Running rich after complete carb strip and rebuild

  • Utton
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Running rich after complete carb strip and rebuild

22 Aug 2025 09:42
#916329
Hi Almighty KZ Forum!

im at a loss with this one - I have completely stripped, ultrasonically cleaned and rebuild the carbs on my 83 KZ440 Ltd but it is running rich. 

starts on no choke, both air screws are completely in - to the stops, not the 1 1/4 turns out as mandated in the manual and the filter is clean. 

yet it still starts and runs like a pig - this is the first time the bike has been run I believe in a few years - I bought it as a non runner in July this year - no running due to broken weights on the ATU - replaced the ATU and set about trying to get it running smoothly 

plugs are getting really sooted up with only a ten min run.
compression test is giving me 150 on both cylinders
temp on both cylinders is 149 left and 173 right
tick over is around 850 / 900 rpm

as soon as you put any throttle on it stalls out - super flooding I think 🤔 

these carbs (Keihin CV36) have been on and off this bike three times to make sure everything is sitting where it should and the float levels are down slightly from the usual - deliberately to see if it was a float problem causing it to flood. 

the only think I haven't looked at are the exhausts to see if they are blocked but I'm getting black smoke out of them so don't think that is the issue. 

I am flummoxed- does anyone have ANY ideas where I can go with this?

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  • Wookie58
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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 09:56
#916330
When you rebuilt the carbs did you use cheap kits or quality parts - if you fitted kits try putting the original brass parts back in if you still have them

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  • Nessism
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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 10:07
#916331
Low float height, results in HIGH fuel level.  
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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 12:46
#916333
Hi Wookie - didn't fall foul of chineski parts, used Keyster KK-0173N for the CV36 carbs and reused what I could of the original brass parts 😉
 
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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 12:51
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Hi Nessism - when I said low float hight I mean I had used sight glass levels for the actual fuel level in the float bowl and adjusted it so it was lower than the 3mm suggested level in the manual - it's around 4.5mm now
adjusted the tang on the float to shut off sooner that needed. 
Hope that makes sense 👍

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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 12:58
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If you are on stock jetting with a good air filter and good compression it would suggest that the choke isn't shutting off completely (possibly leaking plungers)
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Re: Running rich after complete carb strip and rebuild

22 Aug 2025 15:47
#916336
Those Keihin carbs have a choke flap.  No plungers like the Mikuni carbs.

Sometimes the choke flaps hang up, so that's something to check.

A fuel level that's a smig low is no problem.
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