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DT400 advice needed! Sounds like it is 4 stroking?

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Hi everyone,

Me and a few mates recently finished piecing together our dt400 bobber conversion. I have posted on a few other forums, so thought i would try this one as well.

Our problem is this- we are able to start the motor, but it sounds like it is 4 stroking- just an intermittent "bang - bang - bang" as opposed to the regular idle. If we give it some throttle it just dies. It is blowing an absolute shit load of smoke the whole time it runs.

Our motor is out of a DT400b, with DT400c stator/Flywheel/CDI/Coil.

We have disassembled the carb, re-adjusted the float levels to factory, checked all vents, cleaned the pot, checked it again..and again and again. Still nothing. Having said that, we all have pretty limited knowledge on our to tune carbs.

When it is running it really sucks down the petrol, and we are getting a fair bit of petrol blowing back out of the carb.

We had the timing set at factory, but are yet to chuck a timing light on it. Last night I retarded the timing by 1.5deg but it made no difference.
Compression feels good- as it is a pain to kick over (arch in my foot is nice and bruised!)

We do not have the oil pump hooked up, and are just running pre-mix- could this affect the carbs performance?

Could it be an issue with our CDI or timing?

Could or exhaust be stuffed- i.e, expansion chamber is not working properly?

One interesting note is this- we have just been feeding it petrol through the fuel line (tank is still being painted!) - so it just runs until it runs out of petrol. Just before it runs out of petrol, it starts to idle normally. This really makes me think that something is not doing its job in the carby, and there is too much fuel in the pot...

Can anyone help us? Has anyone ever experienced a similar problem? We need to try and get her running by tomorrow for a bike building competition we have entered!




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