kojones,

Do you have the same model carb as we use in the US? Even in the US there are two versions of the Mikuni BS40SS that use different needle profiles.

It's definately running rich now after lifting the needle, have to move the lock ring back to the center groove.

Threads on the idle mixture screw hole are busted, think I'll have to buy and rebuild another carb, the Mikuni VM36 can wait for winter  

justin_o_guy2 wrote on 06/15/17 at 01:14:58:




I have a tap, but no die. The screw is one turn out and glued in place. Got another carb for cheap already.

Sounds like the idle jet may be to large ,and the mix screw is in to far.when you chop the throttle the rpm drops ,and when you pull out the choke the idle speed goes up(mix screw in to far).Twisting the throttle from idle your getting black smoke (pilot jet to large).You have to remember that there are two paths for fuel coming from the idle jet and the mix screw sets in one the other is unblocked,when you blip the throttle vacuum increases pulling more fuel into the carb ,and there is a delay before the side opens ,if the idle jet is to large you'll be very rich ,(your puff of black smoke).Ithink you said your running a 55 pilot ,standard here is 52.5 ,and stock setting for the mix screw is three turns out, but I think 1 1/2 to 2 1/2 would be good for you.I think you said you were at 1 turn that sounds to lean and is why your rpm is sagging when you close the throttle.

kojones wrote on 06/16/17 at 00:52:16:



No choke required when cold ... pull choke rpm increases...black smoke...TOO RICH

So what are the pilot/main jets, pilot screw setting, and needle setting you have now ?

Look up the stock jetting on the carb used on the old DR650's.  
I just don't remember off hand, but it is a Mikuni CV type carb very similar to ours and is also a 40mm.  I cannot remember for sure but it seems like it uses the same type of jets as well.
Anyway, that will give you a place to start.
Remember though, that the DR head has very nice straight exhaust ports, so with our crooked exhaust ports I would expect that the jetting requirements would be slightly less than the stock DR...or at least somewhere between the 2 stock carbs.

Kojones, you never told us what air filter your running ,if your running a K&N or similar an you oiled it, it's likely some of that oil ended up on your carb slide at first ,making it stick slightly ,before moving on.(normal)

Do you have a stock petcock ?or is the float valve sticking ,or the level in the float bowl set to high? If you have gas in your oil,you may want to check your air filter and air box drain too.