So my son has a 2001 Yamaha phazer 500 and at the end of last year he had to rebuild the motor. The crank bearing went out. He did a complete engine rebuild but decided to stay with the stock cylinder size. The cylinders were hone only and not oversized. New piston and rings installed. Engine it back together and he has not even put one mile on the sled due to no snow at the end of the year. I did a compression test on the motor today and see one cylinder is at 125 PSI but the other is only showing at 110 PSI. What would caused this issues and would he be ok running it like this? Older sled so doesn't want to really put any more money into the sled.
no miles on it? Put in a cap fill of 2 stroke oil and check it again. I would guess nothing is set. Also check the reeds.
odds are it will be fine once it breaks in. check the reeds but it might just have a sticky ring from assembly lube.
correct no miles on the motor. When I put the oil in should I turn it over a few times before I take the compression test?
Yes correct. Spin clutch by hand or pull slowly.
So I added a cap of oil to both cylinders and turned it over by hand a few times. Took compression test and PTO is only about 100 psi and the other side is 125. Took reeds out and they look fine. Decided to tear down motor, nothing major that I can see so I am going to have the cylinders bored out to the next size up and purchase new pistons. What is the next size up?
bird
New member
- Joined
- Feb 28, 2022
- Messages
- 22
Did the motor run long enough to "seat" the new rings? There's a break in period after a hone and new rings.
Did you check the compression before he tore it all apart and had the hone done?
Checking Partzilla, there's a .25mm piston.
www.partzilla.com
Did you check the compression before he tore it all apart and had the hone done?
Checking Partzilla, there's a .25mm piston.
Yamaha Snowmobile 2001 OEM Parts Diagram for Crankshaft Piston | Partzilla.com
Buy OEM Parts for Yamaha Snowmobile 2001 Crankshaft Piston Diagram
www.partzilla.com
Reason for the rebuild last year was it eat a piston and took out the crank shaft so no didn't do compression test before hand. I already have the cylinders at the machine shop and going 72.50. A Yamaha tech told me he thought it sounded like a lot of piston slap so thus why I did a compression test and found the one low cylinder. I decide to just do the motor now before winter when it gets cold out then I know going into winter that the sled has a new crank and new pistons for the correct size bore. Before I took the cylinders off I removed the cylinder head and was able to move the piston back and forth a little in the cylinder. Not much but still some