Mikuni problems ???

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hostilecarl

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Feb 6, 2013
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Just picked up a very nice completely restored '74 850 interstate (single carb conversion) with little to no expense spared. Got it off the trailer and the Mikuni VM won't take any gas. I've flushed the entire fuel system tore the carb apart cleaned and refitted everything even installed new fuel lines and an inline filter. I'm at a total loss, wtf is going on ??? Help I just want to ride the damn thing !!!!! I know its gotta to be simple, but I'm exhausted and frustrated. Thanks-
 
A weak battery can supply enough spark for start and idle but will not fire the plugs when the throttle is opened. Put the battery on a charger for a bit and see if it improves. Jim
 
Clogged up from emulsified old fuel. Soak in cleaner and blast out all jets-orifaces with compressed air. But chek for spark at pulled plugs too ,no spark no go.
 
blasted every orifice with air have flushed the tank with fresh gas, dried it and blasted with air. Fuel will run into the carb, the carb won't take the fuel. I've had the carb apart and cleaned it meticulously.
 
Carb cleaner flush through carb everywhere..!!
Is there spark firing..?
Check carburetor fuel level valve...!!!
 
Checked plugs, cleaned and regapped. This is not an electrical. There is some back pressure keeping the carb from accepting the fuel
 
Ran one direct line from tank to carb and fuel wouldn't enter the line. Disconnected from carb and flowed perfectly
 
everything on the bike is new, 300 some miles on it. Good enough for a shakedown, former owner is awesome and wants to send me a new carb but this carb is pristine
 
hostilecarl said:
Fuel will run into the carb, the carb won't take the fuel.
Click to expand...
This statement seem contradictory. Needle and seat? Float operation?

There are at least 3 vents. Find an exploded view, identify them and make sure they are open and a vent hose attatched.

Get basic. Remove the float bowl and run a gas line to it. Whitness the gas flowing or not as you actuat the float bowl and needle against the seat.

These suggestion should get you closer to your road trip.
 
hostilecarl said:
Just picked up a very nice completely restored '74 850 interstate (single carb conversion) with little to no expense spared. Got it off the trailer and the Mikuni VM won't take any gas. I've flushed the entire fuel system tore the carb apart cleaned and refitted everything even installed new fuel lines and an inline filter. I'm at a total loss, wtf is going on ??? Help I just want to ride the damn thing !!!!! I know its gotta to be simple, but I'm exhausted and frustrated. Thanks-
Click to expand...

Was it running when you got it?
 
hostilecarl said:
Checked plugs, cleaned and regapped. This is not an electrical. There is some back pressure keeping the carb from accepting the fuel
Click to expand...
YOU SHOULD BE ABLE TO BLOW THROUGH THE CARB FROM THE FUEL INLET. . IF NOT, THEN TAKE IT APART AND KEEP BLOWING THROUGH TO YOU FIND WHERE THE BLOCKAGE IS. iS THE NEEDLE JAMMED UP IN THE SEAT? CAN YOU BLOW AIR THROUGH TO THE SEAT WITH NO NEEDLE IN PLACE? IF NOT, LOOK FOR THE BLOCKAGE. hAVE YOU TAKEN OUT THE SEAT? THERE SHOULD BE A CLEAR PATH BETWEEN THE SEAT AREA AND THE INLET PORT WHERE THE HOSE GOES [he blow test ]. IF THATS ALL OK, THEN YOU WILL HAVE TO FIND OUT WHY THE FUEL IS NOT GETTING OUT OF THE FLOAT BOWL AND INTO THE INLET MANIFOLD. yOU SHOULD BE ABLE TO TICKLE IT AND FLOOD IT.
if ALL ELSE FAILS, DO IT ALLL AGAIN.
cAN YOU SEE THROUGH THE JETS?. CAN YOU BLOW THROUGH THEM? WITH THE JETS REMOVED CAN YOU BLOW THROUGH THE PASSAGES? iT'S ALL REALLY SIMPLE BTW.
You could always pay a mechanic like me to fix it for you.
All thye best. Dereck
 
now after cleaned and reassemble correctly fuel will not even enter the lines. Pull the lines off the carb, open the petcocks , fuel runs freely
 
hostilecarl said:
would run for about 30 seconds, enough to burn the bowl.
Click to expand...
Then maybe we need to look up. Fuel line, filter, petcock, crude in fuel tank (850, shouldn't be fiberglass), and vent in fuel cap (is it clear).
 
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