Hi, Anonymous 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.
8. 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.
9. 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 for viewing or printing please click on the blue links below. Good luck and have a wonderful day. http://www.400greybike.com/files/NC30%20Carb%20Jetting%20-%20DIY%20Guide.pdf Pilot Jet idle Mixture Screw Settings Honda VFR400R Service Manual https://www.partsfish.com/page/oem-parts-for-honda Road Motorcycles Owning Honda Honda MPE
Hello, I'm new here, honda tmx 155 my motor, my problem is that when I'm up I need one I need to keep the kick out of it, even if it's too long, my sprockets are 14/51, before the lining, when he comes up he's staring at it then suddenly, thank you for the answer ..
This problem can occur on any bike that is carburetted and uses a needle and seat/float bowl system. Basically any bike that isn't fuel injected in other words. The reason fuel is being dumped is because it isn't getting shut off and is flowing past the needle/seat. The cause of this is one or more of the following. Dirt or foreign material interfering with needle/seat/float operation.....Worn needle and/or seat....Malfunctioning float due to leaking float...Is there any thing in the float when you shake it?......Lastly, and I cannot stress this point enough,.....Improper float level setting. This is a critical setting and must be set as accurately as possible according to manufacturer's specs. It is accomplished by bending the tang of the float which will control how much fuel will be in the float bowl when the float bowl is full. Think of a common toilet with a float mechanism because it is the same principle.
Check the timing, replace the plugs. If no better check the compression of each cylinder with a compression tool that replaces the spark plug. Pull all other plugs off while cranking motor. If compression is low on one or all, a valve might be open it rings are gone. If compression is good, if a carby make sure needle if free and bowl is not fill of oil from evaporated fuel.