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.