B50SS Gold Star

[groily]

Never played with one before and never want to again.
Couldn't BELIEVE that to get the rocker box off - not the head, mind, just the ROCKER box, you have to get the engine out. Or 'all-but'.

Friend came round with a '71 model today with a rocker box leak that made an A10 worst case look like a dribble. I'd said, yeah, bring it round, won't take long  . . . But hadn't realised that at 500cc the engines are too tall for the OIFrame. Nor that the equal length pushrods on the 500cc engine would make me resort to the interweb to figure out which pushrod went onto which cam lobe. Luckily Google was my friend because it is entirely unobvious.

5 hours later, after wrestling with  all sorts of side issues as well, the thing was back together.

Very very pretty and super-light, and I see why people liked them when they worked - but for the life of me I can't believe a factory would make ANYTHING so pig-like to play with.
And as for a designer who went for castings that won't allow pretty well any spanner ever made to go on some of the top end fasteners, well, he should have been executed. I have probably a dozen, no, two dozen, AF weapons of all angles and cranks, open, ring, pivoty, whatever  in each of the usual sizes - but even with a selection that most people call me an anorak for keeping, it was a massive pain in the rear.

Ouch!

[muskrat]

G'day Groily.
I feel your pain. I recently had to take the cam cover off my 78 XT500. Same thing, disconnect everything, remove the engine mount bolts and tilt the lump to the side to get at it. Even took the same 5 hours to do it!
Cheers

[KiwiGF]

If yr mate with a B50 visits again you can get advice from here…. http://www.b50.org/phpBB2/viewtopic.php?f=3&t=8989&p=85376&hilit=Rocker+box#p85376

I hope you did the replace studs with allen head bolts trick 😏 (for your next time)

After shortening a couple of studs a mm or two I can get the rocker box off my B44 engine in situ, in my case to fix the de-comp, I guess BSA were just too cost conscious to do that in the factory 

[groily]

Thanks guys!
I'm better now after some vino, but was an unhappy sod earlier on, have to say.

Thought about allen screws kiwi - but didn't have any to hand and even if I had some, wasn't sure on the 500 if one used in the middle would be extractable or not next time unless the amount of thread engagement was reduced. Darn tight for clearance that one, along with two long ones adjacent the frame centre line that hold the head steady and decompressor arrangement. I understand (after rootling around on the web this afternoon in a bad mood) you can do the allen screw thing OK on a B44 - but knowing as ever the square root of bugger all until I start something new to me, didn't know whether it would apply equally on the 500.
There is also the question of my dislike for using setscrews, bolts etc instead of studs and nuts into aluminium, which is just me being picky.
I guess it's what comes of shoving larger motors in dinky little frames to make for interesting machinery - there's a bit of that with my P11 desert sled, so I should be used to it!

I did try to extract the studs, in the hope they'd have clearance when unthreaded from the head - but the problem of access to the forward and rearmost ones on the timing side on which you can barely get a spanner to undo one nut, let alone a pair to get the stud to shift, put me off after a couple of attempts. Decided to head south and shift motor instead.

So we removed engine bolts and the rear plates (awkward to get at), exhaust, carb to air filter bits, box of electrickery between headstock and front of cylinder head, rear chain split link etc and hoicked the engine up and tilted it to the left to get clearance. Ouch, as I said before - but at least a unit assembly is easier than having to remove primary and clutch  . . . small mercies at least. Tomorrow is another day  . . .

And FAR easier than your H-D primary sage Musky!

[BSA_54A10]

The B50 was built to do one thing & one thing only
To regain the world motorcross title for BSA which the B44 had won 3 times in a row but the new beed of two strokes were just too quick & light for the 441 to beat in the new OIF frame
Thus they stroked the 441 to make the B 50
But the frame was designed around the shorter 441 so naturally the taller B50 did not actually fit
And while the B50 did it's job, it was only for one season
The cure is to replace the studs with bolts as previously mentioned but use high tensile fine thread ones and helicoil the holes or you will end up pulling the threads and have a never endng rocker oil leak that makes A 10's look clean & oil tight .
The other trick is to pull the rear engine mounts and the bottom through bolt which will generally allow the engine to drop just far enough to get the rocker cover off with a bit of effort
They do take a bit of sorting out but when they go they really go
I had to put the entire front end off mt A65L on my B50 to keep the front wheel on the ground,,,, occasionally . 

[groily]

Thanks for that Trevor.
If it were mine I'd do these things, and the 'fine threads' for screws makes better sense to me than a simple swap for capheads.
Luckily it's not mine though, so any crosses are all my mate's to bear. He's only just acquired it, so we'll see how he gets on with it when it's up and running properly.
I said the oil leak made a bad-case A10 look oil-tight - I see you must have been there and got that T shirt.  Luckily, the threads in the head on this one are still good and replacing a very broken gasket ought to do get it to reasonably OK, or oil-tight even.
I suspect it might drop round again though - the electrics are clearly a bit dodgy.
That said, she's very pretty indeed and money has clearly been spent. Time will tell whether it has been spent wisely and in the right places. I am always suspicious of the lure of 'shiny' until assured of 'function'.

[BSA_54A10]

The biggestproblem is th timing cam
Or rather the camshaft bush with the points sitting outboard in a cantilevered fashion .
If it has an electronic ignition & it is carefully set up then they become a very reliable bike once you get used to getting the kick start right
The crankshaft is very very light to give the bike blistering acceleration ( still was not fast enough to out run the blue smokes ) so if you start in the wrong position and do not kick all the way through to the stop and hold the pedal tere then you are highly likely to go into low earth oibit over the bars .
This is made even harder because the stop has the pedal slightly forward of vertical down which  the foot peg prevents your leg getting to if you try to start the bike astride it .