So now I have the bike sans gearbox and drive-components on my improvised stand. And what a beauty it is, too. I must admit to having fallen in love with it, such grace and elegance, so well thought out and the solutions to save weight at NO expense to rigidity of the whole plot, simply genius! And what a joy to work on!
This should be the first thing drummed into us at school from the very first day onwards and for every day after that. If we were to learn only that, it would save us more time, money and stress than anything else in our education – in fact, probably more everything else put together (if we haven’t grasped that one concept)!!
What am I babbling on about, you might well ask? Ah yes, we’ve all heard the ‘stories’, the ‘old chestnuts’ and wisdom of ages passed down from generation of ‘Veloist’ to the next, like “90% of gearbox problems are clutch problems” etc, well, here’s a new one! What happened here, I have never seen happen before, but I must admit, is the result of a stroke of genius by the designers of these gearboxes, for whom we should be ever grateful.
Let’s start at the very beginning: Pud came to me a few weeks ago and said that he’d like me to look at his GTP. The gearbox wasn’t right (he’d seen the job I did on one of mine and knew that I wouldn’t butcher it). It was ‘stiff’ were his words, and on further inquiry, the word ‘tight’ was also mentioned. Oops! Not good.
These two words conjure up uncomfortable feelings at three in the morning on the M6 in January at minus whatever on the way from Birmingham back home, with a long way yet to go, with the bike getting progressively slower, despite the road being level and the ‘tap’ turned on at the same opening. Uncomfortable, because it meant either that the engine was about to seize, or the gearbox. Dammit, put the choke on a bit (to help cool combustion) and ease the throttle about a third and gain some time to think… I would prefer that it is the engine, out here in the dark in the middle of nowhere, if I’m honest, as it’s easier to fix. Only one way to find out! Close the throttle, pull the clutch. If the bike lurches to a halt and the engine is still spinning, it’s the gearbox… and if the bike decelerates at a ‘normal’ rate and the engine falters or stalls, it’s the piston stopped going up and down or very tight.
I have wandered off again, sorry… Back to the gearbox in question and my ‘assumption’, based also on the assumption that we both spoke a common language, this is what I understood by ‘tight’, based on some various experiences in my shady past. And so I thanked him for his trust and graciously took on the job to discover which naughty bearing was causing the problem…
The story so far I hope that you have enjoyed having recorded here on the last two blogs and is ‘history’, so to speak.
With the box on the bench, I could now go about taking the thing apart to see what is wrong. The Sleeve-gear bearing can, technically, be removed from the clutch end in situ and to be honest, this was my main suspicion for the problem. I have a couple of L35N Hoffmans and sundry other bearings here, so not a problem, but it IS easier to take out once all is removed. Before the gears can all come out, the ‘striking lever’ BK65/3 has to be removed along with the camplate pivot, BK64/2. Having done that, I thought, just pull out the ‘pins’ and the rest can be pulled out… I had already removed the nut on the striking lever (almost) while still in the frame, but it was all a bit close, which I why I took the box out. Makes it all a lot easier, SO, a few twists and it came off and then…
Wait a minute! What’s this?!
I hadn’t actually seen this while it was all in situ in the frame, but now… Elementary, my dear Watson! (and the sharp-eyed amongst you would have spotted it yesterday on one the photos already – but I didn’t want to spoil a perfectly good new blog for today by mentioning it!). Could this be the reason that he was having ‘difficulty’ with the box? Indeed, but very different to what I had erroneously ‘understood’ (assumed), the stiffness was not so much IN the box, as outside, and actually was a difficulty in SELECTING gear, not in the operation of the transmission as such! OMG!
So simple, and yet would make the bike very difficult to ride. In fact, IF I HAD BEEN ACTUALLY LOOKING FOR IT, I could have seen it before, BUT, on the other hand, it would have been nigh on impossible to remedy with the gearbox in the frame anyway… C’est la vie! The geniality of the whole design, is that the it is MEANT to be so, as the striking lever prevents the pivot from falling out in the road somewhere between here and Novgorod in the middle of the night. Also very nice is, that it is not permitted to unscrew enough to cause the camplate do ‘disengage’ with not only disastrous, but expensive consequences, quite apart from a suddenly heightened awareness and skill required to overcome a locked up back wheel at speed. (Even worse if the chain brakes under the strain, catapulting you forward freestyle for a second, until it wraps itself around the wheel, locking it up again!) What fun. You don’t have to ask how I know, do you?? (Don’t worry, it wasn’t on a Velocette!)
So, the mystery is solved and here are a few shots to show what happened in more detail. SO don’t forget to light a candle for those long-gone designers of these boxes, who went to such lengths to protect us from the evils of gravel-rash, at least until the gearbox casing design was changed for the swinging arm models! At this point, it might be worth noting that next time your Venom/Viper/Whatever gearbox is out, it might be worth wiring or ‘Loctiting’ this particular part in place, just in case!
Having said that, I have NEVER seen this happen before, but it only has to drop out once, to spoil your whole day!
This is how it ‘should’ look, as far as the distance between the parts is concerned, anyway. I still haven’t taken off the lever and cleaned it yet, only screwed the offending ‘nut’ back in…
The offended striking lever from the inside, showing some road crud and the removed paint and metal filings due to the contact with the face of the pivot…
This is what it looked like after a clean-up. Quite obvious rub-marks and some wear on the finish.
The offendING pivot nut, which I am assured used to be painted black…
To effect a cure, it was agreed that I unscrew the nut as far as possible without disengaging it all inside, clean and dry the thread and apply some blue ‘Loctite’, before doing it up tight again. *Note the shim/washer under the nut, which serves 2 purposes: to prevent the nut damaging the alloy of the casing and to correctly space the cam-plate inside on the shoulder of the pivot, lining everything up nicely inside, which greatly assist the smooth function of the box. The wrong shim, or none at all, could certainly have a negative influence on it all, something to bear in mind on these early gearboxes!
The bearings in the box Pud assured me had only done seven or so thousand miles and despite some water ingress through the clutch cable tower, would not require changing. The gearbox was quiet and smooth and unlike a bigger bike, the box has a relatively easy life. When he bought it 35 years ago, it was already 35 years old and had done COSIDERABLY more mileage and the original bearings were still fitted and working fine… So no reason to dismantle or disturb anything any further, after the “if it’s not broke, don’t fix it” principle, which I thoroughly agree with! Anyway, if it does play up at some time in the future, I am hoping that I might have a further opportunity to work on the bike again, which I would greatly look forward to!
Always nice to have and to use the right tools for the job: Above, the massive spanner for the nut!
So everything will get a good wipe-over and clean, the gearbox will be re-assembled and mounted in the frame, the nuts as necessary re-coated with an oil-based black paint after assembly. Tomorrow the clutch and chaincase re-assembly are the subject of the final episode on the repair of this wonderful little machine. I WANT one!
Oh, and here, just by way of anecdote, have a look at the registration / tax document of the GTP; Notice anything slightly unusual??
What is it registered as (since new)? A Velo-Solex?? Isn’t that a French bicycle with an engine balanced on the front wheel, that runs on garlic-cloves and a bread-stick?? Just goes to show that the officials then, as now, had absolutely no idea what do with a name like Velocette! And that in 1939!
Dr. Peter saying toodle-pip for now!
© peter gouws 2013