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One for Graham

fastjeff

fastjeff

Gold Medal Contributor
"Merc 650 triple. Just rebuilt

"Merc 650 triple. Just rebuilt it, including carbs. Starts very reluctantly and, if it stalls, usually requires ether to get it running again. Once running it idles lumpy but keeps going. Juice the throttle and revs instantly.

I know the reeds are in good shape (closing properly), and I doubt if there's a crankcase vacuum leak.

Frustrated and puzzled! Got any ideas oh Great One?

Jeff
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"
 
"Jeff, so just the hard start

"Jeff, so just the hard start and crappy idle, other than that seems good?"
 
"Yes. It'll rev rightup wh

"Yes. It'll rev rightup when it's idling correctly, but if it stalls I usually have to ether the thing back to life.

It MAY have too lean main jets in it. Can't find info on what it should have. Carb is WMK-13 (without the back draft setup). Motor is a 1975 Merc 650 triple.

Jeff"
 
"WMK-13, side bowl design with

"WMK-13, side bowl design with vented bowl cap.

The main jet is a .074" (standard) - also comes in the range of .070 thru .076". If you have a standard jet in there you could move up to the .076" and it would give you that little bit of extra fuel, but that really shouldn't affect the idle.

Did you replace the (idle) needle valve and the idle tube (that slides down inside the main nozzle from the top - if it's crudded up it won't idle for crap) as part of the carb rebuild?

There is also a (vent) jet on top of the side bowl .086" that can give you issues if gunked up."
 
"Thanks a zillion! I have mix

"Thanks a zillion! I have mixed and matched parts on these carbs. They have other tops on the bowls, but there is a vent hole and it's open. (It is not the type with the jet, however--THIS model doesn't have the little hose running over the top.)

The idle tubes don't come out easily, so I did not pull them as I usually do. I'll super clean them today and see if that helps.

Again, thanks a lot! at least, i know that I have the right main jets in there---they are .074 jets.

Jeff"
 
"Found it! One of the four nu

"Found it! One of the four nuts holding the carbs on was...ahem...not tightened. (Doh! Thought it had a vacuum leak...) At least I know it has the right main jets in it.

Thanks again, Graham.

Jeff"
 
"Hmmm, that's why we wait

"Hmmm, that's why we wait untighten the beer cap until after all the powerhead bolts are tightened
"
 
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