Chainsaw has too much compression

egbinor

Member
My chainsaw has gotten very hard to pull the rope. It runs good after I get it started. I;ve read somewhere to put water? in the
cylinder overnight because the rings are cerboned up? Any help out there...EGBinOR
 
I would never put water in it! There are sprays (power tune) for removing carbon, but I doubt if that's your problem. I would suspect the timing is too early. I bought an old beater 621 Jonsered once that had very high compression, got it running well and sold it, made some money on it!
 
Also try removing the spark plug and see how pull starter works, just trying to see if it could be binding in the recoil/starter assy or not.
 
Check for side play in the crankshaft.

Could be the main bearings are loose, look for evidence of the coil rubbing the flywheel.
 
I have a MS250 that has come up on compression since new. Have had it into dealer and nothing wrong with it and dealer said that from time to time they see saws come in with nothing wrong with them but have increased compression.
 
water will not dissolve carbon; it is far too hard to be effected. If it is over loading on fuel the carb may need rebuilt to stop the diaphragm from leaking fuel into the cylinder after the saw is shut off. Maybe take the plug out & pull the cord several times to blow out any excess fuel, then see how it pulls.
 

If you introduce an extremely fine trickle of water into a running engine through the carburettor that may remove some carbon . A drastic and frankly silly thing to do though . Soaking in water will do nothing but rust things up .
 

Little two stroke motors as on chainsaws have to have a lot of compression to make the needed power. Carboned rings will decrease not increase compression. When starting, slowly pull the rope to where it pulls hard before starting your actual starting pull. You will notice the compression less.
 
Ivor from uk here and I have a stihl chainsaw and when I am hedge laying or pletching as it is called the saw only runs for 15 or 20 seconds or perhaps 1 minute at the most if there is a big cut to make the spark plug tip builds up with carbon,i use proper 2 stroke oil at a ratio of 25to1
does any pletching or hedge laying go on across the pond??
 
(quoted from post at 00:57:42 08/18/17) My chainsaw has gotten very hard to pull the rope. It runs good after I get it started. I;ve read somewhere to put water? in the
cylinder overnight because the rings are cerboned up? Any help out there...EGBinOR

Don't put water in the saw-ever. First thing I'd check is the pull start assy. Make sure it's greased and the bushings are good. after that I'd be looking at crank bearings. Take off the side cover, bar and chain and see if there is any play in the clutch side of the crank. Do that to the starter side when you're looking at the starter assy. It's possible the timing is off a little but without knowing the make and model of the saw that's just a long shot. It's also possible the piston or cylinder are scored or carboned up. You need to pull the exhaust to check that. It will be apparent if it is, but usually a scored saw won't run good, if at all.
 
You are misunderstanding WHY water is put into carboned up engines. The engine must be up to operating temperature, spray a light stream of water into the engine carb air inlet and the cold water shocks the hot carbon and the carbon flakes off and blows out the exhaust pipe. I've done it to high hour Kohler engines many times. Would not be afraid to do it to a 4, 6, or V-8.

Not sure it would accomplish anything on a 2-stroke chain saw engine. Not sure I would do it to a saw, but the engine is running at rather high rpm when the water is sprayed into the carb air inlet. Manual for my Stihl saws and leaf blower says to scrape carbon out of the exhaust port. I think that's what I'd do.
 
Don't put water into the 2 stroke. When people did it years ago it was with 4 stroke engines where the water is flowing straight into the cylinder. As stated it is with a hot engine so the water turns into steam in the cylinder and helps bust up the carbon.

On a 2 stroke the water would go into the crank case first and pool up. It would give you rusted bearings.

Does the saw have a compression release? If it does maybe it is plugged. If you still want to try and get carbon out of the saw either take it apart and clean it or use something along the lines of sea foam.
 
No it wouldn't go straight to crankcase because you would spray a light mist through air intake with hot engine and let it run for a while
after doing it.You might want to do it with screen removed from muffler.
 
Also check the air filters and make sure they are clean. I bought 2 032 Stihl saws at auction that pulled very hard. I pulled them over with plug out ,They seemed to pull normal and believe they were fuel locked. Cleaned air filters and both were very dirty. I hook up a drill to the nut on the clutch and start hard starting saws that way . Fine adjust everything and both saws start Normal now.
 
(quoted from post at 08:13:49 08/18/17) No it wouldn't go straight to crankcase because you would spray a light mist through air intake with hot engine and let it run for a while
after doing it.You might want to do it with screen removed from muffler.

What?? Has someone invented a new kind of two stroke motor?
 
Hello EGBinOR,

If A two cycle engine gets flooded BADLY, oil can separate from the gas mix, accumulate in the crankcase
and creates an hydrostatc lock. Try blowing the crankcase out with air. Take off the muffler or the carb to get access. Turn the engine to get under the piston and blow the crankcase out. Low pressure, 20 to 30 pounds is all you need. Also take the spark plug out and do the same. If oil is in there it is what makes the engine feel like it is almost locked up. Try it, it may just do the trick!

Guido
 
Hello EGBinOR,

I will also add that if you have points, then the wrong gap will alter the point of ignition and can have the same results,

Guido.
 
(quoted from post at 17:22:48 08/18/17) Hello EGBinOR,

If A two cycle engine gets flooded BADLY, oil can separate from the gas mix, accumulate in the crankcase
and creates an hydrostatc lock. Try blowing the crankcase out with air. Take off the muffler or the carb to get access. Turn the engine to get under the piston and blow the crankcase out. Low pressure, 20 to 30 pounds is all you need. Also take the spark plug out and do the same. If oil is in there it is what makes the engine feel like it is almost locked up. Try it, it may just do the trick!

Guido

That would be quite the trick to get the oil to separate out of the gas, LOL. It is possible however to flood a two stroke which can cause the plug to fowl. The excess gas can be cleared simply by removing the plug and operating the starter a few times. It is best to put a new plug in after clearing.
 
I used to have a Homelite that would do that if I left gas in it. Apparently gas would seep int crankcase and over several months of setting gas would evaporate leaving oil behind and first time it was pulled would suck oil into the cylinder. Would have to remove spark plug and rinse cylinder with gas to be able to start.
 
Are you sure the starter rope isn't a little too short? All it needs is a few inches missing and it will pull too hard like the compression is too high.
 

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