol. It will cost you big in the long run. Tecumesh just did an E-85 test on their engines, and at 40 degrees it took 21 primes and 38 pulls to get the engine to fire. Then it wouldnt run. E85 in a 2 cycle situation is worse. The alcohol and oil dont like to blend well, but most of all the jets arent big enough to get enough fuel through the fuel system. This is going to be a big killer of 2 cycle stuff.

Hope no one has any problems with snow removal!

Andrew



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PostPosted: Mon Jan 15, 2007 11:51 am 
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A point to add about equipment storage...

When you left that blower full of fuel to prevent moisture from contaminating everything, you didnt prevent the fuel from becoming stale. With the decrease in quality of fuel, chances are you need to drain the fuel in that stored equipment before you go to start it. Just like a boat, there is a process to getting it out of storage just like there is for storing it away.

Drain the fuel, drain the carb. Dispose of the fuel properly.

Fill with fresh fuel, prime, choke, start. If it doesnt start, well, start diagnosing it.



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PostPosted: Mon Jan 15, 2007 4:53 pm 
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Just thought a visual aid might help on why you want to keep water out of your gas.

When your carb fills with water, bad things can happen. First, it wont run. The jets are too small to suck water. Secondly, water freezes at a much higher temperture than gasoline. Here's a carb that was filled with water and sat outside.

Image

The float is usually about 1/2 as thick as the bowl. This is solid ice with a brass float center

New float will be necessary. It was neat taking this one apart... Enjoy-

Andrew



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PostPosted: Thu Feb 08, 2007 12:31 am 
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Chain Saw Cutting systems-

Hi all,

Hopefully this can be informative and also useful.

With todays direct drive chain saws, there are 4 main components to the cutting system. The sprocket, the chain, the guide bar, and the lubrication system. The sprocket is mounted to the crankshaft on a roller bearing, and it uses a centrifugal clutch to engage it. This is how 99 percent of all chain saws operate today. The chain is the worker. It cuts the chips, and does the actual work. The guide bar guides the chain in a loop, at a predetermined distance, Dependant on the length of the bar and chain. The lubrication system oils the bar and chain, to reduce wear, and increase efficiency. Let's talk a little about each individual component, starting with chain.

Chain saw chain is simple in theory, complex in design. There are very few parts to a chain, but the design and engineering that goes into them is phenomenal. A chain will typically spin at 10,000 rpm, load speed. (Final top no load is usually 11,500 RPM) It is crucial to remember how fast this stuff spins, because it is very dangerous. With a typical 20 inch bar, if you touched your finger with the rotating chain for one full second, roughly 650 cutter teeth would have spun through your flesh. Thats one second. Just a frame of reference.

General use chain is intended to cut one thing, and one thing only, and thats wood. If you go into the dirt for one second, that chain is damaged, and should be touched up. Remember, all it takes is one second, less than that even. Hitting a rock for a fraction of a second has impacted each and every cutter head. There are many other types of chain intended for different use, and I will go into those later.

A chain saw chain consists of the following parts. Drive links, cutters, tie straps, rivets. They all work together to cut wood. Its pretty self explanatory, but lets talk about each component.

The cutter head is the most complex, so I will start here. There are 3 major areas of the cutter tooth- The top plate, the gullet, and the depth gauge. The top plate (actually the furthest forward corner) is what actually cuts into the wood. The top plate is perpendicular to the drive link, or the part of the chain that rides in the bar. These are usually chromed for a hard, durable finish. The corner is what actually does the work, and below the corner is the gullet. The gullet directs the chips away from the working corner, and into the underside of the top plate, called the chip channel. This is merely a funnel for chips, as the main purpose of a chain is to cut and remove chips of wood to eventually fell a tree or cut a log. The depth gauge is what controls how big of a bite the working corner takes. They are set at .025 inches lower than the working corner. Thats damn small, but so is the chain. The key is to keep the chain in a workable state. You want the chain to be doing the work, not you. If you grind the depth gauges all the way down, the chain will break. You want to keep a workable load on the chain, not overwhelm it. One the flip side, if the depth gauges are too high, then it wont cut. Its about knowing the chain, and setting it up properly.

On to the rest of the chain components before we talk about wear and care. The drive links are what the sprocket engages, and what drive the cutters around the bar. You can tell a lot about how a saw is used by looking at these. If one side is worn off, you know the bar has problems, and that the tension wasn't set properly. The key here is that all the components work together, and they all need to be inspected for wear. Very rarely does a bar not have significant wear when a chain that has been running on it does. I will have pics up shortly to describe this stuff, so bear with me. Another example of drive link wear would be burrs on the tips of the drivers. This is indicative of a bad sprocket, or a bad roller tip on the nose of the bar. You will also be able to tell if the chain has been run in the dirt as the drivers are the fastest wearing item after the cutters. The term we use is inspecting the 'footprint' of the chain.

The tie straps are the non cutting links of the chain. Sometimes these have humps on them for reduced kickback, which I will discuss later in the article. The tie straps are simple, and need no further explanation at this time.

The rivets are the pins in the chain. Just like any other chain that has rivets. Pretty simple.

I will take a brief moment to talk about chain stretch. There is no such thing. Metal doesn't stretch, it wears. When a chain ends up being longer than it was originally, its because the rivet holes have become elongated. These stacked tolerances result in a longer chain. The chain is longer, but it has not stretched. To reduce initial wear, soak your new chain in bar oil over night to get all the little areas well lubed before running it. Its easy to do, and will lengthen the life of the chain.

Differences in design of the components are minimal, but some chains have oil grooves or holes in the drivers, to better lube the rivets, there are all sorts of different designs out there, and most work about the same. Don't read too much into the gimmicks, and just get a premium chain.

As far as manufactures go, I would go with Sthil or Oregon chain. They are by far the best chains out there, and Oregon is made here in the USA. Oregon is based out of, well, Portland, and Sthil USA is based out of West Virgina, with corporate headquarters in Germany. Sthil saw chain is made in Switzerland. They both use high quality steel, and very stringent processes to make chain, to assure it is of the highest quality. Oregon also has some chains assembled in China, and they do make some export chain in Brazil. But all Oregon chain you buy in America, will be made in America. Sthil is currently expanding their West Virgina plant and they will soon be making some chain here.

Before we stray too far from chain differences, there are some key differences to remember.

Pitch- There are many different pitches to chain saw chain, from micro 3/8, .325, full 3/8, .404, and 1/2, but 1/2 is no longer made. You might ask what pitch is, and here is a definition.

Pitch is the distance between the centers of any three rivets and dividing
the measurement by two. The result is the pitch in inches. That is from Sthil's chain sharpening guide.

So we have big chain, and we have little chain, but what about drive link gauge? Again, from the Sthil saw chain sharpening guide:

Drive link gauge- As the engine turns the sprocket it engages the drive links and propels the chain. The drive link must match the width of the guide bar groove so that the chain exactly fits the
bar. This measurement is quoted in inches or millimeters of the thickness of the bottom of the drive link. There are chains with drive link gauges of .043” (1.1 mm), .050” (1.3 mm), .058” (1.5 mm) and .063” (1.6 mm).

So now we have different gauges and pitches, for bigger or smaller, wider or narrower, beefy or delicate. These two measurements are vital in determining what chain to put on your saw, since the bar is specifically designed for one type of chain to be run on it.

The other differences to consider are cutter type, and what kind of reduced kickback features you want.

There are many different cutter types, from full chisel to half chisel, carbide tipped, etc. One might think that they need the best (read most expensive) chain on the market, but this is hardly the case if you are cutting wood. First and foremost, a dealer won't sell you a carbide chain. These are reserved for Fire and Rescue use ONLY. If a dealer does sell you a carbide chain, he opens himself up for a lawsuit since carbide is very brittle and breaks easily. Fire dept.'s use it because it will cut through roofs and walls with ease.

Many people also think they don't want "safety chain" because it wont cut as well. First, the term "safety chain" is not a good term, because no chain is safe. Reduced kickback chains cut no more or less than their counterparts, so it is to your advantage to use the reduced kickback chain. Loggers and other professionals don't use the reduced kickback because they need more efficient chip removal, and they are more experience with a chain saw, so it is an ok choice for them. Now, we have all been at the point where we think we are at a professional level with everything we do, but a homeowner has no business behind a saw without reduced kickback chain. I have no business behind one, and I have run a saw since I was a teenager. It simply isn't worth the risk.

There are also 'faster cutting' chains with different cutter profiles, and chains designed for trimming, etc. and it is best to talk with your dealer for your specific purpose to get the correct chain for the job.

Then there are skip chains. You might get one on a cheap wal-mart chain saw with a 18-20 inch bar. (I will come back to these in a second) Skip chain places plain tie straps between sets of cutters. There are half, and full skip chains, the former having one tie strap in between a series of cutters, and the latter having two. What I mean by 'series' is a set consisting of a left side cutter, and a right side cutter. Skip chains are used in the logging industry to create more efficient chip removal and are typically found on bars bigger that 24 inches. Loggers don't need all the cutters, so it cuts faster if they can remove more chips, and having more available space for chips to travel will speed up this process. Back to the wal-mart cheap-o saws-

Alot of cheap saws will come with, say, a 20 inch bar, and will be running half skip chain. Now, the reason for this is the saw doesn't make enough power to use a full chain and run a 20 inch bar. The problem is that the chain manufacturer doesn't offer this chain for resale. So if you put a full chain on one of these saws, you will find it won't cut worth a crap. The problem this creates is that since you are loading the saw too much, you run the risk of overheating it and scoring the piston and cylinder. It is for this reason I call these saws 'bic lighters', once the gas is gone, throw them away. :lol:

Overheat, overload? What are you talking about?

Obviously, when you perform a task with an engine, it puts a load on that engine. The "bic lighter" saws dont have alot of power, they just aren't designed to. But to be marketable, they want a long bar, so they compensate with that half skip chain.

Anyway, when you overload an engine, in this case by running a full chain, the saw begins to heat up, just like a car would, and if you overheat an air cooled engine, it usually loses pistons. The internal temp will get so hot that the piston will swell and it will transfer itself over to the cylinder. The oil wont help, it will get too hot that the oil cannot lubricate it and keep it cool.

Now some people may be thinking "A chain is a chain" or "I got good enough chain for the job". Just like any other mechanical thing, there is a proper tool for the job. You wouldn't try to use a 1/2'' socket when you need a 7/16'' socket because 'its good enough', and you are dealing with something much more dangerous than sockets. Use the right chain for the job- it will be easier, and safer, plus it will be better for your saw.

Ok, I think that about covers chain saw chain. Please ask questions if you have any.

On to the rest of the cutting system.

The chain rides on what is called a guide bar, or just "bar". It is a piece of hardened steel, and the drive links ride in the slot in the bar. There are many different types of bars, but in order to fully understand them, we need to know the parts of a bar first.

The tip- The tip of the bar is where there are a few options. This is the round end of the bar. Some have a sprocket in them that the chain goes on, to reduce friction, some are just plain, and some are replaceable. The tip often sees the abuse, even though it shouldn't.

The rails- The rails are the edge of the bar. These need to be straight and not have gouges taken out of them, since the chain relies on these for lateral support. As the rails wear, they will mushroom out. This rolled over material needs to be removed, called "dressing the bar", so that the bar does not become wider than the cutter kerf.

The mount- This is where the bar mounts to the saw. There are many different styles that have been used over the years, so not all bars are the same.

Ok, Now about the different types-

The roller tip has a sprocket nose on it. The bearing in the roller may or may not be greaseable. The benefit of this nose is that chain tension really can't be too tight, since there is a bearing on the end of the bar.

The composite bar has the middle machined out of it, and a composite material in its place. The theory is that you only need the steel for the rails and tip, so why not cut weight? Popular with lumberjacks and arborists, even more popular with trim saws.

The 'regular' bar. This bar is all steel, has no roller tip. Chain tension that is too tight can make the chain bind, but this is the cheapest bar, and is popular with farmers for some reason.

The standard issue is a non-composite, roller tip bar.

Bars are pretty simple, and so are sprockets, which is where I will continue.

A sprocket is what transfers the energy created by the engine into useful work. The sprocket is driven via a centrifugal clutch. The sprocket is designed for a specific pitch of chain, so if you change the type of chain you use, you will need a new sprocket.

The sprocket engages the drive links of the chain, and propels them around the bar. There is really nothing more to them than that, although they do ride in a bearing on the crank that must be periodically greased. There are, however, two different types of sprockets.

The first is a spur sprocket. This is 'standard issue'. The hub and sprocket teeth are one solid piece. A sprocket is designed to run 2 chains (thats just a guideline) through full service life. (thats about 2 dozen each sharpenings if you dont hit a nail or something.) Then you replace the entire assembly.

The rim sprocket is a 2 piece sprocket. There is a rim, which is a version of the sprocket tooth, but is different, and then the hub, which the rim slides over. The hub is designed (again, just a guideline) to run 2 rims to end of life, which, like a spur sprocket, is 2 chains each, so thats 4 chains to end of life. For the professional, this is the way to go. A sprocket is about 15 bucks, and a rim is about 7. The initial kit is about 20, but you do save money this way.

Now, here is a piece of reading that will reiterate much of what I am saying, and give good visuals for it. I was going to incorporate pics through the article so it wasn't so dry, but they proved to be difficult to find.

http://www.stihllibrary.com/pdf/SharpAdvice110606.pdf

There is not a lot of sales pitch in this literature from Sthil, and it is very informative. There are pictures of wear factors, and close ups of the different chain parts.

In conclusion, while there is a lot to be said about them, chain saw cutting systems are relatively simple, and easy to care for. When properly maintained, like anything, they will treat you very well, and if neglected, you run the risk of not only having to work harder, but you are also risking getting hurt. Hopefully this is useful to someone.

Regards,

Andrew


Last edited by andrewk on Sun Apr 08, 2007 1:11 am, edited 4 times in total.


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 Post subject: Re: andrewk
PostPosted: Wed Feb 14, 2007 7:45 pm 
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One thing about snowblowers....check your chains! Good thing I got all the blowing I actually needed to do done, before the chain that runs the impeller blade broke. I was able to fix it, but replacement will be necessary...got the tensioner adjusted as far as it will go, the chain is stretched real nice. So also check the tension, make sure the chain is tight.

Probably why the chain broke in the first place...didn't even know there was a tension adjustment until I actually studied what was going on down there... :lol:

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