Vacuum Issue with 03 Metropolitan? Too much rev at startup

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Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby allergyking on Mon Oct 27, 2008 10:25 am

I recently dismantled and rebuilt the carb on my bike. Now when it turns on, it immediately revs up almost out of control. In another post, someone alluded to it being a vacuum issue. Can someone please elaborate? The scooter has a hard time "shifting" back into "neutral" when coming to a stop. This issue appears to be different than just idle adjust. Is the fix replacing the diaphragm in the carb? Last time, I just cleaned everything without ordering any replacement parts. Any help appreciated, thanks,

It literally fires right up and wants to go crazy.
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby KingTito on Mon Oct 27, 2008 12:22 pm

I'm not too sure. I would first make sure that the throttle completely closes when it is supposed to be closed. Could you have the throttle cable adjusted improperly such that the throttle is always open when it's supposed to be completely closed?
2007 Honda Metropolitan (Sapphire blue and white) "Beastie"
1999 Honda VFR800 Interceptor (Red) "The Girl"
1982 Honda CB900F Supersport (Silver and blue) "Dude"
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby allergyking on Mon Oct 27, 2008 1:18 pm

I will look when I get home, but I don't think so, because after a while, of letting it rev out of control, it will "calm down" and idle normally.
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby allergyking on Tue Nov 04, 2008 5:17 pm

From cold start, at around 65 degrees, if I dial the idle screw all the way counterclockwise and fire it up, it idles just fine and runs well for 10-20 seconds. Problem with this is once it's "warmed up" it stalls because it has no idle. Makes it difficult to ride, coming to stops, have to really watch rpms or it will stall.

If I try and adjust idle to "normal", at cold startup, it revs up out of control for a few minutes then finally calms back down and idles close to normal. Coming to stops, it still has a problem of wanting to keep on going.

Is there an automatic choke of somesort that kicks in somewhere from the carb or a computer chip?

I'm going to go ahead and replace all internal parts of the carb for good measure, all jets, diaphram, and scews.

thanks for any help you can provide, I took a video, but in this case, words were better to describe.

If there were a vacuum issue, would it occur within the carb? Is that what the diaphram is for?
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby KingTito on Tue Nov 04, 2008 5:55 pm

Forgive me if I forgot this detail as I know you posted this a little while ago.

Are you adjusting the idle speed or idle mixture screw?

The idle speed adjuster is just a screw that opens the throttle to adjust the idle speed.

The idle mixture screw is on the carb body itself. It is a d shaped screw and that adjusts the idle mixture (lean - rich).
2007 Honda Metropolitan (Sapphire blue and white) "Beastie"
1999 Honda VFR800 Interceptor (Red) "The Girl"
1982 Honda CB900F Supersport (Silver and blue) "Dude"
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby allergyking on Tue Nov 04, 2008 6:18 pm

thanks for your inquiry, I am adjusting the idle speed screw, accessed from the top of the motor, through the little hole in the seat well
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby KingTito on Tue Nov 04, 2008 7:54 pm

Got it. I had a theory...

The Met does have an automatic choke.
2007 Honda Metropolitan (Sapphire blue and white) "Beastie"
1999 Honda VFR800 Interceptor (Red) "The Girl"
1982 Honda CB900F Supersport (Silver and blue) "Dude"
KingTito
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Joined: Wed Jul 30, 2008 7:02 pm
Location: Minneapolis, Minnesota

Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby BruisedEgo on Tue Nov 04, 2008 11:25 pm

If you dismantled you carb and cleaned it up~ make sure to re-set your ECM!!! I can assure you that's the problem.
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Re: Vacuum Issue with 03 Metropolitan? Too much rev at startup

Postby allergyking on Wed Nov 05, 2008 8:29 am

I did dismantle and clean the carb.

What does ECM stand for?

I found this earlier post from you on how to reset, I will try this afternoon, and reply once I have results,

Try reseting you ECM.

***Make sure you read 12.9 volts on your battery~ anything less sometimes will not work. Charge it when not in use.***

to reset the ECM(ECU):
-Turn ignition to OFF position
-Find the lose blue/yellow wire(located at the fuse box), connect a jumper wire and attach the wire to the battery's postive terminal.
-Turn on the ignition to the ON position, headlight will turn on.
-After 1 or more passes... disconnect the wire. The headlight should turn off~ at this point the ECM is rewriting data.
-The headlight should light up again, which the ECM is finished rewriting.
-Turn ignition to OFF position.

1) Turn the ignition to "ON" position.
2) Right hand grip, click the "engine stop" to "ON" position
3) Grip left hand brakes.
4) Press engine start located at the right hand grip.

This should turn over the engine. Double check you battery capacity~ I had to charge mine even when it reached down to 12.3volts.
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