ISO ideas

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While installing my self given Xmas present (belt primary) I happen to have the primary cases off and thought it would be a good time to check the rear ISO clearance.
I thought about the clearances, with no clearance you have a rigid mount, completely remove the ISO shims, washers and collars to get the full effect of the rubber mount and you'll have too much flex in the frame.
When designed and tested someone came up with the factory clearance spec of .010 inches, a compromise (perhaps) between vibration and stabilizing the engine/tranny/swingarm package.
As I stood back to take a break and scratch my a--(leg) I looked at last weeks project, my home made tie-rod headsteady. It occurred to me that someone could fab up a clamp-on or welded stud mount on the ISO tube with a clamp-on or welded stud mount on the adjacent frame member and install a tie-rod stabilizer to either front, rear, or both ISO mounts (ala Harley). This would allow the ISO to shake freely up-down and forward-backward but not side to side, theoretically providing less vibration to the frame and still stabilize the engine/tranny/swingarm package. No need to mess with shims, take them out or leave them really loose, or maybe just run the rubber boots.
Those tie-rod ends are available from McMaster-Carr for less than $8 each (unless you want stainless), the 1/2 inch size is rated for over 7000lbs, and they even have a sealed lube style.
Oh well, has anyone seen it done before???

justa thought,
74 Commando
02 Bonneville
02 Chang Jiang (Iknow, what the hell is that)

ps. How can I get my letters to post using my user name

Your tie-rod stabilizer idea sounds interesting.

However, Norton engine vibration seems more complex than a Harley engine, not withstanding that they are both twins. If you recall, the Harley engine has a knife-and-fork piston rod arrangement. This means that both pistons are directly in line with each other with respect to the axis that runs from the front to the rear of the bike. As such, much of the engine vibration is restricted to the vertical, fore and aft plane.

In contrast, the Norton engine with its side-by-side vertical piston arrangement develops a certain amount sideways rocking vibration in addition to an up and down vibration.

Having said all that, your tie-rod idea might work fine with a Norton engine; vibration analysis is somewhat of a dark art, and way beyond my capabilities. Give it a try and let us know the outcome.


I am in the process of making a front link kit that will bolt on with no mods like welding and a head steady to. the next will be looking at a bolt on rear rod kit. I also make a kit that fixes the loose swingarm pin with NO welding and is a lot stronger that the welded on nut bodge.

sorry was not loged in.

jerry how do i fix my log in trouble? it is no longer automatic and does not show unread messages

It's all been done and seems to work real well. This is a reprint of an earlier post from another list. It includes a link to a picture of the lower unit. The head steadys can be bought or made. norbsa

Bob Patton wrote to hobot's questions - March 2001:

What I was wondering about or may have foregoten;
1. Is there any motor vibration transmitted with this linkage?
I think I understand the Lords Mount has some good vibe
absorption designed into it.

The idea is to let the cradle move up and down or front to back
but not side to side. The arm has to be lined up on that axis. Any
deviation tilting it up or canting it anything from perpendicular
to the centerline is going to transmit vibration. Maybe you have
seen some of the Buells. They had at one time an outrigger anchor
for their linkage.
The reason is the longer the arm the less acute the arc that the
moveable end is going to travel thru. This arm is about 5" long. I
figured that the cradle moves maybe 1/8" in each direction from
So, imagine a sphere with a radius of 5" Take a slice out that has
a surface area of 1/4" The surface of the old sphere still shows
as a convex surface. If you connect the two corners of the arc
from the surface and make a line perpendicular to it to the
surface in the middle that will tell you how much lateral motion
you get translated fron that 1/8" of motion. I had to compromise
between mounting the Lords right in the centerline and having too
short an articulating arm. Theoretically, you don't need to use a
rubber mounted ballend and you should have that much tighter
alignment with negligable vibration. I was told that regular
rodends wear to the tune of 10thou in no time. Because of the
location, it seemed this is a better way to go, I don't think it's
possible to tell the difference, but I haven't checked yet.

2. Did this one linkage accomplsih what you were after
in controlling the 'hinge' effect at extremes of handling loads?

I can really tell the difference when riding at the limit on bad
roads. Last spring I was riding with Frank Forester and I was just
about at the edge. 40-50mph on 20mph roads that were shot as far
as surface goes. I could hang off the inside and ride it out,
mainly steering with my outside leg, pulling the bike over deeper
or letting it go upright, no handlebar input at all after the
initial countersteer to get the bike leaned over. This bike
wouldn't do this before. The crappy forks really showed
themselves. they would windup and let go but always the sum total
of their deviations ended up ok. Not that much fun.
My completely worn, saged and loose Iso's still allowed
good handling on wavy road sweepers just about scraping
in the 70 mph zone. I assume with rebuildt Iso's it might
help push my luck into the 80 mph zone and with your
geometery added, well beyond my anal pucker factor.

People adjust to what they've got. I had a Kawasaki Triple that I
thought handled ok. I like to ride all day, a stable bike is more
fun and less tiring.

Bob ... 9400vTuKTT

Thanks Bob,
Thats a pretty clever setup (in the picture). Having recently painted the frame and powder coated the cradle I'd like to hold off awhile longer before I start grinding and welding on it again.
However, it makes me think of another alternative mount that Kenny Dreer use to install on his bikes. It was pictured on his old vintage rebuilds website. It mounted directly below the transmission, it wasn't the rod link style, I believe it just used rubber??

thanks again,
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