HELP! carb problems - TwoWheelForum: Motorcycle and Sportbike forums
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post #1 of 22 (permalink) Old 09-22-2006, 03:21 PM Thread Starter
 
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HELP! carb problems

I need serious help here. first my bike wouldnt run, then I tuned it a little and it ran, although quite crappily, at which point I fiddled with the idle mix screws a little to make it run right, and they didnt do anything at all.

now I cleaned both carbs out real good, its a slight improvment, but its still running crappily. help? bike is a 97 EX500. its not lean, because I'd associate black smoke on revving with too much fuel.
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post #2 of 22 (permalink) Old 09-22-2006, 03:33 PM
 
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have you cleaned the jets out?
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post #3 of 22 (permalink) Old 09-22-2006, 03:36 PM Thread Starter
 
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I made sure I cleaned the jets out when I took everything apart, I dont quite understand it though, it shouldnt be running like this at all.
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post #4 of 22 (permalink) Old 09-22-2006, 04:10 PM
 
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i've heard of problems like this before bob, could it be something like a fuel pump or something simular to that on a bike, it sounds as if your fuel is being restricted in some way, i'll ask my mate tommorow!
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post #5 of 22 (permalink) Old 09-22-2006, 04:43 PM
 
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Are they tuned and synced properly?



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post #6 of 22 (permalink) Old 09-22-2006, 06:08 PM
 
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Quote:
Originally Posted by King Bob View Post
...its not lean, because I'd associate black smoke on revving with too much fuel.
There's only a few things that I can think of that will cause black smoke. Main jet not screwed in, float and needle incorrectly adjusted or installed, dirt or wear on the float needle and/or seat, float sticking on pivot pin, or the choke stuck on. You cleaned out the float chamber's jets, but did you also clean the piston and walls under the vacuum chamber on top of the carbs?

Blue smoke is another matter. My dad saw me smoking with friends when I was 16 and knew that the blue smoke meant that I was smoking pot. That was in 1966, a year before I knew what pot was.
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post #7 of 22 (permalink) Old 09-22-2006, 09:05 PM
 
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When i think of black smoke i think of worn valve guides? mmm check your bikes' oil consumption could also be possible blowby passed the rings, quite tricky. easy motor to work on though if your doing valve adjustment. Screw and locknut system!
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post #8 of 22 (permalink) Old 09-23-2006, 03:23 PM
 
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When i think of black smoke i think of worn valve guides? mmm check your bikes' oil consumption could also be possible blowby passed the rings, quite tricky. easy motor to work on though if your doing valve adjustment. Screw and locknut system!

Rule of thumb....

Black smoke= Too Rich; too much fuel. Usually, in bikes that were once OK but sat for a while, caused by stuck or worn float valve; carb overfills and the excess bleeds right out the pilot and air jets, right into the motor. If it does this while the engine is running, causes black smoke; if it does this while the bike is parked and the petcock is left "on" or is gummed up and stuck on, will cause gas to drain into motor, locking up a piston (liquids don't compress) or diluting the oil. I once started up a GSXR1000 in that condition and bathed the garage floor in gallons of oil/gas mix.

Blue Smoke on startup= Worn valve guides (oil drains from top end down valve stem, into combustion chamber, then burns up when you start it); unless you own an Italian bike or and SV Suzuki (check your airbox first, both have poor crankcase vent sytems allowing oil into the airbox, which runs down into carbs/throttle bodies, causing smoking).

Blue smoke on decel= Worn rings (slam the throttle shut; causes low pressure in chamber, drawing oil into combustion chamber past worn rings).

White smoke=internal leak in liquid cooling system...burning coolent smells like burning rubber.

These are only general rules of thumb; always check the cheap/simple stuff first, like pinched oil return or vent hoses, blocked crankcase breathers, evap canisters, ect.; stuff like that, first.
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post #9 of 22 (permalink) Old 10-15-2006, 10:36 AM
 
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So KB, did you get it sorted out yet?
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post #10 of 22 (permalink) Old 10-15-2006, 11:21 AM Thread Starter
 
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not entirely, I'm trying to save up some cash to rebuild the carbs, because I'm positive thats my whole problem now. the needles and seats are pretty worn looking, which I'm sure doesnt help any.
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post #11 of 22 (permalink) Old 10-15-2006, 01:04 PM
 
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You need to talk to birdman... He is getting intimate with Suzi carbs...
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post #12 of 22 (permalink) Old 10-15-2006, 01:23 PM
 
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carbs wont cause black smoke,does it run hot...
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post #13 of 22 (permalink) Old 10-17-2006, 05:49 AM Thread Starter
 
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carbs wont cause black smoke,does it run hot...
umm, I think you're quite mistaken here. too much fuel= black smoke. where does too much fuel come from? carbs.
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post #14 of 22 (permalink) Old 10-18-2006, 11:50 PM
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Quote:
Originally Posted by oldetymebiker View Post
Rule of thumb....

Black smoke= Too Rich; too much fuel. Usually, in bikes that were once OK but sat for a while, caused by stuck or worn float valve; carb overfills and the excess bleeds right out the pilot and air jets, right into the motor. If it does this while the engine is running, causes black smoke; if it does this while the bike is parked and the petcock is left "on" or is gummed up and stuck on, will cause gas to drain into motor, locking up a piston (liquids don't compress) or diluting the oil. I once started up a GSXR1000 in that condition and bathed the garage floor in gallons of oil/gas mix.

Blue Smoke on startup= Worn valve guides (oil drains from top end down valve stem, into combustion chamber, then burns up when you start it); unless you own an Italian bike or and SV Suzuki (check your airbox first, both have poor crankcase vent sytems allowing oil into the airbox, which runs down into carbs/throttle bodies, causing smoking).

Blue smoke on decel= Worn rings (slam the throttle shut; causes low pressure in chamber, drawing oil into combustion chamber past worn rings).

White smoke=internal leak in liquid cooling system...burning coolent smells like burning rubber.

These are only general rules of thumb; always check the cheap/simple stuff first, like pinched oil return or vent hoses, blocked crankcase breathers, evap canisters, ect.; stuff like that, first.
THats what I use for rule of thumb and very well put I might add!!!
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post #15 of 22 (permalink) Old 10-19-2006, 01:24 AM
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THats what I use for rule of thumb and very well put I might add!!!
They can be some of the hardest problems to find too.

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post #16 of 22 (permalink) Old 10-20-2006, 01:41 AM
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They can be some of the hardest problems to find too.
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post #17 of 22 (permalink) Old 10-20-2006, 07:59 PM
 
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Originally Posted by jeeps84 View Post
They can be some of the hardest problems to find too.
Especially when you are positive that it is a fuel problem, when in reality the problem is ignition-related.
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post #18 of 22 (permalink) Old 10-20-2006, 09:11 PM Thread Starter
 
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I only get the black smoke when I rev it up real quick from idle, but still only get like 100 miles per tank, or somewhere around there. air filter is my next target at this point. its the ONLY thing I havent tried yet, short of different carbs.

so far, within the time permitting between going to class during the week, and sleep, I've cleaned the carbs about 20 times, set the floats to the proper height, set the fuel mixture about 5 times, and replaced the plugs with new ones, bright blue freakin spark coming off em btw, and still nothing helps.

Hopefully someone can give me SOME kind of advice.
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post #19 of 22 (permalink) Old 10-20-2006, 11:09 PM
 
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I have a Motorcyclist magazine that tested the '88 superbikes. The 1988 ZX-10 got 38 mpg or 218 miles per tank. It has the Keihin carbs just like my CBR. Your 87 Z should be similar. My Haynes manual on troubleshooting poor running says to check the spark. If you have a healthy blue spark at each plug, it says to next check the ignition timing. I bought my Craftsman timing light in the early 70's and it works great on modern motorcycles. If the timing doesn't advance smoothly, or at all, you've found the problem.

On your carbs, the needle/piston moves out of the main jet by the difference in air pressure as air flows through the narrow venturi. With the engine off, stick your finger into each carb opening and lift the piston. It should rise up with a little resistance and fall smoothly when you let go. If the piston rises with no resistance, you have a leak at the cap (you didn't use Vasoline in the groove) or the piston diaphram is ripped. If the piston stays at the top and doesn't fall down, you have to clean the piston and walls. It seems you've checked everything else except the air filter.
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post #20 of 22 (permalink) Old 10-20-2006, 11:54 PM Thread Starter
 
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oh just so ya know, this isnt the ZX10 I had, sold that about 7 months back. this is my 97 EX500.

I went out after I posted about the air filter, I'm ready to join the I-DI-OT tribe. air filter is pretty grimy lookin, which PROBABLY has something to do with the crappy milage I've been getting. originally I got around 60mpg, now I get around 30-35 at most.
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