Author Topic: Another Carb issue (Read 3005 times)

bombhead · « **on:** November 05, 2005, 02:14:40 PM »

Just another carb issue. If the bike is running rich (i.e backfiring, too much fuel going into the cylinder) then what would make it leaner.......turning the a/f screw inwards or outwards.

Regards

Darren

solman · « **Reply #1 on:** November 06, 2005, 01:44:12 AM »

Running rich when? How it fix a lean or rich problem depends on the range; idle, mid, or main.

bombhead · « **Reply #2 on:** November 06, 2005, 03:27:23 AM »

I've been told now that it's actually running lean. It's when I try to start the bike up so it's in the idle range.
There's fuel going to the 1st cylinder but the fuel going to the 2nd, 3rd and 4th is gruadually reduced, as if the carbs are being held diagonally. There's fuel in the float chamber and I've cleaned the pilot jets so I'm a bit puzzled !!!!

rider123 · « **Reply #3 on:** November 06, 2005, 11:13:32 PM »

If you want it leaner you turn it clockwise, richer is counter-clockwise. A good idea would be to take the carbs off and number the carbs from left ot right 1,2,3,4. Then turn in the screws untill they are LIGHTLY seated and note how many turns it takes(ie. 2 1/2). Write this down and return the screws to what they were before and mark them. Now you have a basis for fooling around with the mixture screws. If you look up in the manual you should find what the number of turns should be for stock jetting (usually a little lean). If you like, another good way is to make all the carbs the same for the stock jetting. For example I have a Bandit 1200 and in the Haynes manual it stipulates that it should be 2 1/2 turns out on the mixture screws. For my bike though, there is a bit of an off idle stumble due to it being slightly lean, so if I back off on the mixture screws a bit it should get rid of this. If you mark where the start and back off in little increments ie. 1/8th of a turn you should be able to fix any problems with off idle smootness/hesitation.

However if your bike was running perfectly before and just now is lean without touching anything you may have a leak in your intake boots. A good way to find out is rev the bike up to 2000 rpm or so to create some more vacuum and spray WD-40 or something that won't hurt the engine around the intake boots and you'll see it getting sucked in to any holes or cracks. Also tighten up any carb retention clamps as well they may have vibrated loose.

If you are having fuel delivery problems it also could be a stopped up fuel filter in the tank or a defective petcock. ALso check the vacuum tube going to the petcock for leaks. Does it run well with the petcock set to "prime?"