1981 V50III frozen gas cap!?

[Tony/CT]

I picked up a 1981 V50III that has a registration sticker from 2002, so it has been sitting quite a while. It's really a nice little bike but needs some tlc. The gas cap is frozen shut. I haven't picked up a service manual yet but  on this bike, the key lifts up the door covering the cap and I think the cap "screws" off in a conventional way. Is this correct? Any recommendations for removal?

[injundave]

This is the cap on my V50II. If they are the same hopefully this will give you some idea as to how they work.

Good luck

[wrbix]

On my III there's no attachment between the hinged cover and the cap which does simply unscrew ccw. Afraid yours being rusted in place portends bad things inside the tank.
What I would try is: remove tank, drain it of all fuel if possible, blow dry w compressed air, while supported upside down get a gracious quantity of 50:50 Acetone:ATF into the tank and let it sit a day or two to hopefully help free up the seized cap. It'll likely ruin any paint it comes into contact with.

[Cam3512]

I would start with penetrating oil.  Let it sit and soak for days and keep hitting it with the oil.  I use Aerokroil.

Won't hurt the paint.

[canuck750]

Head to Walmart and get some Evaporust. It will not harm paint and only removes rust.

http://www.evapo-rust.com/

I bought enough to completely fill a Guzzi gas tank. I have cleaned a half dozen tanks, some pretty rusty ones by filling the tank to the very top and leaving it sit for at least a couple weeks. Once the tanks is clean pour the Evaporust back into the container and use it over and over again. Once the tanks is clean rinse it out with warm water and soap, dry with compressed air and then slosh Methyl Hydrate around inside, the MH absorbs the water so rust won't form in the nooks and crannies.

If you want to go all out a metal etch available from Eastwoods will leave a phosphorous coating on the raw steel.

[Muzz]

quantity of 50:50 Acetone:ATF

This is a really good penetrating mix. I think it was Wayne Orwig who suggested it yonks ago. Used it ever since.

[Antietam Classic Cycle]

Under the flap should be this cap:



Turn it 1/4 turn counter-clockwise and lift up. Maybe use something to pry up a bit.

If that doesn't do it, I'd probably use (low pressure) compressed air in through the petcock (in "ON" position) to try and pop it off. Or remove the petcock first, especially if there's still gas in it. Cover the cap with a rag or something to catch it, of course.

[Tom]

Twist and lift.  If it doesn't move, the gasket degraded and as stated earlier could be rusted on.

[rodekyll]

Be really careful with compressed air.  it takes very little over pressure to burst weak seams, and from what you're describing they are weak. 

Remove the tank and use a cup or so of that 50/50 mix.  It will be enough to flood your problem area. 

Remember that the cap is vented. 

With your penetrant I'd suggest a strap wrench for leverage on the cap. 

I'd use pressure as a last resort. 

Patience.  You can destroy the cap if you need to, but not the filler neck.

Bring a friend.  Don't try to control the tank and the tools by yourself.

That's all I've got.

[Kiwi_Roy]

Under the flap should be this cap:
 
Turn it 1/4 turn counter-clockwise and lift up. Maybe use something to pry up a bit.

If that doesn't do it, I'd probably use (low pressure) compressed air in through the petcock (in "ON" position) to try and pop it off. Or remove the petcock first, especially if there's still gas in it. Cover the cap with a rag or something to catch it, of course.

]

It's as Charlie says, pretty hard to see how that could stick on minimal metal to metal contact, mostly neoprene or some other elastomer in contact with the top of spout,
Perhaps wrap it in rag and turn with a pipe wrench, remember anti-clockwise.
Here's a picture of my Lario

[Tony/CT]

Thanks for all the advice. That is a picture of the cap. I am able to turn it slightly, but not remove it. I will try some of your recommendations. 

[pehayes]

If you can turn the cap slightly, the tangs on the cap may be hanging on rust blockage in the neck.  The gasket itself may still have some resiliency.  Try to push down hard on the cap while someone else turns it with a strap wrench.  Pushing down might be enough to reduce the contact of the tangs.  Otherwise invert and add rust remover as above to free up the blockage.

Patrick Hayes
Fremont CA

[Tony/CT]

O.K. the cap is off. Charlie's method worked. Turned it 1/4 turn, slipped a screwdriver under the cap and popped it off. Smells like varnish in there, and there is some rust.