Cylinder/piston repair ? Many questions, sorry so long.

[Brik]

Cylinder/piston repair – Many questions, sorry so long.

First off – If I am being a PIA, asking too many questions in one post or whatever please let me know.

Secondly – Thanks in advance!

OK – My ole faithful saw has now become my project saw and my ‘learning more about saw engines’ saw. I have made reference to it in a few other posts I started (Search them if you want more background on what led me to this point)

The saw is a Husqvarna model 51, mfgs tag says 1997 if I remember correctly. I have replaced the saw with a 372xp so I can be down for a while as I work on the 51.

The conclusion of my dealer was that a cylinder/piston replacement was in order. Running a tank of straight gas led to the issue (It wasn’t me who filled the tank) and maybe water in the gas. The issue is poor performance under load, stalling, no starting when warm and general bad behavior. I do not think the saw is totally cooked, it still runs, just badly. Dealer said it would be too much money for him to do the repair and I may be better off, if so inclined, to do it myself. Dealer solution would be for new OEM cylinder/piston. I want to see if I can fix her up with a minimal, or zero, outlay of cash.

First off, I have never gotten this deep into a small engine before. I once removed the carb on the 51 and immediately put it back on. I forget why I removed it now. I do recall it being a PIA to get the choke and throttle linkages put back correctly.

OK – So on Sunday afternoon I decided to blindly dig in. I removed the bar and chain, spark plug, paw/muffler bracket, muffler, handle, I then loosened the 4 screws that hold the cylinder to the saw body. I was hoping I wouldn’t need to fully remove the carb. Well, out came the carb and the various plastic parts. Then out came the cylinder, the retaining pin on the piston and then the piston.

This all came apart without any hassles. I think I can get it back together without any issues. My workbench is loaded with parts.

The piston and cylinder do indeed seemed scored as my dealer said. My dealer also suggested (as some folks here also said) to try muriatic acid and emory cloth to clean up, and polish, the cyl and piston to see “if that does it”.

OK – At this point I have a few questions. (My primary questions are in Bold

Scoring
The cylinder and piston scoring appears to only be on the exhaust side. Does this tell me anything?

Compression testing
I think I know what compression means. I do not currently have a good way to test compression. Before I took everything apart I did put a finger over the spark plug hole and could feel pressure when pulling the started rope. I have also read about a leak down test. I do have an air compressor. Would a leak down test and a compression test effectively tell me the same thing? I could envision building a simple device to pressurize the cylinder, reading the pressure, and noting the drop over time. If I built such a device what would be a good starting pressure and how slow/fast would be a good indication of decent compression? Maybe the compression tester at HarborFreight for $5 would tell me, if after polishing, I was even in the ballpark. Should I just clean/polish the piston/cyl and re-assemble and have my dealer check compression?

Polishing cyl/piston
How does this even work? If there is a groove in my cyl wall and/or piston how will polish help with a compression issue? Polishing would remove material, not fill in any scoring, correct?

Cleaning
In retrospect I should have really cleaned the saw of dirt and grime BEFORE opening up the engine. I have a lot of gunk around the saw body and next to where the cylinder attaches. I have been careful not to get any gunk into the engine. I figure I should clean up things before putting the cylinder back on. Any suggestions on cleaning w/o contaminating the open engine?

Gaskets
I presume its good practice to replace the cylinder, exhaust and carb gaskets during re-assembly. Is this correct or can I re-use the old gaskets? How about liquid gaskets?

Cylinder and/or piston replacement and other parts
I am thinking that I may just go ahead and do the cleanup of the existing cyl/piston and put it all back together to see how things work. Good or bad plan? Are there any must replace parts, or good to replace, parts I should consider at this point? The cyl/piston after market parts are about $90+ on ebay. Piston only is about $30. I would love to just clean up things and have it work properly again w/o all new parts. BTW – The carb is newish and looks to be in perfect condition.

Piston Ring
Maybe just a new piston ring would be in order. $7 or so. It isnt obvious to me how the ring is removed. How is just a ring removed and replaced? Is that good insurance as part of my proposed polish and re-assemble to keep the cost down plan?

What I am missing?
When I put this all back together what do I need to consider? Side note - I once removed push rods on a 4 cylinder car engine; there was an alignment procedure that had to do with the position of the crankshaft in relation to the pushrods. I don’t remember exactly. Anyway, anything like this I need to consider when putting everything back together? Timing? (Not that I really know what that means or how to adjust it or if its even required)

OK – So I want to try and do this on the cheap, w/o parts if possible, and w/o spending money on test equipment. Am I doomed for failure? Is this post too long? Am I being a PIA? Suggested online reading? Sorry if I’m not using the correct terms, feel free to gently correct me, I’m learning.

Thanks all!!!

 

[Mad Professor]

First off – If I am being a PIA, asking too many questions in one post or whatever please let me know.

Secondly – Thanks in advance!

OK – My ole faithful saw has now become my project saw and my ‘learning more about saw engines’ saw. I have made reference to it in a few other posts I started (Search them if you want more background on what led me to this point)

The saw is a Husqvarna model 51, mfgs tag says 1997 if I remember correctly. I have replaced the saw with a 372xp so I can be down for a while as I work on the 51.

The conclusion of my dealer was that a cylinder/piston replacement was in order. Running a tank of straight gas led to the issue (It wasn’t me who filled the tank) and maybe water in the gas. The issue is poor performance under load, stalling, no starting when warm and general bad behavior. I do not think the saw is totally cooked, it still runs, just badly. Dealer said it would be too much money for him to do the repair and I may be better off, if so inclined, to do it myself. Dealer solution would be for new OEM cylinder/piston. I want to see if I can fix her up with a minimal, or zero, outlay of cash.

First off, I have never gotten this deep into a small engine before. I once removed the carb on the 51 and immediately put it back on. I forget why I removed it now. I do recall it being a PIA to get the choke and throttle linkages put back correctly.

OK – So on Sunday afternoon I decided to blindly dig in. I removed the bar and chain, spark plug, paw/muffler bracket, muffler, handle, I then loosened the 4 screws that hold the cylinder to the saw body. I was hoping I wouldn’t need to fully remove the carb. Well, out came the carb and the various plastic parts. Then out came the cylinder, the retaining pin on the piston and then the piston.

This all came apart without any hassles. I think I can get it back together without any issues. My workbench is loaded with parts.

The piston and cylinder do indeed seemed scored as my dealer said. My dealer also suggested (as some folks here also said) to try muriatic acid and emory cloth to clean up, and polish, the cyl and piston to see “if that does it”.

OK – At this point I have a few questions. (My primary questions are in Bold

Scoring
The cylinder and piston scoring appears to only be on the exhaust side. Does this tell me anything?

Compression testing
I think I know what compression means. I do not currently have a good way to test compression. Before I took everything apart I did put a finger over the spark plug hole and could feel pressure when pulling the started rope. I have also read about a leak down test. I do have an air compressor. Would a leak down test and a compression test effectively tell me the same thing? I could envision building a simple device to pressurize the cylinder, reading the pressure, and noting the drop over time. If I built such a device what would be a good starting pressure and how slow/fast would be a good indication of decent compression? Maybe the compression tester at HarborFreight for $5 would tell me, if after polishing, I was even in the ballpark. Should I just clean/polish the piston/cyl and re-assemble and have my dealer check compression?

Polishing cyl/piston
How does this even work? If there is a groove in my cyl wall and/or piston how will polish help with a compression issue? Polishing would remove material, not fill in any scoring, correct?

Cleaning
In retrospect I should have really cleaned the saw of dirt and grime BEFORE opening up the engine. I have a lot of gunk around the saw body and next to where the cylinder attaches. I have been careful not to get any gunk into the engine. I figure I should clean up things before putting the cylinder back on. Any suggestions on cleaning w/o contaminating the open engine?

Gaskets
I presume its good practice to replace the cylinder, exhaust and carb gaskets during re-assembly. Is this correct or can I re-use the old gaskets? How about liquid gaskets?

Cylinder and/or piston replacement and other parts
I am thinking that I may just go ahead and do the cleanup of the existing cyl/piston and put it all back together to see how things work. Good or bad plan? Are there any must replace parts, or good to replace, parts I should consider at this point? The cyl/piston after market parts are about $90+ on ebay. Piston only is about $30. I would love to just clean up things and have it work properly again w/o all new parts. BTW – The carb is newish and looks to be in perfect condition.

Piston Ring
Maybe just a new piston ring would be in order. $7 or so. It isnt obvious to me how the ring is removed. How is just a ring removed and replaced? Is that good insurance as part of my proposed polish and re-assemble to keep the cost down plan?

What I am missing?
When I put this all back together what do I need to consider? Side note - I once removed push rods on a 4 cylinder car engine; there was an alignment procedure that had to do with the position of the crankshaft in relation to the pushrods. I don’t remember exactly. Anyway, anything like this I need to consider when putting everything back together? Timing? (Not that I really know what that means or how to adjust it or if its even required)

OK – So I want to try and do this on the cheap, w/o parts if possible, and w/o spending money on test equipment. Am I doomed for failure? Is this post too long? Am I being a PIA? Suggested online reading? Sorry if I’m not using the correct terms, feel free to gently correct me, I’m learning.

Thanks all!!!

If the piston is scored it is toast, you will need this along with a set of rings, circlips (do not reuse) and gaskets minimum. I'd recommend replacing the upper conecting rod (piston pin ) bearing too. The cylinder may be saved if it cleans up, if not get a complete cyl/piston kit. Any gouges that you can feel with your fingernail is too deep to clean up, get a cyl/piston assy.

I geneally clean up an engine BEFORE taking it apart. You can rinse the bottom end out with some mix before putting it back together. The compression (pressure) you should have tested BEFORE taking it apart is that the cranKcase seals are still good, a dealer will charge you about 1/2 hr. labor to do this if you have the engine stripped down with the carb/muffler off. DO NOT resuse gaskets.

It would also be a good time to replace the impluse and fuel lines.

The reason the piston was bad on the exhaust side is that it runs hotter on that side so that lack of lubrication effect that side first.

Good luck!!!

 

[bcorradi]

First off – If I am being a PIA, asking too many Scoring
The cylinder and piston scoring appears to only be on the exhaust side. Does this tell me anything?

Yes the saw was run with a lean condition (either an incorrectly adj carb, an improper gasil ratio, or an air leak)

Compression testing
I think I know what compression means. I do not currently have a good way to test compression. Before I took everything apart I did put a finger over the spark plug hole and could feel pressure when pulling the started rope. I have also read about a leak down test. I do have an air compressor. Would a leak down test and a compression test effectively tell me the same thing? I could envision building a simple device to pressurize the cylinder, reading the pressure, and noting the drop over time. If I built such a device what would be a good starting pressure and how slow/fast would be a good indication of decent compression? Maybe the compression tester at HarborFreight for $5 would tell me, if after polishing, I was even in the ballpark. Should I just clean/polish the piston/cyl and re-assemble and have my dealer check compression?

Compression testers are fairly inexpensive, but in order to get one that accurately reads compression on chainsaws you need to get one where there is a schrader valve close to the fitting that screws into the sparkplug hole. If you want to get by cheap you may be able to reassemble it after doing some polishing/cleaning. If have a good relationship with your dealer than just bring it there to get a compression reading.

Polishing cyl/piston
How does this even work? If there is a groove in my cyl wall and/or piston how will polish help with a compression issue? Polishing would remove material, not fill in any scoring, correct?

Right now with material built up on your cylinder wall the piston ring isn't able to get a good seal against cylinder so pressure is escaping. Once you clean up the cylinder wall it will allow the ring to seal better allowing it to build up more pressure.

Cleaning
In retrospect I should have really cleaned the saw of dirt and grime BEFORE opening up the engine. I have a lot of gunk around the saw body and next to where the cylinder attaches. I have been careful not to get any gunk into the engine. I figure I should clean up things before putting the cylinder back on. Any suggestions on cleaning w/o contaminating the open engine?

If I was you I would take an airgun and gently blow any dry loose particles that may have fallen into the crankcase out. After you do this you can spray wd-40 or something similar into the crankcase and bearings and gently swab it out with a paper towel. In order to do this, just take a sheet of paper towel and keep folding it into a square till your able to tightly stuff it under the crank weights. Now manually turn the saw over by rotating the flywheel and repeat this technique until the crankcase looks free of debris. After you do this you may want to blow out the crankcase again to remove any paper towel particles.

Gaskets
I presume its good practice to replace the cylinder, exhaust and carb gaskets during re-assembly. Is this correct or can I re-use the old gaskets? How about liquid gaskets?

You may be able to get away with reusing the old gaskets, but its dependant on how cheap you want to be. I would stay away from using liquid gaskets on anything. If the saw was running fine before this happened you will most likely not need to rebuild the carb. The gasket that is going to cause you the most grief if it doesn't properly seal is the cylinder gasket.

Re - Piston/Cylinder or Piston or Piston Ring

Since it doesn't sound like you will using this saw repair as a learning tool more than anything else. Since your trying to spend as little as possible I would do this in order of cost effectiveness until you achieve an adequate compression reading.
1) Cleaning up the piston and cylinder and take a compression reading.
2) Replace the piston ring
3) Replace both the piston and ring
4) Last resort is buying a new piston and cylinder. I doubt you will have to to resort to this since I don't imagine your cylinder being in very bad shape.

 

[romeo]

Just buy one of these http://cgi.ebay.com/50-Husqvarna-Chain-Saw-Piston-Assembly-44mm-New_W0QQitemZ140135052522QQihZ004QQcategoryZ79666QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
and remove the material from the cylinder, the scoring is piston material that has transfered to the cylinder wall which causes the ring to lose its seal. I don't bother trying to clean pistons up unless they cant be found anywhere.

 

[rickyrooster]

Husky 51

Your cylinder will most likely clean up. If it doesnt I think you have the option of replacing it with a Husky 55 cylinder if you wanted to. You would then have a 55cc saw and you can get them that come with a tapped hole for a compression release. Just something to let you know if you have to buy a cylinder. good luck with your project. Rick!

 

[timberwolf]

If the scoring in the jug is more than 1-2 thousandths deep it is never going to be much good. If your not going to put it back together with new parts then it is not worth replacing other things like fuel line ect. Going at scoring that has cut through the plating (wich is only a few thou thick) with acid will eat the aluminium behind the scratch and realy finish it off. Very light scoring on a piston can be smoothed with wet sanding paper, but if it is enough that the ring is sticking then the piston is toast and to try to use it will only cause more damage.

Like Romeo mentions it could run like new or better as a 55 cc saw with a new 55 jug and piston. Otherwise no amount of wishing and rubbing with scotch brite is going to do much.

 

[Dan Forsh]

Okay, you are a PIA for such a long post. I can't read it all and remember what you said at the start and the finish all at the same time at this time of night.

So I will deal with the bits I can remember.

1st off, straight gas will melt your piston first, water in the gas isn't such a problem (if we are talking a little water got in the gas, not the saw fell in the water and sat for two months before I could be arsed to do anything about it)

The transfered aluminium, yes I did say aluminium, from the piston on to the cylinder wall will cause the rings to compress off the wall of the cylinder and result in a leak or blow by meaning lost of compression. If this is the only problem you chuck the piston and clean off the cylinder wall. By the way, at no point are you going to do this for no $. I'm cheap too believe me!

Clean up the cylinder with a scotch brite and/or emery paper. If you can catch your fingernail in any significant vertical scratches, forget the cylinder, its gone. If you don't, change the piston for a cheap after market one.

bcorradi has given you the best cheap guy advice up to now, although I don't agree with his thought process. By his rationale you will buy a ring, then buy a piston (which always comes with a ring), then by a cylinder (which always comes with a piston and ring). Lots of spares that way. A saw will only need just a ring if its always been run correctly and has just had too many hours on it such that the ring has worn down from use, not abuse. A piston is aluminium, a cylinder is chrome or nikosil lined so will alway be damaged after a piston, not before. Determine if your cylinder can be saved before you decide what parts are needed. Clean it up and take it into your dealer for his opinion if you don't trust yourself. I can't see that he will charge you for that.

I don't use new gaskets unless they obviously need to be changed. Don't use liquid gaskets on the cylinder base. The thickness of the base gasket determines the compression/squish gap at TDC, so if you replace a gasket that was say a 1 mm paper gasket with silicone, you are going to change this and 1 mm could soon become a 100 microns. Worst case, your new piston hits your spark plug and you have an expensive rattle.

Keep the crankcase clean, yes it's always better to clean the saw up before you start to delve in, but I'm just the same, I get straight in there. Schit will always find its way into the crankcase. Fill it with mix, slush it round and pour it out, do this 2/3 times and after the second time revolve the crank a few times to dislodge any schit. Once emptied, visually check for anything left behind. Swarf will generally fall to the lowest point, the bottom of the case, so swish it good and anything potentially damaging will find its way out.

Don't bother trying to buy or make a compression gauge. You want to fix one saw. I can tell the addiction hasn't caught you... yet!

You can think about fuel lines, carb adjustments and such once you have the fundamental things sorted.

 

[Brik]

How do I remove the old ring?

Thanks all - I'll keep my questions short and to the point.

To comment of a few things brought up by the responses.

This is a project saw and a saw I am using to learn about things. I DO also intend to use the saw once I fix it up.

Part of doing it on the cheap is to help me learn. Sure, I could just throw a truck load of parts at it and have a new saw but what fun would that be? Oh, new saw fun.

I have looked at the cyl/piston with the decomp valve that would essentially give me a 55. That's a tempting route to go.

It makes sense that first the piston goes then the cylinder. That's why, as was pointed out, they sell only rings, then pistons/rings and whole cyl kits. I will look later this week when I begin to clean things up but I suspect that ONLY my piston is damaged. The ring, as I recall, actually looks OK. The scoring is more on the body of the piston, not too much near the ring. The ring moves freely.

When I picked up the saw at my dealer he offered to give an opinion on the condition of the cylinder and piston. I may take him up on it. His hours do not mesh too well with my current work schedule though so its tough to get in there.

Boy, I'm getting ling winded again.

OK - A question - If, after cleaning and closer inspection, I determine that I just want to replace the ring. How is the old ring removed and the new one installed?

 

[PB]

With the old ring you don't need to be so careful with, just open it up enough to slide it off the top of the piston. Do the reverse with the new one. You can buy a special tool for this if you want. There are quality new piston rings from www.cutterschoice.com for I think 2.19+ shipping, and they are in Erie, PA.

I don't do this for a living and someone definitely knows better than I do.

 

[timberwolf]

Yor saw as such is not worth much, so there is little to loose. The more you try to run it the more likely it is to further damage the jug or sieze it up good.

Step one- pull it apart, check things out. it should be fairly clear if anything can be saved or not. If you arnt sure, post some pics, or just take the jug and piston to someone like your dealer and they should be able to tell at a glance if there is anything worth saving.

No mater what the saw needs to come apart to be fixed, so have at it!

Rule number one of doing things on the cheap, "If it aint broke don't fix it". Never mind all the other stuff, just deal with the problem. Though you want to make sure you don't have any air leaks or an intermitant lean carb problem before you put a new piston or jug on it only to have the same thing happen (in cases where that could have been what contributed to the scoring/siezing).

 

[bcorradi]

He is correct. Just make sure to take note of what the ends/tails of the piston ring look like on the old one before you remove it so you don't install the new ring upside down. Also make sure to rotate the ring to position the groove pin in between the ring tails/ends before compressing it to install the cylinder. Cutter's choice does have reasonably priced rings, but you have to ensure they are the correct thickness. The rings that cutter's choice sells fits most older stihls, but not the new ones. I'm not too fluent in husky or jonsered so I cannot tell you if they will work with your saw or not.

 

[cityboy]

Part of doing it on the cheap is to help me learn. Sure, I could just throw a truck load of parts at it and have a new saw but what fun would that be?

Anyone who repairs machinery often will do just the opposite of what you're trying to do and replace things that aren't technically bad, but they know will eventually fail over time. A lot of people value their time more than the cost of the parts, so for them it makes sense to refurb the saw to like new all at once, rather than one part at a time as they inevitably fail.

Since you say you want to reuse the saw once its repaired, it would seem to me you'd want to spend your time running the saw rather than disassembling/assembling it several times, but that's just me. Your plan works fine if you're more interested in finding out "what if" than getting the saw running ASAP, don't mind doing the job again (and again), and you have lots of spare time and very little spare cash.

The few times I've tried to cheap out and not do things the way a professional would do it, I've ended up eventually fixing it a second time, which to me was far less fun than "throwing a truckload of parts at it" to fix it right the first time. Granted these were cars/motorcycles and not chainsaws, but the same principle applies.

 

[timberwolf]

True got to decide what you want out of it, but to do that you need to take stock of what it is, what condition it's in and what value it has.

I sure don't put top of the line brake rotors on a old car that I think may only have 10-20k left in the engine. And after having cheap brake rotors warp after a few thousand k of my wifes driving habits I will fork out the cash for the top quality parts on a newer car.

 

[blsnelling]

Let me preface what I'm going to tell you by saying that I'm some what of a perfectionist and would not do this to my own saw.

My Dad has an old 011AVT he bought new years ago. He never did like it. Said it was too under powered. Anyway, he loned it out and the exhaust screen plugged up, over-heated the piston, and seized up the saw. We're talking a significantly scored piston with aluminum transfered to the jug. He and my brother tear into it. Dad says he's not spending any money on it. My brother being a fixer sands the jug clean with fine grit wet/dry paper. He sands the piston smooth, cleans the ring grooves out, and reinstalles the rings. Dad did spring for a new set of gaskets and we put the saw back together. Here's the crazy part. The saw runs great! Seriously. It starts easy, revs out good and has as good of power as ever. Grant it, that's not saying much. But, it was going to be junked anyway and we "fixed it" for the cost of gaskets. Yes, we even reused the old rings.

The moral of the story is this. If you've got the time to play with it and you don't set your expectations too high, you just might be surprised what you can get by with.

 

[RiverRat2]

A hour pound hammer,,, @ 5mm drift or a cold Chisel on a 100 lb Peter Wright anvil

Thanks all - I'll keep my questions short and to the point.

To comment of a few things brought up by the responses.

This is a project saw and a saw I am using to learn about things. I DO also intend to use the saw once I fix it up.

Part of doing it on the cheap is to help me learn. Sure, I could just throw a truck load of parts at it and have a new saw but what fun would that be? Oh, new saw fun.

I have looked at the cyl/piston with the decomp valve that would essentially give me a 55. That's a tempting route to go.

It makes sense that first the piston goes then the cylinder. That's why, as was pointed out, they sell only rings, then pistons/rings and whole cyl kits. I will look later this week when I begin to clean things up but I suspect that ONLY my piston is damaged. The ring, as I recall, actually looks OK. The scoring is more on the body of the piston, not too much near the ring. The ring moves freely.

When I picked up the saw at my dealer he offered to give an opinion on the condition of the cylinder and piston. I may take him up on it. His hours do not mesh too well with my current work schedule though so its tough to get in there.

Boy, I'm getting ling winded again.

OK - A question - If, after cleaning and closer inspection, I determine that I just want to replace the ring. How is the old ring removed and the new one installed?

Be sure to wear your Eye protection!!!! that would be a four lb. hammer,,,,, not an hour!!!


Just Kidding BTW!!!!!:monkey:

 

[andrethegiant70]

This is just the kind of back-alley, hack-job mechanic stuff that I do so often... Yes, I'm going to blow my own horn and say that I'm good at being a bad mechanic. So here's my advice.... do stuff in this order and you should be ok....

1. Clean up the cylinder....don't do ANYTHING else until you do this because you just don't have a clue what you need until you see if you've got a cylinder to work with. Cylinder good? (I think it will be ) Move to step 2

2. Buy a piston, it comes with a ring. After all your bad mechanic effort in taking the saw apart and putting it back together, all the while getting a bunch of crap and confusing advice from a slew of drunk guys over the internet, you're going to kick yourself for being such a cheeseball and gypping your now high-personal investment saw out of a good future 'cuz you were too cheap to ante up 20 more beans for a piston. After you're done fixing the saw, you want to be proud of it! If you don't give it a new piston, all you're ever going to think about is how long that meteor you stuck back in there is going to last and just how badly it will detonate when the emaciated piston skirt finally goes blooey.

3. Replace the cylinder gasket... read number 2 again, kinda the same issue.. being cheap is no crime, just don't be "four-bucks-is-too-much" cheap.

I think you will find that the Giant's emminently reasonable, tightfisted approach to second-rate saw repair will not only provide you with a decent-running and reliable econo-saw, but you will also be convinced you could now fix the space shuttle with just a bit of guidance from the boys on AS.

 

[timberwolf]

Got to agree with everything above, except maybe [3.

Replace the cylinder gasket... read number 2 again, kinda the same issue.. being cheap is no crime, just don't be "four-bucks-is-too-much" cheap.

Gaskets are like panties, a fresh change is good, none at all is beter. Given the jug was salvagable and just to save four bucks i'd seal the jug on with permatex and shave a gasket thinkness or so off the top of the exhaust port, maybe a little on the transfers too. But that's just me, I can't resist adding a little port work to an engine that gets disassembled whatever the reason.

 

[Brik]

Thanks for all the great advice.

The consensus was that the cylinder would likely be OK since the saw still ran.

Well, I got around to cleaning the cylinder, I used emery paper and a little muriatic acid as suggested by my dealer and here. I think I still need to do some more polishing but it is coming along nicely. I can feel one vertical imperfection with my fingernail still (versus several), I am hoping its like the others and was a bump not a groove.

The piston is definitely shot.

My question - If the cylinder has just one vertical score, that doesn't polish out, on the exhaust side, about 1/2" long, toward the bottom (far end from spark plug). Would it indicate a new cylinder is in order? In other words, should it be perfectly smooth?

Thanks again!

 

[timberwolf]

As long as it does not protrude and contact the piston it should be fine. A small score below the port won't hurt compression ans wouldn't be enough to hurt the seal of the skirt.

Worst case it could trash the new piston, but I think that is unlikely if the scratch is smoothed off.

 

[Al Smith]

Sicker cats than that have lived,so to speak.

They make Scotch brit flap wheels which will not cut into the cylinder plating but will remove the tramp aluminum.

If the rings aren't toast and the piston not completely shot,it may still run,although not perfect.If you can remove the high spots on the piston it may still run for years.

Clean it up,put it back together.If it holds a reasonable amount of compression,fuel it up and give it a whirl.You aren't out a thing,except a little time.