Old bikes and modern fuels??

[Dooma]

My missus just got an old 1955 Triumph speedtwin from her Dad and it came by sea from Denmark, I spent a day polishing it and a day tightening everything and chasing spark around, finally fired it up and have done a 20 km ride to feel it out,
(great fun) but I think it's running a bit hot with 95 and some valve master in it,
as I've never ridden anything so old before I dunno what the hell to run it on?? can anyone help me out ???

[Motu]

Nice one,she's lucky.Depends on how standard it is,after 50 years it will have been apart at some stage....regardless of how ''original'' her father says it is.A stock Speedtwin will have pretty low compression and 91 will be a higher octane than it saw when new.The trouble is it will have soft valve seats,and there could be valve recession with extended use.(Personally I saw a lot of valve recession back in the leaded fuel days,but never seen it now.Mainly because the old cars are all off the road).If someone has fitted higher compression pistons then you'll need to move up to 98.Modern fuels go ''off'' quickly,so if it's not going to be used for over a month drain the carbs,or run them dry before putting away - fresh fuel in the bowl and it'll fire up no worries,with old fuel you'll have problems getting it going.

Distributor or magneto? A Speedtwin should have an alternator,and the first thing I'd do is convert it to 12 volts....no need to change the alt,just a rewire of the rectifier and a few other mods.

[Dooma]

It's got an alternator / distributor set up, has been restored somewhat I think,
as it has a 12 volt coil so my localautosparky sold me a 12 v battery. but the dude was just the storeman so???
I'm a fitter turner but not that big on electrics so I hope I'm not cooking everything etc..

[Ixion]

Presume it's still got the iron head. Those 5T engines ran pretty hot, I've seen the cylinder heads glowing dull red. Didn't seem to bother them over much. Back then petrol was about 70 octane, so even 91 is excessive. 91 octane (even more so 95) will burn slower than the fuel it was designed for, so you may need to VERY CAREFULLY advance the ignition (this is where a magneto with manual advance is nice). Since the ignition is , effectively retarded (even though it's correctly s et) , that may contribute to hot running.

Nice bike. Very nice. I had a 57.

[Dooma]

Thanks Guys, I will try a wee tweak and change to 91, and see how she goes,