Identify 038 and Re-ring Question

[james04]

I have an 038 with no tags left on it. How can I tell what flavor 038 it is (AV,Super,Magnum)?

This saw was a dumpster find that was missing the carb and plastics. When it tested 150 psi compression. I deemed it worth buying the missing plastics and carb. It was working great. Till a friend advised I should be running high test gas. So I got some. Then decided before putting the saw to some massive burl cutting I would tune it for the new gas. Being lazzy I tried using a screwdriver that was too big and with all the fumbling around I scorched the piston. Lesson learned!

My question is. Is it sometimes possible to do a re-ring and hone. Or is it more common to need a new piston? What about the head?. I have not taken the head off yet. But looking in the exhaust port the damage is in just a fairly small area there.

James

[qbilder]

I have not rebuilt a chainsaw, however I have rebuilt dirt bikes many, many times. Most times only a ring replacement was needed. If riding hard or racing, I would pretty much have to replace the rings seemingly weekly to keep the "pep". I understand a chainsaw isn't that finicky & high maintenance, but my point is that you may be able to get by with only doing a ring job if nothing else is damaged.

[nmurph]

There is no need for "high test" gas in a stock saw. Medium grade is all that is required for modern saws. If you bump compression, you MAY need increased octane.

As for re-ringing-

I generally operate under the premise that if compression is low enough to warrant a new ring, then it is likely that the skirt is beginning to wear and the cylinder to piston tolerance is going to be an issue before forever. If I'm going to the trouble of pulling a cylinder to re-ring, I may as well spend the few extra dollars and have a solid top end that will run for many hours. I know you can measure pistons, both their taper and their clearance at the cylinder, but I replace them if the skirt is shiny and there is little to no machining marks near the rings.

BTW, 150 isn't that low on an 038. I would guess it was probably 165-ish when it was fully broken in. You will improve the performance some by re-ringing, but it won't be like adding 20cc's to the saw.

[james04]

Thank you for your input. I think I will take your advise and get the piston as well. I more or less felt like that is what I should do. But I figured I should ask of those who know more. So what should the criteria be on determine if the head needs to be replaced? I should also note that the compression is now down to 90 psi and the saw will not even start. I hope I didn't do too much damage. I ordered a T- handled #27 torx that should be here tomorrow. That way I can pull the head for a better look.

Any help on identifying the saw? I want to make sure to get the correct parts. Are all the piston and ring sets the same for 038's?

Ps. My friend recommended the high test not for detonation. But on the premise that it has less ethanol. Don't know if that is true or urban myth. But he is a good source of knowledge in general. So I tend to trust him when it comes to care of equipment and machines.

Thanks again,
James

[Al_Smith]

High test gas would not have cooked it ,retune or no .You can't hone it but you could use scotch brit pads with kerosine and remove the tramp aluminum .If the piston isn't that bad you could sand it out and possibley reuse it .Generic  rings are cheap and they work .

Sizes --038 av 48 mm ,038 super 50 mm ,038 magnum 52mm .

If you are going to the trouble to do a top end job you'd just as well change both crankcase seals .Check the carb boot because 038's are noted for tearing them plus all the av mounts .

[james04]

Hi Al,

Thank you for the sizes. So when I pull the head. I can just measure to identify my saw. I assume these are diameter?

Just to be clear. I was not blaming the gas. It was me fumbling for too long with wide open throttle that did it. I should just have gone and got the correct size screwdriver and this would never have happened.

Is there any exploded diagrams are perhaps a walk trough for doing the top end rebuild?

James

[Al_Smith]

There really isn't much to it .Remove all the AV mounts ,two forward ,one aft clutch side and one flywheel side high .Remove the carb .Shove the boot through the hole on the handle  and demount the engine .

Remove the muffler  and 4 cylinder mount bolts which are t-27 torx head screws and lift the cylinder off .

Stuff some clean rags around the rod so you don't drop something down the crankcase and do what needs done and reassemble the thing .

There's incidental stuff like fuel lines and wires but you'll figure that out .

[Al_Smith]

Once you get it torn down myself or someone will put on some pictures of a simple way to get the boot through the hole and other little tid bits if you run into a snag .

Really it's not that difficult .

[Al_Smith]

One thing more if that thing has a die cast aluminum lower handle assembley it's a pretty good chance it's an av which also has a hemi domed piston and an offset combustion chamber .

[james04]

Ok I got the cylinder off. It looks like I will at least need a new piston. It is 50mm in diameter. I need to determine if the cylinder is good. What is the best way to remove the welded aluminum from it without doing damage. Once I get that off. I will be able to see if it is scored. I tried to feel for grooves but with the aluminum on there I cant tell what is what.

Also. Should I be automatically be changing the shaft seals? Can that be done without opening the crank case?

Are there sources for acceptable aftermarket parts? I see some listed on Ebay. But I don't know if they are any good.

By the way. There is no die cast aluminum as part of the handle.It is all plastic.

James

[Al_Smith]

You have a super then ,50 mm .

The best way I've found to clear the tramp aluminum is with a 3m Scotch brite pad and kerosine .Some use easy off oven cleaner or muratic acid but the fumes could put you down .

You might be able to sand out the piston or it might be too far gone to save .It doesn't have to be perfect to run and run well .

Scott at Chainsawr might have a piston or you might be able to land one from flea bay .I'm not certain if they make an aftermarket piston or not ,never was in a search for one for a super.--more--

[Al_Smith]

I have to do  it in two posts because the software makes it tough to do a long post .

So I'm not certain if they still make an OEM top end for a super but if they did the cost would exceed the value of the saw .

Now they do make an aftermarket kit for a magnum which is 52 MM bore but I'm not certain if it's adirect bolt on without alterations of some sort .People have taken an av at 48 mm and used a 52 mm cylinder but with the alterations to me it wouldn't be worth the effort .More simple to find a mag in the first place .So weather a mag would fit a super somebody who knows will have to address that question

[Al_Smith]

More I guess --seals .You can pull the seals by using a drywall screw .Punch a hole in the metal portion with a stout ice pick,prick punch and thread a tiny bit into the metal and pull it out just like a bad tooth .Refrain from getting the notion to drill a hole because it could force metal into the bearing then before long you will learn to split the cases and install bearings .Not a bad thing to know but to be avoided if at all possible .

[james04]

Al,

Thank you. I sent Scott a message. So you feel I should change the seals as a matter of good practice. Or are you just saying how to do it. I don't want to go lookin for trouble if it is not a good idea to change them out. Should the seals be OEM or are the aftermarket good?

[AdkStihl]

Should the seals be OEM or are the aftermarket good?

Do you know why the top end fried in the 1st place? Reason I ask because you could have a bad seal. Some use aftermarket seals, I prefer OEM.
If you buy OEM seals separately, its pricey. If you buy an OEM gasket "set", the seals are included and normally not more than $20 for the whole bag of tricks.

[celliott]

Should the seals be OEM or are the aftermarket good?

Do you know why the top end fried in the 1st place?

This! Gotta find the cause of the burndown, and fix it or else you'll rebuild it, and it will probably fry itself again.

[james04]

The cause of the meltdown was me taking too long tuning it. It is in my original post. Now that does not mean that the seals aren't bad. Because if they are bad. That would totally explain why taking too long at WOT toasted it. Or is taking too long a sure fire way to go thermal nuclear? I would say I was fiddling for about 30 sec. after warming the saw up in a cut.

James

[Al_Smith]

It's probabley not the greatest  idea to throttle them WOT for extended periods of time running lean no load.It's a learning experiance .

[james04]

Definitely a learning experience! That and no more Walmart 2 cycle oil!

Good news is. I cleaned all the aluminum off with muratic acid and a few swipes with lubricated 600 grit paper and it looks pretty good. There are some score marks just at the side of the exhaust port. You can see them but not feel them. But my not so local Stihl dealer offered to hone it for me for $5. I will get the gasket set while I am there. But he is unable to get a piston as he only handles OEM. So I will order the piston kit and get the rest from a good shop. They are where I got my plastics from after my local shop advised me to throw this saw in the trash. After only glancing at it (literally). He is a nice guy. But perhaps he was in a snooty mood that day. Perhaps because he does not stock any used parts like the other shop.

[Al_Smith]

 I'd be reluctant to hone that thing .Done incorrectly it will eat through that plating in a heart beat .

FWIW I have a Lisle precision micrometer adjustable hone with the special stones for plating I never use it on a plated cylinder .

If you feel the need take a piece of that 600 with kerosine and rough it up some ,long cross hatchs .All they do is trap a little oil film which the cylinder will get any way weather it's honed or not .