Midrange power on YZ125 problem

[Brodie Sinn]

Hey guys, I recently picked up a 89 YZ125. I bought my Clymer for it and tuned the carb according to that to try and fix my midrange but the bike was already at factory settings. It is really sluggish in midrange, I have to keep it WOT for quite a while before it will get to the high RPMs and it's powerband. The bottom end and very top end of the RPMs seem fine though. Any suggestions?

 

[spw1993]

buy a 250 my 1981 yz 125 is the exact same way

 

[Brodie Sinn]

Well I have the carb apart right now, cleaning it all out to see if it helps, all the parts seem to be in fine condition. Hopefully this does the trick.

 

[Brodie Sinn]

Well I cleaned it and threw it back in and it started right away and ran for about 1 minute then bogged down and died. Pulled the plug and its wet. Did I do something wrong?

 

[motodr9]

:coocoo:

buy a 250 my 1981 yz 125 is the exact same way

Nice help...huh.
Did you check the float level when you had the carb apart? Too high or sticking open?
Is the needle clip in the stock or middle position? How is the compression? Inspect the reeds...do they look chipped or warped? Use a new plug and see how your spark is, by kicking it over while grounding the plug/wire on a head bolt...try it out.
Also jetting will need to be adjusted for temp, elevation, and rider. Don't be afraid to go up or down a few jet sizes to get what you want. I forgot to add...needle clip position has the largest influence on the mid-throttle performance.

 

[whenfoxforks-ruled]

If you really feel its the jetting and not something else, replace the float valve and seat if applicable.

 

[Coop]

In Eric Gorr's first book he talks about how the 1985-1989 YZ125 suffers from lack of midrange. He gives jetting specs that are supposed to help. I just picked up a 1988 YZ125 yesterday so I was just reading that section. Mine has a flywheel weight and aftermarket pipe but it doesn't seem to have that lack of grunt down low. But I only rode it around the yard.

 

[whenfoxforks-ruled]

Call JD jetting, ask him if he has a needle to help it pick up. Trying to get the motor to pick up better, and having a flywheel weight seem to contradict each other.