G: Gearbox (Twin) New Gearbox: Help Needed

ehb86

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Thanks Ernie and Robert, I'll add these to my list for Wednesday/Thursday when I'm back and report in.

Mark
 

vibrac

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The 5 speed boxes have their own "Can of worms" to sort through, including the cam plate spindle that can foul on one of the three selector forks, but the 5 speed selectors are quite different in operation to the stock 4 speed.
Dont say that Greg I have a 5 speed about 1 day from testing...
the last one (1999) I fitted gave no problems back then there was a question about where a spacer fitted but that was fixed. there is a bit of a lack of instruction with the cluster and the photo of the cluster is back to front
Any more info about the can of worms?
 

greg brillus

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I just bought a 5 speed cluster from the Uk, and like you say, no instructions........That in itself is quite poor in my opinion, not everyone can work out these things. There have been several versions of the 5 speed box that I know of, the ones here started back in the 90's when the RTV's were being created. The cam plates of the variants have all been different, and the ones here need more rotational travel than a stock 4 speed plate. This meant that installing one to an assembled engine was very difficult, as the bevel stop in the roof of the gearbox housing needed modification to allow for this extra travel. The kits made by Quaife don't suffer this issue as they seem to have worked out how to select all gears with the same travel as a stock cam plate. I did have an issue with one where the spindle protruded below the hole in the cam plate bevel gear and this fouled on one of the selector forks, as there is one that passes under this area. The ones from here did not have the small parts that limit the travel of the G 66 AS lever either, probably because of the extra travel mentioned before needed for the cam plate. Like all these mods to these bikes, you have to trial fit everything and assume that some fettling will be necessary........... I'm well use to it now. The 5 speed box which was one of the later ones that Terry supplied for a time, was the one I used in the HRD twin racer I built. I had to carry out some re-shimming of the gears and shaft end floats, this was because the cases had the centers machined from weld repairs that had left a gap in the cases, my guess is we lost about 0.020" from the joint face. Apart from that, the gearbox has performed perfectly and it is fabulous to use, coupled to the Bob Newby belt/clutch kit that we used............ Just for your info Tim, we run 40 weight Morris castor oil in the box. Cheers................. Greg.
 
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Robert Watson

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I have fitted 2 Quaifes and one of Terry's 5 speeds. The only issue I have encountered apart from the "Check that the shim is in the right place" which probably took less time that them actually putting the shim in the right place, was the spindle sitting just below the cam plate and fouling the center shifter fork.

Quaife I think made the first 5 speeds for Sportspower (John Surtees Co) and the first batch were all close ratio with a tall first gear. Dan Smith got probably the first one sold and made some new bits (as one does) to give it standard ratios. That was pre 1989 as it went into his short rod Shadow from new and it was first on the road in 1989, so they have been around for ,more that 30 years now!
 

Monkeypants

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As an easy trial, you can just back the detent pin spring holder out a bit and see if shifting improves.
I ended up with 2 sealing rings the holder, things were a bit clunky with just a single ring. As others have mentioned, a little extra spring tension here changes operation quite a lot.
Re instructions lacking for the 5 speed- I have a full set of 5 speed instructions from Surtees Sport Power here. If anyone needs these, I could try emailing photos, should be legible.

Glen
 
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Little Honda

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First off, thanks very much to everyone for great suggestions and such quick help. I'm going to try to answer questions in order.

Robert, putting it together and getting them to settle in was kind of where I was headed. The layshaft is in correctly, I measured it on assembly after reading about that length difference in another thread here before I started assembling. I'm going to go check out the G9/G10 and G9/G7 mating per Greg's suggestion and if all is well there I think I'll reassemble and try running things in a bit. Also thanks for your generous offer of help. I would definitely take you up on that if I can't get it straightened out.

Greg, thanks for that valuable insight. I'm going to be away from the bike for a few days. I will check the gear mating out when I'm back and report what I find. That sounds like a very likely culprit. It would fit with what is happening very well.

Bill, thank you, I've tried it both ways, cover on it's the same result. Then I've pulled it off to switch out cam plates, etc. and ensure that I can get it to move through the gears with a little help. I've swapped pinions on the cam plates as well to be sure they weren't binding due to height differences, etc.. Thanks for the suggestion though and I'm sure you're correct, the plate takes care of shaft alignment and stiffness.

Vibrac, thank you, I believe I've got it right but never hurts to double check..... a few times with me.

Chankly, I will look at that as well.

Thank you all... I will report back mid week after I've had a chance to check things out.

Mark
My friend reported similar problems on a box of his and could not find any fault, until he found out, that
the spring-loaded peg which fixes the cam plate on its outer surface was machined at a wrong angle.
(Supplied by VOCS). Fitting an old original solved all problems. If you still have the old one, why not try?
 

vibrac

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One strange item in the kit there was a G112 in the kit together with the pin that is riveted at the end of G66AS but the roller G112 was alloy! I already had a new G66AS and I am reluctant to fit another pin and an alloy roller I know these components were not in my 1999 kit
There was also a G59 (the toothed part) and a rivet to make a G59AS this I did use, but back in 1999 I did not as I could see no difference in the tooth forms and everything worked OK (Ben one the championship twice on that box)
It should not be guesswork a simple sheet of notes would suffice
 

oexing

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Well, I was alerted by tales of " slow" gear changes on the Vincents. So when I found that gear lock detent plunger I was quick to realise I did not like the design: When trying to rotate the camplate the plunger gets a lot of side load from spring action pushing it into the v-slot that prevents the camplate from turning. So the plunger gets high side load when it has to lift a bit and side load in its bore creates quite some friction - that I would not want in gear changes. Also the pointy top of the plunger is not great but essential as there is no fixed orientation for it in the bore. In the end I designed a lever and only a spring is in the old bore for preloading the lever. So I am quite positive about this for getting smooth gear changes. Sure, this will be a bit more agricultural than on smaller bikes when you look at the massive gears inside which I guess would easily handle 200 hp no problems. Now compare this with gears inside some Ducati or the like !!

Vic

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P1050798.JPG
 

greg brillus

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Tim that extra G 112 and the rivet you mention are not for the roller on the end of the G 66 AS. The alloy sleeve slides over the peg section of the G 49 lever stop, this is the peg that the legs of the G70 spring sit around. The other rivet part replaces the same rivet in the G 66 AS lever, near the pivot point again where the same G 70 spring sits around. These parts then limit (reduce) the travel of the lever G 66 AS so the gearbox does not overshift. Well that's my take on it anyway............ Cheers.
 

Monkeypants

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John McDougall played with the cam plate on the standard box.
He copied the general shape of the Norton AMC camplate. The AMC box is well known for slick shifting
This camplate change made the 4 spd Vincent gearbox shift like a Norton.
So it would appear that it's not the heavy gears that slow the shifting, as is sometimes suggested.
He was considering producing small lots of the modified camplate, but never got around to it.
One thing the 4 speed Vincent box has that a 5 speed Quaife doesn't is a 1.19 ratio (3rd) , a single gear that pulls hard from 60mph to up to 100 mph without over revving. It's an excellent ratio for hills, two up. You can run along at 70 or even 80mph two up on an 8 percent grade and have the engine right in the sweet spot , not overly busy with revs but producing lots of grunt.
This is 3800 rpm at 70, 4300 at 80mph.

Glen
 
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