MX Tank filler neck/cap leak

[Doug Bridges]

I just finished restoring an MX tank for my Jackpiner. It looks great on the bike and I am very happy with how it turned out except that it is leaking bad between the cap and the filler neck. I have tried three different caps and used a new cork cap gasket and one of the caps has a rubber gasket and seals great on my toaster tank. I am sure that the problem is that the filler neck is not flat on top. If anyone has any suggestions on how to fix this I would be grateful.

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[joe novak]

Hello,  Inspecting the filler neck to determine if it is flat is a great idea, Doug.  I have not used this technique, but what I might suggest is to place a piece of glass or mirror over the neck.  Glass is usually very flat.  Then look to see if the the neck is irregular for flatness.   Maybe use lead or solder to fill in the low or irregular areas.

[firstturn]

Doug,
  You can use the glass as Joe suggested or just a flat surface and find the high spot(s).  You can take a a high quality fine file and file off the high spot(s).  I do like the die of using the glass, but I also have a piece of granite I use.

Ron Carbaugh

[Doug Bridges]

Thanks guys! I determined yesterday that the filler neck was not flat by using a flat surface to compare it to as you suggested. I used some epoxy to build the surface up and then used some 100 grit self adhesive sand paper on a flat plane to sand it down even. I tried it this morning and it sealed things up very well. I am not sure of how durable the epoxy will be in this situation. I used a quick set variety just to see if it would work, but I also have some other types that may be more suited for this application. I am reluctant to try soldering or applying heat to the tank as I have already painted it with two part acrylic enamel and am afraid of damaging the paint or fiberglass. I had leak checked the tank before painting, but had not thought of the filler neck leaking like that and I still can't figure out how it got like that in the first place. This tank was in very rough condition when I got it and I am kind of proud of how well it looks now. I will post some before an after photos later in the week.
Thanks again.

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[joe novak]

Looks like we are going to learn a lesson from you.  The epoxy is a great idea.  I also would attempt epoxy always before adding heat to a sensitive area.   The great thing about fibergass is that it is so easy to repair.   You probably know that the ceramic tiles on the surface of the Space Shuttle are epoxied on....  Yeah, that is how great stuff like "epoxy" is invented: for the space program.  Then it makes it's way to the public.   If I ever buy a Penton gas tank, I will check the surface of the filler neck.  Thanks for that tip.  joe

[Doug Bridges]

Yes Joe, epoxy is amazing stuff. I have a wood boat that I built and use on the Strait for Salmon fishing that is held together for the most part with epoxy. I have to trust the stuff and I am always looking for new ways to use it. If I could get my hands on some of that space shuttle epoxy I could probably just throw away the welding equipment.

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[Charles Gresham]

The expoies are priceless.. universal uses !


1974 Penton 250 Hare Scrambler
1974 Yamaha MX100
1973 Honda CL 100
1978 Suzuki RM 125
1983 Honda XL 185
1993 Yamaha RT 180

[242]

I though all old dirt bikes gas caps leaked, bad brakes, and a lot of spark plugs. As a old Penton dealer I used to sell slopper stoppers for the cap, brake seals for the brakes, and a spark plug holder for extra plugs, that was in the good old days. Also we carried extra gas on the handlebars and water in a Army cantine.