Bike loading up when fuel turned on.

[bigk]

Need some ideas from the brains trust please.
I have a WR430 Husky which has had a complete engine build (rod, bearings, seal, piston etc), done may & nothing is different to any of the others. The bike loads up & won't run with the fuel tap turned on. Turn the fuel tap off & as it leans out it runs clean until it runs out of fuel. If I crack the fuel tap (even 1/4 open), the bike immediately begins to load up again. It used a litre of fuel in about 5 mins of static running, most of it out of the exhaust pipe. Standard 38mm Mikuni with standard jetting for the model.
I have checked, the needle & seat, floats, reeds, air cleaner with nothing out of the ordinary or obvious. I have tried a second carby which I know for certain is good with the same result. So the bike gets too much fuel or not enough air, but I can't see why either should be happening. Anyone experienced this or have any ideas on what is happening?
Cheers,
K

[Curtis]

I would have thought float level, leaking float valve?? but you have tried that.
Is it a after market fuel tap?..maybe its too much flow?

[John Orchard]

Is it a reed-valve engine?

[John Orchard]

Could both carbs have too high float level?

[pokey]

Not many things to go rsup in a mic and im sure youve had a look but maybe check and see if there has been a rookie error. Missing washer under the jet or seat. needle in upside down , that sort of thing. Im assuming you can start the big girl okay with that shark hook that they call a kick starter so your on the right track of air or fuel. Could try when its running, spraying crank seal and intake tract to see if the revs change to indicate an air leak. Also check the overflow tube  to see if she is dribbling. if the tube is located on the base of the bowl, raising it vertical will give you a ballpark idea of the actual fuel level. if its higher than where you think it should be then issue is between the tube and the needle and seat.

[bigk]

Tried pretty much all of that & yes it's a reed engine John. The second carb came straight of a good running bike, same make & similar capacity, carb should have worked without an issue if it was a carb problem. It's bound to be something so simple, it's stupid but it has me & everyone I've talked to about it stumped.
K

[Mick D]

Also check the overflow tube  to see if she is dribbling. if the tube is located on the base of the bowl, raising it vertical will give you a ballpark idea of the actual fuel level. if its higher than where you think it should be then issue is between the tube and the needle and seat.

Fuel will only run out of that overflow tube(connected to the bottom of the bowl) when the level exceeds desired norm and reaches the top of this brass overflow tube


If you really want to witness fuel bowl level when static or engine running?
You first have to remove that brass tube. Then and only then will the clear tube display an accurate fuel level when raised up vertically.
Sacrifice a bowl. Call it workshop equipment.

Remove the plastic bag from the new air element?
Rag from air boot? Just being a SA now

[smed]

Tricky one that, the ignition & timing all good? Blocked exhaust? Correct piston & top end?  Sounds like the fuel is getting in but not being burnt properly or escaping out the exhaust before being burnt, Or forked if i know

[tony27]

5 minutes a litre seems excessive, has to be a carb fault of some form.
When you tried the other carb did you have access to the tank as well, trying a different tank would eliminate the tap flowing too much and overpowering the float valve as a reason

[pokey]

Fuel will only run out of that overflow tube(connected to the bottom of the bowl) when the level exceeds desired norm and reaches the top of this brass overflow tube.If you really want to witness fuel bowl level when static or engine running?
You first have to remove that brass tube. Then and only then will the clear tube display an accurate fuel level when raised up vertically.
Sacrifice a bowl. Call it workshop equipment.

 true mick , if you can see it that would point to a pressurised fuel tank/blocked breather/ faulty needleseat. being as it does it on both carbs Im leaning to it not being a carb issue now. Its had new seals so perhaps a lip isnt seated

[Mick D]

Tricky one that, the ignition & timing all good? Blocked exhaust? Correct piston & top end?  Sounds like the fuel is getting in but not being burnt properly or escaping out the exhaust before being burnt, Or forked if i know

Yeap, forked if I know too

If you were drinking when you did? give up drinking and start the rebuild from scratch again.
I have stopped drinking completely, everything is different now.
I used to spend at least an hour everyday looking for my keys and wallet,
Got it down to 55minutes now

[Mick D]

That pressurized thing would be worth eliminating Pokey.

Actually, I was giving a friend a hand on a 430 husky with a Mikuni, only 2 or 3 months ago.
Ignition problem.
After we tried to sort it again a few days latter, it was pissing fuel out of the Mikuni for apparently no reason, I abandoned it then and went home and left it to the owner
I should have popped the cap Pokey
Uuumh, non vented cap on a non vented tank?

Bike didn't come from Newcastle recently, did it?

[80-85 husky]

it appears the carb isn't the issue if the 400 carb does the same thing. exhaust or muffler? can you swap the 400 ign system?
reeds arnt stuck open or shut?
the turning of the fuel is the clue and momentary clean running
the carb to filter boot isn't sucking in and blocking air?

just musing.... but if it runs clean on leaning mix there is too much fuel in the motor. we know the carb aint doing it.... thus there is not enough air getting in per firing stroke....air filter but you've checked it...airboot? no loose flap sucking across the carb. airbox is pretty open so should be visible...air cant get out..blocked pipe? will it idle? but not take any throttle?? wasp nest  in the muffler??wack a stick in it to check...

if it was electrical, turning the fuel on or off shouldn't affect it.

this is a good one!

[pokey]

yeah mick that vent issue has got me twice before (im a slow learner). It usually makes them starve for fuel but depending on the temp of the tank they can build up pressure too. worth as you say, Popping the cap to eliminate that possibility.  that fuel usage as one of the guys mentioned is of a concern as it does seem excessive. This is going to be an interesting thread i think.

[Mick D]

What about the little plate doovy that goes under the big throttle slide return spring and holds the slide needle in position?
Is it there doing its thing?