Sportsman 90 new rings, no compression?

[yamaha28]

I am rebuilding a Sportsman 90 2-stroke for a client. He said his son was running it and it died, his son beat the crap out of it. They let it sit for a few months until they called me. When I brought it in, it had around 40psi compression. I took the cylinder off and the rings looked worn so I replaced them with all the gaskets. I honed the cylinder out and it looked good. Now I am getting 50psi exactly, it will not go above or below that ever! Standard compression is 83psi. What is going on?

 

[quadsrus1]

Sounds like there is to much clearance and it needs to be bored to the next size if that cylinder is even boreable (misspelled)

 

[Blaaster]

If the compression did not go up with new rings the cylinder is possibly worn and needs rebore and new piston.

 

[yamaha28]

I figured it out! haha it was a bad battery. It way showint 12.2 volts but it wasn't cranking it hard enough. I jumped on the kickstarter and the compression rocketed up to 85psi. Thanks for the advice though guys!

 

[quadsrus1]

NO problem glad to see you got it fixed bro

 

[blowncash]

So dare I ask? Was that why it had low compression to start with?Low battery?

 

[yamaha28]

yep, I had a battery sitting around and used that. Using a bad battery could never do anything good for a quad! haha

 

[blowncash]

What Im saying is. Before you put new rings in you checked compression and it was low. Was that caused by a low battery. Basically....Did it NEED the new rings?

 

[yamaha28]

ohhhhhh, I see what your saying, didn't read it right my bad. When I first got it I used the kickstarter and there was barely and compression at all. It almost seemed like there wasn't even a piston in there!

 

[blowncash]

Cool then your work was worth doing!!

 

[Paulie B]

Glad you got it figured out and yeah if the battery can't crank it over strong enough then it not gonna show correct on the tester.
You will prolly gain a few pounds after running it a few times.