Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Hello everyone, so I got this issue that is stumping me.... My bike does this...http://www.youtube.com/watch?v=C7fC44Tsa4k and has all summer.

It's a maxi with a 74 airsal, hpi mini timed at 2.5. Vm20 with a 170-180 main. 17.5 idle. Uni Air filter. Estoril pipe. 17x38 gearing. Screams like a bat outta hell at throttle but does this crap at idle.... I also have a hammer clutch v1. Tried two different cases, all the ranges of idle jet up to 25 I think. There's no external air leaks detected by soaaaaking the gaskets in carb cleaner..... I was thinking maybe my timing is jumping at idle? Or somthing in my clutch is grabbing making me think the idle is fucking up. Also. I never had issues with temperature but today on a short ride it got to 380 rather quickly. Then while putting home it jumped to 450 so I cut the engine and pulled over, then limped home. Any ideas on what to check first? I'm lost.

Re: Ongoing puch idle jumping/seeking issue...(video)

Overpriced Parts /

Air leak/incorrect jetting/blocked jet/fuel system

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

I don't think it's an air leak. It's done this with two different rngine cases, through 2 rebuilds with new seals. Never have found leaks with generous soaking of carb cleaner. I'm gonna try cleaning out the carb but I've done that before and it didn't help. My carb and tank are currently very clean. Fuck .....Could it be my intake maybe? Honda atc90 curvy thing?

Re: Ongoing puch idle jumping/seeking issue...(video)

Definitely air leak, check for flaws or casting imperfections in cylinder...Scary...

Re: Ongoing puch idle jumping/seeking issue...(video)

170-180 main is HUUGE on a vm20. I was rich even at a 120 main on my k-star 70. I'm down to 115 main now. My money is on air leak.

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Yeah I'd say scary. Never had a more reliable bike.... Untill now. I donnnnny think it's a casting issue since this cylinder ran for a good 4 months last year without this issue. I'm noticed also when I was coasting at speed yestersay.... It's almost like my clutch was clanging together. But that's probably just because the idle is seeking. What's a normal jet for the big airsal? My friend has the airsal 72 and is only 2 jets under me. Time for a leak down tester? Maybe I'll switch Intakes and carbs for shits

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Forgot to add. Gas shoots out of the right side overflow near the slide top screw at very high revs.... Don't know if that's related

Re: Ongoing puch idle jumping/seeking issue...(video)

Check needle valve or float level.

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Correction I actually had a 165 main

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Also I had a 22.5 idle. Lowered that to the 17.5 that should be in there. Cleaned the entire carb. Float is perfect. Float valve works perfect.http://www.youtube.com/watch?v=KBJt2AZh2EQ still sounds like this. I got another can of carb cleaner and almost used the whole thing and couldn't find any exterior leaks around the base, exhaust, intake, carb, head and spark plug. One thing I did realize also today.... I've always used resistor plugs since I learned I should..... But for some reason I noticed there was a bu type plug on the bike withouuuut a resistor boot. Would this cause problems? Here's the plug ...

image.jpg

Re: Ongoing puch idle jumping/seeking issue...(video)

Did you properly tune that idle circuit? It may or may not fix the issue, but it looks like you're kind of setting that idle air screw to some arbitrary setting.

If you look in the vm20 manual on Mikuni's site, it will tell you how to tune it (very easy).

Also that plug looks like youre running really rich. (edited)

Re: Ongoing puch idle jumping/seeking issue...(video)

Well I guess it would be hard to tune it if the idle is all over the place. Try closing that air screw all the way (not too tight, you can damage it) then back it out about 2-2.5 turns. Then see if you can get it to idle with the idle speed screw. As I said might not be an idle circuit issue but I'd want to make sure that air screw isnt open way too much or too little.

Re: Ongoing puch idle jumping/seeking issue...(video)

ian van opijnen /

Yeah that's what I was actually attempting to do with the camera on, show you guys the idle range it's at now. But gave up while trying to holding the camera.

Yeah the mikuni idle tuning is different then the del. del says tune for the snappiest response, mikuni says turn the mix screw to obtain the highest idle, then drop the idle speed screw to set idle. Which seems wierd to me..... Because what happens when you have an air leak? The idle runs wild....

Pulled the clutch out, no oil in the tranny fluid so I don't think it's leaking in there. It does the same seeking idle with a 22 to 17.5 idle. Air filter or not, doesn't matter

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