Last month I bought a 88 lt250R and have recently completed rebuilding it. Everything was put back to stock condition except the silencer (FMF Turbine Core II). After a break-in exercises I took it out for a test ride. I noticed it has Good low end and GREAT midrange however, high end was horrible, does not want to wind up. By comparison I have a 03 Z400 and a 86 Honda TRX250R. I expected the LT to be a bit slower than the Z on low end but faster at the top(4 stroke vs. 2 stroke), Not the case The Z is faster all around. I expected the TRX205R and LT250R to similar, Nope! The LT is faster and smoother on the bottom but not even close on the top end.

My question is do I have a problem with the LT250R ? or is this just the way a stocker runs.
Note: Also replaced stock air filter with K & N with outerwear(inside stock air box with lid ON).
# 250 main jet – plug reads OK

Any comments appreciated

 

Hello,
I had a similar issue on my 86 lt250. I went down a jet size or two and that smoothed things out. My plug read a little rich but ran completely different just by changing the jet. Also, make sure the jet is clean. Do some experimentation. Also, adjust the powervalve on you quad. Set it to the top end "mode" if you havn't already. In the end, you should be fast than the z400 and close to the 250r(depending on how the 250r is modded) Also, just as a possibility, you didn't leave the choke on did you. Does the quad "stumble" on the top end. Spitting/sputtering, anything like that, or does it feel like a lack of power.

 

The power valve is adjusted per manual (1 turn CCW on the spring) are there options to this setting ?
The top end does seem to sputter a bit. And YES the choke is off.
Thanks for the reply. I'll try a smaller jet I have a #230

 

I have an 86 and a 91 LT250r. The 86 has higher than stock compression, a FMF silencer and K+N filter. It pulls pretty evenly from top to bottom and runs overall just a hair slower than a piped 250r with a 50lb smaller rider up to 60mph then he crept away from me. The 91 has a FMF pipe/silencer, unidentified aftermarket reeds/reed cage and a K+N filter. It also looks to have a bigger carb than normal and may have had porting done, I have not yet determined for sure. It pulls good on low end, extremely good lower mid range but top end is not so impressive. The 91 is drastically faster than the 86 and would easily smoke the 250r I raced before so I assume it either runs like that normal or mine has been ported for low end.

 

The power valve can be adjusted for more lowend or more high end. The sputtering sounds like mine did. try some different jets. It could be not getting enough fuel and starving, or too much and drowning itself. Change a jet and ride. the plug may say one thing but the quad will do another, of course don't run it too lean.

 

How do you adjust the power valve on the 88 LT250r and what is the right plug and fuel mix?
Thanks

 

The power valve is adjusted by a "****" on the powervalve cover. A good plug to use is the b8ev or b8egv (the "g" is for gold). 32:1 is a good mix if run castor based oil. If using synthetic, you can run 40:1 pretty safe. Some run 50:1. I use Maxim gold castor, and I run 32:1, with the above mentioned plugs