Coming down to idle "whumps",,

S

SinNH

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about 80% of the time coming down to idle after trail riding it idles right down to 16/1800 maybe with a hang of a few seconds at 3-3500. But,after I think of a few blasts of WOT and coming down to idle,when it gets to idle it doesn't backfire,it sort of WHUMPS through the exhaust,a couple of times. No hang.
I've beat the search engine to death on TY, whumps LOL not mentioned.
Idle Jets 45's
pilot screw @ 1 7/8

So,when the exhaust backfires/farts, it's rich fuel deposits right ?
Plugs are a touch rich,running a quart at about 11 gal.
I was thinking of backing out the screws to 2 or so but don't think that is the issue.
Carbs were spotless or better 600 miles ago and I run two fuel filters.
Just kinda seem like the beast is shaking out it coat after a short hard run ,but I like PM.


well thx again,,,,,,,,
 
Thx Bob,and staggs,,,figured it was ok,it runs like a raped ape otherwise,no lag at all off idle or anywhere.

S
 
stein700sx said:
What was it?
Click to expand...
I don't know what really causes it and it still does it. Slideshowbob agreed that he thought it was a bit of not fully burned fuel in the exhaust and is normal for three cylinder engines.
I dunno
 
daman said:
i don't think theres a problem here,if it gets worse post back
Click to expand...
thanks,what's weird sometimes on a 40 mile ride it happens once or twice,and then on a 20 mile ride or so, it happens 30% of the time.
Same fuel.
 
You can try to lower the idle speed and richen up the pilot circuit. Also if its starts a little hard when hot the idle could be a touch high.

If its backfiring when its cold the pilot circuit needs to be richened.

Maybe you have something loose in the muffler also.
 
jwiedmayer said:
You can try to lower the idle speed and richen up the pilot circuit. Also if its starts a little hard when hot the idle could be a touch high.

If its backfiring when its cold the pilot circuit needs to be richened.

Maybe you have something loose in the muffler also.
Click to expand...
It's idle is between 16 and 1800,I am thinking about changing the pilot screws to 2 instead of 1 7/8, starts fine when hot,no backfires at all when cold,thanks for the reply,I'm probably just going to run it for now,when it whumps the idle drops a bit then comes right back up.
 
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