2003 yz125 yamaha engine problems

[water]

can you help,
just bought a used yz125, it ran great for a week then my son ran it out of gas. he filled the tank but it wont start normaly or run correctly now. checked the carb and it is getting gas, took the plug out and we see spark. We have primed the cylinder with gas also and it wont hit. We did pull it and it barely started (very low power) only when he opened the throttle fully but will not stay running.

please advise, we don't know if this is a simple or serious problem.
thanks
dw

 

[chevy383cid]

Get a compression reading,sounds like he might have hurt the rings( running it dry).

 

[QKENUF4U]

did you mix OIL w/ the gas ?

 

[water]

we did mix oil with gas, i plan on buying a manual and will check the compression. do you know what the compression is supose to be?
tks

 

[QKENUF4U]

needs to be 100+psi to run unless you pull start it. but in your case a good compression will be 150+psi

 

[water]

will check the compression asap. thanks

 

[MX-727]

Since he ran it out of gas, there is a chance that some dirt from the dregs of the tank may have got into the carb. Did you take the carb apart and check for blockage in the float and the jets?

 

[daniel 40]

Snound like you need to do a top end, I had a 94 cr125 it did the same thing and I had to do a top end. About 125 to 175 psi on a 2-stroke engine. You'll find the actual specification in the appropriate service manual. Good luck! check out motopowervideocom DVD's mc maintenance there good whatever you need for what you are working on ;)