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Idle problem.

J

jaseihc

Contributing Member
MFS9.8A3S serial#025673XH.Having a problem when going from WOT to idle.
When I come down from WOT to idle the rpm's stay at 1200 to 1500 rpm's
for about 1 to 2 minutes,then drop to normal idle.This engine was not
running well after winter storage.Took the carb apart,soaked overnight.put
in carb kit.Ran great till now.I run the carb dry everytime I use it.Is the new
shop manual out yet?
Thanks,
Jack C.
 
Jack,
Sounds like you may have the idle stop set very close to the transition from idle to midrange/power. There's a possibility that the idle circuit still has some minor varnishing in it, which requires you to have the screw set that high to get normal (under 1000) RPM idle. If that's the case, when you cut the throttle and the intake vacuum goes way up, it could draw fuel through the midrange/power circuit briefly. If you don't want to go through another soak, you could try using an injector cleaner additive such as Chevron Techron (in higher than normal concentration). Some swear by using Seafoam for minor varnishing, but I don't have experience with it, so can't say one way or the other. Another possibility is that the high-idle cam for the choke is restricting the full/immediate return of the throttle plate, so verify the choke cable (if tiller model) and high-idle cam operation. Your problem may go away by itself with continued running. Haven't seen the new service manual yet, but I know it was being proofread/reviewed a few weeks ago.
 
Took it out today with a good shot of carb cleaner.Seemed to ran normal after about an hour.If it acts up again the carb gets a resoak.Do you need to put a new kit in every time
you tear the carb down?I put a kit in after winter storage in March.Sure wish I had a good
tech close to me,the one's around here seem lost.
Thanks again.
Jack C.
 
The carb kit is usually not needed. You may just have run through some contaminated fuel. Glad it's working well now.
 
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