Centering Iso mount bolts in the iso mounts

Got the iso boots from OB the other day and was prepping to install them. Bike on centre stand (frame), top head steady bolts loose. Right away notice that the front iso bolt (14) and mount collar (25) is hanging down pretty severely in the front mount (10) from the engine weight (http://www.oldbritts.com/1971_g9.html). Put floor jack under engine and jack up so pressure is off the bolt so I can loosen it and take it out. Get to thinking, with the engine suspended in the mounts off to the bottom, the vibration dampening is starting at a compressed situation right off the bat. Wondering if I suspend the engine from a spring off the centre tube, like I have seen on some of the head steadys, if it wouldn't be in a better position to reduce vibrations? I do notice when I add my almost 200 lb on the seat the bolt is a bit more centred in the mount, but not totally.

Here's the front mount bike on prop stand, about the same on the centre stand.


Here's the front mount with the engine supported at the bottom with a floor jack.


Ideas? I'd like to see some spring setups. I wonder if the bikes with the centre stand on the engine if the iso mount is better weighted?

Dave
69S

Re: Suspending the engine with a spring

Dave, the Dave Taylor is excellent, cheap, and has the optional mark3 type spring exactly as you desire.

Re: Suspending the engine with a spring

DT is an option, but for some reason I'm fighting it. I do like the CNW, but boy the price.

Dave
69S

Re: Suspending the engine with a spring

Dave, I just sent you an email.

I'm renaming this thread because that's where I'm going with this.

I also notice that my rear iso bolt is about 1/8" forward of the center of the cradle iso mount hole. I can lever the cradle against the frame and make it centered but it springs right back. I am thinking that if the iso bolts start centered in the mounts, there would be less compression of the donuts and thus possibly less vibration transferred to the frame instead of being compressed to one side or the other to start with, like mine are now. Anyone else mess with this?

Dave
69S

Spring support is good aid to help isolation start earlier. Will not help hi rpm isolation if that's the annoyance to solve. All the top links seems to help increase the smooth sense besides tame some the isolatic weave-wobble onset.

That's where all my vibration is, idle to 3K then fine.

Dave
69S

DogT said:

That's where all my vibration is, idle to 3K then fine.

Dave
69S

Click to expand...

This is fairly common, as you must know by now.
I do not think that these mount are usually centered when in a running unsupported status. That is when the secondary internal bumpers come into play.

For this reason, I do not like the Dave Taylor type or other link type head steadies. They lend to even more reliance on the secondary internal bumpers to take the weight. Although the springs may help, I still have a feeling of the unit dangling there.

My riding experience was an uneasy one with the DT steady. Sold it shortly after using it. The stock boxed system was better IMHO. The PR headsteady, I now have installed, offers much more support in this regard and tunable to the inconsistencies from iso mount to iso mount.

If you'd pm me on what was sensed unpleasant about a link head steady, it might help me understand what all matters about head steadies in general. Isolation should set in good by mid 2000 rpm, not 3000, ugh.

When I put the bike away in maybe 77, there was hardly any vibration that I can remember, except at idle. But by then the iso washers were probably dust (like I found them in 05) and the clearance was probably on the order of 1/4", so no vibes could get through. Not that I noticed the handling that much, since I didn't race around the corners at 90, even then.

I just have been concerned since I tried installing Jim's sump breather and my frame brace is so close I couldn't install it, and the only reason for that is iso centering or layout. Why is it the rear cradle iso mount is skewed towards the rear, one would think it would self center unless the dimension from the front mount to the cradle mount is wrong?

I know, I should have looked at this back in 09 or so when I was getting the engine/gearbox/cradle ready to mount in the frame.

Dave
69S