Bottom end

Powereng03 · May 19, 2011

Well the bottom end looked ok when we finally got it apart. Only the cam and crank bearings are needing to be replaced (even though they were still ok).

Now I just need some time to clean it up and get at those bearings. I don't know how my wife will feel about me bar-b-queing my motor!!! Oh well, I guess it will be done on a day she is at work!!!

comnoz · May 19, 2011

So does that drive side race in the case mean the race is loose on the crank? Jim

Powereng03 · May 19, 2011

Nope I'm going to have to reheat the crank too to get the race off. Just had a look at it tonight and it is tight!

Hobot · May 19, 2011

Heat races, cool the crank. Some have put whole crank + races in freezer then el flamo the races with a puller already on ready to suck them off nil strain.

builder · May 19, 2011

Powereng03 said:
Nope I'm going to have to reheat the crank too to get the race off. Just had a look at it tonight and it is tight!

Huh? The inner race is in the bearing, that shouldn't have come off the crank...or are you saying you only did one and left the other on?

DogT · May 19, 2011

It looks to me from the pics like the drive side inner race came off the crank with a shim on the inner side crank, but the timing side inner race did not, that's kinda backwards. I remember my timing side inner race came off my crank because it was a one piece ball bearing (bearing stayed in the case), but the drive side was a problem getting off the crank (2 piece), and when I replaced with the superblends, I had to have both inner races pressed on at a shop.

Both inner races should be press fit as far as I know.

Dave
69S

comnoz · May 19, 2011

DogT said:
It looks to me from the pics like the drive side inner race came off the crank with a shim on the inner side crank, but the timing side inner race did not, that's kinda backwards. I remember my timing side inner race came off my crank because it was a one piece ball bearing (bearing stayed in the case), but the drive side was a problem getting off the crank (2 piece), and when I replaced with the superblends, I had to have both inner races pressed on at a shop.

Both inner races should be press fit as far as I know.

Dave
69S

That would be correct , and if they are not tight it will eat the crank in short order. It is not unusual for the drive side inner race to get loose on the crank as it is the side with extra load from the primary chain. They can be spray welded and ground or ground and a thin sleeve installed to correct it. Jim

Hobot · May 20, 2011

Ken Canaga recently fixed this in Peel's undersized crank. Chrome then mill to size is the preferred way but nitride prevented that in Peel so Ken copper plated ~0.0004325" or something like that, just right for proper interference fit-crush for a C3 clearance superblend.

Loose bores in Al are whole 'nother issue I've not really heard a lasting solution for. I'm a JBWeld missionary but also familiar with how pliable putty it can be near its rated temperature. Gear box I can see but not sure about engine. Best I've heard is screw in stakes and pins in the seam, not pinched from outside pressure.

Josh Cox · May 20, 2011

Do not forget to split the crank, there is a sludge trap in there, here are picture of the 750 crank, not sure if there are differences.

The bearings will literally drop out of the cases if you heat to about 250F in the wifes oven, suggest ensuring you do not get caught doing this.

Matt Spencer · May 20, 2011

Looks like the Cam may have been one of the soft ones :lol: :shock: .

Followers would need refaceing . Just lap smooth on flat stone or plate / glass , with paste .

I want to be able to see my face in them !

.

bwolfie · May 20, 2011

The best and easiest on the marrage is to check craigslist for a free electric rang. Throw it in the garage with the bike. It's useful for lots of things. I do powdercoating with mine.

pete.v · May 20, 2011

With that idler spindle sitting out, it begs the question of the condition idler spinle bore.

jseng1 · May 20, 2011

Those cast iron cams are failure prone - all that metal coming off the lobe and circulating in your oil. Get one thats hardfaced or better yet a radius lifter cam.

Hobot · May 20, 2011

To stay happy married - woman's work and tools belong in kitchen. Oven range take of a lot of room in a home shop. I use LPG tank top pancake heater as way quicker and can warm you and area when not cooking a Norton menu. 250' F only works if bores slightly worn already, think higher heat than that to get bearing to come out with some pounding down on robust wood surface.

Powereng03 · May 21, 2011

A spare stove is a no no cause I have no extra room for it. I think I will wait till Monday or Tues night and bring it all into work and heat it up on the bbq here. won't waste my propane then!!! As for the idler shaft, it came out when the case was warm, and the race was loose when the crank was warm as well so i will clean it up real good, warm it back up, then pop the bearings out, then put the new races on the shaft, and bearings in while it is still warm. Well, it sounds good now so we will see how that works out.

Hobot · May 21, 2011

Get ya self organized for the putting back in phase as if case cools down too much and the bearing don't drop-driven in pretty much square all the way in, bearing can absorb the heat and cool its bore to be locked in catywhompus and really take fry pan oil smoking heat to get it out for next attempt. 3/4" drive socket set is handy for this.

ML · May 22, 2011

Powereng03 said:
A spare stove is a no no cause I have no extra room for it. I think I will wait till Monday or Tues night and bring it all into work and heat it up on the bbq here. won't waste my propane then!!! As for the idler shaft, it came out when the case was warm, and the race was loose when the crank was warm as well so i will clean it up real good, warm it back up, then pop the bearings out, then put the new races on the shaft, and bearings in while it is still warm. Well, it sounds good now so we will see how that works out.

You haven't mentioned checking the crank end float? It is difficult if you don't have a proper inner race extractor, but end float should be considered as important to engine life and noise as well. I'm fairly convinced the factory didn't do this for all of the Commando range from new as its time consuming and production engineering costs particulary for Norton at the time would have been critical. However, the proper crank shims are available and its worth the extra effort to set up the bottom end with around 0.010" to 0.015".

Here's tip when pressing the inner race onto the crankshaft: Cut a block of hardwood to be a firm fit between the journal cheek and the flywheel, so that when you press the inner race on it doesn't put a bending load stress on the cheek.

Mick

Hobot · May 22, 2011

Bottom end

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