Afternoon all, well, what a headache I have been having with the clutch on my 1968 Starfire ... I was hoping to post pictures of the build etc and final results very soon ... but what seemed like the simplest of jobs has really got me, typical I say to myself!
So, inserting my new clutch plates and clutch rod into place, and then everything else ... I'm using the kick starter to turn over the engine (engine runs sweet and no issues in the gearbox) when I feel some resistance that should NOT be there, it comes and goes. Engine fires, goes into gear nicely, good oil return ... when I try to pull away, engine struggles and dies. Side casing off, inspection of the clutch reveals the plain clutch plate inserted first, so at the back of the basket, has managed to slide between the clutch hub and the basket, causing the resistance mentioned above ... stripped down I can see there is a raised lip on the clutch hub, which has been machined in ... do I have the correct clutch hub (according to the drawings I do) or is there something else I am missing? The new plain clutch plates and new friction plates were from a reputable seller, apart from thicker plates or grinding off this machined lip I am at a loss ... has anybody else had this experience ... photograph included! Thanks in advance, Jan. :-\
Looking at your picture, the hub doesn't have the lip. When your B25 left the factory it would have had a lipped cush drive, where the bottom plain plate would have rested against this lip. BSA realised this setup wasn't the best as the pressure against the bottom plate caused it to distort. On later unit single clutches the lip was dispensed with allowing extra plates to be fitted. Also the rear of the clutch basket was machined to allow for a thrush washer between it and a modified hub suitable for the thrust washer.
This mod is easily done as I did it with my B44 clutch when I rebuilt it.
Ok, think I may have read something about this before ... but this clutch set up must have worked at some point, so what's different now I can't help thinking! When I took the clutch to pieces originally, there was the spoken of EXTRA plate inserted and I think, from memory this was at the back of the clutch basket, ie thicker than the plain plates in between the friction plates, therefore it would not slip between the basket and clutch hub. Does this sound right? I was always under the impression a plain plate should be inserted first ...
The photo included is the clutch hub with the lip as described machined in or out depending on your perspective on the right hand side, as I understand it, apologies if this is not the case.
Thanks for your reply 👍
Jan
The first plate inserted should be a Friction Plate, then a plain plate and so on... You should end up with a plain plate for the pressure plate to act against.. If a friction plate is falling between the hub and the basket, you have too large a gap there which should be investigated.. Please also bear in mind that if your setup doesn't have the later style hub with thrust washer, there may be extra wear in this region. HTH
Ah, ok thanks Ian, the manual indicates this should be a plain plate first, I shall try adding a friction plate first this time, ending up with a plain plate ... a friction plate will definitely not get caught up due to its thickness, there were 5 friction plates in this basket when I stripped it down, although the manual states 4 ... I'm not sure how this bike would have run prior to me getting a hold of it, lots of parts just don't add up or don't belong! I'll post how I get on once the new set of roller bearings turn up, lost one!!
PS I see what you mean about the lip on the clutch hub now, was looking this up all last night :'( ...
Cheers 🍻 Jan
Yes Jan, with the lipped hub you would place a plain plate first but you use a friction plate first for the unlipped hub. You should use service information for the later style clutches.
Ok, right thanks Ian, good advice ... I'll start to put that back together this week, hopefully get that issue sorted, I'll let you know ... ! Thanks again ...
Jan 🍻
Well, this is all very odd ... I'm thinking clutch springs maybe? I assembled the clutch plates as per the later b25 models without the lip on the centre clutch hub ... but this time, on attempting to gently turn the engine over with the kick start, the clutch assembly spins with friction, without the engine turning over, only sometimes sporadically engaging to turn the crank ... I'm thinking clutch springs perhaps ... or just a complete nos clutch basket and assembly ... so far I have used new clutch springs, new rod, new friction and plain plates ... new able also.
I am assuming the clutch pressure plate needs to be pressing hard on the plates to enable to kick start mechanism to engage with the crank? Does that sound right?
Thanks in advance ...
Jan 🍻🤔
The clutch set up can take a bit of tweaking to get it just right.
Have you got a manual?
Make sure the operating lever on the engine is in the correct position. The correct position is slightly inclined outwards by a small amount. When the clutch lever is pulled in, it should take up a position approximately parallel to the timing cover joint face.
If that lever needs adjusting, it's simply a case of releasing the push rod lock nut, winding it into the desired position and tightening it all up again.
Check the slots in the clutch basket that the tangs on the plates run in are smooth. They have a tendency to get gouges in them. Simply clean them up with a file.
If I were you, I would release the clutch cable completely adjust the lever on the engine as above. Tighten up the clutch springs so clearly too tight. Kick the engine to check for slip.
If it slips, I would expect something wrong with the plates. Check if they are completelyfalt, maybe it's the springs, maybe an issue with the material, these things are om new parts, but who knows? The issue must in the basket somewhere.
If no slip then I would work backwards. Attach the clutch cable and loosen off the springs a bit at time, kicking the engine over each time checking for slip.
Once you get the lever working smoothly, Check the plates are running true. To do this, I pull in the clutch lever and tape it to the handle bar, then with a ruler measure the lift of the pressure plate in several places to ensure its lifting evenly. Tweak the clutch springs a little if you need to.
When it's written down, it sounds complicated, but it's not that bad.
Good luck and let us know how you get on.
Hi Beesy, many thanks for the explanation in setting up the clutch, I think I was naive in thinking the clutch was one of the easiest parts of this build, learning all the time as they say! I have got a manual, but it hasn't been much use in the actual intricate manner in which these clutches have to be set up.
I shall certainly let you know how I get on, how to have things in place by the end of next week ... thanks again, photos to follow touch wood!
Hey Jan,
As it turns out, I do have a picture of the clutch from my '70 B25. It doesn't show too much detail, but may be of help.
Best of luck,
Oliver
Hi Oliver, many thanks for that, I can see you have the same clutch centre hub as I do, which according to the manual for my 68 starfire is not the right one, it is in fact the modification BSA came up with, requiring the 5 plates ... I never would have realised that without this forum I don't think ... thanks to everyone, updates to follow!
Jan 👍
Jan,
Good that the photo helped. I was nosing around in Rupert Ratio, vol. 1 (p.125) and there is mention of the "four plate to five plate conversion".
I have also received help with this forum; a knowledgeable and enthusiastic crowd.
Onward, through the fog!
Oliver
Well, I have to say, thanks very much for all the advice, it seems I had the clutch hub modification to my 68 starfire already in situ, when I was trying to fit a clutch as per the Haynes manual for a 1968 model ... fine tuning has been a sod, but got there in the end, I can see that it is very minute adjustments ... thanks again, don't think I would have figured this out if it wasn't for starting this conversation on the forum! Apart from the normal teething issues after sitting idle for over 20 years, I have ridden this bike around the village with a big smile on my face twice today!!! I love it!! Hope the photo shows the bike off properly, yes I have had a few beers to celebrate!!! Happy days and thanks again ... onto the next one (but not a basket case this time, honest!!!)
Cheers, Jan 🍻🍻🍻🍻🍻🍻🍻🍻🍻
Glad you got it sorted, great feeling isn't it? Nice looking bike.
Certainly is, cheers Beesy!! 🍻