My chainsaw rings froze and so saw wouldn't Start. Compression tested @ 30psi. Took apart cylinder looks fine piston slightly burnt but not bad ring clearly was stuck. Replaced new piston and ring and now I have 0 Compression. Plugged intake and exhaust and blew in spark plug hole zero leaks. Turn startor by hand or with a impact gun absolutely zero compression with both intake and exhaust plugged with a piece of rubber and without plugged both cases 0 compression. Cylinder seems good so what am I missing as it was 30 psi stuck ring good piston and ring now gives 0. Help
Husqvarna 450 rancher zero compression w/new piston and rings
- Thread starter alanvan69
- Start date
Explain more about how the rings "froze".
If the saw was running lean, scored up the piston pretty bad and welded the rings into the grooves- I can wear that, but froze?
Photos of the old piston will speak volumes.
My first guess is- the cylinder wall of the exhaust side is still splathered in remains of the old piston and this is the "slightly burnt" condition you are referring to.
If you had 30psi beforehand- your gauge is incorrect for the application- using an automotive gauge and not one designed for a small engine- as a saw generally will not run below 120psi compression (although I have struck the odd one still barely running at 90psi).
Are you 100% sure the piston and rings you fitted are the correct ones?
What saw are we talking about? Some saws had slight changes where the bore was stretched slightly and people will sell you (especially Asian aftermarket people) the original smaller piston and rings for the newer oversized bore and guess what- it wont run!
Have you actually fully assembled the saw and tried to start it- or are you just baffled by the low compression reading?
If the saw was running lean, scored up the piston pretty bad and welded the rings into the grooves- I can wear that, but froze?
Photos of the old piston will speak volumes.
My first guess is- the cylinder wall of the exhaust side is still splathered in remains of the old piston and this is the "slightly burnt" condition you are referring to.
If you had 30psi beforehand- your gauge is incorrect for the application- using an automotive gauge and not one designed for a small engine- as a saw generally will not run below 120psi compression (although I have struck the odd one still barely running at 90psi).
Are you 100% sure the piston and rings you fitted are the correct ones?
What saw are we talking about? Some saws had slight changes where the bore was stretched slightly and people will sell you (especially Asian aftermarket people) the original smaller piston and rings for the newer oversized bore and guess what- it wont run!
Have you actually fully assembled the saw and tried to start it- or are you just baffled by the low compression reading?
It's a 450 rancher was actually cutting best ever was my comment then the sprocket drive went out. I turned saw off took home and replaced sprocket. Went to try and start it wouldn't start at all. This saw has always started so easy. I then checked compression.lookedin exhaust and could see ring stuck ie not movable. Pulled it apart and cylinder wall look very good no scuffs, piston was also probably good just top part some darkness most of it looks good. Ring will it broke prying out of groove. Ordered new piston ring from Amazon very cheap and installed. Confident everything looked good tried to start it and nothing pull way too easy too. Compression gage reads zero now same gage as before. Finger plugged hole no pressure at all either that way. Blow in spark plug hear air coming from exhaust and intake. Covered those blew in air notta sealed tgt as a drum. Turned saw over with both plugged still no compression via gauge or via my finger. Now wrong piston rings maybe I haven't checked that yet but it literally got worse after the repair. Seals all are good crank looks new saw lives at coast property year rd so I'm guessing I know bad gas from sitting but it did start everytime until now.
I think u have already told me the problem. I have a 42mm piston for a 450 rancher but there is also a 44mm piston for the 450 rancher. I bet my old one was 44mm not 42mm. Will my rings fit my old piston?
rings off a 42mm piston will not fit a 44mm piston nor vice versa.
My advice would be stay away from the Amazon stuff- measure your original piston, buy new OEM piston kit.
I am guessing it was pretty easy to fit the cylinder back on the new Amazon piston? You should have to compress the rings into the grooves in order to get the cylinder over the piston.
Yes it wasn't too hard. Amazon stuff is same as any store since all these stores sell on Amazon. What u meant I'm sure is Stay away from the cheapo Chinese stuff sold on Amazon. Amazon sells oem stuff u know. This wasn't Amazon fault but mine and the internet. 47cc 450 husqvarna uses 42mm piston the 51cc 450 husqvarna uses 44mm.
What u meant I'm sure is
Well if you know what is in my head better than I do- you go right ahead and have fun in your adventures.
Well if you know what is in my head better than I do- you go right ahead and have fun in your adventures.
EggShooterist
Member
You get it figured out?
AirConditionerView
New member
Husqvarna 20 Inch 450 Rancher II Gas Chainsaw is a very amazing & powerful chainsaw. It has a lot of interesting features that are .....
- 20 HP of engine speed.
- 20 inches of bar length.
- 2 cm³ of engine displacement.
- 95 US pint of fuel tank capacity.
- 6 Nm of max torque.
- 325 inches of chain pitch.
- 2,700 RPM of idling speed.
Last edited by a moderator:
TLCary
New member
Replaced sprocket. Went to try and start it wouldn't start at all. Found zero Compression. Exactly what happened to me. Did anyone ever figure out how changing the sprocket would cause a complete lack of compression? Or better yet, how to fix it?