Bike starts up fine when I turn throttle it back fires

I suspect that the throttle cable is out of the end setting from removing and replacing the carbs or a return spring for the cable has broken off and not pulling the throttle back to idle position

need a er diagram on post office

The choke is on the carb. Check if the carb set screw is set right, turn it all the way in and then back out 1 1/4 turns. then fine tune by 1/4 turn increments.

bike is 10yrs--carbs are varnished and dirty-clean the high speed jets-u need a clymer manual

The only thing that I can guess is happening is the engine is spitting back while you're trying to start the engine. This ignites any gasoline that is in the carb or throttle body and the flame is burning you air filter. The thing to do is to continue to turn the engine. This sucks the flame into the engine. It won't hurt anything because after all, you are trying to start a fire in the engine.

If your bike equipped with a carb, pull the enricher out, milk the throttle about twice, turn the ignition switch on, and then push the start button while leaving the throttle completely closed. This is very important, leave the throttle closed. This is how an enricher circuit works. If you crack the throttle open even the slightest bit, the air is drawn through the carb instead of the enricher circuit and this causes the spit back in the carb. It will do the same thing with fuel injection. Start the bike with the throttle completely closed. It should fire and go to a high idle with the enricher out or with a fuel injected engine.

Good Luck
Steve

Since you didn't say anything about the engine not cranking over, I'm going to assume that the engine is turning over fine and everything else is as well. Some people do experience trouble getting their bike started on cold mornings because they are not familiar with how the enricher circuit works.

The enricher circuit works differently from the old fashioned "choke" found on older bikes. To get the enricher to work as it should, the throttle must be completely closed. A lot of people get ready to start their bikes and open the throttle just a bit. Do not do this with an enricher like your bike is equipped with. If you do, the air the engine draws in does not pass through the enricher passage but rather through the carb throat itself and then the mixture is too lean to get the bike to start.

The way I tell everyone to start the bike is first turn on the fuel at the petcock. If you're bike has the original petcock, it is vacuum operated and you don't have to turn it on, it'll turn itself on. Then, prime the carb by twisting the throttle grip two or three times. Then, turn the switch on and with the throttle completely closed, push the "start" button. The engine should fire right up. If not, twist the throttle one more time and try again. If it doesn't start up then, you may have a problem.

If you get the engine flooded and you smell gasoline strongly. Turn the throttle wide open, then push and hold the start button. Do not hold the button for over 15 seconds at a time under any circumstances or you may burn up the starter.

If this doesn't work, please repost and give me more information about what the bike is or is not doing.

Good Luck
Steve

DRAIN CARBS FROM PETCOCK AT BOTTOM OF EACH CARB MAKE SURE FUEL DRAINS COMPLETELY THEN TURN FUEL BACK ON, IF THIS IS AN INJECTED MODEL DRAIN TANK AND FLUSH THEN RUN IT HARD FOR 20 MILES OR SO, MAKE SURE YOUR OIL LEVEL IS OK

If you need further help, I’m available over the phone at https://www.6ya.com/expert/michael_00678fd4800d19c5

Your bike has a diaphragm on the carb. Every time you twist the throttle a shot of gas goes into the cylinder. Chances are you are flooding the engine by twisting the throttle too often. Flooding can create a backfire. Start with a clean dry plug. Twist the throttle once then leave it alone for about six kicks. Repeat the process if needed.

hi would be good idear to also check spark and and timing also if you just got bike give it a good service this includes fuel filter

hope this helps

does it have spark??