Post by buttybach1932 on Aug 22, 2024 9:23:36 GMT
My Friend Ivor has been having problems with the clutch on his 1957 swinging arm D3 Bantam. When I had a look at the bike I found that the hole for the clutch pivot was badly worn and this allowed the clutch lever to come halfway back to the handlebar without actually operating the clutch.
On the D3 and most other Bantams the Clutch and Brake pivots are welded to the handlebars and on Ivor's bike the handlebars were nicely chromed when the bike was rebuilt. I would normally get over the pivot wear problem by brazing up the hole with bronze weld and re-drilling it, but this was not an option because it would have damaged the chrome.
The alternative was to drill out the hole to make the worn oval hole round again and fit a bronze bush. Drilling out an oval hole can be a problem but if you use a 20mm Conecut CC1 bit to make the top of the hole round and then drill through with a normal HSS twist drill it makes a good job. You just have to make sure that the centre of the enlarged hole is in the correct position for the lever pivot.
On Ivor's bike the new bronze bushes were 8.5mm OD by ΒΌ" ID and 4.5mm long and this took all the wear out of the clutch lever. However when we set up the free play on clutch cable I was not happy with the feel of the clutch as it was rather heavy.
A look under the engine confirmed that the clutch operating arm on the gearbox was being pulled beyond a 90 degree angle to the clutch cable and there was a lot of clutch adjuster screw sticking out beyond the locknut. I disconnected the clutch cable and measured the difference in length between the cable inner and outer which was 85mm. Ivor also had two new spare clutch cables and the difference between the inner and outer length was 67mm on both of them.
I stripped back 20mm of outer cable from the original clutch cable to give 105mm of difference. The gearbox clutch operating arm is now in a much better position and does not quite reach a 90 degree angle to the cable with the clutch lever pulled back to the handlebar. Plus the clutch adjuster screw now only has around 3 threads above the top of the locknut with the correct free play set. The clutch lever now feels lighter and sweeter in operation.
Bantam clutch cables tend to be sold as a universal fit for all models but this is not quite true. It depends on what handlebars and clutch lever you have fitted on your bike. Some clutch levers need more free inner cable particularly if they are fitted with a screw adjuster at the lever.
Regards
Butty Bach
On the D3 and most other Bantams the Clutch and Brake pivots are welded to the handlebars and on Ivor's bike the handlebars were nicely chromed when the bike was rebuilt. I would normally get over the pivot wear problem by brazing up the hole with bronze weld and re-drilling it, but this was not an option because it would have damaged the chrome.
The alternative was to drill out the hole to make the worn oval hole round again and fit a bronze bush. Drilling out an oval hole can be a problem but if you use a 20mm Conecut CC1 bit to make the top of the hole round and then drill through with a normal HSS twist drill it makes a good job. You just have to make sure that the centre of the enlarged hole is in the correct position for the lever pivot.
On Ivor's bike the new bronze bushes were 8.5mm OD by ΒΌ" ID and 4.5mm long and this took all the wear out of the clutch lever. However when we set up the free play on clutch cable I was not happy with the feel of the clutch as it was rather heavy.
A look under the engine confirmed that the clutch operating arm on the gearbox was being pulled beyond a 90 degree angle to the clutch cable and there was a lot of clutch adjuster screw sticking out beyond the locknut. I disconnected the clutch cable and measured the difference in length between the cable inner and outer which was 85mm. Ivor also had two new spare clutch cables and the difference between the inner and outer length was 67mm on both of them.
I stripped back 20mm of outer cable from the original clutch cable to give 105mm of difference. The gearbox clutch operating arm is now in a much better position and does not quite reach a 90 degree angle to the cable with the clutch lever pulled back to the handlebar. Plus the clutch adjuster screw now only has around 3 threads above the top of the locknut with the correct free play set. The clutch lever now feels lighter and sweeter in operation.
Bantam clutch cables tend to be sold as a universal fit for all models but this is not quite true. It depends on what handlebars and clutch lever you have fitted on your bike. Some clutch levers need more free inner cable particularly if they are fitted with a screw adjuster at the lever.
Regards
Butty Bach
