stihl 010, bad compressin HELP.

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Callum

ArboristSite Lurker
Joined
Apr 14, 2018
Messages
26
Reaction score
11
Location
Australia
hi. I have done a search but have not found anyone with a similar problem. I have a stihl 010 with poor compression, reads about 50psi, crazy thing is it will start and run but flood at idle. I swapped out a the pistion and cylinder with one off an 009 that had just pumped 140psi. again it only pumped 50psi on the 010. am I missing something else, I am going to put the 010 p&c on the 009 and test it tomorrow just to see what the tester shows.

Regards Callum
 
The cylinder and piston only make compression after the crown of the piston closes /passes the top of the exhaust port. The fit between the piston and cylinder wall needs to be very close, like .002 .003 and a tight fitting piston ring meaning it must be the correct ring for the piston lands/grooves to seal tightly. The end gap for the ring must also be quite close, in the .008 - 009 to reach top compression, seen lots of rings worn down that had .015 -.019 ring end gap but the comp reading would be low. Also the squish clearance needs to be close to .020 to give a high reading, some AM cylinders are really too much squish gap, some are close to .040 and the comp will be very low on them. If there is a compression release on the cylinder they can fail and release a lot of compressed air/fuel. Therefore we would need more info to help you much further in your quest to up your compression.
 
Sudden thought:

That series came in 36, 38 and 40 mm bore, all the same stroke.

Possibly a 36mm piston in a 38mm bore. [emoji15]

Measure please.

The cylinder and piston only make compression after the crown of the piston closes /passes the top of the exhaust port. The fit between the piston and cylinder wall needs to be very close, like .002 .003 and a tight fitting piston ring meaning it must be the correct ring for the piston lands/grooves to seal tightly. The end gap for the ring must also be quite close, in the .008 - 009 to reach top compression, seen lots of rings worn down that had .015 -.019 ring end gap but the comp reading would be low. Also the squish clearance needs to be close to .020 to give a high reading, some AM cylinders are really too much squish gap, some are close to .040 and the comp will be very low on them. If there is a compression release on the cylinder they can fail and release a lot of compressed air/fuel. Therefore we would need more info to help you much further in your quest to up your compression.

36mm in 36mm, as I said, a P&C that pumped 140psion one saw is only pumping 50psi on the problem saw
 
All the needle bearings back in the big end of the rod on the crank, the piston may not be reaching its full travel leaving too much squish area lowering comp.
did a bearing count last night, it was missing one. replaced that, the saw still only has about 100psi, I managed to get it to run but it wanders up and down and then floods itself
 
UPDATE.
the basted is running. the cylinder must have been a bit dry when I did the first comp test because it now pumps up to about 120psi. not great but better then it was. the basted air filter I put on it had a grommet around the carb hole. it must have been choking the saw when the air filter cover was on, removed the bit and the saw runs like It used to.
 

Latest posts

Back
Top