[Steve_M90]

For the solution, see the post titled "Residue in petrol tank".

[Graham9]

Steve,
A tank previously treated with petseal will cause problems with modern fuel. I have since treated 2 tanks with 'POR15' from Frosts and their cleaning agents. All I can say is great results, but it does take time.
Be careful with chemicals that remove old petseal as they can be aggressive.
Graham

[VicYouel]

I too have had loads of problems with old Petseal reactions causing blocked carburetters and even seizure of valves and black crystalline build up in the heads.

I recommend http://www.tankcareproducts.co.uk/  who will still send all the dodgy fluids whereas I don't think Frost will?
Vic

[shorrog]

Hi Steve
I am not sure if I can answer your questions authoritatively however I had exactly the same problem on my model 9 which had been laid up for a few years. In the end I decided to clean it and then treat the tank. I purchased a tank repair kit from Frost http://www.frost.co.uk/por15-motorcycle-fuel-tank-repair-kit.html I then cleaned the tank following their instructions,  I used a couple of handfuls of shingle and rocked this in the tank for a good 30 min or so with the chemical cleaner. I then used their sealer on the tank. I did it at the beginning of the summer and touch wood it still looks good.

Hope that helps.
Graham

[Steve_M90]

I have a 1932 M90. I have a residue in the petrol tank (see attached photograph) as the tank was not drained after the bike was last used in 2004. The deposit can be removed by gentle scraping but there is clearly not enough access to clean the whole tank. Do I need to clean it out? If so, which chemicals should I use and do I need to seal the tank after this?