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Pumper Carb Help

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I bought an XR400R with the T36 68A carb on it already. It has a fresh topend and I am still having starting issues and it falls on it's face from 3/4 throttle on; I mean literally I slow down if I go beyond that. I have found tons of videos on the stock carb but I can't seem to find anything on this one. Can anyone point me in the right direction? I don't even know which jet is which on this thing. Also there is a spring actuated plunger that gets pushed in when the throttle is open. Can anyone tell me what purpose it serves and how it should be set? 

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We use this .pdf for tuning our TM 36 from XRs Only. It may help you too.

http://www.mikuni.com/pdf/hs40_manual.pdf

If your carb has the white plastic pump rod actuator, I've found best throttle response with the pump come-on screw(#1 in the .pdf picture)turned all the way in.

What is your elevation?

You need to find out what size main and pilot jet is in it. The .pdf will show you which is which. Also look at the needle clip setting. Check the float level while you're in there.

What kind of intake and exhaust mods, if any, have been done? Stock air filter?, snorkle under the seat still there?, stock exhaust or aftermarket?

Out of spec valve clearances can cause hard starting too. That being said, be sure you start your kick from TDC every time. Kicking from anywhere else in the stroke is a wasted effort.

With the stock carb, you don't touch the throttle when starting. With the Mikuni, I've found you can wick the throttle open at the moment you reach the bottom of your kick with good results.

Be sure the carb vent lines are clear.

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