Huasheng 4 stroke revs up and dies when choke is turned off

[Maddmatt]

My 4 stroke Huasheng ran fine, but then sat for 3 months. I've stripped down the carb and cleaned every nook and cranny but it only idles with the choke on and the second i turn the choke off, it revs up and dies within seconds.

It's driving me mad. I can't for the life of me figure out whats wrong.

The spark plug is good and gapped correctly
There are no air leaks between carb and engine
Wires are all connected correctly (kill switch etc)
New gasoline, 92 octane
gas cap is vented correctly
black hose from air intake is connected with the engine block
Air/fuel screw is currently at 2 1/4 turns out
New oil in sump

If I leave the choke on it will idle for ever, the second I take it off it revs up, tries to take off and dies. WHY!?!?!!

Help me.

 

[sparky]

Sure you're not mistaking on and off?? Ya don't have 'em backwards, right?

My carb says off when the choke is actually doing it's job of choking.

 

[skyl4rk]

Change the fuel filter. Take the petcock assembly out of the tank and blow some air through it.

 

[Maddmatt]

Already checked that.

New fully functional petcock, clean, working.

New fuel filter.

Still doesn't work.

 

[HoughMade]

It's got all the signs of fuel starvation. Runs with choke on, but not when off.

When you say it revs up when you turn the choke off, does it rev up like it is "running away" on its own, or does it just rev a bit and smooth like it should when the choke is turned off, or it it you revving it up after the choke is off?

When you say you cleaned the carb, did you take the jet out, all the adjustment screws and needles and pry out the plastic plug under the plastic idle speed screw? In taking my Honda carb apart in the last week, I discovered a lot of additional nooks and crannies I never knew about before. Does the float seem like it is moving freely?

Here is a link to a post that has good pics of the disassembled HS carb.

http://www.motoredbikes.com/showthread.php?t=6312

 

[Maddmatt]

It's got all the signs of fuel starvation. Runs with choke on, but not when off.

When you say it revs up when you turn the choke off, does it rev up like it is "running away" on its own, or does it just rev a bit and smooth like it should when the choke is turned off, or it it you revving it up after the choke is off?

When you say you cleaned the carb, did you take the jet out, all the adjustment screws and needles and pry out the plastic plug under the plastic idle speed screw? In taking my Honda carb apart in the last week, I discovered a lot of additional nooks and crannies I never knew about before. Does the float seem like it is moving freely?

Here is a link to a post that has good pics of the disassembled HS carb.

I took apart the entire carb. it was bare parts, I cleaned those bare parts, then re-assembled.

Sure you're not mistaking on and off?? Ya don't have 'em backwards, right?

My carb says off when the choke is actually doing it's job of choking.

Yes I understand the difference of on and off. I can see the choke doing it's job.

 

[Emmased]

Mine behaved in much the same way. I removed the filter inside the tank and used just the aftermarket one I installed between the tank and the carb. Never had a problem since.

 

[MotorbikeMike]

H/S Carb blues?

HI well I had a very similar problem with mine, after neglecting to drain the BAD CA. gas when the gearbox croaked.

I cleaned and worked in that carb twice, unsucessfully, and have obtained a new replacement carb, so I can continue testing.

Mike

 

[POPS]

H/S carb Blues

Hi...Maybe try putting some clear line on from gas tank to carb so you can see whats going on??? Could also be the float level set too lean ( Not enough fuel in the bowl )??? Just some thoughts,Trying to help. POPS

 

[Maddmatt]

Ok so I have an update.

I ran the engine with the choke on, then sprayed an aerosol carb cleaner at the joints to see if I had a leaky gasket. In theory if anything is getting sucked through then i would hear it in the idle.

It worked. I found my air leak.

But it's not from a gasket. It's from the throttle arm. I'm familiar with this problem with VW carbs, once an old VW carb is taking in air from the throttle assembly it's done for. Time to buy a new one. Anyone know if this can be rebuilt? Should I just order a new carb?