Bonneville Ep.2 - gearbox stripdown
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- Опубликовано: 5 окт 2024
- I'm eager to see the level if distruction in this gearbox. I'm pretty confident we will see a few teeth scattered around as if it's gone a couple of rounds with Mike Tyson!
But there could be less obvious damage too & what really happened to cause this damage? Was it just a faulty casing on the gear, old age or just bad luck? Right now we have no idea.....but maybe, just maybe we will come across a few 'tell tail' clues that will help solve the mystery...
Enjoy
Andy
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Thanks for all your support, until next time...
Andy
I have a 1973 Tiger 750 that has a similar gearbox but righthand shift.
I have close to 64,000 miles & never had the inner gearbox cover off.
Years ago I replaced the "U" shaped plate that retains the two cat paw plungers.
It had grooved on the inside ramps & plungers were sticking.
I was told years ago that the transmission should last forever.
The five speed came out - sometime in 1972 & I heard there were problems with the first ones before leaving the dearship parking lots.
The 1972 transmission had leaf springs to index the cam plate.
The spring plunger design is better or so I have been told.
Some guys with 1972 transmission use some type of a jig to tap a hole in the gearbox - to convert to a plunger.
Sometimes mine makes a clucking noise when dropping into first gear from neutral at a stop - but I think this is normal.
I replaced the clutch springs; clutch plates; clutch hub assembly that includes new rubber shock absorbers - couple of years ago.
I basically replaced the whole clutch assembly except for the chain wheel, which ment that I had to reshim the engine sprocket to keep alignment within .005 inch.
The new clutch components made a big difference:
Plates do not lock up even after sitting over the winter.
Clutch does not slip.
Smoother shifting due to new rubbers etc.
Always use a new center locknut when mounting clutch.
Some people will say you can.reuse the lock nut just apply red loctite, but I don't think that is a good idea.
Anyway good luck!
I was nervous when you first decided to leave that shaft in.. Glad you decided to pull it out for inspection. Better safe than sorry. Carry on.
I like this gearbox. It's so much more simple than the few Japanese ones I've been in. Good call to check for run out of. the shafts . I'll be honest I probably wouldn't have thought of that .
Peace and live brother ✌️🧡
When I took my crazy shifting box apart the two tiny rollers on the selector forks that go in the cam plate were not to be found. The box still shifted but it was full of neutrals and would jump out of gear.In the manual it tells you to put the gearset back in with both shafts and the slector shaft at the same time as the two selector forks. What a battle but I finally got it together but it took many tries. Still difficult to find neutral when stopped.Crazy that you have to diassemble the whole primary side to get the mainshaft out.
As stated above on a Honda for example you undo 2 6mm bolts and the sprocket comes off.Triumph and HD were archaic in the extreme.
Excellent diagnosis !
Very good investigation Andy.
Your the real deal. Look fwd to nxt video. Take care.
Good film Andy, the guy who was in there last is a bodge merchant!
That was fun to watch. Like an FAA investigator putting together why a plane crashed. Now we know what that awful noise was that Allen heard. I'm learning how to work on my bikes but I haven't had a reason to go into my gear box yet. I feel like I'd forget how all that stuff goes back together. I wonder if the guy who rebuilt that engine will watch your video. Do we think something was put together incorrectly, or did it break because Allen is rough on his shifting. : )
Triumph makes it a huge pain in the butt to get to that front sprocket, you have to take off the primary case, remove the stator and the clutch assembly with the primary chain. I'm not looking forward to replacing the sprockets on my 64 Triumph. On the Honda CB750 you can get to the front sprocket by removing two screws and a small cover.
Hi Andy when I used to take bits of a engine in a order so I know how thay when back in order I used a plastic cable tie so it kept the parts al together and in order
Getting that gearbox out if he had lifted the selector forks back of the shifter plate with a long Narro screwdriver it would have come out the pins on the selector forks are in the selector plate grooves at a right angle and won't allow the shafts and gears free to come forward. or pull the shifter fork shaft out first the forks will collapse out of the grooves. now you know why so many of these types of bikes are F up...
I built a 5 speed Bonnie years ago that suffered the same failure. The inspection revealed that it seemed that the gearbox ended up momentarily in two gears at once. The mainshaft was bent but I can’t recall if the layshaft was also bent. Coincidently the timing side ball bearing had also failed because the ball separator had come apart. I repaired the entire engine successfully. I never understood why the gearbox ended up in two gears at once. I bought the bike in its damaged condition.
Ah, very helpful Richard, thank you. I'll be returning to this project soon as the special tools I needed have now turned up :-)
Cheers Andy
Hi Andy your 57-4378 is the part number for that gear , Id say maybe someone has done some aggressive starts or accidentally bumped the gear change without the clutch , and or a combination of a bad heat treatment etc during manufacture . And my tip for you today is Bunnings sell 600ml cans of CRC brake clean for $9.79 alot cheaper that most other places at $ 18.50 +
Cheers matey, I'm working away shortly then on the Monkey bike trip for 3 weeks so I'm hoping the Special tools for the primary drive are supplied by then. I'm fortunate that Forch NZ provide the channel with the necessary workshop sprays & yes, I now have lots of brake cleaner!
There will be more videos on the Bonny repair, just a little delayed due to other, more pressing activities.
Thanks for your advice, unfortunately this bike only did 6km with it's new owner before the gearbox fail & previous history isn't available so it's a real autopsy!
All the best
Andy
Bolts are loose because the sealant is holding the bike together.
at one point i was starting to thing the gear was put in broken until the teeth came out. may have been worth getting some crack test dye for the rest of the gears
i think the gear set was dropped or hit with a steel hammer at some point before assembly and put a facture line
andy look into anaerobic sealer
hi sir,
check your email
thank you
No more stunning intros?