Front isolastic & engine mount fitment problem

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Luke Turner

Luke Turner

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Hi all,

Had a challenging couple of evenings in the garage trying to replace my front isolastic.

It's a '74 MKIIA with the appropriate pre-MKIII isolastic & MKII engine mount from Andover.

I can't get the damn thing in.. so far I've knocked a bit of timber up between the two tubes, taken the fuel tank off along with the top engine mount & then jacked up the engine to rock it backwards a little..

I've well & truly scuffed the paint of the new engine mount which isn't the best but it's the least of my worries at the minute.

I disassembled the isolastic to see if I could at least get the engine mount on to make sure that fits, but, it doesn't!

Front isolastic & engine mount fitment problem


You can hopefully make out in that photo where the engine mount fouls the casing.

I'm going to remove the paint from inside those two tabs to see if that helps at all.

I'm also going to remove the carb so the engine will tilt back a little further as the throttle cable from my Mikuni fouls against the top tube.

Any tricks, tips or words of wisdom?
 
Buy yourself a digital vernier. With parts for old bikes it's always best to measure EVERYTHING first.

Martyn.
 
It can be an absolute bas***d to get in. When you get it right it just rolls in easy and you think how the hell did that happen and why and how?
 
Is it the space between the ears on the mount which is inadequate to fit over the engine casting? If the mount is powder coated you might have to remove the powder coating in that area.

Glen
 
It's actually quite easy :mad: Just try everything for a couple of hours and when it pops you'll be real sad that you don't know how you did! Best I can tell, there is only one angle that works and by the time I get them in, I'm so frustrated that I really don't know how I did it. I think I'll make a video next time. I've never accomplished it in under and hour!

It is helpful to put some wood under the engine on top of the frame to align the front of the engine approximately where it will end up.

We should have a pole: Which is most annoying. Front engine mount, carbs, head, rear hub with new rubbers, installing felt in the inner chain case.
 
marshg246 said:
It's actually quite easy :mad: Just try everything for a couple of hours and when it pops you'll be real sad that you don't know how you did! Best I can tell, there is only one angle that works and by the time I get them in, I'm so frustrated that I really don't know how I did it.
Click to expand...

I agree with Greg on this one. i'm a bit of a noob, only did this once, but on the front, I fought with it for hours - took a break, came back, and the damn thing fell into place - then you say "WTF!" I had the engine supported with a floor jack, and it seems to me. you need to pivot the thing into place up from the bottom. just make sure the Vernier adjustment is on the RH side of the mounting bracket. the adjustable end, the locked end, and gaiters all need to be in place prior to final installation. pay close attention to the diagram (fig. F21) in the andover instructions especially how the gaiters mount. make sure the fixed end and adjustable end (especially the adjustable end) are fully seated prior to frame installation. seems to me, you need to get the top bolt flanges started on the engine, and pivot the thing up from the bottom, working the mount into the frame. it's a snug fit, but a light tap with a plastic mallet is all you'll need. once in place you can set the adjustable end - I set my to .010" when fully torqued. good luck - if I can do it, anyone can do it....
 
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Luke Turner said:
It's a '74 MKIIA with the appropriate pre-MKIII isolastic & MKII engine mount from Andover.
Click to expand...

What was wrong with the old mount?

Luke Turner said:
I've well & truly scuffed the paint of the new engine mount which isn't the best but it's the least of my worries at the minute.
Click to expand...

Are you saying the new mount doesn't fit the crankcase lug or just won't slide into position at the left-hand end?

Don't be afraid to lever the engine around to get it to line up.

This might help? Refit from 14.40
 
I have removed and replaced my front mount quite a few times and it was not a problem once I figured out the correct way, which is sliding it in from under where it goes. Have you not reused your original mount, because if you have, it should fit easily.
We have all heard the some parts are made to fit because all Nortons are not the same.
Dereck
 
Mine didn't fit either.... until it did. Levered, prised, beat, twisted, swore, etc. for hours on end. Then after a long break I came back and WTF.... it went in just as I grabbed the 3# shop hammer to threaten it. Endeavor to persevere for there is no room to spare.
 
Will have a proper read of your replies when I've got time but to quickly answer the question about reusing the old mount. A previous owner had cut it down to fit a MKIII isolastic before pre-MKIII isolastics were available.

I bought a pre-MKII isolastic (before realising it was cut down) & couldn't return it as I'd assembled the whole thing.. so thought the best option would be to buy a new MKII mount to suit.
 
Luke Turner said:
Will have a proper read of your replies when I've got time but to quickly answer the question about reusing the old mount. A previous owner had cut it down to fit a MKIII isolastic before pre-MKIII isolastics were available.

I bought a pre-MKII isolastic (before realising it was cut down) & couldn't return it as I'd assembled the whole thing.. so thought the best option would be to buy a new MKII mount to suit.
Click to expand...
If the mount you have doesn't fit in a dry fit, PM me. I have an original. BTW, if it doesn't fit the cases, look closely at them - I see a problem in the picture. The mount needs to slip on without much play and you could dress the cases a little if that's the problem. If it's the frame, and it's only a little, just pull it apart a little.
 
Top engine mount off= correct
pipes loose
Drop engine down onto frame rail front crossbar 71+
Install mount on engine
Lift engine with iso components while tweeking frame rails. Don't scratch the paint

Seems like last time I did it, just before the michigan rally, it was well under 15 minutes from "on engine stand", 3 bolts on rear of engine and 2 bolts on the front then lift engine then 1/2"(edit) bolt slipped in. Dressing the rest of the engine is what took all the time....
 
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Digital vernier arrived today so had a quick minute in the garage to measure up.

Inside of mount tabs with paint removed: 82.88mm (3 17/64 inch)
Either side of engine casing: 84.08mm (3 5/16 inch)

So I'm 1.2mm or 47.24 thou of an inch out.

Will try a few of your tips & see what happens!
 
Luke Turner said:
Digital vernier arrived today so had a quick minute in the garage to measure up.

Inside of mount tabs with paint removed: 82.88mm (3 17/64 inch)
Either side of engine casing: 84.08mm (3 5/16 inch)

So I'm 1.2mm or 47.24 thou of an inch out.

Will try a few of your tips & see what happens!
Click to expand...

I measured some spares:
The iso mount long ears and short ears were 83.7-84.0
The engine case was 84.05
The mount pushed onto the cases with just a little pressure.
Your 82.88 measurement area should be able to open up that needed 1mm.
 
That size difference is bloody ridiculous. A 5 thou interference fit may be acceptable but 1.2 mm is not. If you spread the mount apart you are going to have to reshape it so the flanges are parallel or it may/will always come loose. Send it back to the suppliers and make them send something that fits.
Dereck
 
Luke Turner said:
Will have a proper read of your replies when I've got time but to quickly answer the question about reusing the old mount. A previous owner had cut it down to fit a MKIII isolastic before pre-MKIII isolastics were available.

I bought a pre-MKII isolastic (before realising it was cut down) & couldn't return it as I'd assembled the whole thing.. so thought the best option would be to buy a new MKII mount to suit.
Click to expand...
Where did you buy the new mount from?
 
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