B50 clutch issues

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SlowDave
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B50 clutch issues

Post by SlowDave »

I am having some clutch isssues with my new to me B50MX. I can't seem to get it adjusted. It either slips when kick starting or doesn't fully disengage. There just doesn't seem to be a sweet spot.

My searching online sources has left me confused but very aware that many have clutch problems. What I have been looikng for is step by step guidance like try this first, then this and then this. I am not adverse to spending money on the bike and if it needs an expensive aftermarket clutch I will do that but I think for understanding the bike I have to work through the process and not just throw parts at it.

So if you guys with years of experience could enlighten me on how you would work through the problem I would greatly appreciate it. I also think that having a coherent explanation in one place would help others in the future. maybe there is such an explantion out there and I have missed it, if so, please link it.

Thanks

Dave
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Re: B50 clutch issues

Post by KiwiB44 »

Having just spent quite some time getting my B44 clutch right my 2 cents worth is not to assume you have all the correctly specced parts!

I know the B50 clutch is different but one issue I did find (with B44) that may also apply to the B50 was that if the correct (1 1/8” long”, accord to Rupert) spring cups are fitted, and the plates are worn thinner than when new, there is potential for the cups to hit the basket and therefore spring pressure to not be applied to the plates, and cause slippage.

I’ve read people add a plate to fix slipping clutches and I wonder if this is the root cause of the need to do that.

It is also possible that the spring nuts can bottom out in the cups and make the clutch action very “stiff” in operation, and drag.

I also found with springs that were a bit under 1 5/8” long (instead of the correct 1 1/2”, according to Rupert) I had to make custom (longer) spring nuts to make it possible to get the spring pressure down by adjustment (and also make it easier to fit the springs).

With new plates fitted the B44’s clutch is now light to operate and does not slip or drag, it’s marginal with slippage when kickstarting, but only if I don’t use the de-comp lever like I should. I could tighten the springs a bit to stop the occasional slippage during kickstarting, but that would make it harder to pull the clutch lever in so I’m leaving it as it is.
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SlowDave
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Re: B50 clutch issues

Post by SlowDave »

Thank you. I guess the first thing for me to do is pull the cover and inspect/measure everything. When I ride the bike it seems fine but if I try to roll it in 1st with the clutch lever fully squeezed the rear tire is locked up. If I adjust it so I can push the bike freely in 1st with the clutch fully squeezed, it will slip like crazy when I try kick starting. The previous owner told me the bike had not been rode in 4 years prior to selling it to me. I have read about clutches sticking on these the they have sat for a while so maybe that might be part of the problem.

Are there after market springs and plates that people here have had good experience with or the opposite? I hate leaving things openned up waiting a week or two for parts to come in.

Dave
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Re: B50 clutch issues

Post by SteveS »

Hi Dave

I think your plan is a good one -
I guess the first thing for me to do is pull the cover and inspect/measure everything
Also agree with your comment
I hate leaving things opened up waiting a week or two for parts to come in.
- parts can get misplaced, you forget how it came apart, you lose enthusiasm....................

Barnet clutch plates seem to get a good write up your side of the pond but I've no experience of them. The pressure plate is susceptible to distortion so one of the CNC machined aluminium ones in my opinion is a good option (*). While the clutch is apart it's worthwhile inspecting the clutch centre which contains the transmission shock absorber rubbers which can deteriorate over time. Speak to Ed at E&V, he has the knowledge and parts to help you,

There is a lot of info on this site that you may not be aware of. It may help you to have a quick check over the Tech Tips section. In particular the 6 Plate Clutch written by Mr Mike (mentioned by KiwiB44)

* If you go for the 6 plate clutch conversion and fit a different pressure plate you may experience clearance problems with the outer case
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Re: B50 clutch issues

Post by SlowDave »

Thank you. I have read the 6 plate posts. Normally I would just order a set of plates an springs and then open it up and make quick work of it. That is what I did with the bike I just finished before this one. However, I have no idea what the previous owner did inside this one. What I do know is that he threw a lot of money at this bike. Not in an appearance manner but for performance. The bike really has some unexpected get up and go. From the outside there are Ceriani forks, Works shocks, top of the line Amal carb and electronic ignition. The previous owner was a former professional flat track racer who owned a company that built race engines and bikes for pros. This bike was from his personal collection and he was wavering on selling it. He didn't hype up any of the modifications to the bike as sellers usually do. So I think there may be some surprises inside. I am going to try to get some time this afternoon to open it up and see if it isn even a BSA clutch and then go from there.

Dave
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Re: B50 clutch issues

Post by beat »

Hmmmmm,- has you checked, - dos the clutch wobbling or not ?

is the long rod free all the way ?

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Re: B50 clutch issues

Post by skippy »

I went for 6 plate clutch and spent a bit of time with a dial gauge getting as much wobble out as possible.
My clutch just stays in the basket.
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Re: B50 clutch issues

Post by SlowDave »

Thank you both. I didn't get any free time today to dig into it. Tomorrow is looking busy too and I will be out of town on Wednesday. So Thursday or Friday I will get to it. I have a larger Noga magnetic base for a dial indicator so I think I could attach that to the frame and see exactly what the clutch is doing wobble wise. After that I will take the plates and springs over to the surface plate and see what is up with them and mic them too.

Dave
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Re: B50 clutch issues

Post by KiwiB44 »

SlowDave wrote: Tue Sep 14, 2021 3:38 am Thank you both. I didn't get any free time today to dig into it. Tomorrow is looking busy too and I will be out of town on Wednesday. So Thursday or Friday I will get to it. I have a larger Noga magnetic base for a dial indicator so I think I could attach that to the frame and see exactly what the clutch is doing wobble wise. After that I will take the plates and springs over to the surface plate and see what is up with them and mic them too.

Dave
Just my opinion but when using a dial gauge to get the pressure plate lift ”even” I think its best to measure the actual lift of the plate rather than check for wobble, this takes into account any “wobble” introduced by a (slightly) bent mainshaft, inaccuracies in baskets and clutch centre etc.

In practical terms, you just look at how many turns the dial gauge moves when the clutch lever is pulled all the way in, eg 1 3/4 turns, 2 turns etc, at 4 points 90 deg apart, then adjust the spring nuts to make the turns/movement equal. On a dial gauge where one is turn is 1mm it’s quite easy to get lift even (on all 4 points) to 1/4mm, or better.
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Re: B50 clutch issues

Post by ghislain »

I use barnett clutch plates , and my clutch is lighter in operation (means springs are less comprimed ) and slips no more . And yes, fitting an alloy pressure plate is a good thing too .I fitted a PES one . ;-)
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Re: B50 clutch issues

Post by baz »

When you say the clutch slips during kick-starting you don't mean you are kicking it through compression?
After many problems with my b44 clutch slipping I decided to hand deck each side of all of the clutch plates IE plain and friction
It was very tedious I made a tool to hold the plates by hand and worked them in a figure of 8 on some medium grit paper on a sheet of float glass
This showed all the high and low spots particularly on the plain plates
I decked them until they were completely flat and Matt grey it completely cured the slipping
I had already tried the extra plate and winding the adjuster screws right in
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Re: B50 clutch issues

Post by FGF »

ghislain wrote: Tue Sep 14, 2021 3:42 pm I use barnett clutch plates , and my clutch is lighter in operation (means springs are less comprimed ) and slips no more . And yes, fitting an alloy pressure plate is a good thing too .I fitted a PES one . ;-)
Hello Ghislain ,.
Do you use 5 or 6 couples of Barnett plates ? ( 0.13 thickness for new Barnett friction plates )

About the pressure plate , when you change the gear , the pressure plate can be bended if it 's not stiff enough.

But i don't understand why it could be bended when it 's applied against the plates by the four springs and you don't use the clutch cable .
So , steel or alloy are apllied equally in that case .

I 'm going to use PES heavy duty springs and sand my plain plates as BAZ wrote.

Francois
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Re: B50 clutch issues

Post by SlowDave »

Yes the clutch slips while kick starting. I can adjust it so it doesn't slip while kick starting but then it doesn't disengage fully making bump starting rather difficult. If the plates need decking off I might try doing it with a magnetic chuck on one of the mills. I picked up the magnetic chuck in one of my convoluted machine trades. I have never used it but I see no reason why it wouldn't work on a mill for very light passes with a face cutter. In the scheme of things replacing the plates isn't that big of a deal financially.

On other matters I found a used parts source in Phoenix so while I am in Phoenix I'm going shopping. He has many small items I need and a clean B50ss fuel tank. I am sure my wallet will be lightened substantially today.
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Re: B50 clutch issues

Post by ghislain »

Five friction plates, four plain plates, the PES pressure plate being the fifth and closing one .
And check plain plates for perfect flatness ....I bought some new ones that were severly bended... :werd

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Re: B50 clutch issues

Post by mlb50 »

Have you checked the worm screw actuator position? According to Rupert Ratio, the angle of the arm needs to be at 1 o'clock looking down on it, then the pushrod clearance set and then the cable slack set.
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Re: B50 clutch issues

Post by SlowDave »

Thank you all again. I have been reading the Rupert Ratio, many manuals and all the other books I purchased. My wife thinks I am a bit crazy to have them all piled on the night stand but I think you guys understand. I am struggling this week time wise but maybe tomorrow I can dig into it. I will do so with all the books at my side as well as all the info you have shared with me. The bottom line for me is do no harm and be methodical working my way through the issue.

I was in Phoenix today for a medical appointment and I went by a BSA collector's home to purchase some parts including a B50SS fuel tank for more capacity. The seller was a great guy, something I am realizing is common in the BSA community.

Thanks again

Dave
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Re: B50 clutch issues

Post by eebtr7 »

Shhhhh! Don't let the secret out! We prefer to let the Triumph people think we are just a bunch of drooling ogres.
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Re: B50 clutch issues

Post by mlb50 »

Great to know your doing all the right research on the B50. I'm just speculating, but that worm screw can be a problem if the drive cog has chipped or lost a tooth. I think what happens is you get a stop - start motion on the linear motion which is tantamount to the clutch freeing and binding.

I could be wrong but I guess its worth taking the cover off and checking it. If all good whack some grease on the bugger and set it at 1 o'clock.
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Re: B50 clutch issues

Post by ghislain »

mlb50 wrote: Fri Sep 17, 2021 1:23 am Great to know your doing all the right research on the B50. I'm just speculating, but that worm screw can be a problem if the drive cog has chipped or lost a tooth. I think what happens is you get a stop - start motion on the linear motion which is tantamount to the clutch freeing and binding.

I could be wrong but I guess its worth taking the cover off and checking it. If all good whack some grease on the bugger and set it at 1 o'clock.
Worm screw in the bottom of the case, of course !!! :oops:
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Re: B50 clutch issues

Post by SlowDave »

I have the primary case off and this is what I have found so far"

Rotating the clutch I found .009 difference by one of the spring retainer nuts and 0 variation by the others. This was measured with a dial indicator and the results were consistent through several revolutions. I suspect this is just a matter of tightening the one spring nut. When I check the retainer plated on a surface plate there was no wobble.

Spring measument by its nature isn't all that precise but I measued the following for uncompressed springs:1.613, 1,595,1.618, and 1.55. The manual states that they should be 1.66.

The plain plate thicknes was as follows: .065-.066 no wobble on the surface plate, .064-.068 slight wobble on the surface plate, .064-.065 slight wobble on the surface plate, .064-.066 slight wobble on the surface plate, .065-.066 slight wobble on the surface plate. I thought some of the wobble might be caused by burrs on the tabs. No burrs were visible but by touch it felt that burrs might be a contributing factor. To test this I took one plate that wobbled and supported it upon two 123 blocks on the surface plate, thus elininating the tabs from consideration and I still had the wobble.

On the friction plates I measured as follows: .115-.121 slight wobble on the surface plate, .119-.122 no wobble, .112-.117 no wobble, .116-.120 no wobble, .116-.122no wobble. The manual say they are supposed to be .167 and that if they are worn more than 0.30 they should be replaced.

At this point I think I need new friction plates and I may as well replace the plain plates too just on general principle and the wobble observed. The springs should be replaced too.

I do not know what kind of oil the previous owner had used but my understanding is that with a wet clutch the oil used should be formulated for a wet clutch. I have purchased a jug of Casrol 20-50 4t synthetic motorcycle oil.

I haven't opened the other side yet so I have not checked the worm gear. I figure I will take care of one side first and then go from there.

So do you think I am on the right track? Where should I order the plates and springs from? I don't like cutting corners on parts but then again I am not a racer and don't want to throw crazy money at parts when the marginal increase in quality or performance only makes sense on the track.

As always, thank you for all the help on this.

Dave
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Re: B50 clutch issues

Post by KiwiB44 »

modern aftermarket plates may or may not be made to original thickness specs....I fitted new friction plates “surflex” brand I think but cannot recall what thickness they were.
An interesting check you could do (as I mentioned before) is check if the spring cups are contacting the basket, given yr plates are thin.
The aftermarket does not seem to have a clue about the correct length of spring cups!
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Re: B50 clutch issues

Post by SlowDave »

Thank you all for the further info. I didn't measure the basket for wobble but it looked pretty good by eye. The cover plate had .009" variance by one screw but when I checked it on the surface plate it had no wobble so it appears to be fine. I am going to get on the phone in the morning and order the parts. While waiting for those I will do some further inspection as suggested.

The more I dig into this bike the more I love it.

Dave
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Re: B50 clutch issues

Post by Mr Mike »

Take a few minutes to read my write up on the six plate clutch with your primary open. If you think about it, every little thing in the assembly process affects something else. Plate thickness, spring length, spring pressure, adjusting screw, length of the push rod, setup of the actuation lever arm. With a little study you will be able to figure out what is going on. You don't have to do the conversion (which is quite simple) requiring no special tools.
Then some cold winter day do the conversion for a "No slip" and "Light spring pressure" clutch. I have had two B44's, a B25 and a B50 and the B50 six plate is far and away the best of all of them. Also th4e B50 uses the engine oil so I am not sure if synthetic might be too slick but I will trust others that have used synthetic. It may be just fine. After a couple of years the clutch began to slip under real hard acceleration in 3rd and 4th. One turn on the pressure plate nuts and viola....no more slip...the way it oughta be.

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Re: B50 clutch issues

Post by SlowDave »

Thank you. I will read the write up. I greatly enjoy trying to understand machines. Those moments when the light comes on and you understand are some of life's great moments.

Dave
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Re: B50 clutch issues

Post by Mr Mike »

Dave,
Also note Rickards comment at the end of the "Six plate clutch" writeup. It is an excellent idea to tack weld the pressure plate to the top steel plate. I did not do this but would certainly recommend it. I can't remember but I think the Rupert Ratio book also suggests this modification. that book is a must for your library if you do not already have it.
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Re: B50 clutch issues

Post by gunnag »

I can recommend Surflex clutch plates as they seem to be made of a modern grippier compound and have helped stop clutch slippage on my B44, however they do seem to turn the shared engine oil black quickly.

If a previous owner has used an oil not compatible with wet clutches then you might need to wash the plates with solvent to remove any traces of friction modifiers which will cause slippage, only use motorcycle oil intended for use with wet clutches.

I agree with all the previous comments regarding spring cups and lengths etc. its often the case that the wrong or mismatched parts are fitted, so measure everything carefully.

Not sure about the B50 but earlier models need the spring screws lock-wired in place as they work loose easily and cause slippage.
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Re: B50 clutch issues

Post by Mr Mike »

gunnag,
I like those Surflex plates too. I also think that the B50 engine oil shared with the primary is not the way to go. I liked the B44 way better. It would be simple to convert back but I haven' done it. I am getting pretty old now and the B50 rides are much fewer. The B50 is the last BSA that I own.
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Re: B50 clutch issues

Post by SlowDave »

Thanks to all. I have plates and spings on order. I am replacing both the plain and friction plates. For now I am going to limit the work to that and see how it goes. It isn't a big deal to open it up again. However I am going to do futher close inspection as has been recommended above. That may expand the scope of my current plan. The oil thing has me concerned. The previous owner was extremely experienced with a lifetime of BSA ownership. But mistakes happen so the oil thing has me concerned. I am thinking maybe I should clean the primary case well with solvent, drain the sump and flush out the in frame tank before refilling with the proper oil. Then change the oil again after running it a bit. That would certainly lower the amount of substances contrary to the health and wellbeing of the clutch. But then again, it doesn't take much to ruin friction plates.
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Re: B50 clutch issues

Post by Ian Hingley »

SlowDave wrote: Thu Sep 23, 2021 5:51 am Then change the oil again after running it a bit. That would certainly lower the amount of substances contrary to the health and wellbeing of the clutch.
I think you'll find with the harsh environment of the primary drive, it's the amount of clutch friction substances contaminating the shared oil that are contrary to the health and wellbeing of the engine.

Cheers

Ian
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Re: B50 clutch issues

Post by Mr Mike »

Ian is right on. That slipping clutch puts all the material from the plates into the oil. I have put a spin-on filter on my b50 to help clean it up but I cannot imagine what BSA was thinking when they decided to share primary oil with the engine, and that oil-in-frame idea where you can't clean the sludge out and add weight to the bike. But its a nice old fashioned ride, turns a head now and then, and reminds me of an era that is many years behind me.
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Re: B50 clutch issues

Post by nopdog »

Splined mainshaft and up-graded clutch. PES or NEB.
Cost a bit but worth every cent.
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Re: B50 clutch issues

Post by SlowDave »

Thank you for all the info. The parts have arrived and I will put it together on Saturday. Hopefully take it for its first real ride in the desert on Sunday. Having it here the past few weeks and not getting a real ride in has been driving me crazy.

Dave
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Re: B50 clutch issues

Post by beat »

SlowDave wrote: Fri Oct 01, 2021 1:25 am Hopefully take it for its first real ride in the desert on Sunday.
have you organised the rescue - truck :?: :?:
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Re: B50 clutch issues

Post by SlowDave »

Yes, my riding buddy will be on his bike so I I have a mechanical he can head back to the trucks and come pick me up. I have done several multi-day desert crossings on my mountain bike so I know the risks and respect them. I also carry a In Reach satellite texting device so I can get help no matter where I am. The desert is not something to take lightly.

Thanks

Dave
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Re: B50 clutch issues

Post by beat »

SlowDave wrote: Fri Oct 01, 2021 10:47 pm The desert is not something to take lightly.
the B 50 likewise
:lol:
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