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R&D power bowl adjustment help!

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I bought a 07 Crf 150R for my son last year, at the end of the last season the bike started bog alot, my son almost fell over in every sharp turn because the bike hesitated. The bogging comes when going from idle to full throttle, it will just die, i can rev it with half throttle, then going full throttle when the bike has gained som rev. So during the winter i have been fixing the bike. I have adjusted the valves, there was no gap in one of the intake valves. So i hoped that would be the reason the bike was bogging so much, but i wasnt that lucky.

I now noticed there is a R&D power bowl installed, and i have tried to adjust it with no luck. The jetting was 45 pilot and 138 main, that should be an ok jetting in my mind. Ive tried 48 pilot and 138 main, and then 48 pilot and 142 main, and finally 48 pilot and 150 main. But none of the jetting made any difference. The bike was nice and warm during testing every time.

As this is the first time im jetting a 4 stroke i need to learn some things.

I have a screw just above the exhaust, and one screw at the bottom of the carb.

which screw is the pilot screw, and which screw is the leak jet screw? Is the pilot or leak jet the same as a fuel mixture screw? And finally, is there no air screw on these bikes?

Any help would be apriciated:thumbsup:

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Leak jet screw should be attached to the R & D bowl pointing slightly down, rearward and to the shifter side. If not there’s no external adjustment and the bowl is an older one. Low speed screw is on the front bottom of the carb and you will need a short flat screw driver.

If everything in the motor good, the bog would come from the AP circuit. Is the pump squirting?? When is it squirting and how long/amount?? To verify this you will need to remove the rear sub frame and look thru the carb. Twist the throttle and you should see a squirt just as or just after the slide moves. On exhaust side of carb pull off the black plastic and this is the timing for the AP. Many people tie the AP arm to the throttle linkage so both move together and reduced any “soft” pump do to flex. Adjust the screw so the squirt is just as or just after the slide moves.

Now if you have an external leak jet adjustment set it for 38-42. You will need to get the info from R & D to verify turns for the setting. If not you will buy the size jet and install it in the carb bottom, remove the bowl and AP cover. Lower the number the more fuel goes to the motor. Motor needs to be warm, air screw and pilot jet correct for a smooth idle before leak jet adjustment. Adjust the leak jet to remove the bog when riding the bike. Do not stand tune the bike! Start there and report back.

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Thanks for the answer!

I will try to look at the things you mentioned.

But where is the air screw? i cant find it.

On my Yz250F i have a boyesen quick shot ap, can that be used with the power bowl?

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Air screw is in the front bottom of the carb. There is a cutout in the bowl for it. Many people replace it with a knob for easier adjustments. Easy to see when the carb is off. Did it fall out??

If the R & D bowl doesn't have an adjuster then go buy one. It add the ease of adjustments however you don't need it to elimate the bog. Will the Boyesen QS work?? On paper it should but mounting and changes inside the R & D bowl could create issues.

My jetting for 850' @ 50-75*F

142 main

42 pilot

45-48 leak QS3

3/4 turns out air screw

needle mid (stock)

o-ring mod (tied AP arm)

MRD header

backfire screen removed

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As weantright said front midd bottom of the carb

Just google "fcr-mx carb pilot screw" then image you see them

If it not there or there I get the R & D Flex Jet (Remote Fuel Screw)

The leak jet screw should be attached to the R&D bowl but it dose depend on which ver bowl you have the Original model was on the exhaust side and a bit of a plain to get the newer Power Bowl 2 are on bottom of bowl attached to the accelerator pump cover which much eazy to get to.

You clean out the bowl just in case

It possable that accelerator pump passage are plug up or a bad Diaphragm

I have a screw just above the exhaust

That maybe the idle screw you bike must be one very frist ver of 2007 mine 2007 is a remote idle screw on the left side of the carb

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