Fuel delivery for bench test

[Brendan65]

I'd like to check my float valve seals with the carbs off the bike and I'm looking for suggestions on how to rig up the fuel line.
I guess I could take the gas right from the bike's petcock, but that doesn't sound safe ... or might not deliver enough fuel pressure without the pump or extra height.
So I was going to have an elevated container with a fuel line - just trying to figure out the best way to go about it.
Any tips would be appreciated !

[WingAdmin]

I'd like to check my float valve seals with the carbs off the bike and I'm looking for suggestions on how to rig up the fuel line.
I guess I could take the gas right from the bike's petcock, but that doesn't sound safe ... or might not deliver enough fuel pressure without the pump or extra height.
So I was going to have an elevated container with a fuel line - just trying to figure out the best way to go about it.
Any tips would be appreciated !

That's the normal method - hang a bottle up high, and a fuel line leading down to the carbs, kind of like a gasoline IV for your bike.

You can get them on Amazon for $10, and they have a petcock built in as well: https://www.amazon.com/Royal-Vintage-Sp ... ref=sr_1_2

[Brendan65]

Thanks for the link - that's what I was thinking of. I'd buy one locally if I could find one. But $20 shipping to Canada and I need it today means I'll fabricate my own, I'll just check my fire insurance first !

**edit** I found it on Amazon.ca for $15 delivered, so I bought one. Shipped from India so I'll still use my jury rigged system this time.

[Brendan65]

OK - I had fuel coming out of carbs 1&3 ... also had a fair amount of fuel in the plenum.
The carb assembly was level so I'm wondering if the gas could run from the carb throat into the plenum ?
There's no other way for the fuel to get in there ?
Anyway it's good to know - I plan on checking everything regardless ... we'll see what the "post service" bench test reveals.
(probably leak just the same with my luck !! )

[DenverWinger]

Fuel goes into Carb #3, then flows thru passages in the plenum to get to the other carbs. Likely bad seals between plenum halves.

[Brendan65]

Fuel goes into Carb #3, then flows thru passages in the plenum to get to the other carbs. Likely bad seals between plenum halves.

Excellent info. I was hoping not to split the plenum this time around, looks like I might have to.

[Brendan65]

Update ... I rechecked all the float seals and float levels. I made some adjustments ... but now they appear to be sealing properly and I don't think there's anything more I can do there.

When I split the plenum I found that I had previously put one of the guide pegs/tubes in the wrong hole ! Rather than in the bolt hole it was in the air hole right beside it. Moved the peg and used a new gasket (though the old one was still fairly new) and decided to try another bench test before going further.

Still leaking - watching carefully, the gas is filling up the plenum from the carb side and not the middle where the gasket is.
Also, if the float seal was leaking I don't think the gas would run uphill to the plenum, which makes me think it's leaking somewhere where the carb attaches to the plenum.
Once the plenum then fills up enough, the gas begins to run out the carbs. (all 4)

So I'll remove each carb from the plenum and look for trouble where they attach ?

[MattMcCoy]

Did you replace the o-rings between carb bodies and plenum?

[Brendan65]

Did you replace the o-rings between carb bodies and plenum?

I don't remember ... but they look pretty rough, so probably not !
If you look closely at the photo the face of the carb is covered in gas (you can see it around the locater pin). I'm guessing the fuel has leaked past the O-ring, and then on to the plenum.

Thoughts ?

I really appreciate any insight !!

[Brendan65]

Update - all 4 carb faces are coated in gas. Looks like the O-rings (which I did replace) are too thin and are not sealing.
The O-rings are from a cheap eBay carb kit ... live and learn !

[Brendan65]

Just a thought while waiting for the "carb-to-plenum" o-rings to arrive ...
Maybe the fuel o-ring isn't too thin, but the large air o-ring is too thick, keeping the fuel ring from contacting the plenum.

Looking at it, the air ring is obviously thicker ... though I guess it could be softer. I still have the old air o-rings and they appear to be the same, which may have been the problem right from the start (4 months ago ! ).

Well time will tell when those fuel rings arrive.
(sorry for the rambling )

[Brendan65]

Update - got the new O-rings installed. They were definitely thicker .. but carbs still leaked gas.
I gave up and bought a rebuilt carb set and now the bike runs great.
The rebuild guy was fairly sure it was the float seal - though I had tried 3X to fix it (need more experience !)
So the bike is on the road just in time for winter !