KDX 250 running too rich?

[antferny]

Late last year I brout a 91 kdx250 it had done 11 hours riding after a full rebuild , I have since done 8 hours riding and Ive just fitted a 2nd new sparkplug , this is my 1st 2 stroke but Im pretty sure that I should be getting more then 4 hours out of a plug???? am i running it to rich or could the 2 stroke oil I have be dodge. The previous owner was mixing it 35:1 and thats what ive keep too. any help much appreciated

[F5 Dave]

Should be in dirt forum not electrical, never mind

Hi, 35:1 on that will be fine, it isn't your issue. First replace the airfilter if not already as they get scoady & won't flow as well. Obviously check for airleaks as this will throw things out which will become important if you jet down.

Also check the needle & needle jet are not too worn, I assume PWK Keihin carb on this so not replaceable needle jet, but could machine an insert if there was a problem, get back. Look down needle hole & check for the slightest ovality. Also the slides wear a groove in them which can be a pain & they aren't cheap (like $180).

There are a heap of jetting sites more than I can type info here, try Canadian Dave's KDX sub site of DRN.net.

Since it has been rebuilt it can suck harder so leaner jetting may be appropriate. it might be a start to lower the needle & twist the idle mixture screw out a touch, but after that you are changing brass. The biggest mental hurtle is that the carbs are position dependent, not revs.

Read that again & write it down.

Then decide where it isn't running cleanly & change one jet size at a time. Often they foul bumbling around on low throttle, that would be the pilot. If it takes a while to clear out, burbles before it takes off on full throttle then that will be the mainjet.

[antferny]

Thanks,will start with those issues today. Will also buy the kids a bike as they always want a ride and thats when im just idling round the yard.haha.