Fuel starvation. Run only on choke. Stumble. Won't rev. Petcock?. Synch?.Vent Hoses?.

[Guest]

I want to share this in case someone runs into same.

So Im resurrecting a GS1100E. Supertrapp Header. Added pods and Stage3 Dynojet.
Everything gone over. Checked. Carbs cleaned oh so many times.
Timing, valves checked. Rechecked. Electrics all good.
I even changed all the 30+year old rubber hoses.

And I even made the main fuel line a bit longer so I could lift the rear of the tank up higher to facilitate the removal of fuel/vacuum hoses and electrical connectors.

Turns out that when the tank was in the full down installed position there was a slight upward tilt of the fuel hose as it looped around to go to the carbs.

Could not get the bike to run properly. Started always but Stumbled badly. Always starvation like symptoms.
Pulled carbs a lot. Redid valves and timing a lot. Electrical all checked out.
Pulled the vent hoses. It had to be the pods right. Needed a bigger petcock?.
Nope.


When I set up a remote gas can to do the carb synch the bike fired up and ran perfect.
About two minutes with the CarbTune and I was scaring the neighbors.
This bike rocks.


I was getting an air lock of sorts with having the fuel line not oriented down over its entire run to the carbs. Couldnt really see it with the tank on.
Shortened the line.
Running issues Solved.

Just sharing.

[Brendan W]

Interesting. When light aircraft switched from Avgas to Mogas there were restrictions placed on refuelling temperatures and operating altitudes. The word was the road gas was more prone to vapour lock. I can't imagine gas has improved in that regard. IIRC ball park 10% ethanol increased volatility by 10% or 1 psi.
I suppose it gets hot in there and a hose any longer than it needs is just a bigger heat exchanger and that's before you start to look at extra loops in the wrong direction.

[TiiMuch]

Good add.
Yes. The heat too.
This bike would start perfect and the longer it ran the worse it ran.
Shorter, more direct fuel line completely cured almost all the weird running issues.

[TiiMuch]

I thought it could be the vent hoses and/or the cheap emgo pods too.
So Ive got the APE filters on there now.
The APE filters DO look better. They are bigger and also dont have a lip that partially hides the vacuum apetures on the intake end of the carbs.

So when I get a chance I will test those back to back and see what kind of effects those have on my bike.
Will reinstall the carb vent lines and check for any adverse effects with those on too.

I will post about that here at GSR.

As far as carb covers for a non running/used bike the emgo pods are working well.

[hikermikem]

So Im resurrecting a GS1100E. Supertrapp Header. Added pods and Stage3 Dynojet.
Everything gone over. Checked. Carbs cleaned oh so many times.
Timing, valves checked. Rechecked. Electrics all good.
I even changed all the 30+year old rubber hoses.

Just curious, what size mains are you running?

[TiiMuch]

As per what DJ recommends I'm running the DJ138. That's the largest jet that came in the kit.
Seems good to me so far. I'm at sea level so big makes sense. I will get on fine tuning the setup as I have time.
I've got an additional set of carbs I'm not using and have the adjustable Canadian spec needles. I'm going to set those up and run/tune those for interest.
With seaching this forum I found what seems like a great place to start with jetting for my bikes combination of components.

(142.5 Mikuni main jet, clip in middle groove of 5 on the Canadian spec needle. 47.5 pilot jet which is stock in the Can spec carbs.)

[geol]

Suggest the curve in your fuel line may be kinked. I had a hard time with this when I installed the carbs back on my bike for the first time after rebuilding and putting new fuel hose in place.