Isolastic Centering?

Tornado said:
I went ahead and replaced the Hemmings adjuster on the rear with the vernier setup, sourced from AN. The rubber units coming out, less than 2 yrs old, sourced likely from RGM, were like hockey puck hardness while the AN rubbers were more like running shoe sole stiffness. This was likely a major contributor to high vibration levels past 2 yrs. Bike has been liveable with since, but I still feel it has more vibes than it should based on what others describe as right for a Commando.
One possibility, the rear iso end caps that go over the cradle large diameter tube, didn't seem to come off easily and new ones from vernier kit didn't go on easily. I later realized this might be due to the frame getting powder coated two yrs ago and it could be preventing end caps to fully seat or seat squarely...thus giving uneven clearance at the iso teflon washers. Have left it this way and any re-work here will need to await a future strip down.
Click to expand...
Mr. T.
I have a straight 850 cradle and not wallowed out for you , for free , if you find the cradle plates are bent from an omitted spacer washer .
I fly to B.C. every later summer to fish .
 
I suspect my issue has more to do with where my engine sits in the frame. My rear verneer ISO unit was never a snug fit in the frame and needed a generous spacer to take up the clearance. It's hard to find a definitive answer to where the engines centerline is in relation to the centerline of the frame. My engine sits about 3/16" to the left of that. I'm assuming that's not right as I tried to fit a box section head steady and there wasn't enough room for the ISO spool on the right side. If I where to make it fit I would have to move the whole cradle assy to the right closer to the centerline.
 
When I put the 920 bike together I neglected to coat the iso rubbers with grease. The bike vibrated badly at all but fairly high rpm. It would break loose and go somewhat smooth at around 4500 rpm.
After a couple of days of that I took the iso rubbers out and coated them in a synthetic rubber grease.
That made all the difference, now it is just as smooth as my MK3 except the smooth running comes in a couple of hundred rpm lower on the 920.
I suspect that the rubber grease allows the iso rubbers to centre up in the tubes in a neutral position. This tubes on the 920 are alloy, so they might be a bit stickier than stock steel tubes, I'm not sure.
In any case, the grease solved the problem.

Glen
 
zotz said:
It's hard to find a definitive answer to where the engines centerline is in relation to the centerline of the frame. My engine sits about 3/16" to the left of that.
Click to expand...


1/8" to 3/16" to the left of frame centre is correct for the cradle (thus the engine, gearbox and front end of the swingarm) and the head steady has the same offset.
 
L.A.B. said:
1/8" to 3/16" to the left of frame centre is correct for the cradle (thus the engine, gearbox and front end of the swingarm) and the head steady has the sam
Click to expand...
You're right and that's how mine has been set up and yet a box section head steady won't fit. I am using a rod end head steady by the way and have been for a long time but just wanted to do a quick swap for comparison purposes. Something is clearly amiss so I'm just trying to sort out what.
 
When I added the suspensory fittings to the 850 box steady I drilled the holes offset by 1/8" so that the spring was vertical as per these instructions. It all lined up when finished

Isolastic Centering?


Here are the pieces you'll need, with Norton part numbers. From left: spring retainer (065585);
spring bracket with trunnion and nylock nut (065458, 065456, 067892); head steady spring (06
5454). You'll also need two 1/4 x 5/8inch bracket bolts, plus corresponding nuts and washers.
With the mount removed, make a mark 1/8inch to the right of center (viewed facing forward) on the
base of the mounting plate. Mark the center of the spring bracket and line it up with the mark on the
plate, flush with the bottom of the head steady.
Click to expand...
 
Torontonian said:
Mr. T.
I have a straight 850 cradle and not wallowed out for you , for free , if you find the cradle plates are bent from an omitted spacer washer .
I fly to B.C. every later summer to fish .
Click to expand...
Thank You for the offer. As detailed earlier in this thread i was able to bend the distorted plate flat again using a jack screw arrangement. There was no longer light passing btwn a straightedge and the plate surface. It did not make any real difference in the vibration. Using softer AN rubber did make a significant improvement.

I believe the remaining problem vibration could be from the end caps not seated fully/squarely against the frame tube ends due to powercoat interfence.
 
Tornado said:
Thank You for the offer. As detailed earlier in this thread i was able to bend the distorted plate flat again using a jack screw arrangement. There was no longer light passing btwn a straightedge and the plate surface. It did not make any real difference in the vibration. Using softer AN rubber did make a significant improvement.

I believe the remaining problem vibration could be from the end caps not seated fully/squarely against the frame tube ends due to powercoat interfence.
Click to expand...
O.K. , time to remove powder coat from the cradle tube ends . My buddy Barry says both ends should be squared flat . It's also part of " World's straightest Commando " thinking .
 
Torontonian said:
O.K. , time to remove powder coat from the cradle tube ends . My buddy Barry says both ends should be squared flat . It's also part of " World's straightest Commando " thinking .
Click to expand...
Yes it's ok, once the powder coat is off wax the bare steel to protect against rust without recreating the powder coat problem.
 
kommando said:
Yes it's ok, once the powder coat is off wax the bare steel to protect against rust without recreating the powder coat problem.
Click to expand...
Well such efforts must await a future engine removal to access those cradle tube ends, so not something Im planning to perform anytime soon.
 

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