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Discussion Starter #1
Does anyone know what parts would be involved and what procedure to follow to change a Unit four speed into a five speed? I'm sure that this must be possible, but would appreciate the knowledge of those on this group before wasting time and money finding and putting togeather parts only to find that they do not work togeather!!
 

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i found ,two years ago on ebay a guy who solded a long study about the subject for a few bucks and i think he is still selling it(it was a pdf file i think)
ben
 

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As the lay-out of the four and five speed gearboxs is the same,and the shaft positions and overall lenghts were unaltered, it is very possible to fit the five speed gear clusters into engines that were originally built with four speed gearboxs. If possible the fitting of the 1973 cluster and later is preferable to the 1972 cluster due to a number of week points, these were sorted out by 1973. Also there were many variations to the sleeve gear in the early five speed boxes so try and steer clear of them. All the twins used the same components so clusters from twins can be fitted. Don't try and fit a five speed cluster from a Trident as they were different.


H.T.H. Regards TripleGuy :cool:

[ This message was edited by: TripleGuy on 2006-11-26 05:54 ]
 

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This is a VERY GOOD mod for a 650 and totaly transforms the motor. Post 1973 as Tripleguy says but if you are offered a Trident cluster, grab it! Only the main shaft needs to be changed and these are redilly available.
The 5 speed cluster will fit ANY B range gearbox from 1950 through to 1983. Try to avoid the 3 spring index locator used from 1971 to 1973, these can be changed to plunger spring with a little drilling and thread tapping.
If you are using cases from pre 1971 ,Imperial timimg side main bearing) you will have to remove metal from the inner gearbox cover where 1st / 2nd main shaft gear passes through AND the casting where the sleeve gear passes through. These are only clearance and can be done with the engine in frame.
The biggest problem is finding the cluster at the right price in the first place :???: Try to get the camplate, index plunger body and plungers, selectors and selector rod as these are different to the 4 speed ones. The gear change spindle can be knocked out to make right OR left hand change.
Roy.
 
J

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Discussion Starter #5
Is it correct to assume that there will be no drop in the top end RPM since the final drive ratio is 1:1 on both the five and four speed boxes? If this is the case where can I find either a larger engine sproket or smaller rear wheel sproket, and what would be recommended set up be? I'm looking to cruise at around 75MPH for hours at a time. I still plan on going with the five speed, but am trying to put togeather a total package that will work best for my riding style.
 

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[ This message was edited by: KADUTZ on 2007-01-28 19:43 ]
 
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I'm not sure that displacment is the issue. I don't think that given the HP and Torque figures that this is an unreasonable goal. Undoubtably a 750 kit would help, but I've seen WL servicars with lower numbers cruise at that speed with the right gearing. I too had the same concerns so as far as breaking goes I was planning on upgrading to the Grimeca DS brake. Is this a crazy goal? IMHO as long as the engineering is sound anything should be possible?
 

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[ This message was edited by: KADUTZ on 2007-01-28 19:43 ]
 
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Discussion Starter #9
thanks for the heads up on the front end. Round here the speed limit on the highways and interstates is 70, but most people go about 80-85MPH.
 

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I just finished driving 22 hours over two days across Nevada, New Mexico & Texas at 80 - 90 steady, with troopers passing me both ways. No sweat.

You can go 200 miles with only 2 - 3 degrees steering input on some of those stretches...
 

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Great info on that gearbox swap. I just happen to have a blown up T140 over there, and my '69 Bonneville over there.....hmmm....

I gotta go with Kadutz on that speed/ mileage thing. I personally can't go more than a half hour or so, at that kind of speed, on any of my Triumphs,or BSAs, without stopping to shake some blood back into my hands. And that advice about the safety wire is not to be ignored.

Not to ruffle any feathers here, but if I were going to do that mileage, at that speed, on an old British Twin it would be on a Commando.
Cruise all day at 80 in comfort.
Triumphs are for mountain roads, not the super-slab.
:cool:
 

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I agree about the mileage at speed comment. I did a 400 mile day up to and through the Texas Hill Country on my '75 Commando, with both over and back stretches of 150 miles at sustained 80 MPH. Never missed a beat.
 

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The 64 is a good enough starting point for a cruiser with it's heavy flywheel. My 68 is a decent enough highway bike and it still has it's light flywheel, but I am considering changing to the heavy one for the upcoming rebuild.
My 68 has the 78 gearset fitted and I heartily endorse the swap, it is the smoothest shifting, shortest throw, most positively engaged gearbox in any British classic. I use the 20T sprocket.
On the rear wheel, fit a 43T sprocket/drum combo. These are about $120 or so, but you get a new drum surface and new sprocket teeth, so fit both new brake shoes and a new chain at the same time. These two changes will dramatically alter the road manners of your bike. Adding a 750 kit is a great idea, as is fitting hardened camshafts, in the case of the 750 kit, I would consider either the Megacycle 51060 or 51015 ( replica of Jomo #15 cams....these are in my bike, with 500 R tappets and special pushrods. A light valve train is always a good idea for longevity and for security.... a floated valve can ruin a ride.)
The DLS Triumph/BSA wheel can be fitted to your forks, but I would use the later, wider forks from a 68-70 650 or Trident, or from a 68-74 500, although most of these had the rigid mount top yoke, which I would change for the rubber mount bar type of the 650s and Tridents. These forks are the "shuttle valve" damped type, with damping on both the compression and rebound strokes. New hard bronze bushes and new springs and seals will make for a nice set of forks and these DO bolt straight on to your frame. New hard chromed stanchions are available as a nice upgrade.
The disc forks do not bolt straight on (unless they came from a Trident), as they use different bearings...you need the adaptors that the Trident's used.
If you are into the engine, consider changing the con rods to the later, thicker ones found in the 68 and later 650s and then balancing the engine.
For security, safety wire is a little cumbersome and a bit of a hassle, I use loctite...there is even a type which will wick into already assembled nut/bolts. If you have a nut and bolt situation, you can use NF bolts and locknuts...I favor the Jet or Kay nuts, as found on aircraft, as they are quite strong, self-locking, and have a reduced hex for easier access.
My bike put on 85K miles.....and the engine is still running in another bike...a friend is using it while I rebuild his TR7 engine. The chassis is being powdercoated. I will be pulling the engine down and doing a report on it's condition early next year. I'll just say, I suspect it is in pretty good shape, from what I have seen of it while doing the engine swap. I have used synthetic oil, mostly Mobil One, for most of it's life.
I was able to run at 75 to 80 mph all day........rather the BIKE could, but I am in the stop and walk around a bit every so often group. Old guys aren't quite so durable, unlike well set up old bikes.
 

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[ This message was edited by: KADUTZ on 2007-01-28 19:43 ]
 

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The adaptors are top hat type...a flanged bush...they bush down the bearing id to the smaller stems of the 71-on forks. I got a set from JRC some years ago, and made a drawing with the measurements.....but don't know if I could lay hands on it right now. Simple machining job. Just measure the diameter of the stem and the ID of the bearing and make it a push fit in the bearing....about a half thou clearance, and a thou and a half for the stem clearance...a sliding fit. You'll need two. I believe the flange thickness was .100", or thereabouts.
Can't do that here, but you can on the Big Island of Hawaii. Lotsa roads and not many people. I used to go there every year, but haven't done the Labor Day thing for a few years now. When I finish the house and the new interisland ferry starts running, I'll do it again. I am negotiating with a guy on the Big Isle to buy his 72 Commando, which I'd keep there and ride there.
Jhat......yes, the top gear ratios are the same, but the first of the five speed is a little lower. So, you don't lose as much of the first gear grunt when you change the final drive sprockets. With the 20/43 replacing the stock 19/46, fourth of the five speed is pretty close to fourth of the four speed, and then fifth feels like an overdrive.
 

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[ This message was edited by: KADUTZ on 2007-01-28 19:44 ]
 

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[ This message was edited by: KADUTZ on 2007-01-28 19:45 ]
 

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Maybe he went to Peculiar, Missouri. I just love that name! I'm sure I'd feel right at home there. A duck to water as it were.

I found a slimline featherbed frame with a title and a NOS Roadholder front fork, so I've decided I'm going to quit making excuses and build a Triton. I've picked up a ton of useful information laying back in the weeds and listening to you guys. Keep up the good work! Just don't send me a bill, OK? :cool:
 
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