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Rough Idle then quits, on my Suzuki LT-F250

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Carburetor is a Mikuni BS29SS, single


I just bought this quad for my son and rode it all day Sunday and then it just didn't want to hold a strong idle. The Idle surged and then the engine would die.  If you pump the throttle it will keep running.

I removed the bowl and cleaned the jets, I drilled out the fuel mixture plug removed the pilot and cleaned in there as well.  I screwed the mixture screw back in and gave it 1 1/2 turns, to the same result.  I then turned the mixture screw all of the way IN and the engine didn't quit.....?  Why is this too big, its a sealed screw from the manufacture.

The choke enters through a 90* steel pipe into a body that threads into the side of the carb.  This pipe is able to pull out...? Is it suppose to? Prob not, if its able to pull out is this possibly keeping the choke engaged/on to some degree?

The spark plug was sooty black.

The vacuum petcock, I have found gas in the vacuum line to the carb.  I'm thinking that's not right.

I've sprayed carb clean around the intake manifold, and the idle didn't change.

When you throttle up from idle in neutral the Idle will stay up for a bit, for quite awhile.  At this point I can take the idle adjust screw and bring it back down......? Confusing because why wouldn't the idle be up all of the time if the idle screw is able to bring it back down.


The previous owner said that he just rebuilt the carb as it has sat for the last 2 yrs. maybe he's not the best.  So I want to remove the carb and totally go through it, however I don't know how to remove the fuel linkage. The linkage/cable enters a box(ish) on the side of the carb.  The butterfly shaft and the throttle idle also enters this box.  Even if I was to remove the cable from the cam I still wouldn't be able to pass the cable end through the passage of the box.  So is it in the thumb control?

Also on all of the carbs that I've been in the idle adjust screw really adjusts the idle...this one doesn't seem to.


I would appreciate some expertise here.  All the carbs that I've been in were so very easy this is a CV carb and just not to sure.

Edited by Trail Days

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