Dragster blues

Had a couple of weeks of the scoot running cock on have developed a intermittent loss of power. It's a bit wierd really still pulls nice and smooth and still makes full power it usually occurs on bumpy roads. It's like the throttle has been closed, I'm usually around 3/4 throttle and if I twist the throttle open it stays the same but if I fully close the throttle and carry on as usual it rectifies it.

 

Sounds like the carb float height to me. Closing the throttle would allow the carb float bowl to refill if it's emptied as result of the float being forced upwards by the bump, causing the fuel flow to stop. You could try bending the tab that connects the floats to the float needle down very slightly, but don't overdo it or you'll have fuel coming out of the overflow.

 

That does make sense as I was messing with the float with the last problem I had. I think the tab on my float is plastic though.

 

Should I just replace the float and float needle? I think there available together in a kit. This is the type I have.

http://www.ebay.co.uk/itm/291109771897

 

It's certainly worth a try if they aren't expensive.

 

Just ordered one from Italjet uk to give it a whirl. They suggested a whole host of other things as well but I'll keep my fingers crossed.

 

That didn't cure it. I'm a bit stuck really. Could the rollers cause it?

 

Loose electrical connection ? Some shit in the carb ? Stopcock valve on the tank playing up and not letting enough fuel through ? Sticky needle valve ?

 

It certainly seems mechanical rather than electrical as it rectifies itself after closing the throttle. It's weird but only happens on rough ground. It's a new fuel tap as well and I also replaced the needle valve and float. Was thinking of getting it on a rolling road to see if that would help with diagnosis.

 

A bubble in the fuel line. Do you have clear tubes?

 

No there black. What would cause the bubbles?

 

I'll throw some thoughts into the hat.

Do Italjet Dragster bikes have a fuel pump, like Gileras Runners and DNAs? Gileras have a small tank underneath the main fuel tank that feeds the fuel pump and it can get air-locked. If your Italjet has the same setup, you could have an air-lock in the tank and that will cut the flow of fuel. The air may need to be purged out of the system.

Or...

It could be the carb floats being set too low, causing the float bowl to empty before the floats kick the needle in to refill the float bowl.

 

Have you checked or changed the plug cap at all, and does it have the waterproof boot on it?

 

The carb float is new. It's got no adjustment on it so I don't think it's the float height unless I'm missing something.

I had the tank off recently to change the pet cock and there was no small tank. Is the pump near the tank if so there wasn't one.

 

It's the red rubber insulated type.

 

Ok, whats the condition of the brass inside where the spark plug connects? Nice and clean and a tight fit on the plug?

 

New needle valve with the new floats ? Hmm. Still got the old valve ?

 

Yes still got old float and needle.

 

It's possible the new needle is sticking. Try new floats, old needle

 

I'll give it a go.