Bike revving to 5k RPM after carb clean

[dartagnanphd]

Hello all I have a 1982 GS 650 that I’ve been trying to restore for a long time. Just clean the carbs and put them back on the bike and without choke or any turn of the idle screw, the bike runs at 5000 RPMs. Also, gas will overflow if I set the petcock to prime. I thought I had set the float correctly and replaced the needle seats with some aftermarket parts (I know, bad, but I didn’t have $80 to spend.) I’m totally flummoxed as to how gas can be getting to the engine because the choke and the idle were completely backed off? Is the cable getting stuck?

 

[chuck hahn]

I would take them off and see if the linkage snaps back freely. Then take the idle knob well off the linkage and see if they snap fully closed. Check the links where the sync screws are.. no mis installations or missing springs. If all is well then turn idle knob in just till it makes contact with the linkage and the go 2 turns in. Look at the throttle plates and see if they all have the same gaps. If not redo the bench syncing. And be sure all the diaprams are seated properly..

 

[dgates1]

Just thinking.. could be faulty seals on your choke plungers.

 

[dartagnanphd]

dgates1 how would I go about checking the choke plunger leakage? They all seemed tight to me but it’s probably worth investigating. Is it the typical vacuum leak method of spraying carb cleaner on the seals while the bike runs?

 

[chuck hahn]

They have an oring on the brass nut at the top and rubber tips that seat against a raised ring in the bottom of the bores. What your describing doesnt sound like chokes to me. Doesnt hurt to grab them at the top and see if they snap closed freely though. TO ME anyways, 5000 is a pretty high rev even with full choke applied from my experiences. Yes do the starter fluid trickle on the intakes to see if theres air leaks. Put a red straw from a carb spray can on the starter fluid for more precise control of the spray.

 

[dartagnanphd]

chuck hahn would an improper bench sync lead to an idle that high? The throttle valves did seem a little sticky when I was cleaning, so I’ll look into that. If the sync is off on one carb, does it push all the carbs up the rev range?

 

[chuck hahn]

I suppose if they arent closing when the idle knobs backed off they high rev. Id just do like i said with the idle knob backed out then 2 turns in after just touching the linkage and see how they look. Maybe 1mm gap at the bottom of the butterflies is a good starting set point. Once they're all the same back off the idle knob and watch to see if they're closing. IF they work together rest the idle knob and start it. A bench sync gets them close enough to run but the final step is vacuum syncing.

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