Skyhawk GTA2 Air in Fuel Line Problem?

[Hello Moto!]

So lately I've been havin a hell of a time with air in my fuel line. Before I start the bike I can see that the fuel line between the carb and the inframe tank is empty. When I turn the petcock on..it remains empty. What I then have to do is basically squeeze the tygon fuel line repeatedly to get fuel flowin. Once I get fuel goin and all the air squeezed out, it will start and idle fine. During riding I can see air bubbling through the fuel line and eventually the engine dies. Once stopped I have to repeat the squeezing process to start and the cycle just repeats itself.

What I'm riding is a Skyhawk GTA2 frame with the in frame tank and tygon fuel line with an SHA clone carb. What I've noticed is that when I completely remove the plastic gas tank cap, The problem goes away. Well...I can't likely drive around with fuel splashing everywhere. So, what do I do?

If it's a ventilation problem with the cap how can I go about resolving that issue?

If I can ride it a little further my tank will be near empty and easy to drain so I can inspect the petcock. That's another thing I thought might be causing problems but I don't know. I even tried completely removing the inline fuel filter and still no better.

What do you guys think? Anyone had a similar problem?

It's incredibly annoying!

 

[Frankfort MB's]

To fix air in the fuel line push the tickler button on the side of the carb.
I don't have experience with that frame but it seems like you have a fuel lock.....
There should be a vent in the cap but if there isnt you will have to make one by, all that should be is a small hole

 

[Frankfort MB's]

Oh I'm sorry. The tickle button is only on the NT carb that I remember..... I'm not sure

 

[Steve Best]

Hello Hello!
It is not a problem unless you have an upward bent in the fuel line. As long as the line runs downhill, no problem.
Fuel flow is so slow to the carb that the bubble stays in the line.
It is not blocking fuel and is not a sign that no fuel is getting to your carb.
It is just a pressurized bubble trapped by capillary action in the line with fuel trickling past it to the bottom of the line.
No worries.

Steve

 

[Neufcruz]

Had same issue. Drilled the holes out 1 size and prefect. To answer your suspicion of petcock or cap ventilation trouble, go ahead and close petcock and remove line going to carb. You then (with cap on, open petcock and observe fuel flow out of fuel line (into clean container) while fuel is flowing (or not) remove gas cap and observe if it flows any better. Should be able to figure it out if one or the other. I'm bettin on cap.
Good luck and report back.
Mike

 

[Hello Moto!]

Had same issue. Drilled the holes out 1 size and prefect. To answer your suspicion of petcock or cap ventilation trouble, go ahead and close petcock and remove line going to carb. You then (with cap on, open petcock and observe fuel flow out of fuel line (into clean container) while fuel is flowing (or not) remove gas cap and observe if it flows any better. Should be able to figure it out if one or the other. I'm bettin on cap.
Good luck and report back.
Mike

I'm now for sure that it is the cap that's not venting right. How exactly did you go about drilling out the holes a little bigger? I'd like it to vent properly but I don't really wan't to have gas sloshin out. I've found that it works perfectly just by not keeping the cap fully tight but I get a little spillage.

 

[Neufcruz]

I'm now for sure that it is the cap that's not venting right. How exactly did you go about drilling out the holes a little bigger? I'd like it to vent properly but I don't really wan't to have gas sloshin out. I've found that it works perfectly just by not keeping the cap fully tight but I get a little spillage.

Mine has holes on the inside oration. Not the outside. I reamed these out and that solved the problem. I'll post some pics early next week when I get back.
Mike

 

[Hello Moto!]

EBay has "fuel tank breather" tubes for MX bikes/quads. These have a one way valve so you can lay your bike down without spilling fuel. Maybe "gas tank breather" in USA. UK ebay has them from £0.99 I would think they can be pushed onto a "barbed & threaded hose connector", self tapped into a hole drilled in the cap, if the cap is plastic (?). Brass barbed & threaded hose connectors are from £0.99 too, same place.

I actually have some of those from an old project where I redid an old lawnmower tank to use on the rear mount of my first bike. I actually made a thread on it in the gas tanks section called crusty old gas tank project lol. I didn't think about it but I guess I could try that as a last resort as I don't really wanna do that without trying something a little simpler like making the existing holes on the cap a little bigger. I think I'm going to have a better look and possibly try what Mike suggested. We'll see how it goes but for right now I'm just riding around with the cap a little loose and it seems to work fine.I'm not losing a lot of gas this way but I'd like to make it work and lose no gas. thanks for the replies guys.