Hi guys can anyone let me know how the speedo drive comes apart on a Bantam B175 please
It would be worth saying why you want to take it apart? If you carefully prise off the large circular dust cover and remove the felt washer, you can then clean out the old grease although it can be a bit of a challenge to get it completely clean before re-greasing everything including the felt washer.
Thank you for your reply, The gear is locking up when your turn it, after about 1 1/2 turns it locks solid I was hoping to clean it out and get it running free. Is it just general purpose grease I use on asssembly?
Hopefully, cleaning it out will get it running freely again. I normally use a high temperature wheel bearing grease for speedo drives. In the old days, this would have been Castrol LM grease!
Before you take it apart, it might be worth checking that the grease nipple is not jamming the worm gear - simply unscrew it and see if that makes any difference.
you could try "flushing" it through with 20-50 oil and se if that frees things up - usually the crown wheel and pinion wear badly and lock up - if you look for a replacement then the ration is 19/10
thanks guys I will let you know the outcome
ok guys upon further inspection it looks as if the worm drive and main gear are badly worn causing it to lock up every now and then any suggestions for a replacement unit?
I am sure you could eventually find one on eBay but they can be bought new from, for example:
https://bantamspares.webs.com/frameswingingarmetc.htm
The original part number was 19-9207 (assuming same as a D14/4) but the above website says the one they do (99-9976) is compatible.
the B175 ratio is 19:10 im not sure what kind of discrepancy this would produce
You would have thought the bantamspares website which specialises in BSA Bantam spares would give correct information - they list speedo drive 19-9207 used on both the D14/4 and the B175 as having a 2:1 ratio, the same as part number 99-9976 which they have available as being compatible.
However, I think IANAGC could well be right and a ratio of 19:10 was what was originally used with an 18" rear wheel. That said, the difference between these two ratios is not that great. If you use a 2:1 ratio rather than a 19:10 ratio speedo drive, the speedo will read 31.5 mph rather at 30 mph or 42 mph at 40 mph which I personally would not worry too much about.
Looking into this issue a bit further, a Bantam with a 18" x 3" rear wheel theoretically needs a 19:10 speedometer drive. However, if a 2:1 drive is used, the speedometer will read 31.25 mph at 30 mph. Bearing in mind that a 50 year old magnetic speedometer will almost certainly produce a much bigger error than this, using the wrong speedo drive is probably not worth worrying about.
The bigger problem in finding a replacement will probably be to find one that suits the 5/8" spindle diameter used by the Bantam B175 compared with the more standard 3/4" size. Bushing the latter type to fit might be worth considering.
I have found in my garage a 19-10 speedo drive with a small centre hole.