Need some help with jetting an '88 TRX250R, done the basics - compression check (~210psi), air leak check (none). I've recently taken the quad out of storage (ran great several years ago), cleaned the carb and airfilter, changed the tranny oil and spark plug, etc. Mixed up some fresh gas (50:1 ratio with Golden spectro) and it ran great. Then I realized that I'm running too much compression for pump gas and switched to AV. Hasn't run right since. I've played with the main jet some, and run it with and without the airbox cover, and all I've really been able to do is change WHERE in the powerband it ran lousy, but not eliminate it. So I'm looking to start over. Can anybody suggest a starting point for the slow and main jets?

It's an '88 250R ported,polished and set up with a 20cc? dome by LRD. 3/16" spacer plate, '86 style piston, ATC style head gasket. K&N filter, FMF Fatty pipe and silencer.

Thanks in Advance
-Dan C.

 

I have a similar setup on my 89. When I had the stock carb I think I had a 50 or 52 pilot, needle clip on second position from bottom, and a 160-162 main jet. Here's what it had...
-no airbox lid and uni filter
-spacer plate and 86 piston
-CT midrange pipe
-coolhead with 21cc dome
-CR style head gasket
-210 lbs compression
-RAD valve
-@650-700 ft above sea level

AV gas might have a different specific gravity than pump gas so it may run rich?
ERIC

 

Eric,
Thanks for the info, I think I'm going to try going down a few sizes on the pilot - the previous owner was running a 65- and I thought that was too big.

Tell me, at 210 psi, do you run race gas, AV gas or pump gas?

 

I run a mixture of race gas and premium.
ERIC