Gas cap won't unscrew

[Armen]

After 23+ years of sitting, the gas cap on my '79 won't unscrew. It just jumps over the little ratchets and makes fun of me with the little SNAP SNAP sounds. I tried shooting some WD-40 under the lip of the cap, but that did nothing. I seem to remember that you can drill into the cap at an angle, leave the bit in place and unscrew the beast. Then cut the cap in half horizontally and remove the cylinder (to install into a new cap).
Anyone chop/savage/threaten their cap into submission?
thanks,
-Armen

[Bob_Roller]

The most common method to get the fuel cap off, is to pull up on the fuel cap handle and then try to loosen it up .

There's a thread by bruce launceston in the R65 Technical FAQ / Procedure section on how to repair the cap after you get it removed .

[georgesgiralt]

Hello !
When I bought my bike new, the dealer was so nice she had only half a litre of fuel inside the tank.
So I went to the station, and, was, how could I say it, somewhat irritated. So I screwed the cap too tight.
When I was for the next refill, impossible to undo the cap. So I went to the dealer's shop and they used the following method to open it without destroying the cap :
One guy sat on the bench, put a towel in the loop of the cap, knotted the towel around it's neck and pulled the cap.
Then the other guy used a metal bar on the loop of the cap to turn it off, unscrewing it. And it worked. you have to adjust the force you use to pull the cap otherwise you hear the ratchet sound if too low or unsnap the cap if too high...
Since then I've been gentle with the cap and hard on the dealer's ....

[CaptainSlow]

I've also read that there is a small hole in the side of the cap (if it has the BMW logo on it) - the hole is on the edge of the cap alongside the logo. Put some small wire (welding rod, coat hanger etc) through the hole and rotate the cap slowly until it sits into a recess in the filler neck. Keep the wire firmly in that recess and turn the cap and it should come off...

I haven't tried this, but I will be this weekend - I have the same issue which I haven't gotten around to sorting out yet.

[bruce_launceston]

Hi Armen, check out my thread in the R65 FAQ / Procedures section and let us know if it works for you.

edit: I see you have a '79 model, if the cap is original and has the bmw logo on it it may need a different technique than the '84 style cap.

[Luca]

My 82 cap did the same thing.  Remove the plastic-ish trim ring from the cap and spray some real penetrating oil around the cap liberally (use the real stuff, it will work better than WD-40).  Then do as Captain Slow says.  I used a bent nail in my case

[flybot]

My '83 sat for 25+ years. The cap was rust welded and it got destroyed during the removal. I think I did the pull and turn and eventualy the black portion broke off. It then took quite a bit of effort to get the threaded base to let go of the tank and rotate. I found a good used cap on ebay. I dont think there are a lot of options for off-brand fuel caps. At least for the '83.

[Luca]

You could also do this...

Drain the gas tank.  Rinse it and fill it with water... you're going to be drilling.

Get the cap lined up as you would like it closed, meaning get the flappy handle and logo set in an aesthetically pleasing manner.

Then do the "snowbum fix."  Drill a small hole, using plenty of lubrication to discourage sparks, in the cap (put it under the handle to conceal it) and drop a nail in there.  Some epoxy might help keep everything together and nice and tight.  This will lock the two halves of the cap together.  You can now get some decent torque on that handle (with a healthy dose of penetrating oil to help keep things smooth)

Once you unscrew the cap, drain the tank and thoroughly dry it out.  You should probably slosh some etchant around in there, as not only will the tank probably be pretty rough inside to begin with, but it will take care of any flash rust you might have encouraged.  You could also reline the tank.  I've got to do mine soon.  The liner doesnt like sitting in a half empty tank for years and years.  Snowbum seems to think that an annual treatment of etchant is sufficient... but he isn't quite god  [smiley=wink.gif]

You can get the measurements for where to drill the hole on his site, www.bmwmotorcycletech.info

[Luca]

also, that will eliminate the locking feature of your gas cap.  But unless you have some real enemies I wouldn't worry about people pouring stuff in there.  If they wanted to steal you gas, they could just pull a hose and turn on the tap.  Come to think of it, they could pull a hose and pour contaminants down it!