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Discussion Starter · #1 ·
Okay, so this is my third carb rebuild, and this is the first time this has happened to me.



1983 CX650C carburetors in a GL650I, cleaned with a sonic cleaner, and rebuilt with a Randakk kit, butterflys are confirmed not sticking, but as soon as I fire the bike up, it revs to 5000 rpm, and stays there.



I pulled a LOT of crap out of these carburetors; the previous owner had definitely not run any kind of fuel filter.

(I could have sold the stuff to a gravel company!)



The carburetor action is smooth, and the manifold boots are confirmed as sealed. (there are no air leaks)



Thoughts for a plan of attack?



Is it possible that a reversal of the emulsifier tubes could cause this, or is it more likely that I did not get all of the crap out of the circuits?
 

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Are your vacuum pistons hanging up? When you flip them up thru the choke side with your fingers, do they smoothly drop back down? Did the jet sleeve that the vacuum needles go into maybe fall out and didn't get replaced? Maybe have them in upside down?
 

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Okay, so this is my third carb rebuild, and this is the first time this has happened to me.



1983 CX650C carburetors in a GL650I, cleaned with a sonic cleaner, and rebuilt with a Randakk kit, butterflys are confirmed not sticking, but as soon as I fire the bike up, it revs to 5000 rpm, and stays there.



I pulled a LOT of crap out of these carburetors; the previous owner had definitely not run any kind of fuel filter.

(I could have sold the stuff to a gravel company!)



The carburetor action is smooth, and the manifold boots are confirmed as sealed. (there are no air leaks)



Thoughts for a plan of attack?



Is it possible that a reversal of the emulsifier tubes could cause this, or is it more likely that I did not get all of the crap out of the circuits?
timothy,is it possible since they were so dirty that previously the curdled adjuster nut was turned up to compensate for a blocked low idle jet......

can you turn it back down.

i know its stating the obvious,but it seems[other than internals]you have covered most things
 

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Discussion Starter · #5 ·
Choke butterflies are closing, throttle butterflies are moving freely.

Vacuum pistons move up and down quite readily,

Idle adjuster nut was completely backed off so that it wasn't even touching the plate.



I also loosened the throttle cables so that there is plenty of free play.



The jet sleeve is definitely not upside down. (round end up, tapered end down)



The valve floats are closing, as evidenced by the tubes not overflowing.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Any chance the PO may have oversized the jets during a "cleaning"?



R
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Sorry about the multiple posts. The forum got really flaky all the sudden.



R
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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How about an air restriction? My 500 will idle up to about 4k if it's overchoked.



R
 

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Discussion Starter · #12 ·
Possible. But it's the choke butterflies that usually cause that issue.



Was hoping to not have to remove the carbs again, but looks like I might hafta.
 

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I don't know much about those carbs, but is there a fast idle adjustment that's maybe away off where it should be?
 

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I loaned my carb book to my son, but I'm not sure that the vacuum needle sleeve goes with the round side up. I could be very wrong here, but I don't want to pull my carbs just to check that.



Timothy, I respect your knowledge on this forum, so I can't imagine that you forgot something in the rebuild. If your were a complete newbie, I would question things like having the top gasket on the vacuum cylinders right side up, forgetting the spring inside the vacuum tubes, shimming the vacuum needle so now it is too tight, leaving the black plug or a emulsion tube out of the carb body, or reversing the jets.
 

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just looked in Mr. Honda`s book. In Chapter 4 page 11 there is an instruction for adjusting the fast idle. It looks like you have to bend something.
 

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just looked in Mr. Honda`s book. In Chapter 4 page 11 there is an instruction for adjusting the fast idle. It looks like you have to bend something.



Sorry about the double post. If I knew how to delete one I would.
 

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Did you remove the throttle plates(butterflys)when you cleaned the carbs?

I had a bike that I got from the U.S. for parts, when I put the carbs off of it on my bike it started but revved really high, around 5 grand,,I found the throttle plates were installed backwards.I took them out and turned them around,,problem fixed.
 

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Discussion Starter · #20 ·
Interesting. Personally, I did not pull the throttle butterflies, but the P.O. may have.

I'll take a look at that.

Thanks!
 
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