Whats wrong (pops and misses - jetting)

[desertrider15]

OK guys i just got my top-end rebuilt and all that. I just got one of those Pro Circuit quiet end caps the 1 3/4 for my pro circuit full system and under hard acceleration my bike pops and misses, changed my jet Main jet from a 165 to a 168 and nothing seemed to work what do you guys suggest.My bike is a CRF 450X and i have the top of the air box cut off and a pilot jet and leak jet and needle but i don't know what they are.

Thanks,

Thomas

[cubera]

You were running fine before exhaust mod and top end job? Not much difference between a 168 and 165 maybe. Valves are not seated yet?

[desertrider15]

You were running fine before exhaust mod and top end job? Not much difference between a 168 and 165 maybe. Valves are not seated yet?

Yea it was running great. Yea the valves are seated because i went for a 50 mile ride on saturday before the race and it was doing it during the race too. And i also spoke to the mechanic from PC but he said it must be dirt in the carb and there wasn't.

[cubera]

I had a similar problem with the tank vapor locking....clogged vent......but it would only do that after sucking down a half of tank of gas. Hummm.....You pulled your bowl cap off and no dirt?

[desertrider15]

Yea when i pulled the main jet it was really clean and there wasn't a speck of dirt in the bottom of the bowl. It has to be my main jet doesn't it because the main jet is 1/2 throttle and up right.

[cubera]

That's right. Seem like the problem would be a partially clogged main jet but what else could it be?

[weskc35k]

Maybe running rich from the end cap and warmer weather.

[desertrider15]

Maybe running rich from the end cap and warmer weather.

shoot its like 70 degrees here in the desert in California.

[weskc35k]

The end cap will or should make it richer and is it warmer than when you were riding before rebuild?

[desertrider15]

The end cap will or should make it richer and is it warmer than when you were riding before rebuild?

No its about the same in temperature wise. But i dont know why the cap should make it richer.The end was a 1 1/2 before and now a 1 3/4 why would it make it richer is it because the more air coming out the exhaust.

[arock]

If you restrict air flow you have to also restrict fuel (smaller jetting).

[desertrider15]

The end cap is actually way bigger than stock Eddie in jetting told me it was probably timing.

[cubera]

Timing like cam chain off a notch?