70' Proper way to Shim? Step by Step?

Hello,

I have a 70 Commando that is vibrating way too much and is riding dangerously loose on back roads with lots of turns. I'm loosing more engine bolts than expected and would really like to dial it in with some shims. I've bought the proper shims and I don't have a clue on how to shim the bike correctly. Could anyone offer a bullet point, step by step (including how to measure correctly) that I could print out, take with me to the garage and complete this. I'd like it to be best suited for 40-60 mph for winding hills, back country roads type of riding.

I'm pretty inexperienced but I'm learning my bike pretty quickly so any help would be very much appreciated. Cheers! Brian

PalmerNorton said:

I've bought the proper shims and I don't have a clue on how to shim the bike correctly. Could anyone offer a bullet point, step by step (including how to measure correctly) that I could print out, take with me to the garage and complete this.

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I presume you've not actually read any workshop manual instructions on how to do it?:

http://britmoto.com/manuals/Manuals/750_man.pdf (Section F)

I have read through the manual but have always found that advice from someone with the experience of actually doing it always offers more tricks to the trade. Thanks for the link to the manual though!

RE: Pressure Gauge
I'm sorry I don't know what type of Dial Gauge your referencing. Could you describe it a bit so I can track one down. Cheers for that!

Brian

We could just make it easy for him
Why don't you get your feeler guages and select a 10 thousands of an inch one, then see if you can
put it between either end cap, right or left, and the shim next to it, talking about the front iso here.
Then see what what the other side clearance says. Let's see how loose your front mount is.
Basically, as a starter, you should be able to put a 10 thou feeler guarge in there, and that would
in theory be at one end, with the other end having no clearance, or 5 thou on each end.
Usually the clearances become looser over time because the shims slowly wear away, while at the
same time the rubber donuts inside deteriorate.

How old are the rubber donuts?
What measurement are you getting now at the front and rear?

maybe we can help you some more if you can tell us the above?

I found this site helpful, but you have to understand how the isolastics work. You will have to figure it out, it is very hard to explain, but if you can understand the principle, you will get it. It is not rocket science. Start with the whole front iso off the bike and you will see what I mean.

Forgot to put the link in, but others have already gotten it.

http://www.members.shaw.ca/randell/isolastics.html

Dave
69S

You could have a whole bunch of issues here, like if you are loosing engine bolts that's indicative of something more than incorrect isolastics. What makes a Commando feel or handle badly is a combination of things, all can be cured. For example, if isos are set too tight you get more vibration but tighter handling. But the swing arm is attached to the iso cradle, so if that is worn the whole back end swings around in corners.

I'd recommend you do these basic steps to get an understanding of what needs attention.

1. Put the frame up onto a crate so the gearbox - engine cradle is not supported. The iso mounts are a trinangulation of rear, top and front. All have to be set accurately to get both smoothh running and stable steering. If the swing arm pivot is worn the handling will be affected irrespective of the iso condition.
2. Take the fuel tank off.
3. Remove the rear wheel.
4. Peel back the Iso rubber boots front and rear so you can see the shim collars.
5. Get a friend to hold the bike firmly or strap it down.
6. Grab the end of the swing arm and pull and push it left and right. Observe the movement of the engine and top head steady. The top head steady on the pre-72's was not too strong and could crack. The rubber buffers can split and perish. The head steady really needs to be set up carefully once the front and rear isos have been sorted out.
7. Keep the swing arm pulled over and see if you can insert a feeler gauge into the gap at the shim collar at the front and read isos. Anything greater than .010" indicates it needs attention. Ludwig is correct, you should from this point onwards use a dial gauge to measure the actual gap and the correct shim stack to reinstate the gap to .010" and not less than .005".
8. To check the swing arm pivot for wear, you have to make the iso cradle ridgid. Insert a wedge of wood between the frame and the gear cradle so the isos mounts cannot move. Grab the end of the swing arm and push and pull to the left and right. If there is any discernible movement at the end the swing arm, it means the pivot axle and its mounting are worn. There is a single bolt in the top centre of the mounting tube between the gearbox cradle plates. This must be firm in the mount as it retains the axle. The bushes in the fork ends don't wear too much, but if oil lubrication has not been maintained, these will get worn and you may have to recondition the whole lot with a oversize axle. The existing bushes and centre tube can be line reamed oversize to suit and it is worth upgrading to the double lock bolt modification at the same time. This means the removal of the rear iso cradle entirely including the gear box and removal of the entire primary transmission. Worth checking and sorting out anything else at the same time. I know I just did it and the bike feels like new and I won't have to mess with it for many miles to come.

Its not an easy job for a new comer to the Commando iso system, but read the manual and preferably get a expert mechanic to assist so next time round you will be comfortable dealing with any handling issues.

Mick

Wow Mick, Thanks for that. I will follow that step-by-step. I did measure the front iso's and they came to 20thou. - Regardless, I will follow your step-by-step and probably replace the regular iso's with CNW's adjustable iso kit so down the line I'll be able to re-adjust without 2 days of work. I'm sure that I will have more questions this weekend when I get to it (I;m using this week to prepare). I'm new to this much mechanical work but it's the only way to go owning a Norton and I'm hell bent on getting it perfect. I've sucessfully re-wired the whole bike with a hand-made harness having no prior experience so I'll keep with the right attitude and I'm sure I'll get through it.

I'm still not clear on what a dial gauge is... Is that the same thing as a "feeler gauge" as we call it? If so, I've got one.

Cheers for the input I'm sure I'll be asking more about it soon enough.

Brian

dial gauge



feeler gauge



Dave
69S

Thanks for clarifying...

I have a article by Mike Randall but I can't pull it up on the net. The address is a dead end. It's titled "Norton Isolastics the Easy Way". I found it easier reading than the Manual. Only thing I have is the E-mail address of Randall. randell@shaw.ca

Anyone know where this article is?

take the front iso off, it is easy, use a floor jack and piece of wood under the motor so it won't sag off, take it apart,
my guess is it look like hell in there, rubbers shot, not much money for new iso rubbers front and rear, if want to get it right

I found this: http://members.shaw.ca/randell/isolastics.html. I think it's the article Diablouph mentioned. I also found this - http://rides.webshots.com/photo/2417635 ... 440PwIzjI- whilst looking around. Good luck!

-- David

PalmerNorton said:

Wow Mick, Thanks for that. I will follow that step-by-step. I did measure the front iso's and they came to 20thou. - Regardless, I will follow your step-by-step and probably replace the regular iso's with CNW's adjustable iso kit so down the line I'll be able to re-adjust without 2 days of work. I'm sure that I will have more questions this weekend when I get to it (I;m using this week to prepare). I'm new to this much mechanical work but it's the only way to go owning a Norton and I'm hell bent on getting it perfect. I've sucessfully re-wired the whole bike with a hand-made harness having no prior experience so I'll keep with the right attitude and I'm sure I'll get through it.

I'm still not clear on what a dial gauge is... Is that the same thing as a "feeler gauge" as we call it? If so, I've got one.

Cheers for the input I'm sure I'll be asking more about it soon enough.

Brian

Click to expand...

Also if you add your location to your profile there might be someone local who would be able to show you what to do.