770r compression

[jedw79]

Hi what should the compression @ sea level be for a '99 ts 770r. I checked one and it is at approximately 135 psi on both cylinders. I was thinking this was a little low, but was pleased to see both read approximately the same compression. The ski seems to run fine top end wise but doesn't run very well up to about 1/3 throttle or so. I'm figuring it has something to do with the low speed jets or possibly a restriction in the fuel supply (internal filters). The ski came from up North (Minnesota) and I was told that it may possibly need to be rejetted to be ran in Texas due to altitude and climate differences. Does this sound feasible or is it simply bs. I feel like the engine is sound based on how well it runs at the upper rpm range. Thanks for any input

[Technical Support]

Given they are equal I wouldn't worry, that's close to around stock, I would suspect your gauge is just off.

[jedw79]

Hey thanks for such a quick responce!! Gotta love that. I'm pleased to hear your response is along the lines of what I was hoping for. I'm considering purchasing this ski and don't want to be rebuilding anytime soon, but you can bet that when I do, I'll give you guys a call. I have really learned a lot from this site and pretty much visit on a daily basis. Thanks again

[lownrangr]

I'm just curious, does anybody know the compression of the 1100R?

[jedw79]

Now I'm baffled. I put a 3/4" reach adaptor on my compression gage and the compression decreased from 135psi to 125psi. This seems odd to me since I thought that when you decreased the volume in the cylinder, the compression should increase. I verified it 3 times that the compression decreased when attaching the long reach adaptor as opposed to using the gage with no adaptor at all. I know that the compression ratio is the ratio of the volume of the combustion chamber with the pistion at bdc divided by volume with piston at tdc. That's why I think my observation was wrong for some reason or other. Maybe a bad gage?

[Technical Support]

Your adaptors need to have the schrader valves right at the tip, if not they increase cc's via the air in the tube.

The 1100 should be around 120.

[ June 17, 2003, 10:43 AM: Message edited by: Technical Support ]

[jedw79]

Alright I can understand that now. I'll have to get me a new compression gage with the right adaptor. Thanks