JMStar 250 won't go over 45mph By acvw74 (Read 1,543 times)

[acvw74]

I have a new intake manifold I am going to put on...I agree with the mainjet...Do you have a suggestion for a size? it is a stock engine.

[acvw74]

Bit of an update...some good new and bad

The bike is a bit better, however I messed up a bit..broke my own rule...I changed 3 things.

1. Cleaned the variator - Bought a new air gun and started it - the drive boss was completely dry - cleaned, greased the boss and reassembled.

2. The new intake I bought...didn't fit...so I cleaned the old one...no apparent cracks, it was silicone on...no real O-ring. So after cleaning I applied a bit of form-a-gasket and used the O-ring from new.

3. Carb - since it was out - decided to see the mainjet size - it appears to have been a 130 or 135. Took it out and installed a 120.

Now the bike accelerates smooth from the start (it was real jerky before) and will continue to accelerate to 55 then start the jerking/hesitation again.

Fairly sure it isn't a vacuum leak now - unless it is the carbon cartridge.
Is it still too big of a mainjet?...and would that cause the jerking/hesitation?

[acvw74]

Had some success tonight!

Took 30 minutes and swapped the 120 mainjet for a 110...Out on the ride it ran right up to 60ish then surged/hesitated but soo much better.

Oddly - with the 120 jet, the temp remained in the normal range - with the 110 it ran to the high side of the gauge...just like at the beginning...still thinking about this one.

[cyborg]

Bingo

[cyborg]

It was lean at high throttle

[acvw74]

That's what I thought too - before swapping out the 130 mainjet - the temp was running hot...running the 120 seemed to run cool ...now the 110 seems to be toward the hotter side.

Still feeling some surging at WOT but reduced...

I think I am going to get 2 or 3 plugs and run it for a while and keep an eye on the plugs....let them tell me which way to move the jet.

[acvw74]

Been riding with the 110 mainjet and seeing elevated temps at highway speeds...additionally getting surging at low speeds when the choke is on.

Swapped the main for a 115 and dropped the slowjet for a 32 - Highway speeds feel much smoother and stronger acceleration to them and the idle is better when the choke is on.

The extra mainjet appears to have dropped the high running temps to a normal range.

FINALLY! Now it is so nice to ride