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#856623 08/20/21 7:10 pm
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650 race bike, 4 speed with late high gear. I've had 2 aftermarket trap doors with a bearing to try to control mainshaft deflection and both were too "thick".
I have found a shielded ball bearing that will fit both the stock trap door and the mainshaft. Been using it this season and it has worked ok but I remove it after each race weekend to check it , remove the shields, clean and re grease. But it is only 1/4" deep and it seems it could be pretty fragile.
So, what have I gotten for the aftermarket doors? Maybe BSA? Do A65's have more room behind the clutch basket?
And what has anyone done for Triumphs? I know others have done bearings there, how and what has been used to get more support there?
Thanks, Mike

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There is a trapdoor out rigger bearing for the Unit Singles mainly fitted to B50's, wil check if it could fit later.

[Linked Image from images.ctfassets.net]

Last edited by kommando; 08/21/21 9:10 am.
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There is less room on the trumpet.
I used a 42odx 20id bearing machined out a fraction to run on the mainshaft
just cut the sleeve off. It was 10mm thick i think. The beezer allows a 15mm bearing.
doing the same thing. You may need to skim a few thou off the sleeve pinion too.
They won't seal perfectly but the grease seals are ok for racing and just weep
a fraction, getting them lined up spot on is the trick.

just checked it was 20x35x9 6804

Last edited by NickL; 08/21/21 7:02 am.
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A Triumph gearbox sprocket cover fits a Unit Single crankcase, the ID is likely different as the mainshaft is thinner but the PES trapdoor I referenced needs a sleeve for the bearing to fit.

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The bearing that I found to fit the factory trap door is 1.062 x 1.5 x .25". Only found it in 1 catalogue- Boca Bearings. It seems to be a pretty light duty bearing.
Required no machining and the assembly slid right in, alignment was good on this motor. Still, I think a wider bearing would be better, 9 or 10 mm would seem to be the limit.
I'll look at that Pearson product
Thanks

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Performance engineering or CCM Great Britain.

https://pesltd.uk/?product=G5&ptno=G5

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This appears to me to be a worthwhile investment when I rebuild my 650 TR6R engine, even though it will be for 'steet use."

There is a lot of reciprocating clutch weight on the end of that mainshaft. This may help control it, maybe?

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I'm not usually the guy who adds complexity to a project unless it needs help. In all the years of riding triumphs, I never saw the need for an outrigger until I started racing. Probably the combination of making decent power, sticky tires, frame flex, etc., I saw the sprocket/ chain gouging the insides of the cases. That indicated to me that something in there was moving. For my other bikes, I don't see any need.
Got it, Kommando, thanks

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Originally Posted by Mike Baker
I'm not usually the guy who adds complexity to a project unless it needs help. In all the years of riding triumphs, I never saw the need for an outrigger until I started racing. Probably the combination of making decent power, sticky tires, frame flex, etc., I saw the sprocket/ chain gouging the insides of the cases. That indicated to me that something in there was moving. For my other bikes, I don't see any need.
Got it, Kommando, thanks



shocked


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...I had and aftermarket door with the bearing in one of the T140E. I had some oil slippage there; then RPM (big D cycle) commented that he never used one in any of the racers so I removed the aftermarket and installed a new OEM with the seal.

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They are a must on a racing sidecar outfit.
A65's were known for breaking the rear of the box off without one.
The mainshaft would flex so much it also caused the layshaft top
gear to shed teeth.
4 speed Unit triumphs did the same thing.
Putting a roller race in only made mainshafts snap like carrots.
The outrigger was the cure but not really required so much on a solo
or on the road.
The old saying with the a65 sidecar racers was "if you aren't breaking gearboxes,
you aren't getting enough power"
Sidecar racing was not prevalent in the 'states so maybe they never had the problems.

Last edited by NickL; 08/22/21 1:29 am.
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We've got tri and bsa outfits at our events. Not usually front runners but they go pretty well. Sidecars are becoming more popular every season, probably one of the fastest growing classes.
Maybe I'm chasing a problem that doesn't exist. Aside from some gouges around the sprocket, nothing has happened. Yet.

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On the A65, if you cut back the high gear sleeve there is room to use a 6005LLU bearing with a pressed in inner sleeve that is slip fit to the mainshaft. LLU - double contact seals. It would be nice to get an NU (snap ring groove) type to keep it from moving in against the high gear but I am not sure those are available in LLU.
I did not get an exact measurement but I could slip a 0.585" piece of material between the hub and high gear. With a 12mm (0.472") width there is 0.113" clearance. A square O-ring between the sleeve and high gear will seal there and another between the sleeve and hub. or just one between the sleeve and hub.
Instead of the door bearing I put a housing in the primary cover and used an extended hub nut. The nut has three slots for the lifter to pull the pressure plate. A triple lifter was outside the cover bearing.

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A good solution no doubt, Dave. Unfortunately too complicated for my skill level and paying someone to do it could take too big of a bite out of my budget.

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I have an excellent such product ( support bearing plate) supplied by Jaye Srait's ' Britech' concern for my ' too bloody long' T140 race project .

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Originally Posted by Triless
I have an excellent such product ( support bearing plate) supplied by Jaye Srait's ' Britech' concern for my ' too bloody long' T140 race project .

Blimey, Hi Stephen, wondered what had happened to you..........
Not on the track yet then?

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Hell, no , Nick, not yet ! Slow as a bloody wet week at the best of times, me ! Been a few things going on, including the inexorable encroachment of anno dommini ! I've been a bit active on some other Triumph orientated sites, where it's more convenient to post pics, but have been in occasional contact with Tony ( 'Hillbilly Bike ' ) !
Sometimes I had a look on 'Britbike ', and I must say, what you have been doing with that BSA outfit is bloody fascinating, but way above me !

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Originally Posted by NickL
There is less room on the trumpet.
I used a 42odx 20id bearing machined out a fraction to run on the mainshaft
just cut the sleeve off. It was 10mm thick i think. The beezer allows a 15mm bearing.
doing the same thing. You may need to skim a few thou off the sleeve pinion too.
They won't seal perfectly but the grease seals are ok for racing and just weep
a fraction, getting them lined up spot on is the trick.

just checked it was 20x35x9 6804

WRONG it's a 6904 not 6804
20id 37od 9w

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Triumph Bonneville T140v 1977
Triumph T120R 1971
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Triless-
If you have not installed the piece would you mind measuring the total thickness?
Yea, Nick. Noticed that...
Thanks, all.

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Made some measurements on a T140 and B50.
B50 back of hub to high gear thread - 0.441" (11.2mm)
T140 back of hub to high gear thread - 0.484" (12.3mm)
That is removing any extension of the high gear bush.
A bearing that will fit is a 63805-2RS 25 x 37 x 10mm or a 61907-2rS 35 x 55 x 10mm
The Triumph chainwheel (B50 and T140) is flat on the hub side with a slight step, an A65 is dished.

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Sorry, Mike, I have the component installed, but I'm sure the dimensions for the Britech piece are identical with Dave Madigan's as per T 140. I could never get to grips with posting pics here, but have some up on 'OIF Triumph ' site.


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