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Carb Problem

NMPete

Just got it firing!
Joined
Apr 4, 2011
Messages
6
Hi - I usually do O.K. tuning carbs, but this one has me frustrated so need help.

Bike: '79 SP 1000

Problem: When I let off the throttle, it wants to keep running at the same RPM and then eventually and slowly drops in revs.

Here is what I know:
Timing is O.K.
Sync is good.
Idle is good.
Carbs cleaned and jetted to near original spec.
New throttle and cables that snaps back quickly and the slides drop quickly with a loud click when not running.

What can be causing the slow return response when running?

Thanks
Pete
 
You may need to polish the slides and possibly the bores of the carbs. Vacuum from the engine pulls the slide to the engine side and there may be enough friction to prevent the rapid drop when running. Or stronger springs may be needed to overcome the friction.
 
Sounds like an air leak. Check your inlet manifolds for cracks and where they mount to the heads.
 
You may need to polish the slides and possibly the bores of the carbs. Vacuum from the engine pulls the slide to the engine side and there may be enough friction to prevent the rapid drop when running. Or stronger springs may be needed to overcome the friction.

Hi - Thanks for the suggestions. I did polish the slides and put in the stronger springs and it did help, now it drops to idle more quickly than before.
 
Sounds like an air leak. Check your inlet manifolds for cracks and where they mount to the heads.

Hi - Thanks for the note - I did check for leaks and sealed up the intake manifold better. It is running better now.
 
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