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1980 CX500C
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Discussion Starter · #1 ·
Hey ya all! I have an '80 CX Custom "barn find" situation. Stripped and cleaned carbs, new oil/fluids, re-did brakes, all the usual stuff. Rebuilt starter. Bike starts and idles good. Stops good. Only one small issue I can see so far. The bike stumbles in 1st and 2nd gear, 3rd-5th the power band is smooth.
In 1st and 2nd, it grabs as the throttle is cracked than stumbles mid way with normal power in the upper RPM range.

Thoughts? Carb issue? Maybe the advance? Clutch?

Thanks in advance!
Pat
 

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"Cleaned the carbs" means different things to different people. What all did you do to clean the carbs? The reason i ask is these carbs tend to be finicky and are 40 years old. A very thorough cleaning as described in Larry's book is usually recommended.

CX500/Gl500 Carb book (donlhamon.com)
 

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1980 CX500C
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19 Posts
Discussion Starter · #6 ·
Oh yeah, I stripped them down, used a bunch of break cleaner, ultrasonic, then replaced all o-rings and seals. Reassembled and they worked well. The bike had been sitting for several months over winter but it had stabilized non-ethanol fuel so I'd be surprised if deposits are the issue. That said, I figure I'll pull the carbs and double check.

The odd part, to me, is that they seem to function fine outside of 1st and 2nd gear? Bike idles fine, is good off idle, and has a smooth power band in 3rd-5th?

I guess it could just be some break in pain as it was a non runner for several years prior to me picking it up...
 

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High float levels? Just a guess but maybe having worked through 2 gears the engine has sucked the excess fuel from the bowls?

Easy checked with some clear fuel line on the drain nipple held up the side of the carb with the drain screw undone a couple of turns and the petcock on.

Level will show in the fuel line and should be about 2 mm below the bowl to carb joint.

The other possibility for the issue only manifesting in the higher gear may be related to the rolling mass of the bike having a similar effect to a flywheel mass and damping out the stagger so that you no longer notice it.

My 2 cents.
 
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