Hi, this is my second year of owning my BSA and I've never owned a bike so old so have very little experience, i'd like some help with some issues please.
Apologies if you have covered these in other posts.
1) my front forks seem to have very little (if any) shock absorbency, When i hold the front forks and push forward, the forks seem to bottom out and spring back and forth several times. yes there is oil, and the previous owner said he recently changed the seals and overhauled the forks. i know how front forks should work, but these don't seem to be doing the job. I've come to the conclusion that this is either a characteristic of early forks (1948 model). they might not have been overhauled properly or they have not been overhauled at all. your opinions appreciated.
2) my bike fires up fine, lovely tick over revs and picks up nicely, however whilst cruising (word used lightly) at 50mph i get intermittent surges . its fitted with and Amal 930, (engine is a wm version) which i don't think is the right carb, but should it be working ok?
3) i know this one will cause a few chuckles but at the risk of embarrassing myself here goes. i'm not quite sure i know how to use the advance/retard mechanism correctly. i push it forward to start the bike which seems to work, then at higher revs, i increase it….i'm sure there must be more to it than that ??…… (wally awards accepted)
i think thats about it for now….thanks in anticipation
Hi Richard...Welcome to the forum...
I'm guessing you have a tele fork M20 fitted with a WM20 engine?...
Regarding the forks I would say they have either not been correctly (or fully) overhauled or they might not have the correct oil in them or perhaps the right amount....
Modern fork oil is too light for forks of this period..A straight 30 grade oil is needed...Also verify the amount and type that is in there by draining and refilling with the correct amount and grade...
Working on the principle of doing the easiest things first this tell you whether that is the problem or something more fundamental...
The carburettor you have is the wrong size for an M20..A '930' concentric has a 30mm bore...The size that is effectively the correct size for an M20 is a 26mm or '926' carb...and of course it should be jetted correctly and have the correct slide cutaway etc...
The M20 predates the concentric carbs but they will run OK on one if correctly specified..The original carb was an AMAL '276' of 1" (25.4mm) bore/choke size...
I'm guessing that as the carb size is wrong it may well not be correctly set up to run on your engine either...
The simplest solution if you are not familiar with the carbs is to obtain the correct carb set up with the correct jets etc...
You don't really need to use the adv/rtd lever much....There is a lot of nonsense talked about this feature of the machine....
If you can start the bike with the lever in the fully advanced position do so and don't move it at all when running...
If the bike 'kicks back' when you try to start it 'fully advanced' move the lever to about 1/4 retarded and it should start OK without kicking back...
Once running set it back to fully advanced and leave it there...
If you look at the end of the magneto you will see the points cover...If the adv/rtd cable enters the mag body to the right of the points cover the timing is fully advanced with the cable pulled tight by the handle bar lever...If the cable enters the mag body to the left of the points cover the timing is fully advanced with the cable slack (so with the adv/rtd lever NOT pulled)...
It is worth going to the 'technical section' of this website and looking at the article on 'Setting the ignition timing'...In there you will find a description of how the adv/rtd lever works and an explanation of what advance and retard are....Ian
email (option): ian@wright52.plus.com