Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board 71 b50ss lost ability to shift, help!

Last night while riding, the bike popped out of fourth and I stalled. After that i couldn't manage to downshift at all. I could get the bike started, and shift up into fourth but not down into anything else. I managed to get home, which of course was all uphill, by feathering the clutch. What would be the first thing i should check?

The cam plate spring (in the tranny) broke??????????????????? Not sure why you stalled???? When they've broke on me the bike jumped out of gear and it was a pain to get it back in and then when I finally did....I only had one gear and the shifter felt solid (almost no movement at all)

At least that's my guess.

You can do all the work from the timing side and not have to mess with the Primary. I "think" the directions for doing that are on b50.org. It's a bit of a pain getting it all lined up so it goes back together but a lot quicker than going into the primary too. If you're on the side of the road...you can lay the bike over on it's side and save most of the tranny oil while making the repair. I always carry an extra spring or two. :bigt

Opie Gone Bad (aka Gordon in NC and The Skipper)

And when you change the spring take a grinder to all the peaks on the camplate and reduce them, follow up with a polish. The peaks rub on the spring and wear it out, gearchanging will be easier and the spring will last longer.

it might be a plunger stuck in on the gear shaft where they engage the quadrant

Since you mentioned it kommando, if you could post a pic or two of these "peaks" that should be ground off the camplate and for those not in the know to get a visual on what you are talking about, that would be great.

CT,
I am not sure that it is only the detent spring. I broke a couple over the years and they broke going into 4th gear. I could hold it in fourth by holding up on the shift lever but couldn't keep it in any other gears. Pull off the right side of the engine as Gordon says and everything can be done without messing with the other side. Take care in lining up the spring so the shifter forks don't hit it when going into fourth.

Mr Mike

These peaks




not these

HI Ct B.

+1 what all the others said. If no joy then try this:

I have had some luck with my Thunderbolt when the shift lever wouldn't grab the cam plate by extending the reach of the Plungers.

To do this you take the shift selector out of the bike and remove the Retaining Plate between the two Plungers. There is a screw in the middle holding the plate down. It is usually "punched" so it may be difficult to get off. Find a really thin washer and put it on the the shift selector first, then install the Retaining plate and the screw. Be sure to use some Locktite on this screw. The washer "lifts" the Retaining Plate a bit extending the reach of the plungers.

Good Luck.

Cool,you guys are lots of help-thanks. This may be a dumb question but how does the bolt that holds on the kickstart lever come out? Just tap it? Because it only tapped so far and stopped and i dont want to screw it up.

Yes....it's "wedged shaped" and will come out by tapping on it.

Lame stuff but.....make sure the nut for the threaded part is flush with the threaded end. (to help protect that end of the cotter) Better to use a LONG drift to keep the hammer away from the side cases.

A lot of the "new" pins are made out of a real cheezy material. I think the thought is to sacrifice the pin instead of the kickstart shaft......BUT....some of them are so cheezy you can't get them to stay tight and turn to mush when you're trying to remove them. Dave Carter of "Mike and Dave" fame makes the BEST kick start cotter pin I've ever used. If you mess the one up you have...you might try him to see if he has any.

Good luck.....if I remember correctly....pulling the pin that holds the cam plate with one of the case screws is one of the tricks for this fix (if you're not going into the primary)

Opie gone bad

Oh my.....beautiful.........Scotland?

No, Swiss alps, ours aren't as high.

Well....that'll just be another one of those places I'll never get a chance to visit so thank you for sharing.

I will get a chance to visit Scotland one day.....but it'll be to carry my father home so I'm really not looking forward to that.

Opie Gone Bad

I am sure it will be the detent spring. I rode a B44VS 1970 for 14 years & replaced this spring 4 times.

Cheers Elijah.

So I got the timing cover off and now I guess I have to go a little further in, right? (Pic below) I left the wire going to the contacts attached because I would have had to cut the wire because of the PO's last wiring job.

A couple questions:

1) The kickstart quadrant came off with the cover and I can't seem to get it out through it's bearing. Is it buggered up? Should I just give it a wack? I would think it might be hard to put everything back together that way, to attach the spring and all. And because it came off with the case I wasn't able to see the original positioning of it for reassembly. I just heard the WHAP of the spring coming off.

2) Is it necessary to drain the oil from the crankcase to go any further? And if so, my shows the drain as some simple little bolt on the bottom but in reality there's a large bolt (maybe 7/8") and the line that comes from the drain in the bottom of the frame. Which bolt would be the drain plug?

3) If I make a mark on the camshaft and the case, or something, will it be enough to not have to set the timing when I put everything back together later? 'Cause I don't really know how to do that.

4) Most importantly, what bolts/screws do I need to take out to go further? I'm assuming all of them....

to go further the primary side of the engine needs to be striped completly.the kick start quad will knock thro and the cam will have marks on it but i would try not to disturb this as you will have to take the rocker box off if you do, if you dont mind me saying would it not be wise to get someone involved whos done this before?

Well, I'm kind of on my own unless I want to trailer it up to my mechanic and pay through the nose.

But I was under the impression from the posts above that it would not be necessary to disturb the primary side and all could be done from the timing side.

You can leave the primary on but it does require more fiddling. The pin holding the camplate onto the inner cover has to be removed and you have to push the mainshaft through the bearing in the inner cover as it comes off which can be tight. Make sure you press on the camshaft so it stays in position and does not come off with the inner cover.

Leave the kickstart quadrant in the outer cover if it was working.

You don't have to drain the sump but if the bike is wet sumping you will make a mess.

Yep...what kommando said.

The kick start quad probably has a burr where the tappered cotter sits on it and if you force it out without cleaning that up you could damage the seal.

One of the screws that you have removed from the two side covers (inner and outter) will fit into the pin that holds the camplate to the inner cover. Screw it into the end of the pin and work the pin out. Now you can remove the inner cover. You probably want to go ahead FIRST and drain the tranny oil if you haven't already? (that large bolt head you see under the engine). You can save the tranny oil if you're on the side if the road doing this by laying the bike over on it's side.

You have a good start....hang in there and you'll soon see the problem that caused you to go in there in the first place.

Opie Gone Bad

CT, Do you have the Rupert Ratio Unit Singles Engine book? That would help in your quest to understand how to take this all apart and even better how to get it back together right. Also there are BSA workshop manuals for this model. Skip the Haynes manual.

Peter

I can not see how you can get the case back together the paws on the gear shaft will push the cam plate off the selecter forks thats why the gear assembly is built up on the inner cover ,including the main shaft so the primary as to come off.you can do distributor engines as they discribe but not later side points models.PS the kick start does need to be in the inner case as it locates the lay shaft.

Wak, it can be done but it is a pain, have done it myself, its worse putting it back together and the last one I did needed it to be in third, the camplate needs to be kept sort of in place using a rod until it just enters the slot in the inner cover, you can then push home but stopping at the point the hole in the camplate lines up with the hole in the inner cover for the retaining pin, after the pin is in you make the final push. The camplate is pushed out by the camplate springs so the hole lines up before the cover is fully home. If you push home all the way first you then have to push the camplate in whilst trying to get the pin in.

But what about the paws on the gear shaft,i take it this will be already in the inner cover and on its spring locator?how do the paws get past the cam plate without dislocating the forks?

CT before you do anything else have you tried adjusting the eccentric gear shaft return spring adjuster?its the screw with the lock nut, put your kickstart shaft back where it should be before rocking the engine

If is difficult but through the gap between the inner cover and the crankcase you use anything to hand to press the pawls in as they pass over the camplate. Until you try it it does look impossible but it can be done.

ummm not sure as a guy who as never touched one before will manage this !

IMO it's something that's was done since day one. The instructions for doing it are on the web somewhere but I can't seem to find them. I've done it myself a couple of times....all with later models....and no problems. Back in 2003 I helped a fellow at an AHRMA Vintage MX do it between motos and all together it took us less than 30 mins. We had the bike on it's side and never lost a drop of oil doing it.

I kinda wish I'd never said anything about it.....but it's been around for a LONG time.

Opie Gone Bad

Hey CT....we haven't been doing a very good job at ansewering your questions....sorry for that.

I think we've answered 1, 2 and 3.....#4 is all of them AND the stud that held the kickstart spring.

Keep at it, take your time. Photos and questions will get you through this. I'm going to pull an engine off the shelf and be ready to photo a step if you need it. Take your time....you're doing well so far and keep in mind, it's a BSA unit single....pretty much lawn mower technology...one of the reasons I love them so much.

Opie Gone Bad

Probably to late but we'll find out.

Sorry for the out of focus photos but I was having a time doing all of this with just two hands....and in a hurry.

To remove the pin that holds the camplate to the inner cover,

Use one of the small screws that holds on the outer cover.



Screw it into the end of the pin,



Remove the cotter



You should be able to pull the pin now....make sure you line up the hole for the cotter when you put it back.

Also make sure you have all the screws out of the case and the stud that holds the kickstart spring needs to be out too.



You should be able to remove the inner cover now....and have a look inside.

Opie Gone Bad

I worked on the bike a little more last night. I'm taking small bites out of this, and remembering to walk away and learn more, before doing thing that can't be undone. That being said....

I was having difficulty finding the drain plug for the crankcase and I think I know why. I think it fell out. I did manage to locate the one on the primary side and it had some oil dripping out of it. Well turns out it was stripped (I may have helped it do that, but im 100% sure it was pretty much done)

1) At the bottom of the case there is a hexagonal protrusion with a hole that has threads in it (pictured below). The hole is about 5/16". Is that the crankcase drain plug?

2) I removed all the hardware holding the inner cover on (except for the cotter pin, thank you so much for the tutorial on that) and the auto-advance unit. I made a mark on the camshaft and the cover. Now, how do you keep the camshaft from spinning in order to take out the bolt? My manual, (the original red one) just says to take it out, but not how.

Gordon, and everybody helping, thank you so much. I know im in way over my head, but I want to get this going again to enjoy the fall riding season, but don't have the funds really to have it done.

Here's two pics. One of where I think the drain plug must have been (and if not, where the F is it?)as the only other holes have hose connected to them. Unless it's that bulbous hex/bulb bolt thing coming out of the front??And the other is where im at right now.

There is no crankcase drain plug, there is a large square sump towards the front but leave that alone, its a dry sump engine so there should be little oil to drain from the engine. You look to have found the gearbox drain plug which for some reason has an early plug fitted with a level hole (there is a tube which only allows excess oil to drain out, to remove all the gearbox oil remove the large hex, and buy a proper B50 gearbox drain plug to replace it.

Unscrew the bolt holding the AAU on, the engine will stop the camshaft rotating as it will attempt to turn the engine but spring pressure and compression will stop it.

So you're saying the hex in that picture above IS the drain plug? Because it appeared to be molded to the case. I did try but because of the frame you can't get a socket on there. I can try again with a wrench when I get home..

CT...hang in there. We'll get through this in spite of ourselves. You're doing the right thing by taking your time.

Here's what kommando's talking about.

The Transmission oil drain plug



The Transmission oil drain plug you have




The crankcase sump cover (in a dry sump engine...MOST of the oil is pumped back up to the oil tank)



Okay, I'm just grabbing stuff lying around so some of it is dirty (don't hold that against me).

I'm also using an earlier model..(that's why my cases don't look exactly like yours)..BUT if we need to I'll pull a B50 engine off the shelf and start using it for the photo's.

Hang in there....we'll get it.

Opie Gone Bad

Awesome, thank you so much for all the pics! So will I need that bolt that goes into the bottom of the drain plug eventually? By all that grease and oil wasn't there a few months ago when I started riding, I cleaned it verrry well. Im a little embarrassed...

Don't be embarrassed, they all look like that.

I see no rust, that oil and grease has its uses

Yes you need the bolt or the later single piece one to replace the whole thing, the later single piece one has a O ring which cuts out another leak.

Also- what do you guys think I should I do about the stripped out primary drain plug? It threads in, but then doesn't tighten. I probably shouldn't worry about it just yet, but at the same time if it's a part I need to order and etc...

CT, you'll need one type of plug or the other. The second one (the one you have?) has that tube with it.....the top of the tube (with the plug installed) is supposed to be the oil level. You remove the smaller bolt and fill the trans case with oil until oil comes out and then you know you have the proper amount. See.....BSA meant for there to be some oil on the bottom of the engine, it keeps things from rusting.

Being a cheap arse myself....once you have that main drain plug out..if the threads for the smaller bolt are stripped...retap it for another bolt or epoxy it closed and become a PDO yourself!!!! We've all (well, a lot of us) been there.

Wow....we're answering you so quickly I can't keep up.

Primary drain plug, I need to take a look at that. you wouldn't want it falling out while riding.

Re tap for a larger bolt/screw?

Helicoil? (the fastener sponsor on this site might have the correct one?)

It's just a plug and not holding anything on...just keeping the oil in.

Your call on that one....Opie Gone Bad

I just took a look at my B50 and it would be hard to keep an eye on that primary drain plug while riding. If it fell out and you lost the oil....it could get ugly.

So for me (and I'll jury rig something in a heartbeat) that kinda rules out jury rigging stuff like teflon tape and Loctite Thread Fixer.

Maybe somebody has a better fix than retap or helicoil type fixes.

Opie Gone Bad

I had taken the spark plug out and used a t-handle to find TDC (the manual said I should do this prior to taking the inner cover off) so I guess this is why it did not build up compression allowing me to remove that bolt from the auto advance unit?

CT. So it seems you have the earlier type gearbox drain plug, the one with the pipe in Gordon's pic, and that the smaller drain bolt is missing. Running the bike will fling small amounts of oil into the pipe and without the smaller drain bolt to stop it, the oil will gradually leave the gearbox and, instead, protect your frame from rust.

How much oil came out when you removed the outer timing cover? The specs say 280 cc in the box. (And could a far too low oil level be part of your gearbox malfunction?)

Maybe im stupid, but how the hell are you supposed to get a wrench or a socket on the damn drain bolt with the frames crossmember in the way??!!

Also, now that i have the cam bolt out, how does the auto advance unit come off?

So, i took a thin 19mm wrench and bent it with a torch, and although it slightly rounded corners, that bolt didnt budge. It looks seriously as though its just a part of the case. Molded there. Theres no seam.

Okay, gonna break out the vise grips, heavy hammer, and the for sale sign.

Now, I have little to no real unit single experience....

But, is it possible, those who know, that some DPO didn't put some sort of sealing washer between the drain plug and case, and since they sinched it into place, it bound up the first thread, and now will require getting a socket onto the hex, so it can be turned loose, without boogering up the hex's shoulders??? It's gonna be tight...
And as thin as the shoulder looks, vise grips aren't gonna hold onto that drain plug for long...

Looking at the pic given, I see some possible ... joint?

This means the engine will need to be removed from the frame for CLEAR access to the drain plug...

Here's hope-ing you haven't yet attacked the drain plug...

Gosh CT you were doing so well. Calm down and take a breather

First off......FORGET about taking the tranny drain plug out if it's that much of a pain. It might have some of Mr Healy's famous red loctite on it...so save it for another time. Look for a bolt that will fit in it's over flow and move on. You'll just have the tranny oil coming out when you take the inner cover off....no big deal. (if you can't find a bolt to fit PM me your snail mail addy and I'll send you one)

The auto advance is a tappered fit....where you took the bolt out....it has internal threads. If you can find a bolt that fits those threads....screw it in and then LIGHTLY tap the bolt sideways...and the auto advance will fall off.

I just got called back into work.....so I'm outa here for a bit.

Good luck.....somebody will fill in the spaces...hang in there.

Opie Gone Bad

Follow Gordon's advise and instead stick a tray under the inner cover to catch the oil when you take the cover off. Wonder if BSA changed the threads in 71 and by forcing an old drain plug in a DPO has jammed it in tight, if so no biggy, leave it for later.

The outer cover is already off. There can't be much oil left in the gearbox, or am I missing something here?

You're 100% correct Pelle. Most of the oil should have passed through that crossover hole into the outer cover.

Good point.....

I just hope CT hasn't gotten frustrated enough to have given up. I know a lot of us feel his pain.

Opie Gone Bad

That's right, no reason to give up. I think your pictures are very helpful and I'm sure CT can sort it all out.

Theres been a steady flow of oil out of a weep hole that has slowed down so it must be at or close to that level. Im going to put a pan under it and give it another go after work. But the auto advance is now off (thanks gordon) and ill get the cotter pin out next. I know its slow goin, but when i get frustrated i hop over to my 78 Honda cafe project. Ill post updates later-thanks!

CT.....Pelle is right, the oil is pretty much gone by now. There won't be much (if any) left in there.

Let me tell you something......I know you can do this. You've asked questions, taken photos and answered the replies you've been getting. NONE of us were born knowing this stuff so we've all been in your shoes at one time or another.

Add all that stuff up and the fact that you heated and bent that wrench....my bet is you have the skills to do this.

We'll answer questions, take as many photos as needed and try our best to get you through this. Once it's done....it'll be a snap if you ever have to do it again.

Take care and glad your hanging in there.

Opie Gone Bad (who was know as Gordon in NC until my bad side showed up)

In a past life i was a steelwoker/overhead crane mechanic so ive got some mechanical ability, its just the fine motor stuff like this thats daunting. But im confident ill get there with the help from you fine folks.

Is this a fine motor stuff, its as Gordon said Briggs type technology and crude at best but nice and easy to work on but you need the experience first so you know when to use the hammer and when to be more subtle and use the rubber mallet .

Ha, you should see my lawnmower! lol

Ive got the cotter pin out and all the bolts/screws, but somethings getting stuck on the kicker side. The camshaft side is free though..what could be hanging up in there? The left side oft.he inner case pulls out just a little bit, butt hen theres an audible little knock and it stops.

Have you undone the mainshaft end nut ?

Matter-a-fact....no. i thought it stayed on the assembly.

CT....sorry for the slow reply but I was trying to catch up on my house painting duties.

Also sorry for being so lame.....wak is correct. Remove the nut off the main shaft and remove the kickstart gears/spring/sleeve (they will just slide off). I forgot (happening a lot lately) that step....sorry.

That should do it......Opie Gone Bad

Undid the nut, it came off a bit more. But still hung up on something.

Can you tell if the shifter shaft is staying in place or is it trying to come out with the cover?

If it's trying to come off with the cover you might LIGHTLY tap on it as your pulling on the cover...once the cover starts to move off of it it should come loose.

You got the nut off the main shaft...AND removed all those other bits....two gears, a spring and a sleeve...and maybe a shim??????

Make sure the cam plate (the thing you pulled that pin out of) is staying in place. If it's trying to come off with the cover LIGHTLY tap on it with a drift to make sure it's free of the cover.

Opie Gone Bad

The cam plate and shifter shaft needs to stay in place...so you're only tapping on them LIGHTLY to make them come loose from the cover.

I wish I was sitting there instead of here.....it would be SO much easier.

Opie Gone Bad

As you pull the cover off you also need to tap gently on all the items that are going to stay in the box, mainshaft, camplate, shifter shaft. When they are in normal position they can wear where they rub and then they stick as the marginally thicker areas come into contact with the inner cover holes.

Newsflash on the drain plug photo. What appears to be a hole in the gearbox drain plug doesn't go all the way through into the gear box. I have a couple of these plugs taken out of OIF singles and have always thought WTF since the hole is blind. Just took one out of a B25T last night. So what you have is an overly tight drain plug. It is unlikely its a wrong earlier one cross threaded in. Try sticking a wire into it and you'll see what I mean. I bet threading a smaller bolt into it will bring no joy either.

Peter

if you think its hard taking it apart then wait until you want to put it together, its why bsa recomend taking the clutch off ,all the gears and selectors then stay on the inner cover almost like a cassete type box.

Okay, so this is where I'm at now, I had to pry a bit behind the left side of the case to get it to come out about 1/2 inch (once I had taken the main shaft nut off). And it doesn't seem to want to go anymore. And it doesn't seem to want to go anymore. In fact, I'm afraid it would be hard to get it to go back to where it was at this point. The right side seems to be freed up though.

I read on a b50.org thread that "Mine was very hard also to take off without disassembly of clutch, but when I bought new mainshaft, its been easy after that. Maybe my mainshaft was bend a little and stuck on bearing??" The entire thread HERE

Maybe that's the problem....?

It seems like I only get five minutes here and there to work on the bike before someone needs me for something. Arrgh...

Well, when you think about it the only things he's done that he wouldn't need to do if he ends up going through the primary is....

Removing the cotter and the pin out of the cam plate.

Removing the nut/gears/sleeve/spring off the main shaft.

Everything else he would have had to do anyway.

CT.....there should be nothing else holding the inner case on except for any friction/sticking of the mainshaft, cam plate or shifter shaft.

When and if you get the inner cover off...try to keep everything in place (not hard to do if you go easy)and those three items should slide back into their slot/holes without to much trouble (at least IME)

If you fail to remove the inner cover this way. Put the kickstarter gears/and bits back w/nut. Put the pin and cotter back in the camplate and have a go at the primary side.

Opie Gone bad

CT we were posting at the same time and you beat me to it.

You say the cover has moved 1/2"......but the cam plate looks (from the photo) like it's still stuck in the case. If you have moved the cover....the camplate should be back inside the case 1/2"?????

Hard to tell.

See what I wrote about giving up going in this side and going into the primary.

Opie Gone Bad

If it doesn't come off tonight with a little coaxing I guess I'll delve into the primary side.

Just wondering though, does the ring clip ( LIKE THIS ONE ) that's on the main shaft have to come off?

It's right here:

What Elijah says.........unless some how the shaft is stuck to the bearing (which I don't think it is???????)

I'm out of here for a bit.....probably a good thing because I'm not sure I'm not making it worst.


Opie Gone Bad

The circlip holds the ball bearing in place , mainshaft should slide through the bearing.

If that circlip is ON the shaft, I'd have to say YES!

But, if it's located in the case, right at the point of the arrow, NO! It would just be retaining the bearing in the case...

Was this clear?

It looks like the camplate is the problem, have you removed the pin, pull it out if you haven't, if you have place a screwdriver blade in the slot and push the camplate in, it will compress the spring and should move back out a bit when you remove the screwdriver. The camshaft looks to be hanging on the oil seal so push that in too.

Yeah, I removed the pin already, and the camplate doesn't seem to be hanging up at all. I think it's just out in the pic because I had been pushing the inner cover in and out trying to get it freed and the camplate moved. As I pulled the cover off, I would push the camshaft back in, but as of now it's kind of stuck where it is. Should I tap it in?

Yes, tap the camshaft back in or the cam followers will drop and you will also lose the cam timing, not that its difficult to redo just you want less to do not more. Hopefully the cam followers have not already dropped, check the rockers do not have excessive clearance.

CT.....you do understand that the camplate shoukd stay in place and the cover comes off of it. Same with the shifter and the main shaft....if the shifter and or the camplate moves with the cover when pulling it off...push them back too.


Sorry this seems to be such a pain....I've never done this with a B50 but I don't think we've left anything still attached....that puppy should come off.

Wish you were closer.....I'd be there in a heart beat....opie gone bad