When i'm coming off of throttle to idle (say driving down the road coming to a stop sign) the RPMs drop down to about 800 before coming back up to normal idle.  This only happen when i'm running at about 3000RPMs+ and pull the clutch in.  The RPMs drop all the way down and then it returns to the set idle speed.  I just recently rebuilt the carb and everything is clean.  What's the deal?  The slide is as clean as it's ever going to get but I figured if that was sticking I wouldn't get the drop,.  Instead I would remain at higher RPMs.

What's the deal??

I think that's normal.

Suddenly closing the throttle starves the engine of air to slow it down and the fuel/air ratio is optimized for idle, not for running full bore.  So what does get in there is a little rich.  And maybe wets the plug a little.  So by the time it reaches idle itaint running so good.  And the idle is going to be slow untill the excess can be burnt off.  Returning it back to the set idle speed.

ok?  

I think the float bowl is a little low from the hard running and the idle suction on the petc0ck needle valve isn't enough flow for a fast refill on the float level -- temporary slow idle comes primarily from a slightly lower bowl level.   Get same sort of action each time you try to run out of gas, don't you?

Plus engine is max hot from the exertion and all the running fits are a bit tighter right after you slow down (air flow goes down too).

Take your pick, or say it may be a combo of all the above.  In any case it's normal enough on my bike.

Oldfeller

I run my petc0ck on prime all the time to avoid any issues from the On/Res petc0ck so that can't be it.  

I guess I could re-adjust the floats a hair higher to give the bowl a bit more fuel.

Paladin. wrote on 12/31/69 at 16:00:10:


Wow, that is low.  Idle should be ~1,100RPMs (at least that's what it says on my front manufaturers plate).

This happens even after highway riding so I know it's been warmed up.  I've been setting my idle to ~1,250-1,300RPMs so that when it drops I don't stall.  All the diaphrams seem free from holes, air filter is new, and I just cleaned the carb, so i'm at a loss.

With tickover revs dropping then coming up suggests a rich mix.

Clive W  

HI- foggy brain this am..too much Halloween I guess. Your idle drops way low, bike actually stalls when coming into a stop, but Only with the clutch pulled in. This is a little backwards=No?  Usually a bike rpms fall when you come into a stop, then you engage the clutch taking the engine off load, allowing it to turn more freely(quicker) and the idle stays up and you don't stall..  Hmm
Forgive the dumb question..you are downshifting as you come into the stop situation?  And you ride with the pet on pri to eliminate vacuum issues..   No kink in the fuel line..
Great question (not a great situation) Have you tried it with pet in on positon..maybe partiallly clogged pet unit..curious how it does on vacumn.
Good luck and keep us posted.