Chainsaw compression

[hemlock]

Hello,
I was out using my 262xp, and it was acting a little cranky. It had not run since last season. I did a compression test on it and got a reading of 70psi (cold). Is this considered good, bad, or average? It seems a little low. The saw did run and cut well once it was going. I was also using an old automotive compression tester, so I'm not sure how well they work on small engines. Thanks.

 

[TreePointer]

That is low, but tell us your procedure for testing. Also, what model of tester are you using? Does it have a proper Schrader valve?

 

[hemlock]

That is low, but tell us your procedure for testing. Also, what model of tester are you using? Does it have a proper Schrader valve?

Hello. I edited my intital post with a bit more info. I was using an old automotive tester, so I don't know how accuarte it really is. I installed it in the plug hole and pulled until the gauge topped out and stopped climbing.

 

[smokinj]

If it was 70 psi or anywhere close even up to 135 It needs rings!

 

[hemlock]

If it was 70 psi or anywhere close even up to 135 It needs rings!

Can I get away with just changing the rings/base gasket? Thanks.

 

[Naandme]

Put it on and give it 5 pulls it should be over 150psi if not you got cylinder piston problems (rings or scored piston/cylinder) Really surprised it would run at 70psi Anything under 140 usally indicates a ring, piston, cylinder problem.

 

[CTYank]

If it starts & runs, you aren't going to hurt it by running it.

If not, THEN it's time for a compression test, done accurately: soft-spring schrader core in cylinder end of tester, engine warm, throttle open, cranked until reading settles.
Below 90, ng.

Of course, before pulling cyl., pull muffler & inspect cyl. & ring(s) through port.

Unless you have time, gasket and ring(s) on hand, and are itching to get in there. There are good references, see Dempsey.

 

[hemlock]

The cylinder walls seam like nothing out of the ordinary. Would changing just the rings make a difference? Thanks.

 

[Singed Eyebrows]

The cylinder walls seam like nothing out of the ordinary. Would changing just the rings make a difference? Thanks.

Look for stuck rings, they cannot bind at all in the lands. The cylinder bore should be as smooth as glass, Randy

 

[Thistle]

weifeng,

Stop spamming every topic you see.Its very annoying.

 

[hemlock]

The cylinder walls seam like nothing out of the ordinary. Would changing just the rings make a difference? Thanks.

Look for stuck rings, they cannot bind at all in the lands. The cylinder bore should be as smooth as glass, Randy

Hello,
I'm not sure I follow you about "stuck rings". Could you eleborate at all? Thanks.

 

[smokinj]

The cylinder walls seam like nothing out of the ordinary. Would changing just the rings make a difference? Thanks.

walls are good then yes few dollars on rings will bring it back to life.

 

[HittinSteel]

I'd run it if after it warms up it still has good power. Most likely your piston and rings will need replaced down the road.

 

[smokinj]

I'd run it if after it warms up it still has good power. Most likely your piston and rings will need replaced down the road.

I read the first post again...+100 run it!

 

[hemlock]

Would low compression cause difficult starts/poor idle? It takes a lot of pulls to get it to fire, and does not like to idle very well (often stalls) unless you feather the throttle every so often. Does the 262 have one ring or two (I can't remember) Thanks again.

 

[HittinSteel]

That could be a carb or compression problem. Best to find a proper compression gauge with a shraeder valve (advanced auto or autozone may loan you one). My old 262XP had a single ring.

Before you buy just a ring though, you might want to check the clearance of the piston and cylinder. An easy non scientific way to do it is to remove the cylinder and piston. Remove the ring from the piston. Turn the cylinder upside down on your bench and and line up the piston in the cylinder and let it drop. If it falls stright to the bottom of the cylinder with little or no resistance, it is probably time for a new piston as well as rings. A ring is like $10-15 if memory serves me right and a Meteor piston with ring from Baileys is around $40.

 

[Singed Eyebrows]

The cylinder walls seam like nothing out of the ordinary. Would changing just the rings make a difference? Thanks.

Look for stuck rings, they cannot bind at all in the lands. The cylinder bore should be as smooth as glass, Randy

Hello,
I'm not sure I follow you about "stuck rings". Could you eleborate at all? Thanks.

The rings must move in the piston without binding as mentioned. Most times when a piston scuffs up a bit the rings will stick & compression will be lower, Randy

 

[hemlock]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

 

[smokinj]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

How easy is it to pull the starter cord?

 

[HittinSteel]

The problems you describe could very well be compression related......get it properly tested to rule it out, otherwise you will be chasing your tail.

 

[hemlock]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

How easy is it to pull the starter cord?

It's not terribly hard - but I don't have anything to compare it to either. My "50" does seem harder though, upon consideration....
Just had a thought - do de-comp valves ever cause issues with compression? The saw has a de-comp, but I've never used it, and often forget it's there.

 

[smokinj]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

How easy is it to pull the starter cord?

It's not terribly hard - but I don't have anything to compare it to either. My "50" does seem harder though, upon consideration....
Just had a thought - do de-comp valves ever cause issues with compression? The saw has a de-comp, but I've never used it, and often forget it's there.

I would have to go with hittingsteele last statement. Really does sound like you need rings.

 

[Singed Eyebrows]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

How easy is it to pull the starter cord?

It's not terribly hard - but I don't have anything to compare it to either. My "50" does seem harder though, upon consideration....
Just had a thought - do de-comp valves ever cause issues with compression? The saw has a de-comp, but I've never used it, and often forget it's there.

Yes, a faulty comp. release will add to a low comp. problem. You will hear a comp. release leaking when pulling recoil slowly. My guess is you will see the problem(if it is compression) if you pull the muffler as I believe someone else mentioned. It is a good idea to shake the gas can every time you add fuel as some oils can separate out. Rings that are just lightly stuck shouldn't need to be replaced. Randy

 

[Danno77]

Thanks for all the help everyone. One last question - if it is a compression problem, what are some of the other symptoms that would go along with it. It is a brute to start (takes many, many pulls), and does not idle well at all. To re-start from warm, you often need to choke it. It has always been a bit fussy, but now is noticable worse. I have re-built the carb, and the problems persisted - this is what has lead me to a compression problem. It gets fuel, spark - just nasty to start and poor idle. It does run strong and cut well, however (once it is running). Is there anything else I could check? Thanks again.

How easy is it to pull the starter cord?

It's not terribly hard - but I don't have anything to compare it to either. My "50" does seem harder though, upon consideration....
Just had a thought - do de-comp valves ever cause issues with compression? The saw has a de-comp, but I've never used it, and often forget it's there.

Yes, a faulty comp. release will add to a low comp. problem. You will hear a comp. release leaking when pulling recoil slowly. My guess is you will see the problem(if it is compression) if you pull the muffler as I believe someone else mentioned. It is a good idea to shake the gas can every time you add fuel as some oils can separate out. Rings that are just lightly stuck shouldn't need to be replaced. Randy

I've heard that an easy fix for a faulty compression release valve is to put a bolt in its spot. Just don't get a long bolt!

 

[Battenkiller]

Just had a thought - do de-comp valves ever cause issues with compression? The saw has a de-comp, but I've never used it, and often forget it's there.

I'd imagine they can fail and stick open. My 2004 357XP came with auto decompression. The hose cracked and allowed air in, making the mixture too lean and causing me to need a new piston. The symptoms were identical to what you are describing. Hard to start, poor idling, but enough power to get the job done once it was up to speed. I'm having a manual decomp valve put in, which would have saved me many dollars if I had done it as soon as I saw the service bulletin recommending it instead of assuming it wouldn't happen to my saw.