greetings. i've been told for years that it can't be done, won't fit. this i've accepted, but i've got a '64 pulled apart on my bench and i can't see the problem. it looks to me like there's space for everything to fit but i figured i'd check to see if anyone's bothered. thanks gents.
Don't know about the early cases but I can't see any reason why not? What I do know of them is the barrel spigot hole is smaller and needs opening to accept other topends but that's it as far as I recall?
Black Widdas S.C. - Taking idiocy seriously since 1999.
It was a while ago that I looked at doing this for someone - if memory serves correct... The axle/shaft for the 4 speed is longer/doesn't space-wise fit & the bearing on the flyside of the case is different (smaller).
lay shaft, axle, and gear stack, looks pretty good
stack in the clutch side case
all assembled with a 2 or 3 mm gap, balls!
on closer investigation the difference is in the lay shaft. the 4spd has just that much more on it to prevent the cases from coming together. solutions would be to either remove material from the lay shaft on the first gear, which could weaken the shaft, or from the kick starter side, which unless i wanna bump start seems like a pita, or possibly mill out the lay shaft bearing housing just that much deeper. either way it's not happening on these cases. eh, so there you go, it won't fit.
Post by jonnysnatchsniffer on Oct 24, 2010 17:50:52 GMT
have you tried the 90 shaft with the 4 speed selector with thinner shims ? looking back ive put a 4 speed box in a 66 v90 that had the small cases and crank as i seem to remember the crank had a bronze bush, but the talk of bush has now fried my head and i cant remember what we did but it worked ok
How time flies! 8 years ago I was building a '64 V90 engine and at the time I thought it might be interesting to look into what it would take to put a 4 speed box in a 3 speed case. For review, the earliest V50s and V90s were just a bit different from subsequent models. The engine case is smaller, the spigot mouth is smaller, the flywheel is smaller and subsequently, generally speaking, there's not quite enough room to fit a later 4 speed transmission.
At the time I had gotten as far as identifying that a commonly available 4 speed secondary transmission shaft was 2mm longer than Its 3 speed brethren and wouldn't fit. And at that point, with the resources available to me, I was forced to concede I could do no more. These days I am building another early V90 engine, have access to a welder, a mill and a lathe, and so my ability to pursue this idea has improved considerably. As I knew the 4 speed secondary shaft was 2mm too long, my first solution was to grind the kick start teeth off a damaged one to make the shaft fit.
That worked just fine and, in theory, was a quick and dirty way to add 4 speeds to this engine. Only problem, you could now only bump start the bike. That may be well and good for you or I, but is completely unacceptable to various "significant others" out there who may eventually be riding this thing. And let's face it, being able to use the kick starter is more than just a little convenient so I persevered.
Next step was to chock a rusty primary driven gear up in the lathe and remove approx 2mm from the length of the kick start pinion bearing surface.
With it assembled in the case an unmodified 4 speed secondary shaft fit, so that's good.
The down side of this modification was to allow the kick start pinion to be in constant contact with the corresponding teeth of the secondary shaft. My solution was to add material to the kick start quadrant so that at rest, the pinion would be moved away from the teeth on the shaft.
I’m no weldor but this will do.
Starting out reestablishing this angle with a file.
Indeed, for a top end I have a 3 port, 100 sport cylinder with a turned down spigot. Additionally I found a Kawasaki dirt bike piston with thin rings that will let me open up the exhaust port a bit and let it breathe.
Regarding the 4 speed work, I still have a fair handful of things to do yet before I can call it done. The kick start quadrant works to some extent, but not quite. With no buffer in place the quadrant can swing far enough at rest to effectively trap the pinion, but with the buffer, not so much.
This is how much lower the pinion needs to sit.
Eagle eyed among you will notice that it’s not much.
I'll grind some material off the leading edge of the quadrant to allow it to sit closer to the case. That will do the trick and so that should be pretty much handled.
As an aside, the quadrant is hardened steel and my weld is not and ruined the temper of the metal a little bit. And I didn’t think of it at the time until the pinion started chewing up my fancy modified quadrant.
Fortunately I was able to reharden that area with good results.
And here I thought the issue of the selector would be a no brainier. I had a notion that I could just cut opposing arms off a 4 arm selector and that would be good enough.
Sacrifices were made.
But the selector arm channels are deeper in the 2 arm V90 axle than a 4 arm axle. This allows a modified 4 arm selector to flop around in the axle like a floppy thing. The V90 selector is correspondently thicker and more robust.
The bottom one is early V90, and the top one is not.
Presumably this makes the 2 arms strong enough for the task and to keep the selector stabilized in the axle. But really, a floppy selector just won't do. Or work.
So I seem to be left with using a 4 arm axle. Now, I'm not opposed to the idea of using a modern axle, but I imagined using the original axle would prove to be a bit easier. And so, in turning my attention to a modern axle I find, low and behold, its maybe 2 or 3mm longer than the original V90 one. Ha!
I could weld it up and turn down that 2-3mm but then I noticed, in my perusing that SIP has this little gem. www.sip-scootershop.com/en/main/base/Details.aspx?ProductNumber=16530160 It's a 2 arm 4 speed selector for a first series 50 special. I now remember reading somewhere that they used a 4 speed box in early cases. I’ve personally never come across one, but that’s not saying much. So the question now is, will that little 2 arm 4 speed god-send work with any old gear box I have lying around here? That seems pretty unlikely. Or do I have to track down, a perhaps unobtanium, early 50 special gear box? That also seems unlikely.
So eventually, I’ll first get that 2 arm 4 speed selector and see what gears will fit. And if that’s not a viable option there’s some pigeon poo welding to a 4 arm axle in my future.
Well, I have yet to get the aforementioned 4 speed, 2 arm selector. I gave it some thought and instead pulled a damaged axle out of my pile and welded it up. At least this way I know that any 4 speed box I may have will fit.
This mess will give some material to machine 3mm from. If I didn’t do that there would be nothing for the face of the bearing to, ah, bear against.
Repaired some damage. I can’t remember how these corners busted out, but it’s “better” now.
And now that I have this in front of me I can think this through a bit more.
Removing 3mm from the axle will push the hub out a corresponding 3mm away from the back plate. From the stand point of tire and break shoe alignment, I can live with that. Except I hadn’t considered that there isn't that much surface on the hub for the rear axle seal.
Raise your hand if you anticipated that.
I can... A. Pack the seal out 3mm. I would consider mounting a spacer btwn the backing plate and the case. Except the bearing would be unsupported unless I make another spacer for that as well.
B. Destroy 3mm of splines in the hub. If I, in essence, come in with a great big drill bit and take out 3mm of splines from the hub, that will allow the hub to sit back deep enough on the axle to catch the seal again. This may potentially weaken that area and would mean that I’d have to similarly modify any hub being run with this motor.
C. Cut a 3mm wide groove at the beginning of the splines. This does the same thing as above but to the axle. I’ve stripped out hub splines but never axle splines so I feel better about doing this. Also, any hub would fit. And it appears that there are a few extra mm of unused splines on the out side face of this drive plate. Bonus!
Subsequently this is the option I’m leaning towards.
D. Cut new splines further up on the axle. This is the most ideal solution but one of the least practical. Really, my ability to replicate these splines accurately is limited.
E. Extended the sealing surface on the hub. Not really an option, but I’m thinking.
When I machine the 3mm off the axle I’ll do “C” at the same time.
However, when the question comes up again of whether you can fit a 4spd box into the early cases, I'm still going to say no!
Please keep posting as you go, it's very interesting.
Thank you for the kind words John! I’ve been thinking about this since the days of the old Smallframe yahoo group. Which is essentially to make a 90SS spec engine for the early V90. Names such as yours, Chris Markley, François, Mike Durso, come to mind from that yahoo group. It’s good to see that you’re still active.
"So, basically it all just bolts in?" After a fashion.
The dead “easiest” thing would be if you could find an, aforementioned, 4 speed 50 Special box. My intention has been to modify the case as little as possible, so that means limiting the bore size. But it also means a correspondingly limited power output, which I think would be appropriate for a 2 arm selector. Although I remember reading on the yahoo group of old about someone modifying an early case and running a 135 Malossi. On a 3 speed 2 arm selector. Not sure how well that worked out.
Anyway. Blurry, action shot! Measure 3mm, scribe a line and cut back to it.
I didn’t have the angle of my cutter quite right as I took out more of the splines than I would have liked. But it works!
The hub butts up against the bearing now. In stock form the hub nestles into the axle splines and stops short of the bearing by a few mm. I’m not sure why Piaggio did it that way but it means that I didn’t need to remove as much of the splines as I had originally thought. Food for thought for version 2 perhaps.
Once it’s functional, make it pretty!
Modified axle and early V90. What's left is to rebuild a clutch basket with a shortened driven gear and put it all together.