Hi, newbie to my B31 here. Managed to put it back together. It ran before I got it (but had been laid up a few years). Main work has been fitting a Refurbished Magdyno. I've timed it according to instructions. When I try to start it, I get one pop, maybe two, but it won't 'catch' and run. Any advice welcome. I have air inlet closed. Tickle carb a little. Timing on full retard. Take it to compression, open valve lifter, turn it a fraction more, then kick with throttle slightly open. Sometimes when I try to turn the engine back to compression, I get a kickback. So I know that fuel and spark are getting there! Many thanks before I have to send the bike off for specialist help!
Is it timed on the correct stroke. Is it timed at 3/8" before TDC.
I'm pretty sure, but will check.
Re check your timing , making sure you are on the compression stroke , once you are sure you are right . Flood it , full retard then pull the decompression lever and kick it over 5 times . Take it over compression with the lifter and then kick it . This is the way I start my DB500 and it works even it has been stood for 6 months .
It's worth taking the plug out after a few tries to see that its not wet and still sparking. If its wet, turn it over a few times with the plug out and wide throttle to clear it out. Mine needs minimum tickling otherwise it floods and wets the plug.
Secondly its worth checking that the pilot circuit is absolutely clear.
Thirdly, all these BSAs need a slightly different routine for starting and you need to learn what's best for yours. There is no chance whatsoever that my B33 will start with the ignition retarded. If I advance it about half way it'll go with one or two kicks, but only with full choke and no throttle.
Many thanks for the advice everyone. I'll take a look again tomorrow. Starting with timing, then will experiment. For a 1954 B31, is retard with the cable tight? Also, after a failed start, when I kick it over gently to get it back to compression, it sometimes "kicks-back" a little. Is this normal?
if the advance cable enters the mag on the left when looking at the points end then it is tight wire retard.
gentle "kick-back" may be the resistance from the valve springs being compressed when you turn the engine over.
if you have "flooded" the engine you can try kick it over a few times while holding the throttle wide open and using the valve lifter. This will often clear the cylinder of excess fuel and you can try starting again.
A daft question I know but I'm now starting to doubt myself: I'm trying to confirm compression stroke (for checking timing). Can I just confirm that it is possible to kick it through the compression stroke using the kickstart - it takes quite a bit of a push (without the valve lifter open)? Or have I got another problem? Many thanks
If you are worried about which stroke you are timing on. Remove the tappet cover and if you can turn both tappets by your fingers then that is the compression stroke.
My B31 (&B33) will always start if I tickle it until petrol drips out of the bellmouth, no choke & slightly retarded - long slow kick and away!
Thanks for your advice everyone. I've found the first problem. My magdyno is cable tight for full advance, and I'd timed it with cable slack :(. So first step is to retime it with cable tight! Will report back how it goes.
Success! Thanks everyone for your help. I'd timed it at full retard (just goes to show you can't always trust the manuals when it says put the cable slack!). Also a bit of technique required, which I'm just getting the hang of.
I got to ride it for the first time ever today. Only up to 20 mph (taking it easy so far), and it is such a charming ride!
Still trying to master the air control valve. Seems to like a bit until really warm...