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Buell Forum » Old School Buell » Archive through June 03, 2010 » S1 with Mikuni - Idling problems « Previous Next »

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Sanchez
Posted on Monday, May 24, 2010 - 02:45 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I got an S1 with a Mikuni, a 1250 kit, a Buell race intake, a Vance & Hines pipe, and some other stuff on it. I'm having trouble making it idle right. I dial in the idle using the adjuster then blip the throttle or ride for a short distance, and it settles down 500+ rpm higher or lower than where I set it. It's either so low the engine dies or it races.

Last night I took the choke off after warming it up for a minute, and it idled beautifully at 1100 rpm for a couple of more minutes while I put my gear on and then dropped down under 500 rpm and died. I started the bike back up, adjusted it back to 1100 rpm, and rode off. At the next traffic light, it was up to 1500 rpm.

Things I've tried:

- Sprayed WD-40 around the intake manifold gaskets (no detectable leaks)
- Replaced the VOES vacuum line
- Adjusted the idle air screw
- The 22.5 pilot jet that came in the carb was too lean (based on how far I had to turn the air screw in to make the motor stumble), so I jumped up to a 30. That one's too rich. Both exhibit the same behavior.
- Ensured the throttle cables aren't binding

If I get the pilot jet right, could that fix the problem? Maybe the VOES unit itself is leaking? Any other ideas?
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The4ork
Posted on Tuesday, May 25, 2010 - 06:31 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

could it be your float sticking?

WD40 isnt what i would use to find a vac leak, starter fluid is better. although spraying that around a hot air cooled cyl, not sure if the flash point is high enough to do that safely, maybe before its warmed up
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Sanchez
Posted on Tuesday, May 25, 2010 - 08:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The float seemed like it was in good shape. It moved freely, and it was in exactly the right position when I measured it. I did also try some carb cleaner in addition to the WD40, but I didn't get a result with it either.
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Road_thing
Posted on Tuesday, May 25, 2010 - 10:20 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I'd try disconnecting the VOES and plugging the vacuum port; if it idles at a consistent speed with the VOES disconnected, it's probably the switch.

Could you expand on "some other stuff on it"? Is any of the "other stuff" engine-related?

rt
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Sanchez
Posted on Tuesday, May 25, 2010 - 02:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I'll give that a try. The only other engine mod is a TwinTec ignition module. It controls the timing advance in response to the VOES signal.
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Sanchez
Posted on Tuesday, May 25, 2010 - 08:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ok, plugging the VOES hose didn't fix it. The Mikuni tuning guide says the wrong size pilot jet can cause a poor idle, so I guess I'll just have to order another couple of jets and try them out.
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