Dear expert, I just bought an xr600 1997. When you start it up with the choke it seems to run fine. But when I take the choke off, it wants to stall and I have to keep feathering the throttle to keep it running. Also when I'm riding it runs better with the choke on, and when Im riding with the choke off and I let off the throttle the engine backfires pretty bad? THe carb was rebuilt not too long ago but I am not sure if the the carb was adjusted properly. give me some info please

Hi,

Carburettors are notoriously difficult things to balance without the correct tools. I could not advise that you attempt to try this yourself as there are too many possible variations on the fuel mix and manifold vacuum pressure in the carbs.

The only way to balance carbs properly is to use a mercury manometer. The manometer measures intake manifold vacuume pressure and this tool is specifically designed to set the carbs properly. This will have a major effect on the overall performance of your bike.

Take your xr600 to a proper tuning shop and for a small fee they will set the carbs up properly for you. You will notice a major improvement in the bike and you will definitely not regret it!

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Needing the choke to be on all the time indicates a lean condition, possibly with the idle screw and/or pilot jet circuits. Special tools like manometers are not useful for tuning your XR600's carburetor because there is no airflow balancing to be done.

Depending on what jets are installed, the idle screw should be between one(1) and three(3) turns out from fully seated to get the idle right. If it takes more than that, the pilot is too small. Less than one turn(or if the idle screw has no effect) and the pilot is too big.

It definitely sounds like a carb problem alright, did the problem start right after you adjusted the carb? Give me a little more info on how / when it started having the problem. I would get the carb re-evaluated, tell whoever rebuilt it the problem (or if it was yourself, check out the carb) and they should be able to check the carb for free since they worked on it.

Thanks

Tim

Could be a adjustment in the carb or it could be a fouled sprk plug without looking at it it would be hard to tell. But it seems to run on choke then you have a carb issue as it is getting spark. It also could be a trottle issue as well check the trottle cable and make sure it aint loose.


Thanks

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