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Fast idle problem

Posted: Thu Feb 08, 2018 1:21 am
by Sundowner
My SPRINTS HS-6's have recently been rebuilt.
Just the other day, before the thing developed a water leak, I managed to get it running beautifully.
The mixture settings are just right, but, I've run out of idle/airflow adjustment with the screws loose-ish in the threads.
Like I said, its running nice with good, crisp throttle response but its idling at 1,000-1,100 RPM (should be 750?) and although I think I can get it marginally lower I'm concerned I'll lose the idle adjustment screws altogether.
Any advice?
Thanks & Cheers,
Rob

Re: Fast idle problem

Posted: Thu Feb 08, 2018 7:09 am
by Magenta Auto Sprint
sounds like an air leak somewhere.

Malcolm

Re: Fast idle problem

Posted: Thu Feb 08, 2018 7:38 am
by tony g
Throttle cable have enough slack~? Choke linkage touching the "cams"? Best to make sure its all slack then see what happens.

Tony

Re: Fast idle problem

Posted: Thu Feb 08, 2018 8:31 am
by Sundowner
"Thanks" Gents.

Re: Fast idle problem

Posted: Thu Feb 08, 2018 10:39 am
by Bumpa
If your SUs have been rebuilt, pound to a penny the throttle discs aren't quite lined up. I have just had the same issue on my 1850. The smallest amount of gap around the discs when the throttle is closed will cause a rise in revs. I took my carbs off again, removed the chamber and piston and then looked through the carb with a bright light behind. The gaps around the disc were obvious. I slackened the butterfly disc screws and wobbled the disc this way and that until the gaps were at their absolute minimum. Put everything back and, presto, it works properly.

Re: Fast idle problem

Posted: Thu Feb 08, 2018 10:31 pm
by Carledo
What he said^^^^^

And just check the choke fast idle screws are not too far in and stopping you from dropping it properly!

Steve

Re: Fast idle problem

Posted: Fri Feb 09, 2018 7:39 am
by tony g
Like I said :) Good call on the throttle blades there:

Tony

Re: Fast idle problem

Posted: Fri Feb 09, 2018 8:09 am
by soe8m
What they said. :nodding: :nodding: Nothing to add.

Jeroen