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Urgent safety briefing for all owners of classic motorcycles with fibreglass fuel tanks or steel tanks containing sealant.

Bioethanol is now a component of unleaded fuel and has been since the beginning of 2008. Currently the concentration is 5% soon to be increased to 10%.

Bioethanol is not compatible with most fibreglass resins, an unknown number of epoxy sealants and some carburettor components, usually indicated in manufacturers lists as not for use with alcohol fuels.

There is a very real risk of unexpected, sudden and catastrophic failure of the fuel tank causing loss of containment of the fuel.

Just as likely and only slightly less dangerous is the risk of stuck throttles, fuel taps and damage to carburettors, likely to be irreversible in the case of Mk1 Amal Concentric carbs. This appears to be due to the dissolved resin reconstituting within the venturi and inlet tract.

First symptoms may be difficult starting and poor running as the carburettor becomes increasingly contaminated.

Interestingly I have an email reply from the Dept of Transport resulting from my enquiry as to what safety warnings have already been issued. They say they are aware of the problem but have not issued warnings nor consulted any relevant organisations but that they may talk to the Federation of British Historic Vehicle Clubs (FBHVC) at some point. I emailed this information to the FBHVC who frankly were less than interested, saying that the had already covered it in their newsletters.

Please put the word out and copy this briefing to any other web site before some poor soul gets killed or suffers serious loss. I nearly lost my entire repair facility as a result of the failure in storage of an Enfield GT glassfibre tank over a warm weekend.

In my haste to get the safety message out I omitted to include any suggested solutions mainly because I have no sure fire fixes that I can recommend at this time. I certainly don't want folk bringing tanks to me for attention as I already have had many life times of exposure to all manner of toxic chemicals and I have no wish to add to it on a commercial scale.

I can report that I am currently experimenting with a phenolic epoxy sealant, said to be ethanol tolerant and suitable for fibreglass and steel tanks alike, although what to do if you already have compromised sealant in a steel tank is anybody's guess. On the up side, I have very recently found an old Goldie tank which is more sealant than steel in which the unknown sealant is entirely unaffected.

Conversely, one of my clients recently purchased a brand new fibreglass tank for me to fit, from a dealer I am not prepared to name, having been assured that it would be suitable for use with current pump fuel. After two weeks with a gallon of unleaded in it it started to melt. It turns out that neither the dealer or the manufacturer had the faintest idea that pump fuel now contains ethanol.

Two final warnings: there is a suggestion that ethanol is quite good at absorbing water and therefore may cause steel tanks to rust, so keep a watch on the inside of your unlined steel tanks. Adding a drop of two-stroke oil, Redex upper cylinder lubricant, or even a drop of castor oil to the tank from time to time might afford some protection. Lastly in the event you have a two-stroke with compromised sealant in the tank all that goo is being sucked straight into your crankcases and may even now be interfering with the roller big end. Just a thought.

Running classics on unleaded fuel.

I thought everyone was up to speed on this subject and so I did not carry the notes forward from the old version of this web site, so here it is for anybody who is still in doubt.

You do not need to have your valve seats replaced for running on unleaded fuel if they are in serviceable condition. Anyone who tells you different is doing so out of ignorance or for some other reason.

Residual lead, or lead memory contained within the seats will probably continue to protect the seats for many years to come. When this protection comes to an end, the early warning will be tappet clearances closing up, and even then you should be able to re-adjust the clearances a number of times.

After ten years of largely lead-free running I have yet to see a single case of valve seat recession due to a lack of tetraethyl lead in road fuel.

Similarly you do not need to use any additives or so-called super unleaded fuels; you may however need minor adjustments to either ignition timing or carburration. If you are suffering from pinking or detonation of any kind, get these adjustments done now or risk piston damage.

Electronic ignition is of course, most recommended on higher compression engines.

Again, in the last ten years I have not encountered a single machine that could not be harmonized for running on unleaded with anything more than minor adjustments - even with the addition since 2008 of up to 5% bioethanol in unleaded pump fuel.

Text and graphics copyright (c) 2008 RJM Classic Motorcycles.