Front engine mount flange dimensions Mk I 850

Hi! Does someone have a moment to check the distance between the two flanges on the Mk I 850 frame for the front engine mount. Mine are almost exactly 6" and I'm having a real problem getting an upgrade vernier isolastic to fit between the flanges. I'm using parts with Norton part #'s and a mount with the tube faced back to 6mm protuding past the flange (both sides). Still coming up about an 1/8-1/4" too wide. Curious if the 1973 end caps I'm using are too thick. I've never seen the end caps from a 1975 but I've got to think they couldn't be much thinner.

I've gone back to the beginning of the forum (page 147 or so) and haven't seen anyone with this exact problem although one poster joked about using a frame spreader to get the vernier assembly between the flanges. Thanks for any input.

The pre-Mark III front mount needs to be trimmed down to accept the Mark III vernier adjustable isolastic kit.

I've got a new supplier for a matched kit in stainless steel that doesn't require machining and saves nearly $100 over the factory bits. They are the best out there now.

I had to sort of wedge mine in diagonally, then smack it around with th right mallet. Not too much fun with the engine right there, but I think you are on the right track.

If I force the vernier assembly into the space between the flanges it seems as if I would lose the ability to adjust clearances to the recommended .008" to .012". I'm probably missing something here but it also seems as if there are several suppliers and even MkIII and pre-MkIII vernier assemblies. Mine came with Norton part numbers and Andover Norton labels. Seems as if I'm going to have to do some research on what's offered out there and then figure out what I've got compares.

The front mount has been faced back to recommended dimensions for the Mk1 to MkIII upgrade. I'm tempted to take even more off.....maybe back to 3mm per side. Anyone had to do that??

Have you checked your frame dimensionality?

I'm not sure as mine started as a mk3 so I knew it was the right size. The frame is flimsy though. I remember thinking the same thing...why won't it fit right back in? Until I literally grabbed each of the downtubes and spread them out by hand. I mean I didn't see it get narrower when I removed it, but it popped out so maybe I just missed it...and there's a crossbeam under the engine so wtf? Knowing I had the right size though and now knowing how easy it was to move the frame made it easy. If you're sure you cut the tube to the reccommended amount...Put it in diagonally, grab one downtube and pull outward, and with the other hand tap the iso tube downward till the other side is just low enough to keep the mounts spread. Now one side will be too low and one too high. Tap it up and down till it evens out, and the downtubes will pop into place. Not the easiest job with the motor in there, but could be worse. Next use the jack that's holding the engine up to adjust the engine heigth until the mount holes line up with the iso assy.

Thanks Pelican. You're experience seems the same as mine. Maybe I'm making too much of it.

If it's this tight how do you achieve the recommended .008" to .012" clearances?

Once it's in it won't seem as tight. Tighten the engine mounts. Put the iso bolt in, but don't tighten. Adjust the iso to tolerance- simple allen wrench in one of the holes will turn the adjuster cap, and tighten the main bolt.

Handy to have :lol:

Don't take it as an insult, I just found it a fitting reply and I do have a big hammer too, but I reserve it's use for cars :wink:

Jean

There's no way I see that as an insult....just good engineering. It really helped to find out that the tightness was not just my imagination. I curious to see how it works in practice. After some touch up spray work on the frame (while the weather here is nice enough for outdoor spraying) I'm planning on fitting the front and rear mounts with the swingarm assembly. Yokes mounted with new bearing and the forks are refurbished and ready to slide back in. I'm going to use my orignal wheels and tires just to have it roll. I'm still looking for new rings but I'll check the gaps on the originals first. Thanks again for all the help to everyone. I've been around motorcycles (off and on) for almost 50 years and didn't know how much I didn't know about Nortons.

There is a knack to fitting the front ISO my Mk3. I know it coz I've done it many times and each time I do it I'll be damed if I can remember how the next time, so I don't use the mallet I persevere. I just sort or turn it in then suddenly and as if by magic it just pops in, and I'll be buggered if I really know how or why.

Getting old is a real bitch.

Cash