I've got a '56 Pan, had it for 35 years, but it's never done this before. It's got a Tilesten (don't know if that's spelled right) carb which doesn't have a float bowl. It starts and idles fine, but when you pick it up off of the kick stand it starts missing, coughing, popping, etc. If I set it back down on the kick stand it starts running good again. I drained some gas out of the tank, so I know there's no water in it, and I don't see any electrical shorts. It will do it even when I'm not in the seat. I'm totally dumb-founded. It seems more an ignition based problem than fuel. Any ideas? Has this ever happened to anyone else? Thanks Dean.

 

Never heard of this type problem before! I've also never messed with tillitson carbs. before either. From the get-go (1974) when I started riding Harleys. I was told these carbs. were junk and to stay away from them. Unfortunately this does not do you any good.
About all I can say that might help is to take the carb. a part clean it good and replace the gaskets with new ones. It sounds like you
might have a very small peice of crap floating around in it. And when you right your scooter up it glogs a jet????....... Hopefully somebody who knows "tillies" can help you out. Good luck, AMF

 

Is the coughing and popping coming from the air cleaner or the pipes? Generally, if it coughs in the air cleaner, it is fuel related. If it pops in the pipes, it is electrical. If it is in the AC, I would look for a fuel supply restriction, causing a lean condition. Possibly a clogged fuel shut off valve or a clogged filter. If in the pipes, for some reason it is getting fuel, but the ignition charge is being delayed, causing the explosion in the pipes. If that is the case, start with the coil and distributor wiring. I have seen the wire at the dist short out on the housing, causing similar problems. Good luck with it.

 

Couple of quick thoughts...when was the last time you cleaned the tanks out for sediment and rust (if they are not sealed). Thinkin maybe the sh** is sitting there and when you stand it up right it shifts into the lines. If you got aftermarket tanks when was the last time you cleaned/changed the fuel filter? Last thought...have you checked to see that your battery positive and negative wires are secured properly, no cracks or splits in lines, +side not grounding out against something it should be touching and only comes into play when bike is upright and putting pressure against a bare wire or frayed wire.

Oh,,one last quick thought, since you are using an o-ring manifold, how about any leaks developed around whehre carb and intake manifold meet due to rubber o-ring being worn out?

When you fix it please let us know cuz that can happen to anyone of us...

 

It's amazing if it runs at all with a Tillotson. If you are not keeping it for 'purity' reasons, you'd do well to get an S&S, Bendix or even a Linkert.

To make sure that it isn't an electrical problem, get a cheap neon timing light and connect it to either sparkplug. (You want the kind that connects one wire to the plug and the other wire to the plug wire) Watch the light and make sure that it flashes evenly when you stand the bike up and it starts missing. If the flashes miss too, you have an ignition problem.