I have a 300ex 1995 . I live in Long Beach CA. It is at sea level, I ride at Gorman CA. It is at 5000 ft. When I run at 1/2 to 3/4 throttle it has no power, sound like it need more air or gas, I think that I need to go up in jet size-- I had the local dealer clean the carb and gas tank-- thay said that my bike is ok-- It still runs bad at 5000 ft,good at sea level,Is it hard to change the jet on a 300ex? Am I on the wright track,I think the local dealer does bad work-- Can I do this job?-- The bike starts good and has a good idle. The spark plug looks good,no carbon or oil, the motor has low hours on it.It look like new!! The motor has 180 psi on the comperession, hope this is just a jet prooblem--

 

Frist change your jet size on your main and go up till your plug is little brown if that dose not help it do I omls test on your spark plug see if your cap is good it may be bad

 

may i ask, is it a stock motor? if not what kind of mods do u have done to it, pipe? filter? ect.

 

stock , uni air filter that is it--

 

well if u ride at 5000 ft most of the time im pretty sure stock main is 122, so i would recomend going up to about 126-130 main, if it still sputters at 5000, then maybe move the clip on the needle down one slot.

if you need instructions or something ill take pics of how to do it.... i got my old one just sittin around i can tear apart and stuff lol

 

Today I talked with the guy that did the work on the carb,he said that he will look at the jet size and check the float level, I told him to get it right this time,It is a honda how hard can it be to work on,LOL. I will post the findings after I get it back in a few days Thank You for your help!!!

 

just got my atv back from the guy that worked on it he said that it had a #122 main jet in the carb,the float he said was the plastic non adjustable float-needle and seat check ok, he said that the uni filter is the problem,said that the stock filter will make the quad run better? The atv seems to run better now, I have not gotten a stock filter yet,I think that he is full of sh-t,just trying to cover his tracks(fixed clog jet?) I dont think that the a air filter is a problem.Time will tell!! will post in a few weeks when I go out to Gorman. To ride----

 

well i can see where the guy is coming from, the uni lets in more air making it a little bit leaner, and if u restrict the airflow with the stock filter, it lowers the air-fuel ratio.... i never thought of that.