My aux tank has been a juice bottle on a microphone stand. It required a pump to draw the fuel out (rather than gravity feed). I had been planning on making a proper aux tank, and bypassing the pump, but I kept being led down paths that made it look like it wasn't the pump (so I didn't bother). Will be ironic if it's been the pump all along, and that simple test could have saved me all this frustration. I should know in a couple days when the new pump arrives. Meanwhile, I'll try and build a decent aux tank.

 

Have a look here
https://www.ebay.co.uk/itm/Wrench-X-...sAAOSwmBxa10xr

 

Thanks for the link. I've always thought those were expensive for what they were and planned on making my own. But in retrospect, the value of the time I've spent chasing these bugs (and wasted dealing with my juice bottle), makes their cost insignificant. Ordered...

 

They are durable too ,had mine for quite some years now

 

Well, received the new fuel pump ($195 <sad face>) and aux tank. Got everything connected, and same result. <sigh>

I noticed that the fuel pump is indeed working (just as the old one had). I can see it fill the line, and 'tick' a bit of fuel into the system every few seconds. However, looking down the carb throats, it's completely dry. (When it briefly started working a few weeks ago, I noticed fuel seeping out of the needle jet orifice). But even opening the throttle (which immediately kills the engine), nothing comes out of any of the 4 needle jet openings.

After idling for 4 or 5 minutes, I had to leave the house for 10 minutes to pick someone up. When I returned, I realized I had forgotten to turn off the aux tank valve. Puzzlingly, there was gas pooling on top of the butterflies... leaking from the jet needle orifice! Opening the butterflies with the throttle, (engine off), the carbs made all sorts of gurgling and hissing sounds, and I could see more fuel leak out of the jet needle opening. Fearing fuel was gathering on the piston of the cylinder with open intake valves, I immediately held the throttle wide open, and cranked the engine. It eventually started (and sort of responded to throttle), but not smooth, and would not idle.

At this point, I'm out of ideas. There is obviously something fundamentally wrong with the carbs, but I'm damned if I can figure out what. I've cleaned everything, blown through everything, and replaced everything on them I can think of.

I guess it's time to take it to someone. Either I'm overlooking the obvious, or it's something esoteric that needs an 'expert'.

I'm ready to be riding instead of messing with it. Anyone in the SF Bay Area know of a good bike mechanic?

Thx for all the suggestions.

 

Hi , could you at least take the carbs to a mechanic to set them up, not calling your mechanical skills , but he might see something you missed , easily done,

 

No worries about questioning my skills. Definitely lacking in the experience department. I'm feeling pretty incompetent at the moment. Carbs are not that complicated. :/ The assumption that anything I replace with new is necessarily working correctly is probably not a good one. I still think it's the float valves... but what else can I do besides replace them? I've read of someone polishing the valve seats, but I can't believe that's necessary for a bike with 5k miles (and multiple cleanings). And it's hard to believe all 4 carbs have the exact same problem, but I can't think of any other part of the fuel system common to all the carbs (upstream is tank, filter, pump).

I was thinking the same thing... bring the carbs to someone and see if that can find something obvious.

By the way, that aux tank works well (especially when you have the hose clamps tight enough not to leak!)

Thanks!

 

Yes, you have them all Spark ,Air and Fuel, just a worry why the fuel is getting past the Float Needles , gravity feed is only air pressure whereas the Fuel pump is twice that, but still it leaks into the cylinders. A conundrum indeed

 

Your issue does sound as if it's in the needle jet area. Earlier you were asking about them. Here is a video showing what they should sound like and the amount of effort it takes to move them, hopefully it will be of help.

 

Thanks.
Here's my slides... a bit slower than in the video above: