To rebuild or not to rebuild-dang transmission (Rebuilding)

Classic Norton Commando Motorcycles.

Postby concours » Fri Mar 16, 2012 6:42 pm

:mrgreen:
Last edited by concours on Tue Mar 20, 2012 3:41 am, edited 1 time in total.
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Re: To rebuild or not to rebuild-dang transmission

Postby Guido » Fri Mar 16, 2012 7:10 pm

I can't remember who wrote this but someone said once recently, "What you have is a 30 HP gear box in a 50 Hp bike."
That was enough to make me go through the entire box.
I have replaced 2 broken lay shafts in my day from doing wheelies and being stupid.
I'm old and wiser now.
Old Brits web site is great for the rebuild tutorials.
'73 850 COMMANDO
'74 850 COMMANDO
"Restored" the '74 and "restoring" the '73 this year.
I have 2 parts to buy. Now, if I can only find $5000 lying about.
I live in Woodland, Cal.
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Re: To rebuild or not to rebuild-dang transmission

Postby warpedscout » Fri Mar 16, 2012 7:31 pm

Guido, I have seen that saying too. I will start pulling the tranny out soon as I can. Sold my mustang today so I can get a set of whitworths and a vise to attach to my workbench. Probably pick up a new compressor for my blast cabinet, want to clean everything up while I am going in. May take some time but better not to rush things! Too many things I want to do but don't want to over do it, but then can you over do it!?
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Re: To rebuild or not to rebuild-dang transmission

Postby Niagara850 » Sat Mar 17, 2012 5:55 pm

Right in the middle of going through the gearbox and checking the layshaft bearing myself. Doing it in frame . So far the biggest difficulty was getting the layshaft bearing out of the case. Lots of heat and patience required. I found a standard $10 steel cage 6203 bearing that someone replaced the original Portuguese brass cage bearing with sometime during its life.

Researching the threads and the internet, it looks like there are two suitable choices for layshaft bearing replacement:

- FAG 6203 TB.P63 - a quality ball bearing with a strong phenolic cage that doesn't require shimming. Mick Hemming recommended, along with many forum members.

- NJ203E C3 Roller bearing, also a quality bearing with polymid cage that requires shimming, factory recommended, along with many forum members, see Old Britts and the Norton workshop companion for installation details. As the inner race floats, axial loads are reduced on the cage.

I took my the bearing removed from the gearbox down to the local bearing supplier - Canadian Bearing

FAG 6203 TB.P63 - $69.99 but special order that takes 6 weeks to arrive
FAG NJ203E C3 - $56.07 which I ordered - 4 days
SKB NJ203E C3 - $70.52 in stock

Not having a Dial Indicator, I would have gone with the FAG 6203 TB.P63 to save shimming but too long to receive, and I could use a Dial indicator anyway... I checked prices from various Norton parts suppliers, they can be ordered for more $. It pays to cut out one of the middle men.

Now to get the sucker back together, spring has come early this year, 18c and sunny, 20c and sunny forecast for next week, normal is 4c. We usually get a snow storm around St. Patrick's day...
74 850 Mk2 Roadster
78 Kawasaki 650 SR
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Re: To rebuild or not to rebuild-dang transmission

Postby Guido » Sun Mar 18, 2012 6:53 am

I just did my box yesterday. New shafts and bushings. Did the roller bearing and shimming is a snap.
Had .042 endfloat, took it up with .030 of rear iso shims, done.
The bearing was about $25
'73 850 COMMANDO
'74 850 COMMANDO
"Restored" the '74 and "restoring" the '73 this year.
I have 2 parts to buy. Now, if I can only find $5000 lying about.
I live in Woodland, Cal.
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Re: To rebuild or not to rebuild-dang transmission

Postby T95 » Sun Mar 18, 2012 10:25 am

Guido wrote:I just did my box yesterday. New shafts and bushings. Did the roller bearing and shimming is a snap.
Had .042 endfloat, took it up with .030 of rear iso shims, done.
The bearing was about $25


Guido,
I am curious why you chose to replace the shafts, did you determine they were worn or damaged?

Did you have any issues with the bushings, I have read they require reaming and that it can be tricky.
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Re: To rebuild or not to rebuild-dang transmission

Postby warpedscout » Sun Mar 18, 2012 4:53 pm

I am breaking her down. I had some chores to finish up before I could get some work done:

1. Mow Lawn...Check
2. Clean off back porch....Check
3. Fix push mower so it would self propel...Check
4. Clean up after all chores...Check
5. Get daughter and sons friends over so they all could play... Check

Ok, now my back is hurting I got down to it.

I took off the exhaust last week
Image

Here are a couple of cross over pipe bolts, one broke and one is warped..
Image

Decided to not put on cross over exhaust again, want a cleaner look.

Oil tank, and right Z Plate off...
Image


I got the primary off, clutches out and clutch sprocket nut off..
Image
Image

Going to have to loosen primary chain so I can take off clutch basket and sprocket.

Will post more when I get a chance to do some more work on it.

Maybe by next weekend, have to till out the ground where I went 4X4 with my Mustang getting it out to sell. Ruts were deep enough Mustang was sitting on ground, can see where exhaust burned ground.

Now, I need to clean up the garage, make sure I have everything bagged and tagged and clean up my nasty butt!!
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Re: To rebuild or not to rebuild-dang transmission

Postby Guido » Mon Mar 19, 2012 6:51 am

T95 wrote:
Guido wrote:I just did my box yesterday. New shafts and bushings. Did the roller bearing and shimming is a snap.
Had .042 endfloat, took it up with .030 of rear iso shims, done.
The bearing was about $25


Guido,
I am curious why you chose to replace the shafts, did you determine they were worn or damaged?

Did you have any issues with the bushings, I have read they require reaming and that it can be tricky.


I bought this bike, a '74, in '82 or so as a Dunstall Cafe racer. Converted it to an upright stock appearence.
I never went through the tranny on this bike, just my other bike, the '73.
This one was so worn out that I replaced the entire insides with gears from a gear box I bought on this site and replaced all the bearings and bushings.
The main shaft was badly worn so I bought a new one. The lay shaft was replaced with a good used one which mic'ed out fine and was true between the centers.
I had the first gear lay and the 4th gear sleeve bushings pressed in by Phil Radford and I did the rest. Only one bushing in the 3rd gear lay had to be reamed but since I had no reamer,
I used a brake cylinder hone to open it up.
This box had the super blend lay bearing but the previous owner did nothing to the end float so it had over .042 side play.
Now it is so tight, but not too tight, if you know what I mean.
'73 850 COMMANDO
'74 850 COMMANDO
"Restored" the '74 and "restoring" the '73 this year.
I have 2 parts to buy. Now, if I can only find $5000 lying about.
I live in Woodland, Cal.
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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby warpedscout » Mon Mar 19, 2012 7:41 am

Did not plan on doing anything on the bike today but am off and the morning started off kinda crappy. Decided to go out and get some more done to get my head right and found this:

Image
Image

I was actually reading some post on this (Rotor cupped washer) and low and behold I have one on my bike.

Then as I took off the outer cover and taking the internals apart I saw this:
Image

Do you see it?
How about now:
Image

It is a transmission vent, I have seen this on Old Britt's site where he does the modification on the trans inner cover. I thought these only came on the 75 models.

My engine, trans and frame plate match (317975). Does this mean someone has been in this bike before? The washer (think was called a Kingston washer) I read was put on bikes to compress the rotor on the crankshaft because they had a issue of getting loose and destroying themselves? Am I wrong on this or what.

Would appreciate some information on this from you guys.

Going to read over the rest of the tear down before I go back out and maybe get some more done today.
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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby L.A.B. » Mon Mar 19, 2012 8:07 am

warpedscout wrote:It is a transmission vent, I have seen this on Old Britt's site where he does the modification on the trans inner cover. I thought these only came on the 75 models.


Apparently not, as part: "065199...Breather tube" (same number as 850 Mk3) is in the 850 Mk2/2A parts book (Group 8, Gearbox inner cover)
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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby warpedscout » Mon Mar 19, 2012 12:38 pm

Any tricks on getting rotor off crankshaft?
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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby DogT » Mon Mar 19, 2012 1:15 pm

Put a puller on it, tighten up and heat the sprocket. It will come. I used a heat gun and it popped off after about 1 minute. Not necessary to beat on it.

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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby pete.v » Mon Mar 19, 2012 3:16 pm

warpedscout wrote:Any tricks on getting rotor off crankshaft?

Should slip on and off. Don't overwork it, little heat, very little tappy tap.
72 Commando Combat Hybrid Roadster "Red Hot"
I'm always lucky except for when I'm not.
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Re: To rebuild or not to rebuild-dang transmission

Postby comnoz » Mon Mar 19, 2012 3:34 pm

Niagara850 wrote:Right in the middle of going through the gearbox and checking the layshaft bearing myself. Doing it in frame . So far the biggest difficulty was getting the layshaft bearing out of the case. Lots of heat and patience required. I found a standard $10 steel cage 6203 bearing that someone replaced the original Portuguese brass cage bearing with sometime during its life.

Researching the threads and the internet, it looks like there are two suitable choices for layshaft bearing replacement:

- FAG 6203 TB.P63 - a quality ball bearing with a strong phenolic cage that doesn't require shimming. Mick Hemming recommended, along with many forum members.

- NJ203E C3 Roller bearing, also a quality bearing with polymid cage that requires shimming, factory recommended, along with many forum members, see Old Britts and the Norton workshop companion for installation details. As the inner race floats, axial loads are reduced on the cage.

I took my the bearing removed from the gearbox down to the local bearing supplier - Canadian Bearing

FAG 6203 TB.P63 - $69.99 but special order that takes 6 weeks to arrive
FAG NJ203E C3 - $56.07 which I ordered - 4 days


SKB NJ203E C3 - $70.52 in stock

Not having a Dial Indicator, I would have gone with the FAG 6203 TB.P63 to save shimming but too long to receive, and I could use a Dial indicator anyway... I checked prices from various Norton parts suppliers, they can be ordered for more $. It pays to cut out one of the middle men.

Now to get the sucker back together, spring has come early this year, 18c and sunny, 20c and sunny forecast for next week, normal is 4c. We usually get a snow storm around St. Patrick's day...


If you are wise you will check and shim the layshaft whether you are using a ball bearing or a roller bearing. The result of too much end play in the kicker shaft is the same with either bearing- the gearbox tends to jump out of first. Of course if it didn't jump out of first before you took it apart it isn't going to be any more likely to with a roller bearing so it's your choice but excess clearance there will eventually catch up to you. Jim
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Re: To rebuild or not to rebuild-dang transmission (Rebuildi

Postby Niagara850 » Mon Mar 19, 2012 4:22 pm

I'm going to properly shim it. The gearbox behaved well prior to dis-assembly, no jumping out gear, snicked into gear, finding neutral was easy. The clutch would drag when it wasn't fully warmed up, so I would slip her into neutral just before coming to a stop for the first few miles to save stalling. Cleaning clutch plates and adding clutch rod seal next on the to do list.
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