QuestionI moved to about 3000ft el. from 300ft..and put my stock exhaust back on my 99 model 400EX. It seems to be loading up and I've even seen oil in the breather box! The current jet is a 175 I believe, with a K&N and no other mods. Please advise, help is very much appreciated.
AnswerLogan, is this the stock carburetor?
http://houseofmotorcycles.bikebandit.com/honda-atv-trx400ex-fourtrax-ex-1999/o/m...
They are showing 140 and 148 main jets as stock, using a stock airbox and filter. That is probably at sea-level, too.
I assume the combination of K&N and whatever exhaust system you had installed was the cause of the main jet size increases.
The engine is straining due to the loads being put on it, with incorrect jetting causing lack of power, that is hard on the engine's piston and rings.
You will have to back up to something back in the 140s again, to get the jetting back to where it needs to be. In some cases, you may drop the needle a notch by moving the clip up a step.
Not really my specialty, though... check in with this ATV specific site:
http://forums.atvconnection.com/messageview.cfm/catid/8/threadid/529648&STARTPAG...
Bill Silver
