4th gear bushing

The sleeve gear bushings on Nortons have much more frequent failures than the single bush in Triumph 650 4sp gear.
SSSOOOOO..... I tried one, removed what was left of the originals. the bush od. is about 5 thou too big so I turned it down.
Pressed it in, the bush is an eighth of an inch shorter than the gear so I counter sunk it a sixteenth. A slight deburr and the mainshaft slid in nicely, close tolerance, slick rotation.
I like to point out to Norton owners how much the sprocket wiggles by hand "WHEN STOCK BUSHINGS GO BAD". The ball bearing is stressed, as is the case, and the gears, as the bushings slide around or get eaten by the circlip; as the sleeve gear wobbles around.( My English teachers would be so proud) The sleeve gear ball bearing cannot support its self under load and NEEDS close tolerance of the mainshaft and bushings to support the alignment of the sprocket. Simple.... The TRiumph bushing is scrolled internally to feed oil within 1/2 inch from the outer end, so the scroll must face inward when installed.... I think this will work out fine... Rick

Highway, your review is not wasted on me.
I think you found a good upgrade to a damage inducting factory
bush set up. Wobble be gone!

I know next to nothing of Triumphs, what would I order please.

If you spin er up for fair intervals below 4th, might peek inside
again to decide on standard grade lube or ATF.

hobot

The bush I use is #57-1370 intended for a 650 tri 4sp. The od. has to be turned smaller as pushing it in, as is, will shrnk the bush that would have to be reamed for the mainshaft to fit. I have never seen one of these shift out of place, and when servicing or rebuilding Triumphs, I'll change this bushing once every 15 or 20 gearboxes. On Nortoms the bushing change is near 100%.
The causes are usually; low oil , failure to top it up from kick start, rotting gaskets, or drive seal leaks, and
transmission misalignment with the engine .
It could be do to ovaled engine or cradle holes, the trans poorly adjusted or not tightened enough to hold it square, and I've seen mk.3s' with engine cradles way out of spec. While owners take care when installing a belt drive, adding a second adjuster to insure that the alignment is true. FEW take the same care with PRIMARY CHAIN alignment, it is equaly importa nt. The bushing has a hard life, the lower the gear the faster the shaft spins in the bush, (in top the bushing is not working). I can't remember seeing the combination of the ball bearing being tight in the case and the two bushings being clapped out. I chuckle at the suggestion of pin punching around loose fitting bearings, sure!!! that'll work.
Cheers Rick

I don't know why this is not a long known standard upgrade to AMC boxes.
I learned all about the weakness of these bushes because 750 Commando
moderately hot roded just can't keep up with good sports bikes
w/o reving out in 1st and 2nd, a whole bunch for most a hour a go.

What I found was dry-ness fried oil and melted the metal,
got away with more of the above by 3 bushes and ATF.
What's your take on lube to use for a addicted maniac?

I"ll copy your parts number for my private reference to buy soon.
I needed to know about reducing the OD - thanks.
I'll memorize this shop gem as the highway Triumph bush upgrade.



hobot

Gday Highway,
so what your suggesting I believe is the Trumpy bush is better because of the scroll giving better lubrication? If so the standard Norton bush could be scribed with a Dremel maybe?
Foxy

Foxy said:

Gday Highway,
so what your suggesting I believe is the Trumpy bush is better because of the scroll giving better lubrication? If so the standard Norton bush could be scribed with a Dremel maybe?
Foxy

Click to expand...

It seems to do the job on Triumphs, and I've seen them leak too!. Unlke the two sintered or oil absorbing bronze that seem to starve with no capilary (sic) feed to them. Triumphs rely on oil feed to them, scrolling helps . One long bushing that stays put.
Scrolling the inner bush on stock ones wouldn't hurt

Might take a look at them while picturing them spinning and throwing
oil out as well as way above oil level so none can get back in,
especially heavy lube.

Scrolls will just throw out oil faster and if cut to very end of
the DS one, it will open oil throw to the clutch basket.

High leverage loads and dry bore when spun up in lower
gears creates HI Heat. ATF helped me keep a steady clutch
basket and also less drag to spin.

I wonder if John Hudson advice I followed - add in a middle
used bushing to keep the others in place - would do as well?

hobot

The scrolling is a groove cut in the bushing, starting from the inner edge and spiraling around the bore to about 1/2 inch from the end. Stopping short of the end retains the oil; the mainshaft spinning helps to feed oil along the bushing.
For lube standard hypoid 80/90 for Nortons doing light duty and synthetic gear lube for racers and those who insist using large front sprockets to keep the revs low, and the stress high on the gearbox. Rick

Yes understand the spiral groove function. I grooved Peel's
and stopped 1/8" short of DS end but all the way on other 2.
I just don't believe that hot rodding in lower gears allows any oil to matter
to get inside the long narrow space above oil level.

To really see what I mean requires hi rpm sprints then = disengage
gears and shut down and open tranny and examine the bush interface.
If you lope along in lower gears before opening, the splash
and slow rpm allows some oil to get in, groove or no groove.

hobot


There is some back up to my ATF use

No argument from me that high rpm shaft speeds make it difficult for oil to reach the sleeve gear. Short of re-engineering the gearbox to modern standards and pressure feeding the bushings; Or laying the bike on its left side before flogging it, we are stuck with the short comings of a gearbox from 1957. I'm just pointing out that the Triumph bushing seems to hold up better in use than the commandos, even in Tri and Bsa 4 sp. triples, with heavy clutch, more wieght, and horse power, with similar oil levels, this bushing hangs in there. I'm figuring it will do the same in AMC transmissions.
It is worth mentioning that Triumph went to needle bearings for their 5 sp..re-engineering the sleeve gear and going to needle bearings. Rick

I'm going to take your bush advice to heart, as one thing a long solid
bush should do a bit better is resist the main shaft bending action
of torque on clutch basket hanging off a ways.

Here's a racer finding that helped me select ATF in gear box.
They had primary chain failures until they used
20 grade or thinner oil in there.

hobot

hi there , and why not a needle roller as RGM propose them in their close ratio gearbox sleeve gear???

Needle bearing is over my head to implement myself.
If a kit existed or someone to customize it, maybe then
I could use the feature.

I will have gear box innards cryogenic frozen and then
Ti oxide nano dust dry friction coated for some endurance aids.

hobot