Suzuki T20 Fiberglass Tank

A reader wants to check with tech editor Keith Fellenstein about the fiberglass tank he’s wanting to coat.

Reader Contribution by Mike Corcoran
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by Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.

Suzuki T20 GP kit

Q:I have a NOS GP kit temporarily set on one of my T20 projects, just to get a visual. It is two projects away from starting and I’d planned to Caswell coat the tank for ethanol protection. It will get ridden several times a year and taken to our Western VJMC rally. The tank will be drained when not ridden. My understanding is the Caswell product can be used to protect fiberglass tanks from our wonderful Cal-ethanol “gasoline.” I’ve used it successfully on a couple of needy steel tanks. You recommended that Joe M. replace his GP tank with a steel one, and if it was never coated, I would agree. My tank has never been used and appears very solid. Would you have any reservations about my plan? I can hardly wait to get the first, of three, T20s together with the GP kit and stainless Higgspeed pipes on the road.

Mike Corcoran/via email

A:If it’s a virgin tank, I’d have no reservations coating it in order to use it. Just go completely by the instructions. Being a bit paranoid, I’d probably see if there was enough in the kit to do two tanks, and do a double coat in case there were any voids in the first coat. The tunnel can be particularly hard to coat properly. Another problem area is the interface between the fiberglass and the metal bungs for the petcock taps. It will be difficult to get the perfect seal between the glass and metal. I’m not saying it can’t be done, but it could be a problem. A couple of people with Norton fiberglass tanks have gone to the extreme of cutting the bottom out and coating the parts, then reassembling to assure complete coverage.

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