1974 Norton Commando 850 MK2A - Isolasticity (part 5) 

Thanks very much Dusty! Hope all is well. Best wishes, Mike

Dave - Thanks for the note on installing the front ISO unit to the frame and front engine fittings. In my experience, the front ISO will go in fairly easily if the engine is properly lifted (as you note) and from there it's an easy task to get the fixing bolts lined up and installed. Errm, unless it doesn't -- there seems to be some variation in frames (I'm not sure if from the factory or due to damage or warpage in use) and the width of the "ears" in the frame varies. There have been some Commandos that I've had to pull the frame downtubes apart just a few thou -- and THEN an otherwise, clumsy or recalcitrant front ISO assembly goes in easily. In this regard, I think I prefer a frame that fits well onto the ISO "stack" rather than one that has to be pulled down into place by the centre bolt. I don't think I've ever tried your "setting wide then adjusting down" trick consciously but I think that I've sort of lucked into it a few times. I'm going to give it a try as you note on my upcoming install and I expect that it will work well. (BTW, I had seen some frames for Production Racers with additional bracing installed; the usual seeming to be a horizontal bracing tube across the downtubes near the front ISO and an additional bracing tube tying the rear loop together [also horizontally] below the swingarm area. I discussed this with an experienced Norton race shop technician. His advice was that these mods never seemed to give any benefit and, in his experience, despite all measures being taking to avoid distortion, seemed to cause unnecessary localized stiffness it those areas. He suggested that it's not a good idea so I dropped the thought for my PR.)

("Teflon" also called PTFE, of course.)

Hi Bruce, many thanks for your kind and thoughtful note. I really appreciate it and your tips. Best wishes, Mike

Thanks a lot Kevin. Yes, I might try that, thanks. I still have to do some fine-tuning! Cheers, Mike

Hi Steve Yes, it was a bit of a struggle. I honestly thought that I would just lift the whole assembly up through the front of the frame and it would go straight into place. But it didn't. There was also no chance that I could get the unit installed with the shims set just right, so I soon abandoned that idea. I had to basically pry it and maneuver the unit into place and pushing the unit pretty hard against the metal brackets on both sides of the down-tubes that the main bolt goes through. I left the rubber gaiters on (sprayed with some lubricant) as I thought it would be nearly impossible to get them on afterwards. I was a bit worried about ripping them, but they held up okay. Once the unit seemed to be as aligned as I could get it from underneath, I used a soft mallet to knock it from underneath approximately into place. I then used the mallet to line up the holes with brackets. I hope this helps and good luck! By the way, the little scissor jack bike lift helped a lot, especially when lining the unit for all the fasteners.

Thanks mate, I will let you know how I get on

Hi again, Thought I would give you an update. No amount of maneuvering and hammering would get it in. Could be because my frame has a strengthening bar welded between the two down tubes, I think it may be a Gus Kuhn frame. Anyway I filed of a millimeter or two from one of the vernier thingies and it fits now. Now to start on the rear isolastics! Dread!

Hi Steve, great news that you got the front unit installed. That sounded like a big job. Yes, the frame-strengthening and maybe even due to it being slightly different could have been the cause but glad you sorted it out. I don't envy you doing the rear units! I haven't had the time (or energy) to get back to mine but it's on the must-do list. Good luck!! Mike

Hi Fredi, thanks for your note. They do generally vibrate / shake while at lower revs, but this should smooth out as you begin to ride. It can vary by bike but mine shakes while standing and while riding past 3,000 revs and then it becomes very smooth. There could be a number of reasons for bad shaking but here are a few suggestions that I hope will help. Engine shakes: Front isolastics have worn or need to be adjusted Rear isolastics have worn or need to be adjusted Head steady mounts have worn If there is excessive knocking sounds in your engine, the shaking may be caused by engine problems Bike is shaking while riding: Worn tires Tires are incorrectly fitted or do not match Front forks need attention (springs, oil, dampening) Wheels need to be balanced Rear shock absorbers If you want to take a video of your bike and the shaking and upload it to your RU-vid channel, we could certainly try to help. Best wishes Mike

Alright mity thank you for your suggestions..i'll try to change the fornt isolasticity first.. thank you so much and respect..

Hi mity..how're you doing?I'm sory before..could i get manual repair by file/whatever from you?and how much price for front isolaticity? Thanks a lot..respect

@@fredihardjanto1952 Hi Fredi, I don't know if you can get the file version of the repair manual. But there are lots of websites that provide pictures of repair work. I don't know what model you have but here is the unit that I purchased for my bike. It was approximately $100. www.oldbritts.com/13_067337.html

@@fredihardjanto1952 Here's the video #5ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-KssRr_sRzAQ.html