gasgas jtr 370 carb problems

[nath15804]

Hi, i have a gasgas jtr 370, its fitted with a dellorto carb. the bike starts fine, but is over reving with the choke OFF, i will run for a while with the choke on but will then start to over rev for no reason after maybe 20mins of riding. Its a really weird problem, iv checked most things, but could it be something to do with the jetting??

[chewy]

Does it "knock" when this is happening? It could be an air leak when engine gets warmed up

[jse]

Hi, i have a gasgas jtr 370, its fitted with a dellorto carb. the bike starts fine, but is over reving with the choke OFF, i will run for a while with the choke on but will then start to over rev for no reason after maybe 20mins of riding. Its a really weird problem, iv checked most things, but could it be something to do with the jetting??

You have the "large body" Dellorto on the 370, the only year and model it was on (they are common on Fantics).

I doubt that an air leak or jetting is the problem as the symptoms are not consistant (air leaks and jetting usually have constant, not intermitant symptoms). I'd look for a problem with the cable such as frayed at the throttle housing or kinked by the fork clamp somewhere. You should also check the carb very carefully and look for a problem with the slide hanging up in the bore, sometimes caused by grit getting past the air filter element.

Jon

[nath15804]

You have the "large body" Dellorto on the 370, the only year and model it was on (they are common on Fantics).

I doubt that an air leak or jetting is the problem as the symptoms are not consistant (air leaks and jetting usually have constant, not intermitant symptoms). I'd look for a problem with the cable such as frayed at the throttle housing or kinked by the fork clamp somewhere. You should also check the carb very carefully and look for a problem with the slide hanging up in the bore, sometimes caused by grit getting past the air filter element.

Jon

its a brand new cable, also i have cleaned the carb, this doesnt explain why it will not run or idle with no choke though.

[tltel]

Hi

you could try a new air filter and adjust carb.

I assume you have had it running ok.

TLTEL

[nath15804]

Hi

you could try a new air filter and adjust carb.

I assume you have had it running ok.

TLTEL

iv not had it long and it has never been correct. maybe if i try with the air filter off to see if that is the problem. if it runs ok then it will probs be the filter aye.

[jse]

its a brand new cable, also i have cleaned the carb, this doesnt explain why it will not run or idle with no choke though.

Your symptoms would also be consistant with floats incorrectly installed or hanging up in the closed position.

Although your carb is a little different than the standard PHBL on the new bikes, I had a rider experience your

symptoms and then the engine died (repeatedly)on a new 2010 bike this last weekend at a Trial (he had earlier

taken the float bowl off and very slightly bent one of the rods the float rides on, which stuck the float in the

closed position). You wouldn't have noticed the bent rod unless you were looking for it.

Jon

[nath15804]

Your symptoms would also be consistant with floats incorrectly installed or hanging up in the closed position.

Although your carb is a little different than the standard PHBL on the new bikes, I had a rider experience your

symptoms and then the engine died (repeatedly)on a new 2010 bike this last weekend at a Trial (he had earlier

taken the float bowl off and very slightly bent one of the rods the float rides on, which stuck the float in the

closed position). You wouldn't have noticed the bent rod unless you were looking for it.

Jon

its with the mechanic now anyway, ill get back to the forum with the problem.