Triple gearbox rebuild.

78jotadave said:
Paul at 10,200kms that gearbox is barely broken in no need to change bushes just because it was sitting a while.  Cheers Dave
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Hi Dave

storage conditions were not optimal for this engine, which is why I have been replacing so many parts in such a low mileage engine, but the brass bushes in the transmission did clean up very well, I was just struggling with my borderline OCD to make everything as perfect as possible. I expect you are correct and the original brass bushes will be fine.

Paul LeClair
 
I bought a Kawasaki side-stand (for my Bushman mounting bracket) from Canada a couple of years ago and it disappeared into a black hole. I tried to implement the tracking system but Canada Post wouldn't or couldn't give me any answers. I had pretty much written it off as lost so I bought another one from a different seller in USA, which arrived in about a week. 3 months later the Canada package arrived. I now have a spare side-stand which I'll probably end up fitting to my Ducati, so it all worked out OK in the end.

The moral of the story is don't give up Chris. It will probably re-surface eventually when someone trips over it in a warehouse somewhere.

Cheers,
Cam
 
Dellortoman said:
The moral of the story is don't give up Chris. It will probably re-surface eventually when someone trips over it in a warehouse somewhere.

Cheers,
Cam
Click to expand...

Cam, you are spot on.  It showed up late on Friday, just in time for Wolfgang to work on it today, and then post it back ( :o) before he's away on vacation (until February!)
 
hi Paul without risking the wroth of the OCD brigade I use oven and freezer method, then the vice  and socket,  then use the splines on the shaft to ream the bush and the gear box is as sweat as a nut after using my atomic  micrometer  to check tolerances :LOL:
regards andy
 
laverdas said:
hi Paul without risking the wroth of the OCD brigade I use oven and freezer method, then the vice  and socket,  then use the splines on the shaft to ream the bush and the gear box is as sweat as a nut after using my atomic  micrometer  to check tolerances :LOL:
regards andy
Click to expand...

Hi Andy

I must confess I thought about the bush mechanics approach, which does have merit if the need is great. In this case though with only 6,000 miles on the bronze bushes, I decided to leave them alone until next time the engine comes apart.....

good to know that the bush mechanics approach does work, though!

Paul LeClair
 
Hey Keith

I've got about 0.19 mm clearance between the sleeve gear bush and the mainshaft. So I reckon a new bush is required (book says max clearance is 0.10 mm). 

The mainshaft itself has a bit of wear too. The diameter varies between 16.89 and 16.93 mm. Is that likely to be a problem?
Cam
 
OK. Dumb question time. I'm about to do the re-bushing of the mainshaft sleeve gear. Making a bronze bush to low clearance fit is not something I've done before. Turning the bush from bronze bar is no problem, nor is getting an interference fit on the OD of the bush. But I might have a couple of other issues while finishing the ID:

My small lathe has maximum thread cutting pitch of 4mm, so that's as coarse as I can cut the oil scroll. Is that too fine? I can't see why it would be a problem, but I thought I'd better ask.

Reaming to size: First problem is that I don't have a 17mm reamer. But that's easily sorted. It's only money. But I'm a little confused about reaming the new bush through the old (worn) bush to keep it aligned. It may not be perfectly aligned because of the wear in the old bush. I assume the reamer has a taper on the pointy end that centres it in the hole to be reamed. The back end of the reamer is aligned by the tailstock, so why do you need the old bush to ream through? Am I missing something obvious in Keith's description?

I've never used a reamer before, but looking at Keith's photo, it appears to have a left-hand helical set on the cutters. Does that mean it rotates the opposite direction to a twist drill? Is your chuck rotating backwards in that photo Keith?

As an alternative to a reamer, if I get the ID close enough on the lathe, would it be possible to finish hone the ID to size using a small brake cylinder hone?

Gotta learn this stuff somehow.  :D
Cam
 
Bear with me,this is a bit hazy but worth a mention.I think there is a bush in the gearbox of the 120 Jotas that was replaced by one of the more teck savvy NSW owners during a full rebuild.I think this bush was a bearing in some models but was replaced by a bush.Anyway on a Snowy Run we were doing the Delegate bit,thats 170ks of continues 35kph bends and we were not being gentle.Arriving at Delegate we stop and this 120 Jota has the symptoms of a really badly dragging brake.It wouldn't roll without a huge push,clutch in,neutral,it didn't matter.He discovered it was down a bit on oil,plenty in it but a bit low.Topped up the oil and after it cooled down it was back to normal.I am sure he would have been anal about clearance on this bush.Anyway thats the story.It was not a pleasant episode,be good to avoid similar stuff.
 
Dellortoman said:
OK. Dumb question time. I'm about to do the re-bushing of the mainshaft sleeve gear. Making a bronze bush to low clearance fit is not something I've done before. Turning the bush from bronze bar is no problem, nor is getting an interference fit on the OD of the bush. But I might have a couple of other issues while finishing the ID:

My small lathe has maximum thread cutting pitch of 4mm, so that's as coarse as I can cut the oil scroll. Is that too fine? I can't see why it would be a problem, but I thought I'd better ask.

Reaming to size: First problem is that I don't have a 17mm reamer. But that's easily sorted. It's only money. But I'm a little confused about reaming the new bush through the old (worn) bush to keep it aligned. It may not be perfectly aligned because of the wear in the old bush. I assume the reamer has a taper on the pointy end that centres it in the hole to be reamed. The back end of the reamer is aligned by the tailstock, so why do you need the old bush to ream through? Am I missing something obvious in Keith's description?

I've never used a reamer before, but looking at Keith's photo, it appears to have a left-hand helical set on the cutters. Does that mean it rotates the opposite direction to a twist drill? Is your chuck rotating backwards in that photo Keith?

As an alternative to a reamer, if I get the ID close enough on the lathe, would it be possible to finish hone the ID to size using a small brake cylinder hone?

Gotta learn this stuff somehow.  :D
Cam
Click to expand...


Cut the oil scroll by hand feeding the tool, one in one out to a depth of around 0.020" before reaming to finish size.
A hand reamer has a good lead in before it cuts to size, using the old bush helps as a guide to start the reamer cutting straight. There is of course wear in the old bush that is why we are replacing it but the reamer will produce the new hole round and to size, if it is started off square. The reamer is rotated clockwise by hand and the chuck is stationary, only ever rotate the reamer clockwise turning it backwards will dull the cutting edges very quickly.
You can machine the bushes to finish size when they are fitted by setting the gear up in the four jaw if a reamer is not to hand, just requires a bit more set up time.
None of it particularly difficult to do, try not to over think it  ;)

  Keith
 
Cam, I have a set of adjustable reamers. Without going outside to the shed to check, I am sure 17mm is not a problem. if you want a lend just let me know and will arrange to get them to you from Cygnet.
 
Thanks Keith. I'd thought about using the 4-jaw chuck. My 3-jaw is not centred accurately enough.

JW. Thanks for the offer of a reamer. I'll give you a call some time over the weekend. I have your mobile number, that's if it hasn't changed in the last year or so (last 3 numbers 379).

Cam
 
Dellortoman said:
My small lathe has maximum thread cutting pitch of 4mm, so that's as coarse as I can cut the oil scroll. Is that too fine? I can't see why it would be a problem, but I thought I'd better ask.

Cam
Click to expand...

Cam,

At a guess, you will have extra gears for the lathe for thread cutting etc.  Check out the settings for max. feed, and go from there.  Juggling around with the different gears, especially a very large one on the machine spindle, will result in quite astonishing feed speed!

As an example, the max longitudal feed on the OCT lathe is around 6mm/rev, gears are 40/113/120 on the respective spindles.  By fitting 70/120/113, I attain a feed of 35mm/rev!  Makes a lovely oil scroll.  Does help if the lathe can turn as slow as 25rpm, much more than that will have you on tip-toes for a bit!  My own lathe has a min. speed of 70rpm, I too chicken to attempt it on that!

I actually don't bother with reaming the gears.  I have made up a set of soft jaws to perfectly centre the gears and line-bore them.  Using the correct carbide tipped tool gives a surface finish as good as, if not better, than a reamed finish, which is also consistently square to the gear.

The mainshaft needs to be checked for wear where the sleeve gear runs.  Often as much as 0.15mm diffence in diameter along the length of the stub.  I lap that with emery till it is even to within 0.02 along its length and bore the bushes to suit.

Strange thing I came across recently in a 750SFC gearbox, a TWISTED layshaft!  Never seen that before.  Luckily, it is no more than the standard 750 layshaft, so renewal was easy.  Pays to inspect both shafts closely and check between vee-blocks/centres for bending.

piet

 
Thanks Piet. Soft jaws eh? You've given me something to think about.

Mainshaft stub isn't too badly worn. It has a very slight barrel shape, but only a few thou. I'll try to even it out with emery as you suggest.

I'm unlikely to get to it until next month though. Too much other shit going on at present, including a trip to Broadford Bike Bonanza at Easter and then Red's place after that.
 
Thanks Jeremy. Didn't get around to calling you today. Been doing the headless chook routine trying to get organised to go away next week. It'll have to wait until I get back next month. I'm thinking I might go with the 4-jaw chuck and carbide tipped boring bar option. If I cock that up I might call on your reamers. I have plenty of bronze bar  :D

Cam
 
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