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you might take the top off the Carb and make sure the float is not allowing the fuel level to get too high in the Carb If that is the problem you can bend a tab, or adjust a screw, to shut down the flow of gas from the tank before the carb gets flooded. Also, check the fuel-mixture screw while the bike is
parked and idling to make sure it's not just set too rich. Start by screwing in the mixture screw, half a turn or quarter of a turn at a time. Put the carb back together before doing the running test.
Hi, Kye it should be noted that the "AIR FUEL" mixture screw adjustment "ONLY" manages your idle and has no effect on any other circuit also any intake leaks must be repaired before the A/F adjustment procedure can be performed otherwise you will never obtain a proper idle and you will waste a lot of time chasing the impossible. The A/F mixture screw's purpose is to fine tune the fuel charge entering the combustion chamber. The following applies to both 2 and 4 stroke engines:
1. The mixture screw may be sealed at the factory with a Welch Plug please review the following video for removal. https://www.youtube.com/watch?v=wAXcksgvDkM
2. The mixture screw manages a range of 3 complete 360-degree counterclockwise turns from the bottom/closed position.
3. The mixture screw should have a spring and o-ring for tension and sealing integrity.
4. Turn the mixture screw clockwise until it gently bottoms out, this makes the fuel charge very lean and the engine should not idle if it does then the pilot/idle jet is too big and needs to be replaced with the next size smaller.
5. Turn the mixture screw 1 and 1/2 turns counterclockwise to establish a baseline for starting the engine.
6. To fine-tune the idle circuit, adjust the mixture screw 1/4 turn in or out to achieve maximum idle RPM, wait 15 seconds between each adjustment for the idle to settle.
7. Never go past 3 full turns out this will make the fuel charge rich, foul plugs, and produce black smoke out of the exhaust, if the engine RPM keeps increasing past 3 turns the pilot/idle jet is too small and needs to be replaced with the next size larger.
7. After achieving maximum idle back out the mixture screw another 1/8 of a turn then adjust the throttle cable idle stop screw to 950-1050 RPM.
8. This procedure works great on 99% of all engines, for the 1% that demand a more robust throttle response on aftermarket monster fuel delivery systems additional tweaking outside the box may be necessary.
For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day. Honda CBR 125 few minor problems Life On 2 Wheels Honda CBR125R Owner Manual service http://www.partsfish.com/page/oem-parts-for-honda Honda CBR125RW Owner Manual
turning the screw way out makes the mixture lean, so the problem must be the carb is too rich. check all the jets were installed correctly when the carb was cleaned make sure the carb float bowl is not flooding. Check the fuel tap is working correctly. make certain the airfilter is clean. check the engine has correct amount of clean oil( not fuel contaminated)
Is there an air fuel mixture adjustment screw? I'd try lookin for one and adjust it a little and see what happens. Sounds like your mixture is way too rich. A more lean mixture won't bog down, but too lean of a mixture will bring your idle speed up too high
Black dry deposits are indicitive of a very rich mixture. On your two stroke, rich is a asset but you can go too rich. It sounds like for some reason you're getting too much fuel.
I think I ran into something like this before on a Kawasaki 80. Check the screws that holds the choke plate inside the carb. They will come loose and allow the choke to close on you while riding the bike. If the screw comes out, it will go into the engine and cause serious damage. If the screws are loose, them out one at a time and put a drop of Loctite 271 (red) on them and reinstall them.
Check the float and the needle and seat to make sure that you don't have any trash in the needle and seat. Also check your tank vent. If the tank builds up vacuum, you could be running out of fuel. Sounds funny that you can be running rich but run out of fuel. The problem is that you run out of fuel so quickly that the carbon from the rich mixture doesn't have time to burn off.
Backfiring is usually a symptom of the engine burning too lean. A vacuum hose is not usually the cause of this problem so don't fiddle with the vacuum hose...yet. We need to establish whether the engine is running lean, normal, or rich. The easiest way to tell is to pull a spark plug and examine the electrode. If the engine is lean, the electrode will have a light-brownish color; if normal, the electrode will be black but not sooty; if rich, the elecrode will be black,sooty and most likely wet (excess fuel).
If the plug shows signs of lean burn, you can adjust the a/f screw to increase the amount of fuel. Conversely if the plug shows signs of rich burn, you can adjust the a/f screw to decrease the amount of fuel. Typically, on a stock carb, the a/f screw is at the bottom of the carb and requires a special tool to adjust it.
My recommendation to you is to take your bike to a good indie (independent) bike shop and have them take a look at it. Unless you have been wrenching on bikes for at least 5 years, that is the best course of action. Typically, if you do not know what an a/f screw is, you need to go to a shop.
Fuel pumps just supply fuel to the carb. Either they work or don't
work. I would make sure that the mixture screws on the carb are set
properly. Turn the screws in to lean out the mixture, do one at a time.
You want to turn the screws in to the point where the jeep will start
to idle rough and then back out a 1/2 turn. Check your timing also. If
the jeep has alot of miles on it, the timing chain will stretch and
it's possible that you cannot get the correct timing.