idle not steady when warmed up

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aikidoka

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So she is running again after replacing rusted fuel tank and cleaning carb jet blocks. Idles fine except when warmed up then it isn't as steady. Synched as well. AF mixture is front carbs 5ish rears 3.5 ish based on a post by previous owner (Garrett). As luck would have it he posted they were all over the place after that lol.

so what could be problems? New spark plugs though it flooded plenty of times before cleaning everything. Pulled one plug on a carb that gave me the most trouble and it looked fine to me

I had taken measurements of AF screw depth before starting and they were all pretty close. I'm just not sure I am getting repeatable measurements but maybe that is worth try?

throttle returns quickly to idle when reved and released no drop below and then having to climb back. It sits there stable for a bit then starts fluctuating with a bit of a stumble . Seems most noticeable when warm. All exhaust joints and air passages seem tight.
 
Could have cracked rubber boots for the carbs or vboost joints, its possible the caps for the sync ports could be cracked as well. Check all the rubber thats associated with the intake side of things. I think though that your afr screws are too far out and that when your warmed up all the way, the rich condition is causing the bad idle. Try setting them for 2.5 turns out. Might not be a bad idea to pull the afr screws out and check the condition of the oring on the end of it as well.
 
Unless your running a jet kit and exhaust. 5 turns out for the rear, and 3.5 for the fronts is a bit much.

I'm at 3.25 for the fronts, and 3.75 for the rear (I'm running a jet kit) If its stock, I would second Adams advice, and 2.5 all the way around.
 
Unless your running a jet kit and exhaust. 5 turns out for the rear, and 3.5 for the fronts is a bit much.

I'm at 3.25 for the fronts, and 3.75 for the rear (I'm running a jet kit) If its stock, I would second Adams advice, and 2.5 all the way around.

From what I recall, that bike had a Morley jet Kit and Hole Shot full exhaust? 5 turns out is still is a lot. imho. I'm between 2 3/4 and 3 1/4. All are a little different, as we've found.
 
yeah the measurements I took before shotgun were not so different from each other. .48mm was the largest difference. I forgot I had saved those. I will give it try.

would spraying starter fluid around the rubber be a good enough check? Visually they look fine so far.

yes, it has Morley kit and exhaust mentioned.
 
wd40 sprayed around the boots did nothing. I can get the idle steady for awhile by adjusting af and idle screw then it messes up again. Battery is now low from all the running at idle so charging that now. Taking a break from it tonight.
 
carbs are not dumping fuel from the main jet or other areas and flooding like they did before cleaning so at least that is fine. I will check it tomorrow once the battery is charged.
 
carbs are not dumping fuel from the main jet or other areas and flooding like they did before cleaning so at least that is fine. I will check it tomorrow once the battery is charged.

The battery not being charged or a weak battery in general is the worst thing possible for a Vmax. The wiring is the weakest part and most prominent of its problems.
Check and replace that first otherwise Miles is coming for you.
 
charged battery and tested voltage per the flow chart but numbers dropped as it ran for awhile. Time for a new battery. At least I have a battery tender for this winter.

I do have persistent exhaust backfire on the right side at 5000 or so rpms. Too rich or lean??
 
ok turns out the positive connection to the battery was loose. Battery seems fine now. Just trying to hunt down a good AF setting. Idle is more stable but still a bit of movement. I could see a backfire deep in the can on the left side at idle. Turning the screws out seems to stop that with the rear carb having the most effect.

Is it unrealistic to try for a very steady idle on these? It seems the idle drops down fine after revving but then develops a very slight waver. Up a bit then down. Maybe my ears aren't good enough to.pick up engine stumble as I'm adjusting and that's why this is elusive.
 
changed the AF mixture screw orings and much better now! All screws around 3-4 turns. Runs well. Only had a bit of trouble with the idle going lower last night about half way through my ride. May put in a new battery as all this work and no battery tender in winter has been pretty hard on it.
 

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