Had several new parts on my B31,and most are ok.
However I fitted a new kickstart ratchet pinion and kickstart quadrant and new folding kickstart lever and cotter pin.
The first thing that happened was the threaded portion of the cotter pin snapped off as I was tightening it.The folding kickstart jammed against the silencer and as the exhaust pipe is against the bottom rail it can't be moved.The ratchet pinion has started to jump a tooth,and although the quadrant looks ok,the ratchet pinion has some burred teeth.This has only been on for a couple of months and I have only ridden three times.
These are of course aftermarket pattern parts and I strongly suspect that the material and accuracy are below the original spec.
Are original new,old stock genuine BSA parts available anywhere? Or a supplier of parts that are definitely up to spec?
The thread and nut aren't meant for tightening the cotter pin, only for retaining it. When fitting a cotter pin, tap it in fully from the opposite side until it is fully home then tighten the nut to a sensible torque which be about 9-10Nm for the 1/4" threaded section.
The kickstart lever apparently has an incorrect offset, not unusual for pattern parts unfortunately. I can't comment on the quadrant and ratchet pinion although I suspect thay are not up the standard that they should be. New old stock parts are now very hard to find.
Afraid the kickstart clearance will be by trial and error.
The kickstart ratchet problem is two fold:
Early quadrants (OEM ones have splined shaft and removable quadrants these and matching ratchet gear have flat top teeth.
Later ones have pointy teeth.
Mismatch these and wear is dramatic. Added to that bear in mind that quite a lot of Indian supplied ones are made of hard cheese.
Cotter pins also an issue (also seem to be made of cheese!). I have guillotined two so far on my DBD34 600 kickstarter and suspect the one at the moment is going same way (warning seems to be you notice kickstart is a little loose on the shaft, despite washer and spring washer, so you tighten nut - a week or so later the pin shears). I notice this phenomenon again this week as I have been using bike for commute to work. I grabbed a spare pin and suitable spanner and kept in my jacket pocket. I've got a Barleycorn ss one on my off-roader and that is very secure, so just bought two more ready to find next pin is on its way when I grab time tomorrow!
So I suggest Barleycorn ss cotters and try Kidderminster MC for ratchet gear once you have confirmed flat vs pointy quadrant (these don't seem to wear).
Beware eBay sellers and part numbers as they mix them up assuming all the same.
Good luck.
A lifetime ago when I was interested in pushbikes and riding them through the countryside (but before those new-fangled cotterless chainsets were financially available) we used to file the cotter pin to fit nicely. The thinking was at some point, probably sooner rather than later, the cotter would need to be removed again to change the cranks etc.
Trying to pull them home with the thread or knocking five bells out of them to make them fit was severely derided.
Clearly it must still go on on BSA's as my Goldie has witness marks on the gearbox end cover where someone was a lousy shot with the ball-pein hammer..
Pattern parts are often poor metal and poor fit but that makes fettling even more critical. I file and trial fit cotter pins then tap them home. For crucial parts I try to find good original used parts as I know they are well made.
This is not restricted to BSA or even bikes, I have the same problems with an old Land Rover, if you get a good set of brake drums you hold on the them!
Am I correct, that bike Cotter Pins had to be put in a certain way around, so they would tighten in normal use..? I think the hole in the crank was also larger one side than the other.
Make sure the kick start quadrant and pinion have the same tooth form. They either have straight teeth or rounded. Mix them and if they don't jam they will tear themselves to pieces.
Thanks for the replies.Mismatched teeth on the qúadrant and pinion would explain the rapid wear. I wasn't aware that they could be different.I will check tomorrow to see what I fitted.
When I order a new ratchet pinion I will make sure it matches the quadrant.
I put the cotter pin so the wide part of the flat is on the high load part when you kick.
On scrutinising my ratchet pinion and ratchet,it appears that the slipping kickstart is caused by a rather worn ratchet.
Tried Draganfly but they are on backorder which means probably never,and Classic bike shop doesn't have one.
The part number on Draganfly's list is 67-3167,and looking on the internet there are a few suppliers of the ratchet,but the part numbers don't match up with the Draganfly list.The numbers that the internet suppliers quote are 66-3079 and 66-3080.
Although these are advertised for B31/33,I am unsure about them.
Am a bit stuck as to what to order,so any advice will be welcomed.
For the swinging arm gearbox the 1954-54 parts list shows:-
Ratchet pinion : 66-3080
Kickstart ratchet : 66-3079
Kickstart quadrant : 15-4121
But the 1958 on parts list shows:-
Ratchet pinion : 687-3376
Kickstart ratchet : 67-3167
Kickstart quadrant : 42-3160
The 1957 A10 parts list shows the same as later B31/33.
I would reckon that as long as all three items are of the matching type you should be ok.
The parts 66 3080, 66 3079 and 15 4121 are for the M type gearbox, used on the M20/M21/M33 and pre swinging arm B31/B33.
For swinging arm B31/33 the parts were the same as for the A7/A10. They were modified in 1955, the attached shows the pre and post modification part numbers. The quadrant was changed again later, I think to one piece rather than a spindle with detachable quadrant, that is the 42 part number in post above. The ratchet 67 3167 was not changed.
Quote from: JulianS on 14 Apr, 2026, 15:49 The parts 66 3080, 66 3079 and 15 4121 are for the M type gearbox, used on the M20/M21/M33 and pre swinging arm B31/B33.
You are correct. I was looking at the wrong diagram. :'(
So long as you fit as a pair you should not have a problem.
To be clear he later (pointy):
Ratchet gear 67-3167 that is compatible with
Quadrant 42-3160 (GS scrambles - ie same as B31/3) or
Quadrant 42-3163 (GS Clubmans 42-3163 for forward canted kickstart).
The earlier (flat top)
Ratchet gear 67-3168
Quadrant 67-3178
Ratchet 67-3164 (that goes on the end under the lockwsher and nut is the same for both.
If pushed I have spare flat top (two piece) std quadrant in good condition but the only decent flat top pinions I need to keep!
I am most grateful for the replies.
The new ratchet pinion and quadrant came from the same supplier,but on examination,the quadrant is for the pointy teeth pinion,and the pinion they sent is the old type squared teeth.
Got a new pinion with pointy teeth and fitted it today and seems ok,no jamming.
Just got to fix the Victor Sylvester tickover and the bike will be almost perfect,(for a 1957 B31)Those of you of a certain vintage will remember Come Dancing years before Strictly,and Sylvester used to call out the dance steps,"Slow,Slow,Quick Quick Slow" except my bike it's, Slow,Slow,ignition retarded,then Quick,Quick Slow and stop ignition advanced.
Having exhausted all other possible causes,air leaks,jetting,ignition etc,I now suspect the carb fuel level is too high.When you turn the fuel off with the engine running,it speeds up a little just before it stops caused by the fuel level in the float chamber dropping.
I think too high a fuel level could be the cause of this slowing and stopping,as blipping the throttle it will tick over nicely for a few seconds and then gets a bit too much fuel.
Another clue is it starts easily with the fuel on, but is most reluctant to start when I flood the carb from cold.
The carb fitted has a machined float needle seating so I will experiment with different thickness washers.
Assuming its a monobloc, then if its original / old there should be no washer under the valve, if its a new replacement they have washers. So if its old and has a washer try just removing it.
The dimple on the cover is the level, you can check it by taking the nut off the pilot jet and putting some silicone tube on as a manometer. I've been doing all this the past week on a Matchless and been surprised by how much difference getting the float level right makes. Its worth the effort.
If its got a brass valve you can put solder on the end then file it down to adjust.
Quote from: limeyrob on 17 Apr, 2026, 19:20 Assuming its a monobloc, then if its original / old there should be no washer under the valve, if its a new replacement they have washers. So if its old and has a washer try just removing it.
The dimple on the cover is the level, you can check it by taking the nut off the pilot jet and putting some silicone tube on as a manometer. I've been doing all this the past week on a Matchless and been surprised by how much difference getting the float level right makes. Its worth the effort.
If its got a brass valve you can put solder on the end then file it down to adjust.
[/qu
The carb is a replacement monobloc with a machined face for the float needle valve.Replaced the fibre washer with a thinner copper washer and the tickover on advance is much more reliable,(not perfect) but much better.
Thanks, Terry.
Quote from: Janacek on 19 Apr, 2026, 13:42 Quote from: limeyrob on 17 Apr, 2026, 19:20 Assuming its a monobloc, then if its original / old there should be no washer under the valve, if its a new replacement they have washers. So if its old and has a washer try just removing it.
The dimple on the cover is the level, you can check it by taking the nut off the pilot jet and putting some silicone tube on as a manometer. I've been doing all this the past week on a Matchless and been surprised by how much difference getting the float level right makes. Its worth the effort.
If its got a brass valve you can put solder on the end then file it down to adjust.
[/qu
The carb is a replacement monobloc with a machined face for the float needle valve.Replaced the fibre washer with a thinner copper washer and the tickover on advance is much more reliable,(not perfect) but much better.
Thanks, Terry.
Amal actually supply a set of various thickness washers to get the float height correct.
Quote from: limeyrob on 17 Apr, 2026, 19:20 Assuming its a monobloc, then if its original / old there should be no washer under the valve, if its a new replacement they have washers. So if its old and has a washer try just removing it.
The dimple on the cover is the level, you can check it by taking the nut off the pilot jet and putting some silicone tube on as a manometer. I've been doing all this the past week on a Matchless and been surprised by how much difference getting the float level right makes. Its worth the effort.
If its got a brass valve you can put solder on the end then file it down to adjust.
.
Checked the fuel level with a plastic pipe from the pilot jet and it seemed to be level with the dot on the float chamber cover.Looking at the plug,it's chocolate brown so running a bit rich.Rather than get different size shims for the float needle valve,I attacked the copper washer with grinding paste on a steel plate and measured the distance the float moved with and without the washer.It was 10mm with and 5mm without.Ground the washer to go in between and settled on 7-8mm.Tickover on full advance is now very reliable and the plug is now mid brown.Didn't realise that a tiny movement of the float would alter the overall mixture.Just one tiny thing,when changing gear the engine frequently misses a beat before picking up again which means,er something,but I can live with that.Just the poor brakes to sort out now.There will always be something that needs attention.But it keeps me out of the pub and away from women of dubious character!