Hi all, I am after some help, my Son has bought a GK76a GSXR400 engine and transplanted it into a buggy.

He was told the engine was all good.

It came complete with loom & cdi unit

It starts fine and will tick over for ever. But if you touch the throttle it revs ok but cuts out when you release the throttle, and it has us completely stumped, the carbs have been off and all 3 jets cleaned.

The spark plugs are a little black so its running a liitle rich.

When he got it, there were some resistors soldered into the loom across the ignition pick up, which he foolishly disposed of.

It is the later version with the throttle position sensor, adjusting the throttle position sensor seems to affect the sensitivity to this cutting out when the throttle is released but does not cure it.

When its running it sounds fine and when it cuts out it is like its been switched off, if it were carburation I would expect it to splutter to a halt.

Does anyone have any suggestions what the resistors across the pick up could have been for? is the a bodge to ovrcome the issue of having the wrong pickup for the cdi unit or something? if so does anyone have details of the mod?

Any help or suggestions welcomed. He is at his wits end.

Buggy located in Braintree Essex.

No idea what the resistor was, when you say cross the ignition pickup where do you mean?

Are you running the air box? and if so are all the float bowl pipes connected up as the SP has pressurized floats.

Yes he has the carb bowl pipes connected up.

By across the pickup, I mean between the two contacts, ie across or in parallel to the pickup.

Does anyone have any more information on the throttle position sensor? How can he test it? is there ar setup proceedure, what symptoms does a faulty sensor cause?