TOPIC:

I changed out my carbs,now the only way it will idle is with the air screws all in. my needles are on the second from the bottom, 102 mains. It also will only run on choke with the air screws turned out. any ideas? This is my 77 650, thanks

First question I have is are the VM24 Mikuni carbs? Check to see if the plugs are white or black powder like. White indicates a lean condition. When I had VM24 on a 1977 650 and a 1978 650 with pod filters and a 4 into 1 pipe, I ran #110 or 112.5 mains, needles riased one notch (I see you have done that), and air screws 2 full turns from seat. There where several threads in the archives discussing jetting. You may want to check those out. I believe Wiredgeorge had a post that several members listed thier bike type, type of pipe, elevation, needle setting, jet sizes and other jetting info. Really good thread there.

Make sure you have good fuel flow and no restricted passages in the carb bodies!

Good luck

Post edited by: mellvis, at: 2005/11/27 19:30

I put a set of vm 24 pumpers. I cant read the plugs because it dieswhen I give it gas. I have soaked, blown and sprayed these carbs. I set the valves and got it timed...Im out of things to try!

I gather that it starts and Idles, but when you give it throttle it dies. If you choke it can you give it throttle? If you give it throttle very slow does itdoes it keep running? Does it only die if you open it up quickly? Have you checked to make sure you don't have a fuel blockage?

if I roll it on slow it will bogs out at 1800 rpm. I am getting gas to the bowls. the only thing I can think to try is to pull the carbs back off, should I leave the needle alone or move it while they are off?

First step is check the plugs, they will tell you almost everything you need to know.
Are you getting good spark? Do you have good compression? How old is the gas? If you start it and just let it idle does it die out?(fuel starvation)
When it dies can you imidiatley restart it? When it dies, shut off the fuel aqnd take the float bowl drain plugs out and see if there is plenty of fuel in the bowls.
If iot runs fine with the choke on it is very lean. 102.5 mains are factory main jets with stock pipes and air box. You should REALLY consider #110 or #112.5 mains with the needles raised 1 notch. Make sure you are raising the needle and not raising the clip on the needle. (I don't mean to question your inteligence, but some people don't realize which way to move the needle) Hold the neelde and move the clip toward the point to raise the needle height.

Are you running pod filters or the factory air box?

zippoman... Where is Seagoville TX? Not familiar with that place... In any case, if you get bike started OK and it idles and then go to give it gas, it isn't the main jet or jet needle that is troubling you.

I can't help you with jetting as you didn't mention what type airbox or pipes you are running but the bike should start and run no matter if the jetting is perfect or not...

The problem is in your IDLE circuit. The idle mixture is very likely too lean. What type mixture screws do you have? Pilot air or pilot fuel mixture screws. Air screws are on the sides and fuel on the bottom of the bowl... It could also be that the pilot system is obstructed or your pilot jets are way too small... can't say without having some info...

the carb has air screws, if the idle circuit is plugged why would it only idle with the air screws all the way in? btw it has a 4 to 1 and stock intake, thanks.

It will only idle because air is leaking into pilot system and turning screws out leans the mixture excessively.

nice looking bike!how about bigger picture?

I agree with Mellvis on the jetting. Your problem sounds like plugged up pilot circuits. Just remove the pilot jets, spray some carb cleaner into where they were, plug the pilot air intake in the back of the venturi with a finger and put compressed air to the hole where the pilot jet goes. This is the easiest way to clean them out. It might take a few tries, because the pilot fuel circuit takes a couple of nasty angles between the pilot jet and the venturi. Eventually you'll hear the air coming into the venturi.