Painting plastic fuel tanks (Ty350)

[Alpina57]

I recently bought a tired old TY350 and have been tidying it up in particular the "duco". This involved respraying the frame,plastics and engine. I read somewhere on the Net that respraying plastic tanks was a hit or miss affair and depended a lot on the type of plastic and the method of sealing ( if required ) as some tanks will let the fuel vapours escape THROUGH the plastic causing the paint to bubble within a week or two. As I had purchased a reasonably expensive set of stickers for the bike I thought i would respray first and see if the paint stuck . It hasn't so I am wondering if anyone has had success ? I have only used good quality spray pack enamel over a plastic primer. The guards and other plastics are fine.... The paint was on the tank for a month or more (tank emptied cleaned washed degreased etc well beforehand) before having any mixed fuel put in. The paint was fine at that point. Also no fuel was spilt on the tank when filling and I just let it sit there for several weeks after. The accompanying photo shows the effect of the fuel vapours permeating through the tank and bubbling the paint after about a fortnight. Luckily the tank "sticker" is just a laminated colour photocopy ! I was going to be sure it was ok before I attached and ruined the real one (from USA at around $180....)

I am guessing if I use a sealing kit from the local auto paint shop on the inside of the tank then I might have more luck, but all the TY pics I see still seem to have the faded stickerless "off white" tank (caused by petrol staining) so I am still not liking my chances.
Maybe the TY's had an early type of plastic that wasn't the best for the job (of holding petrol AND vapours inside ! ) Anyone have any ideas ? Am I on the right track with the sealing kit idea ?


Greg
Kawasaki KS125
Montesa King Scorpion 250
Bultaco Alpina 250
Kawasaki KT250
Yamaha TY350

[60trialer]

Hi Greg, that tanks not a pretty sight - i ended up rubbing my 'pinky' tank with fine emery paper and final turtle wax polish to make it look reasonable, but it is starting to get a yellowish stain again as i have not been using it for the last six months - having searched on various forums i have found there is a lot of different opinions on how to restore plastic tanks - i was going to follow a graphics suppliers advice on pre-treatment before applying decals (http://www.ddgraphics.co.uk/fitmentguide.html ) but seems like it is similar to what you have already tried and still ended up with the paint bubbling, so i will have to have a rethink on how to tidy it up again.

Cheers.

[BOGWHEEL]

D & D use the perforated vinyl for decals on poly tanks (this lets the gases pass through)
i am in the sign industry and have not been able to track down this material yet.
i am thinking of a way to perforate the material i have.
i did find a forum article a while back where they restored a Canam tank by spraying a pvc putty over the tank - then painted and applied decals. could not source the spray putty here though.
i am still looking into the above as a new tank is dead money. It's only going to get knocked up again. It is frustating to spend all that time to resto and still have a daggy tank.

[Alpina57]

I actually have the sticker kit from the U.S.
All the decals are a tough stretchy plastic apart from the tank ones which as you say are perforated as well as having a foil skin backing. The fitment instructions tell you that alignment is critical as you only get one chance, & once they touch they will hang on or tear off(up ?) if a second attempt is made. What you see in the pics is actually a COLOUR LAMINATED photocopy ! I was hedging my bets as to whether the paint was going to stick and conflicting info on the Net meant i just had to try it out. Pity about the paint though. The tank sealer that I am thinking of trying (another $50 ! ) is meant for metal tanks but it seals the INSIDE. I have nothing to lose . I'll just strip it back again if its no good. This all reminds me of a Montesa I once had which had a weeping fibreglass fuel tank. Same thing really the vapours would find their way through the glass fibres and weep out. All you ever saw was an oily bit where it had carried the premix oil through and the vapours had long since evaporated.
Greg