300ex jetting with sparks

[drybranch]

Put a sparks exhaust on the 300ex with no lid and a 42 pilot w/ 3 turns out on fuel screw and no changes to needle. Now I have a good idle and acceleration and with a 130 main and a 132 main i have a good plug that is grey to gold with a little black on the top of the threads but the insulator looks good.

My question is this. With the 130 on a wide open straight it will run great with like a hickup near the end of the straight if I am holding it open. With the 132 it seems to take care of this at first but after riding it for a while it seemed to hesitate a lot when I am riding at fairly high rpms.

I guess I want to know what could be done to remedy this or if the hickup on the wide open straight is normal after some length of running this way. Now I have ridden it a good bit and do not believe that the hickup is from the rev limiter

[bwamos]

Probably need a larger main still.

Here's the jetting reccomendation straight from the sparks site.


TRX 300EX 135 stock needle in stock slot 42 2 +/- 1/2

These recommendations are with the Sparks Exhausts, Air filter, the Air box lid off, at sea level.

If you are over 2000ft you may need to drop the main down.

Just posting it for reference. Hope it helps.

[drybranch]

Thanks bwamos,

I forgot to mention that I am at 4000ft and I got to where I am by asking the guys at Sparks. Thanks though I will try the next jet this evening.
I thought that since I got the idle and acceleration good that it had to be the main jet. Does that sound accurate?
Just thought that maybe I was too rich causing it but thought that didn't make since b/c it appeared to be thirsty for more fuel instead of flooding out.

Any more thoughts or suggestions?

[300exOH]

Originally posted by drybranch
Thanks bwamos,

I forgot to mention that I am at 4000ft and I got to where I am by asking the guys at Sparks. Thanks though I will try the next jet this evening.
I thought that since I got the idle and acceleration good that it had to be the main jet. Does that sound accurate?
Just thought that maybe I was too rich causing it but thought that didn't make since b/c it appeared to be thirsty for more fuel instead of flooding out.

Any more thoughts or suggestions?

Sparks jetting specs are perfect for me at about 500ft above sea level so in theory the 130-132 should be about right for you but you might still want to try the 135.

[bwamos]

Are you running stock cam or an aftermarket cam.. generally if you have an aftermarket cam in there, you'll need to go a bit richer also.

However, you may be running rich not lean.
Is the "hickup" a stutter, or a bog? If it' a stutter you may be a tad rich. It could be loading up the engine with a little excess gas on your long straights, causing it to miss.

It's always hard to diagnose on the forums. ;)

Try putting the airbox lid on and see if it makes it worse. If it does you were too rich.

[drybranch]

If I had to guess it seems to be a stutter. I will try the thing with the lid. Thanks for the great reply-it only makes sense.