Hello Everyone,
After reading all the technical discussions on this site I've decided to go ahead and replace the clutch on one of my bikes with a Triumph pre-unit 4 spring. I'm using the clutch hub center adapter that would have been intended for the B31 (part # 42-3170).
This will require a 1/4 inch spacer to get the engine sprocket into the correct chain line. My question is - should this be anything other than a simple washer-type spacer in its construction?
Best wishes,
Allan
email (option): allanmatchless@yahoo.com
Allan, I can't recall the details of the spacer I used, but lining up the sprockets was not a challenge. Preventing the crank nut from gouging through the outer primary cover will require some attention. I used a thicker gasket between the inner cover and the crank case and 2 cork gaskets between the 2 covers. I sealed the outer gasket to the outer cover and the inner gasket to the inner, so the cover can be removed without disturbing them. Even so, I ground down the outer edge of the crank nut.
Use modelling clay on the crank nut to test fit the cover to assure clearance, then LocTite the nut at final assembly. And it's a good idea to remove the cover after a few miles to verify the clearance.
Jeff
email (option): jjbandoo@aol.com
If you haven't already purchased the adapter they are now available with the taper altered to overcome the problem of misalignment....Additionally, you will also need the correct clutch centre nut and washer used when fitting the Triumph clutch to a BSA...The clutch pushrod length will also have to be altered
Finally, there are two types of Triumph clutch spring...A short 'heavy' one and a longer 'light' one...Go for the lighter spring for an easy to use clutch, it's quite adequate for the OHV B Series and SV M Series singles power output...Ian
email (option): ian@wright52.plus.com
Thank you so much, Jeff and Ian, for this most helpful series of guidelines.
Fore-warned is fore-armed as the saying goes, and knowing the important factors I'll have to deal with is very useful in reducing the number of those 'blast-I-should-have-thought-of-that' moments....
With a smile,
Allan
email (option): allanmatchless@yahoo.com
Hi Allan. Have just done clutch conversion on my M20. Kit came from Kidderminster Motorcycles. Great quality and no alignment problems. Clutch is light and engages really smoothly. I would highly recommend this. I have had 6 Spring and Empire Star single Spring clutches in this bike and the Triumph one is much superior. Good luck!
Hello Mike,
Thanks so much for your endorsement of the Triumph clutch conversion. It's very reassuring - especially as you seem to have tried all the clutch variants! I'm just waiting now on some parts so I can, with luck, get it all assembled before the winter weather clamps down. I took your recommendation and switched to the Kidderminster motorcycles clutch center adapter. It makes sense to me to go that route.
Best wishes,
Allan
email (option): allanmatchless@yahoo.com
Hello Again, Everyone,
I'm now waiting (or should I say, still waiting?) for the correct center nut to arrive for the four spring Triumph clutch I've got with the Kidderminster motorcycle adapter. Just one question occurs at this point. There is some space clearance between the outer edges of the adapter and the sliding plate at the back of the primary cover. Should there be any kind of seal there?
Once again, many thanks for all the guidance, and all of it has been gratefully received.
Allan
email (option): allanmatchless@yahoo.com
There is no seal between the adapter and sliding felt seal holder. There is a scroll on the adapter to keep oil in the primary.
Thank you, Dean, for this information.
I now have another question which is wide open for anyone:
I have the 4 spring Triumph clutch ready, and I ordered the center nut. I did my research and requested 42-3171. The supplier said this had been superseded by 42-3267.
It arrived, and it doesn't fit. It's about 7 thou too small.
There's nothing wrong with the mainshaft thread and the original center nut 15-0374 fits neatly. As far as I can tell this is 5/8 x 26 TPI thread.
Am I dealing with a poor quality nut, 42-3267? Or is this in fact a totally different part? What should I have? And where can I find one?
So far the mailing from England to the US has meant that each mistake costs me far more to mail back than the original order......
If I can be sure of the thread size I could even order up a tap and modify what I already have.
All help gratefully received!
Allan
email (option): allanmatchless@yahoo.com
I bought a complete assembly from Draganfly.
First - the clutch is great. Very light and plenty of "feel". Well worth the money. Very easy to fit and adjust.
This assembly came ready to fit and is listed as part number BSA4SPR5
https://www.draganfly.co.uk/index.php/bsa/bsa/a710--b3133--c101112--m202133/category/910-4-spring-triumph-type-without-cush-drive
email (option): cas.vanderwoude@gmail.com