Interesting read on Methanol in Petrol & Plastics

[Linegeist]

Saw this link on the historic car forum I regularly infest. Given the plastic tanks on Skorpions, this might be relevent to you too.

http://www.fbhvc.co.uk/fuel-information/

Bob

[Anders]

Since most cars currently in production use plastic tanks, and that there has been a 5% precence of ethanol in gasoline in many countries the last 15 years or more where the Skorpion has been sold, I would not worry too much about it.

If there was a problem it would have become apparent long ago.

Also some of the other conclusions drawn are greatly exagerated, especially the volatility risks of mixing pure gasoline with a 5% ethanol blend. Switchloading and its inherent risk is well known and the practice regulated in the fuel distribution industry but only in the context of mixing gasoline and E85, or gasoline and diesel in a distribution truck or storage tanks where there is a risk that small amounts of one fuel is still remaining when a new load is recieved or transported.

At any rate any vehicle that can run on unleaded gasoline is modern enough not to be affected by most of the concerns listed in the article as it mainly deals with the running of antiques (well sort of) on modern fuels.

[samandkimberly]

I dunno about that. My Skorpion tank is clearly bigger than it's supposed to be - until I modified it it did not fit in the original brackets, and this is a very clean, certainly never crashed bike. I also have a Montesa trials bike, also with a Nylon66 tank. The tank fits the frame OK, but just barely, not the way Honda made it to fit, I'm sure.

My own conclusion after some research is that ethanol does swell Nylon66 tanks slightly, but then stops as the ethanol is absorbed by the nylon. That may be why many have OEM paint problems. I had to respray mine but after a year it seems fine.

Sam

[Anders]

True, swelling may be a problem, have not noticed anything myself on my -95 Skorpion (owned it since 2000) and there has been 5% ethanol in the tank since it was new.

Swelling of polymer based materials (or shrinking for that matter) can also be contributed to the addition, or removal, of other fuel additives as well. The removal of lead, and later the lead replacement additives, is the main cause of membrane swelling in the CV carb on the 660's.

A curiosity with polymers and exposure to fuels is that the effect on swelling/shrinking can be diffrent depending on how the exposure was made.

For example, substance A and B both cause swelling of an o-ring, but if you first expose the o-ring to A and then also B it can result in shrinking but not if you reverse the exposure then it is still swelling... I have seen this on a few occations when we have tested materials for the effect on fuel exposure in the lab at work (Saab Aerosystems -> http://www.gripen.com).

[Bill Jurgenson]

Gas definitely does swell the tank, but I don't think it is due to the alchohol content because my tanks have "always" been too big. I bought my first Skorpion in 1994 and I don't believe that alcohol was being added back then.
Anyway, when the tnak has been empty for some time, as with my racers or with those bikes I had here for tuning etc, it falls easily into it place with room to spare, but after being in use, it must be forced.