Engine sputters when switched off
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Novice
Joined: Jan 2014
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From: houston
Engine sputters when switched off
Hey everyone my bike just started acting funny. The bike rides great but when I cut it off it it the motor revs up and then dies. Does anyone have any ideas why this is happening?
Thanks for your help
Thanks for your help
Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
Knowing what it is my help. Carb, EFI, year, model....etc. If one is not timed properly, running lean or extremely hot, it can "run-on" or diesel as they say when you shut it off, but I've never heard of one revving up first. But....I've not heard everything either.
Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
Don't think so. It's either getting too hot because it's running lean, or the timing is somehow out of adjustment. If you know how to remove your nose come cover to get to the timing components, you could take a look in there and see if the pick-up has gotten loose and rotated. If it's a used bike....you never know what somebody has done to it. Don't recall when Harley dropped the mechanical advance, but if it had one in there, it could be stuck. When you adjusted the idle....did you mess with any of the screws in the bottom of the carburetor, or just the idle-screw on the front?
It will diesel if it's too hot, too lean, timed to high, or you've added some sort of (or too much of) a fuel treatment like an octane booster. What kind/grade of fuel are you using. If it's dieseling....it's likely also pinging (pre-ignition as you ride it). This could be detrimental to the engine. If you've gone as far as you can in checking things out, I'd get it to a dealer and have it checked out.
It will diesel if it's too hot, too lean, timed to high, or you've added some sort of (or too much of) a fuel treatment like an octane booster. What kind/grade of fuel are you using. If it's dieseling....it's likely also pinging (pre-ignition as you ride it). This could be detrimental to the engine. If you've gone as far as you can in checking things out, I'd get it to a dealer and have it checked out.
Road Captain
Joined: Jun 2013
Posts: 733
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From: Rochester NY
I think the idle screw on your carb points up and is to the right of the carb looking at it from the side of the bike. If you have a stock cv carb and are talking about the screw that is below the carb, that is probably the air/idle mixture screw. If you have a mikuni carb and it's got a screw cable hanging off the side, that's the same thing. Just simply turning those things will affect your idle by changing your mixture, but you're also either making it too rich or too lean. If you turned your "idle" lower, you probably leaned it out too much. Check this out. Just copy and paste. http://www.cv-performance.com/harley-cv-carburetor-tuning-issues/
Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
Exactly. The idle adjustment will be found somewhere in direct contact with the throttle cable assembly and not screwed into the body of the carburetor. The idle mixture is likely screwed-up. A ball-park reset would be to turn that screw you turned back in until it seats (don't force it) and then back it out 3/4 turn for starters. Usually...this screw likes to stay between 3/4 to 1/2 turn out off the seat. You have three circuits in a carburetor...idle, mid-range and high-speed. Getting any of the three out of whack can affect any of the other two.
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Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
We're gonna' have to know what you're calling the "idle screw". Be more specific about what you've turned. Assuming it has a stock CV carb. on it....there is an idle mixture screw in the very bottom of the bowl close to the front. That one needs to be seated (gently) and then backed-out to around 3/4 turns for starters and fine-tuned later. The actual idle screw will be found on a bracket on those "wheels" (getting real basic here) that the throttle cables are attached to. Be sure you have the mixture screw (the one in the bottom of the bowl) turned out "around 3/4 turns". Then....back-out the idle screw on the "wheels" until it appears to make no contact at all. It should not start in this condition. You should have to either hold the throttle open a tad, or run the idle screw in before it will crank.....then adjust it for proper idle.
Have the throttle cables themselves been adjusted? Each one should have an adjustment barrel-n-nut near the grip under a rubber cover (which sometimes get lost or removed). They could be mal-adjusted. Adjust those so that both cables are slightly slack and start from there.
Once you get it where it will properly idle....you can adjust that mixture screw (bottom of the bowl) by slowly turning it in until the motor stumbles and then back out until the motor stumbles and it's final setting is 1/2 way between these two positions.
It could very well be the idle mixture screw has been bottomed too tightly and ruined the seat.....or other possibilities. My advice would be that if you can't make this work....take it to a shop. There are several things it could be and if you can't make it idle by following the above, you probably need to have someone take a look at it. The only thing I think that has not been mentioned before are the throttle cables, so look at those. And....what about the enrichener valve (formally called a choke).
Have the throttle cables themselves been adjusted? Each one should have an adjustment barrel-n-nut near the grip under a rubber cover (which sometimes get lost or removed). They could be mal-adjusted. Adjust those so that both cables are slightly slack and start from there.
Once you get it where it will properly idle....you can adjust that mixture screw (bottom of the bowl) by slowly turning it in until the motor stumbles and then back out until the motor stumbles and it's final setting is 1/2 way between these two positions.
It could very well be the idle mixture screw has been bottomed too tightly and ruined the seat.....or other possibilities. My advice would be that if you can't make this work....take it to a shop. There are several things it could be and if you can't make it idle by following the above, you probably need to have someone take a look at it. The only thing I think that has not been mentioned before are the throttle cables, so look at those. And....what about the enrichener valve (formally called a choke).
Last edited by 0734; Aug 10, 2014 at 05:50 PM.