METHANOL TO PETROL 1

[jsteve1999]

Hi All
I have a 500 cc motorcycle engine that runs on methanol
I only want to run the machine a shows so is it possible to
to convert it to run on petrol,as it will never be racing
The compression is 15:1 ignition advance is 42deg BTDC
lubrication is total loss carb is an 34 mm amal setup for methanol
Also would this be a viable proposition
I the answer is somewhere in the forum I apologize for not being able to find it as it is the largest I have ever seen
Kind regards
Steve

 

[evelrod]

When I was in my late 20's and early 30's I did a lot of hillclimbs on methanol burning Bultacos. A 250 Alpina and a 360 Bandido. The change to methanol from gasoline was pretty severe with specs very similar to what you have stated. I limited my CR to 14:1 and advance to ~50, depending on where I was racing. The mix was de-gummed Castor oil at around 40:1 mix. Changing back to anything less than 110 octane racing fuel would only be possible if you could retard the timing to about 30 BTDC (a guess, you might need more or less).
Jetting in the Amal is easy enough, the larger needle valve will not be a bother on gas, but the timing is not an easy or quick change...at least it was not easy in the 60's era bikes.

My real question is why do you want to do this? I know it was a PITA to flush the system after each event, but I could take the tank off and swish a bit of gasoline around in it...take the bowl off the Amal and clean it. The fuel lines and valves never gave a problem. If you leave the methanol in for any length of time, though....big problem!

Rod

 

[jsteve]

Hi Rod
thank you very much for the info thought it may be more complicated eg. comp ratios piston change etc
the reason is that I will only be running the bike at shows now and again and with all the associated problems with methanol I thought it may be easier to change to petrol and eliminate them all together
the timing is dead easy to adjust down to 30degs or so
as the engine is 1971 and is original I don't want to do any mods that are not easy to reverse
once again many thanks
Steve

 

[swall]

Is this a speedway racer?

 

[evelrod]

If the timing is that easy to change and you can properly re jet the carb, using high octane race gas, 110 or 116 , then I don't see the change as impossible.
I would, however, limit any full throttle or any long time on the engine at the 15:1 CR unless the bike is water cooled and you do proper testing.
I run my '63 Mini Cooper 1380cc vintage racer at 14.98:1 CR and 32 degrees ign. advance on VP 110 octane. Your bike should survive well enough.

Rod

 

[patprimmer]

Cooling and compatibility of seals is the only problems I see. Oh and maybe the idle circuits might be to rich at their leanest settings. A deliberate calibrated air leak, like drilling a small hole where it is not obvious and easily plugged might help if that turns out to be a problem.

Heat will be the most likely problem.

Regards
Pat
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