I have and 89 LT250R it has an 87 cylinder on it, its bored .60 over FMF pipe has mod reeds And K&N clamp on filter.
I need to know what my compresssion should be it has 120 right now cold, if any one could give me a strait answer it would be greatly apeciated. ive had the bike for 2 seasons now and i think it time to rebuild but i dont know what the compression is suposed to be ?

 

I think its supposed to be nothing under 150psi not sure though

 

The bike has 120 cold and has black plugs no matter what i do, so Im thinkin that is time to swich out the piston and rings. where could i go to get the cylinder measured, the guy I bought it off of said it was .60 over but Ive never had it measured, or how much is the tool to measue it and how much is it ?

 

Ok, stock bore is 67mm and the tool you will need is a telescopic bore gauge. you should be able to get one at an auto shop like NAPA, Carquest, or Autozone.
Hope this helps
later
Superstar

 

Sunnen automotive in st. Louis Dial bore gage 500 dollars
Your rich you can afford it

 

The LT250R has 175 lbs of compression (which is on the verge of needing race gas). This if very high compared to other quads but thats the way Suzuki built them. Honda 250R's have about 145 and LT500R's have only 120-125 stock. If you are not using a Snap-on or similar quality compression tester then you cannot necessarily trust your readings. Verify the 120 reading you got with a second compression tester (the cheapy testers are often very inaccurate and deteriorate over time).

 

the compression tester is Snap-on, the guy I bought the machine said it was bored .60 over and i just found out today that it is only .10 over, any way the compression should be 175 stock or what or is that bored over ?

 

175 lbs sounds like quite a bit for a stock lt250r. I have heard from a couple people and I tested mine myself and they were all around 155 lbs.

chuck

 

THanks guys youve been extremly helpful im buyin new piston, and rings and solve this problem
thanks again

 

Black plugs are a sign of rich running. 125lbs is enough to run a motor. 80lbs is required to even get a motor to fire. Sounds like a tuning problem to me.