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Hi, Merlin the carburetor throttle shaft wheel has two cables the cable closest to the right side of the bike is the throttle cable and the one closest to the left side is the idle cable. Right about the middle between the two is the idle adjustment bolt it faces out towards the air filter end of the carb . The engine should be at operating temperature with the enrichener off to set the idle between 950-1050 rpm. Turn the idle adjustment bolt clockwise to increases idle speed and counterclockwise to decrease idle speed. If you have access to your air fuel mixture bolt you may adjust it as well if not there is a video below on how to gain access, make sure you start with clean or new spark plugs. Gently turn the air fuel mixture bolt clockwise until it starts to bottom out "STOP" do not over tighten as it will damage the taper on the end, now back it out 2 full turns to establish a starting point start the engine and check the idle rpm's and adjust the idle adjustment bolt accordingly for 950-1050 rpm if necessary, adjust the air fuel mixture bolt 1/4 turn at a time and let the engine settle for about 10 seconds, clockwise for a leaner mixture and counterclockwise for a richer mixture you are seeking the highest rpm your air fuel mixture bolt can acquire without going past 3 full turns from bottom then readjusting the idle adjustment bolt back down to 950-1050 rpm If you can not detect any rpm change and can not stall the engine by turning the air-fuel mixture bolt all the way in then your pilot/low-speed jet is too big. Final adjustment should be made with a clean air filter mounted to the carburetor. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have nice a day. http://www.r1-forum.com/forums/4-mechanical-help/2215-my-two-cents-carb-idle-mixture-screws.html R6 Carburetor Fuel Mixture Adjustment 2000 2001 Yamaha YZF R1 Service Manual R1 Moto Data Project OEM parts for Yamaha http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals
to much air when mixing with fuel in carb find air mixtur screw on carb an whale running turn in slowley till it stops backfiring turning the screw in adjusts the air mixing with fuel the screw is useuly located on the side of the carb witch the toub hooked up to put fuel in carb is or you could re set it by screwing all the way in then screwing out 3 whole turns then whale running turn out til it back fires then turn screw in haf to three quarters of a turn in hope this helps
Sounds like your fuel air mixture is a little rich. Check your plugs, if they are black you are running rich which will cause some of the excess fuel to be burned off in your exhaust. Two common problems with a bikes fuel air mixture is bad plugs, if one does not fire consistently all the time it will leave excess fuel in the combustion chamber. Another would be a clogged air filter keeping the fuel air mixture unbalanced as well.
Lastly if you are able to, you may adjust your air fuel screws on your carb. However most Honda's are stock with Keihin carburetors and these air fuel screws are plugged so you cannot make adjustments without drilling out the plugs.
I would suggest not making any changes until you find out the problem. especially if the bike was running ok prior. Was the bike sitting for the winter? did you use any fuel stabilizer? Change fuel including draining carbs. Check your air intake passages for spider webs, any mouse nests,... check air filter. change your spark plugs , especially if they look black. The condition of the old spark plugs will tell you a lot. Black indicates running too rich. Whitish or next to nothing indicates too lean fuel mixture. Tanish color is perfect. Start with the simple fixes before dropping money into her
What this sounds like is a carb issue. There are screws that are located on the carb that control the air and fuel mixture, if you are getting to much air then it will crank and run only for a minute or two then shut off. Have you tried adjusting it? It can take some time to get it right as each bike engine is going to be slightly different and all adjustments are going to be bike/engine specific. I would recommend adjusting the air and fuel mixture, that will probably work for ya. Hope that this helped.
Your carb probably need going through. I would suspect that it's your accelerator pump has got a few holes in the diaphragm and maybe your slow jet is partially stopped up. If the bike has been sitting for an extended period of time, this is more likely the problem. The air mixture is not adjustable unless you or someone else has removed the "anti-tamper plug" that covers the idle mixture adjustment screw. And, only then if you or someone else has turned the screw. If the fuel air mixture has changed, it's something wrong inside the carb. I'd either take it apart and clean it or get someone else with the proper experience to do it for me.
It seems the carb/s flooding with fuel and thus it dies, try to reset the float pin and get the correct level of the fuel in the float chamber.
Standard procedure for air-mixture screw setting is u take the screw right in slowly taking care not to over tighten it as it may damage the tip of the screw.
Warm up your bike's engine and thn slowly turn anti clockwise the air-mixture screw to about 2 & a half turns and observe the engine's idling.
Before you attempt this setting(air-mixture) its better too, to replace the spark plug and set the gap to the specs of your bike's engine and check and adjust accordingly the valve clearance.
Hope this helps!
Your Twin Cam plug should be a 6R 12 Harley Plug. Often times the back fire is just the nature of the beast depending on what type of pipes you are running. Harleys do run lean, its an EPA thing thtas why they choke them down from the factory. Since you have a carb you could have an intake leak around the Intake. Also Under the carb is an adjustment screw. Harley plugs it up so people don't play with it. You have to just drill out the plug this will set your air fuel. Whenever I take a carb off I drill out that plug. Heat your bike up operating
temp and ear tune that screw. Only other way is with air fuel analizer or a dyno. good luck.also that backfire is caused by fuel hitting your exhaust when you let off just to let you know.