Plastic Fuel Tank Restoration

[OhioTed]

Hi, all.  As this topic does not apply specifically to Penton motorcycles, please delete it if deemed inappropriate.  

We have an advantage in the fact that Penton Sportcycles' original fuel tanks were of fiberglass construction.  Why?  Well, fiberglass is actually quite durable, repairable, and lends itself very well to restoration.  Case in point, look at all the perfect tanks on Pentons we see at every POG gathering.  Beautiful paint and graphics, with nary a "bubble" to be seen.

Bubble?  Oh, yes.  Everyone who has made any effort to paint a fiberglass fuel tank knows full well that fuel vapors migrate through fiberglass, and/or have already permeated the fiberglass, and do not care one bit to be inhibited by total sealing from the atmosphere by even the most beautifully laid-down paint and clear coat.  The result?  Bubbles - and anguish on the part of the proud owner.  

Fortunately, thanks to intrepid individuals such a Mike Winter, there are practical solutions.  Mike has graciously shared his tank-sealing process, gleaned from considerable trial and error evaluations, and we all benefit from his R&D.  

However, just as Penton Sportcycles were beginning to be marketed as KTM's, so came the demise of fiberglass tanks in favor of those molded in plastic.  The perfect solution to certain drawbacks of brittle fiberglass.  In some ways, yes.  However, in the world of vintage bike restorations, plastic fuel tanks have become the bane of our existence.  Mike and I have recently revisited the process of sealing fuel tanks, and I've shared some questions and proposals with respect to plastic tanks.  Please read, and share your thoughts and experiences.  And again, please take down this post if inappropriate.  Note, my e-mail to Mike included some photos, but process of applying images to POG forum too time-consuming and cumbersome for me to include them here.  

Thank you so much, Mike.  Your insightful and well-researched information is greatly appreciated.

Considering the overall success we've achieved with applying your process to fiberglass tanks, have you ever given any thought to how to address plastic tanks?

This is something, which has been rolling around in my head for several years now, as proper restoration of a vintage dirt bike is considerably hampered, should the bike feature a plastic tank.

I have to date made one effort to process a plastic tank - the original one on my 1975 Can Am 175 TNT.  I first prepped the tank, then applied Caswell tank sealer.  Note, don't know why I departed from your proven method of using POR15 paint.  That detail lost to my failing memory.  I then painted/clear coated the tank, and applied fresh graphics.  In short, it worked!  Despite that old tank having obviously been permeated by fuel vapors for years, the paint and graphics stayed perfect for months (years?) - no evidence of bubbling.  Fuel was introduced into the tank, but of course not stored in there.

We eventually took the bike with us over to the ISDT Reunion Ride, in Massachusetts - to show off, and for Al Buehner to ride around on.  Al was having a great time, and the Canned Ham was turning plenty of heads.  All was right with the world.  Then Al showed me a bubble in the tank-paint.  Uh-oh.  A look inside showed the Caswell sealer has split right down the length of the back-bone portion of the tank, allowing fuel to get in between the liner and the tank.  And, that was the end of my "perfect tank".

Question is - why did the Caswell product split like that?  The process I applied, otherwise appeared to be effective.

Since then, I've been stalled on the whole process.  Bob's son, Quinn, recently made us up some perforated graphics for the Can Ams.  No help.  Bubbled like crazy.  And, interestingly, the perforated graphics likewise bubbled on a brand new tank, stored dry, which I applied to the '75 Can Am 250 MX2, which I built for AHMRA racing.  So, the search goes on for a solution to addressing plastic tanks.

Your thoughts?        

[Richard Colahan]

The Caswell has held up fine in the f/g tanks I have used it on...but I'm not sure it can actually "bite" into the plastic material quite as well. But that's just a guess...I won't pretend to be a chemist.
I'll also say that considering the overall low mileage we do with our vintage bikes (except Rick Bennett...)I use VP Vintage E-0 fuel every time I race. Or it's equivalent. A bit expensive but well worth keeping the ethanol "solvent" out of the fuel system.

Richard Colahan
1969 V1225
Upper Black Eddy PA

[Larry Perkins]

We have Premium Unleaded with no alcohol and 100 octane with no alcohol both of which will work and far cheaper.  Your state may be not as fortunate.

Larry P

[paul a. busick]

I had entered my suggestions here on repairs of fiberglass tanks a long time ago and it is the same with plastic tanks.  The tank must be very clean. Make a rotisserie.  Put a hand full of dry wall screws into tank and let it go round and round.  Next, wash tank out with acetone to wash out dirt, etc..  You will need to purchase a chemical grade EPOXY. It is best to rotate the tank
by hand to evenly distribute the resin to the inside of tank. Check with the WEST SYSTEM people. Email address----
 [email protected]  I'm sure that they have updated their epoxys over the years since I last commented on this subject. Tell them what you are trying to do, they a very helpful and may provide better ideas them I have. I hope that this may be of help to you plastic tank members.  The usual disclaimers are in place-so continue at your own risk Amherst Paul