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Old 11-14-2012, 07:44 PM   #1
alexgg OP
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vac leak?

Hi, I just installed new carby on bigger barrel. Tuned it up and everything seems to be fine within specs except - when I sharply close the throttle (two cables design) the revs gradually go to idle. I mean gradually: 3 -- 5 secs instead just comeback to 1.5k instantly. Cables are fine, carby jetted as most people do for my configuration. Anybody seen that weird behavior?
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Old 11-14-2012, 08:56 PM   #2
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Lean idle mixture.
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Old 11-14-2012, 09:28 PM   #3
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does it mean that pilot jet must go up size or two?
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Old 11-14-2012, 09:46 PM   #4
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Originally Posted by alexgg View Post
does it mean that pilot jet must go up size or two?
Try the mixture screw first.
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Old 11-14-2012, 09:59 PM   #5
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Hmmm if I play with mixture screw it will increase or decrease revs. At the moment I have 1.5k rpm on idle very stable. Mixture screw is 2.3 out after tuning. Originally it was at 2.5.. I was using Mikuni man to tune up mixture and idle screws. Going in and out to extremes of mix screw was killing the engine. Could you tell me exactly how to try.

alexgg screwed with this post 11-14-2012 at 10:10 PM
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Old 11-14-2012, 10:17 PM   #6
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What bike?


Mainly posting so I can come back to this because my Girlfriend's klr is doing the same thing. I still need to drill out the idle screw to clean and check it.
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Old 11-14-2012, 10:47 PM   #7
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Raise the idle speed to ~2500 RPM. Adjust the idle mixture screw until the RPM achieves a maximum, then back out the screw maybe 1/8th turn. Restore the idle speed to the desired level. Go for a ride and see how it does.
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Old 11-15-2012, 05:17 AM   #8
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Check the vac hoses, my KLR did the same thing after I was careless pushing on the vac hose behind the shutoff, not all the way over the bulge. Also, sure you didn't pinch the diaphram or that is doesn't have a small hole in it?
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Old 11-15-2012, 06:04 AM   #9
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Carby is TM36-68 pumper flat-slide. Bike KLX350 big bore. There are no vac hoses on this kind of carby coz it is not CV. I will try to retune at 2500rpm and see what gonna happens...
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Old 11-15-2012, 10:59 AM   #10
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You might check that there's no split in the rubber adapter between the carb and head. To check for vacuum leaks, use an unlit propane torch and go around anywhere a leak might be. RPM will change if a leak is found.
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Old 11-15-2012, 02:22 PM   #11
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Quote:
Originally Posted by ttpete View Post
You might check that there's no split in the rubber adapter between the carb and head. To check for vacuum leaks, use an unlit propane torch and go around anywhere a leak might be. RPM will change if a leak is found.
Thats smart idea... Something to have in mind for general knowledge!
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Old 11-15-2012, 02:23 PM   #12
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Thats smart idea... Something to have in mind for general knowledge!

WD-40 works too but is messier.
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