RPW, that looks suitably hooligan. Time I had another BSA methinks... (C15 @ age 17, followed by a B25 / C15 bitsa - which was a lot of fun and passed my test with)
Mate , it says 4.00 18 on my back tyrepaint a mark on the floor and a correzponding mark on sidewall. air up the tire and sit on the bike. then roll the bike forward until the mark on the tire is against the floor again.meazure between them with a tape measure. that iz the circumference of whatever tire you have
my avons are 81.4 inches in circumference
I,d like some advice on gearing please
I have 1971 Firebird scrambler that I've bought back to life after it had a fourty year nap
Unceazed the clutch , drained all the water out of the gearbox and got it moving again
Seezed oil ring and big rust Mark on the bore , so new 3 size over piston and rings
It goes like a champ and I love it to death but to me it seems to rev way to much
Standard it was doin 6000rpm to do 60mph , which seemed to me way to high , I didn't want to blow it up just keeping up with traffic , not that there is much where I live
I changed the front 18 tooth sprocket for a 20
It's way better , 5000rpm at 60 mph but it still feels to high
The back sprocket is a standard 47
Can I change it for a smaller one , do they even make one ?
Or should I just put up with it , smile and wave ?
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Or maybe this way , like Dave suggestedDon't know if this would work- at least to confirm your tachometer?
A phone/satnav can check speed as can a mate following
Know anybody with a strobe that reads HT pulses?
Hello Kevin,i have an excel spreadsheet that takes primary gear tooth counts, final drive gear tooth counts, gearbox internal ratios, tire circumference, rpm, and road speed, and lets you generate any of these from the others. if you want to know how fast your bike is going at 6000 rpm, you type in 6000 and press enter. you will get road speed in all gears. or if you want to know how fast your motor is spinning at 100 mph, you just type in various rpms until 100mph shows up in the speed cell currently it has columns for BSA A65, T120RV, T150 five-speed, T120 4-speed, T120 4-speed close ratio, T140, and my daughter's 2007 ninja 250. you can edit it for any internal gearbox ratios, tires, rpms, sprockets, whatever. you can add any bike you have the numbers for.
i haven't been able to make it work reliably for tire growth, wheel slippage, and rpm drop between gear changes, but i'm working on that. the solution fields look like his:
i don't know how to make it generally available, but i can send it to anybody who is interested.
thank you, dave. i'll see what i can do. th eprobblem i have is mostly mathematical, as the tire growth macro i wrote up works backwards. so far i've just been setting the multiplier to 1.00, and ignoring it.Kevin, since the end result of the calculation is speed, to factor in tyre growth you have a cell with the growth equation based upon RPM of the tyre then multiply your speed with the growth. Put in a macro that recalculates the result. Hit recalculate until the speed number stops changing.
This is what I do for the oil pressure calculations which are recursive, from the Machinery Handbook.
I have one of those old tach and dwell meters that hook up to the coil. Still works.