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RPM hang at idle throttle.

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Johnny4428:
Hi for what it’s worth I thought that characteristic was something that I was just going to have to live with on my K3. Until I removed carbs for the third time and pulled pilot jets cleaned system thoroughly. It now idles as it should runs smoothly and no longer hangs on to revs. The reason I pulled the carbs was because of the poor starting and rough idle.

philward:

--- Quote from: K2-K6 on June 20, 2020, 08:13:21 PM ---The idle settings are curious certainly,  at three turns out it would ordinarily  be going toward lean and possibly starting to miss a little.

It suggests that the idle jets are larger than need be as you can't lean it off enough,  but would explain why it's set on arrival at 2 turn out which would probably be better for it.

Too rich idle would give you that "off choke early" necessity,  which seems to tally.  Looks like you'd need to pull a float bowl and use a mirror to see if you can identify the idle jet size.

But it would usually "quench" the revs quickly,  for which I'd suspect something else. You've checked the timing,  but did you assess if the advance/ retard is also dropping back fully when you close the throttle?
If it's holding onto advance that could give you the hanging revs temporarily until it closed the mech down.

Also a remote possibility that the intake rubbers are leaking and someone has responded incorrectly by putting in larger idle jets,  giving you a mix of two problems.  Can you assess for air leaks?

--- End quote ---
K2-K6, for my info, when you say 'idle jet size' is that the slow running jet (normally 40)?

K2-K6:
Yes philward,  I usually call them idle but some refer to pilots or mixture. But on a 750 normally about 40 in size.

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