A65 T/Bolt Gear box Issue

[Minnie33]

Good Morning BSA Enthusiasts.  I have very recently purchased a BSA Thunderbolt (1970 / 650 cc).  As I rode away from the purchase there was 100% adrenaline running thru my veins and I did not really notice anything un toward about the vehicle.  I rode approx 55 miles back home and took my time - no excessive speed.  All seemed OK but the ratios between 3rd and 4th seemed pretty close.  I then proceeded to garage for the night and then go on a 150 mile run in the Derbyshire Peak district - wonderful, but then I noticed one or two issues.   Issue No 1 was that there did not seem to be any difference between Gears 3 and Gears 4.  Changing UP was fine - no problems but twhen changing down - this is where Issue 2 reared it's head -  4TH TO 3RD was OK, but changing from 3rd to 2nd and 2nd to 1st meant numerous pushes of the gear lever.   (I noticed that if I just used gears 1,2, 3 then there were no issues with changing up or down).  Here is the question,  Is there an adjuster that can be used to make engaging 4th gear more positive and feel like a proper higher gear or does the Thunderbolt have a high revving top gear?   I have heard about the gear return spring can sometimes get weak,  would replacing this solve BOTH issues ?   I spoke to the seller, and he tells me that he has had no problems with it at all - what I expected really - but it is now mine and my problem.   I live in Cheshire, so if there is someone that is close and could help, or possibly give me peace of mind, I would appreciate it.

[Bess]

Hi,
    From 1971 there is a provision for adjustment of the gear change return spring. The spring cup is pierced eccentrically, these cups can be fitted retrospectively so it's worth a check.

In my experience if  the gear change quadrant shaft is worn gear selection can be a problem, fixed by replacing the quadrant.

Best wishes...

[Minnie33]

Thank-you,  I have purchased a new Return spring and will fit it and try and adjust the bobbin to make a better gear change.  I could have a CR 3rd fitted,  will have to delve further .....
Regards
Ian