Triumph 500 unit gearbox redneck repair

[Guest]

Nice. That's a whole lotta gearing. I run 17/46, Bnr is 2:1, so primary is taller than stock and I do rev the piss out of it, but they don't do much until 4K.

[datadavid]

Nice. That's a whole lotta gearing. I run 17/46, Bnr is 2:1, so primary is taller than stock and I do rev the piss out of it, but they don't do much until 4K.

Yea, whats strange is engine sprocket is huge as well, 24t i think. Its the largest possible to fit in between the stator studs. Also running a 46t rear sprocket. The 16" rear wheel should not do that big a difference. Mine has good lively pull from 3k, and with a lower gearing i should be able to do some highway riding at more relaxed rpms. And be able to hit the ton.. 😀

[Guest]

Oh yeah should be no problem hitting the ton. I couldn't get on the thing without doin it. Except for those shinkos most the 16s aren't much shorter overall. I'm running a 19-3.50

[datadavid]

So you have 3" taller "gearing" on the wheel 😀 yea, really shouldnt do much difference. Mine feels seriously stressed over 7k so im just looking for a good relaxed 4-5k cruising speed. Also found yesterday that crank was a bit generous on the sliding fit to the drive side roller bearing.. might have to redo the crank to cure the high rpm vibes, timing side bush is worn already as well. Well, next time it will get filtered oil from the start thats for sure.

[Guest]

In the wheel yeah, but I think it's 26.5 overall, probably only an inch taller than most 16 tires. I always worried about that timing side bush as that's where all the oil pressure comes from, still I never changed mine, trusty machinist kept insisting it's good.

[datadavid]

Yes, im just gonna ride mine until it shakes apart. 😀 There is observable radial play in both crank bearings so probably wont be long. Still have excellent oil pressure though so who knows. May still be mid-life. Gonna talk to the triumph guru about it when i pick up the front sprocket, he's piled up in the middle of 6-7 engine rebuilds this winter, had almost an assembly line last time i was at the shop, only unit triumphs and bsa's. Maybe this can go another few years before scheduling in a crank overhaul.

[datadavid]

Fit a nice big tire, 2"wider overall.
And cut out notches for the 21t sprocket.
Should be able to maintain highway speeds at moderate revs now!

Gearbox is ready for final assembly soon.

[datadavid]

Got the gearbox bolted up last night, and the transmission almost done. Still gotta find a 125 links long 530 chain, finish altering all the fender and sissy bar mounts to fit the bigger tire. And mod the battery box to also house the boyer ignition. Then i can test out the new gearing, still winter here for a few months so no rush.

[datadavid]

We have a break in the cold and nasty weather here and its a few degrees above freezing so i took it out for a short blast and man does it feel nicer with this gearing. No more high revs to keep up with traffic, finally its where i want it gearing wise. Did not get a chance to put big loads on 3rd gear but pulled to where it used to slip out and voila, nothing. Just steady pull. Now i guess is the time to take apart the top end to fix the last oil leaks..

[Dougtheinternetannoyance123]

Might be redundant to point out, but there is service bulletins (circa 1966-67) on the trans problems and how they updated the cam plate and other bits to deal with these problems. Looks like your cam plate already has the stiffening brace on it, so probably just normal wear and tear.
You can find the service bulletins on the net, but if you cant, chances are I can email them as I have them on digital format as well. (Also some pertinent ones on the pressure relief valve and oil return you might want to look at )
#2) RPM,, yes, without frequent overhauls and or high zoot engine materials, such high RPMS means your parts are not long for this world. The factory considered a motor worn out past its metal fatigue service life after ONE 500 mile race for the Unit 500 twins. Asking old alloy rods to live this long, let alone those RPMS is rather optimistic. Personally,, I try to gear them so on a rebuilt motor with reconditioned original parts I consider 4500 RPM and possible occasional 5000k blips to be the top end.
If you are serious about running a 500 unit twin hard, then heres my formula,, Late model Daytona motor (68-73) Carillo rods, and entire assy dynamically balanced. Light weight forged pistons. Kibblewight Blackdiamond stainless valves with Ampco 45 Bronze guides. Late model daytona head is good but some prefer the early hemi heads if you can find the pistons to run in them. Use the late T140 4 valve oil pump or if sustained high RPM then run the rotary oil pump. Aftermarket full flow oil filter, mod the top end oiling, and a good ignition unit. (Power Arc with VOES switch is best)
On the gearbox main seal, You can segment the clutch pushrod with a ball bearing and resize it, You can segment the bronze bushing in the end of the mainshaft and use Nitrile o rings between segements. This keeps GB Oil from migrating down the mainshaft. Dry clutches dont like it. Nortons have a seal kit they use. A guy named Dyno Dave Comeau sells them.
I do admire you guys thrashing on them and keeping these on the road,, good to see.

[datadavid]

Might be redundant to point out, but there is service bulletins (circa 1966-67) on the trans problems and how they updated the cam plate and other bits to deal with these problems. Looks like your cam plate already has the stiffening brace on it, so probably just normal wear and tear.
You can find the service bulletins on the net, but if you cant, chances are I can email them as I have them on digital format as well. (Also some pertinent ones on the pressure relief valve and oil return you might want to look at )
#2) RPM,, yes, without frequent overhauls and or high zoot engine materials, such high RPMS means your parts are not long for this world. The factory considered a motor worn out past its metal fatigue service life after ONE 500 mile race for the Unit 500 twins. Asking old alloy rods to live this long, let alone those RPMS is rather optimistic. Personally,, I try to gear them so on a rebuilt motor with reconditioned original parts I consider 4500 RPM and possible occasional 5000k blips to be the top end.
If you are serious about running a 500 unit twin hard, then heres my formula,, Late model Daytona motor (68-73) Carillo rods, and entire assy dynamically balanced. Light weight forged pistons. Kibblewight Blackdiamond stainless valves with Ampco 45 Bronze guides. Late model daytona head is good but some prefer the early hemi heads if you can find the pistons to run in them. Use the late T140 4 valve oil pump or if sustained high RPM then run the rotary oil pump. Aftermarket full flow oil filter, mod the top end oiling, and a good ignition unit. (Power Arc with VOES switch is best)
On the gearbox main seal, You can segment the clutch pushrod with a ball bearing and resize it, You can segment the bronze bushing in the end of the mainshaft and use Nitrile o rings between segements. This keeps GB Oil from migrating down the mainshaft. Dry clutches dont like it. Nortons have a seal kit they use. A guy named Dyno Dave Comeau sells them.
I do admire you guys thrashing on them and keeping these on the road,, good to see.

Thats one hell of an answer! 😀 to both mine and torchs thread i suppose?
I have geared mine now so it sits at some 90kph at 4krpm. But it feels really solid up to 6-6500, then the tiny sharps tingly vibes begin which i dont like for more than a few minutes. Dont really mind revving this a bit even with used stock rods. But 9-10000 rpm? Ive never heard how this sounds at that stage and i dont plan to find out 😁
The old race engines usually blew up and never finished, except the few who won races, they were experimenting with everything in the end to make them tougher, last engines even had through bolts as they started cracking cylinders in half!
Obviously we dont want that so better to keep revs and power output on the sober side of things. Its gonna blow eventually, just a question of when😁

[datadavid]

Wouldnt mind reading the service bulletins to see if i missed anything, but yes gearboxes were designed for a 350 to begin with. Mine is the stronger later type and it was just very worn in places.

[Dougtheinternetannoyance123]

PM me a email addy and Ill see if the files will email, if not the Factory service bulletins ARE on the net. You can just read the 500 twin applicable if you like but they ALL are worth a read. Very educational. I have a full set going from 1950 up into the 1970s. There was also a US west coast version and a slightly different East coast version. I used to sell them on the FeeBay but a Aussie (They are ALL criminals you know! ) violated my TOS and reprints on his CD, Fukker, so I offer up his versions of digital files to any who ask.
As to RPMS that is a whole box of spiders in itself.
I was part of a 3 man team who developed and built a Norton Land speed racer, "Sir Eddys rocket" Sadly,, Sir Eddy passed away when the project was nearly complete. I helped his kid sort things out but he took the ball and ran with it. It holds the 500cc pushrod overhead valve class record and partial streamliner too.
270 degree crank and Mid 50s HP and very light weight. It was originally designed to run 12,000 RPM and we nearly did it.
But this is a very long topic. Bottom line is Eddys kid enlisted another guy who helped make it happen. But he has what is called a "Spintron" and uses stop motion and high speed cameras hooked to a mock up of the motor and drivetrain. (There are videos!) Basically,, if you SEE what actually happens past 5000 rpm it will make your cinamon hole (Ballon Knot) Pucker so bad you wont pass gas for a week.
(Bouncy Bouncy) Your pushrods are also doing their best impression of the rubber band man can dance. Increase rigidity and weight and the problems crop up elsewhere.
Believe me.... This was a 10 year project but its in the books now, and motor is being rebuilt. Theres more HP under the bonnet and it can go faster but it take some serious shit to get there.
Guys..... dont over think this. Triumph had a good idea what they were doing and just run the fukkers as designed and be happy. They do REALLY well in that mid range torque pocket. 3500 to 5000. Dyno will tell you the same. So does my calibrated ass cheeks. Twist the wick and gear it right.

[Dougtheinternetannoyance123]

We are getting sideways off the original topic, But to illustrate my point about RPMs... Here is a video of the bike on the dyno. Keep in mind it no longer has a traditional crank, rods or pistons. (Crank is a specially built 270 degree crank-Like a ducati, carillo rods and JE Forged pistons plus some other really special shit.)
By the time this video was shot, I was not really involved anymore. My part was all about working with Eddy while he was alive. I think its great his kid got it to the salt, but its a whole different ball game from where we were. Some I am in agreement with, and some I strongly disagree with. But if you look at the front fender, my name is on there because a lot of the parts and ground work were from my work.
But the point is... The bike did it! It now holds the record.
See: https://www.youtube.com/watch?v=6sqI82yt6Bk

[datadavid]

So i found out that whoever spoked my rear wheel probably was drunk and did a dangerously shitty job. Some spokes are only held by a couple of threads and all spokes are wrong lengths and have been cut down.. new spokes on the way. Good thing winters are long..