Fuel blockage

[Alex_amd2001]

Hey Everybody,

Just had my scoot back after a barrel rebore and now there's no fuel coming through the carb (phbl) . The float bowl is full, so no problems with the flow in, but the spark plug is dry and nothing on my hand when I kick it over with my hand over the carb inlet. Any ideas why or what's blocked? Cheers.

[MickYork]

probably a jet but it seems strange as fuel can come through the choke or pilot je. a carb' strip down and clean looks to be needed.

have you tried pouring petrol through the carb' mouth (an egg cup full) to get it going ?

[Scooter Paul]

A big air leak at carb manifold to barrel junction?

Paul

[Markpm]

Better check carb has been put together correctly
Upside down floats will stop fuel coming through

[sunrisemac]

Have you checked the compression?

[Alex_amd2001]

If anything the carb blows air out from the inlet, can that be right?

[coaster]

If anything the carb blows air out from the inlet, can that be right?

It should suck a lot and then blow back a little as the crank spins through each 360 degree cycle(assuming not reed valved)

[Scooter Paul]

Is the piston fitted the right way? Arrow pointing towards the exhaust port? If no arrow the size stamping should be on the lower side.

[Alex_amd2001]

It's a standard 150 barrel (series 1, because its a winter model) but rebored to 57.6 with the correct piston for the model. I wouldn't be surprised if they've put the piston in upside down, I really can't see any other reason for no fuel to be taken in through the carb, but I'll check the other suggestion that you guys have posted. Cheers.

[Alex_amd2001]

Okay, so I'm trying to check if the piston is in the right way around, but there's no arrow stamped on it. There's an S1 stamped but not much else. Is there any other way to determine the way it goes? Ring pegs closer to the ground...if that makes sense? Truly driving me nuts now. Thanks everybody!

[grandpa]

Hi Alex,
Look at page 103 top right hand corner of Sticky's 2nd edition note shape of piston under gudgeon pin opposite side of mag.
If engine all assembled pour a thimble full of fuel down plug hole refit plug and it should run for a few seconds.


Grandpa

[Alex_amd2001]

Thanks Grandpa, that's really helpful. Appreciate it.

[STREETSLEEPER]

To go back to basics, just as long as your piston is fitted correctly you still seem to have the problem of lack of fuel reaching the combustion chamber. I know you said your float bowl is full, but is there a steady flow to the bowl?
Someone mentioned the carb jets and the float, so just as long as these are working correctly then you still need to check fuel is flowing steadily to the carb. As you know, a lot of stuff gets disturbed when taking the engine apart so just to be sure I'd check the filter on the carb itself (I'm thinking of my own SH2/22), the pipe between tank and carb (for air-locks), and the petrol tap, including its filter inside the tank. Sorry if these checks just seem so perfunctory, but I've seen stranger things happen, including rags left inside inlet manifolds. Good luck, 'cos I know just how frustrating these things can be.

[sunrisemac]

When I had my engine to bits to check it after the first 1500 miles and had put it back together it would not pull fuel through, I put a wee bit of engine oil down plug hole and turned the engine over a couple of times to seal the rings which I thought might not have seated properly after being disturbed, put plug back in and tried a kick and it fired up after 3 kicks, been no problem since.