Dumblastics Questions

Hi peeps,

New to commandos but not Nortons.

Have been playing around with the isolastics of late as the measurements were outside of the 10 thou clearance. I have re-shimmed to get it down to 18 thou front and rear.
The manual i had was very misleading and said to in the case of the front iso to push the bolt through enough to clear the collar and shim retainer on the left side, change shim/s out and re-tighten to 25 ft/p. The same procedure for the rear but obviously on the right side. Seeming as i pulled both sides out and re-shimmed will the alingment be out. I have heard the driveline is offsett somehow because of the z plates. If someone could shed some light on proper measurement and what / where and how i should be doing this, please direct and correct.

Regards

Kenny

I think you want a total of .010", sometimes more, sometime less depending on how it rides. You should snug the play over to one side and measure the open side. Seems like no two are quite the same and that also goes for ride style and personal prefferances.

As far as offset goes, .005 to .010" to one side or the other will be negligable. The general rule is if you need to add a .010" shim, put .005" in each side.

Power unit does not center in frame but more/less 3/8" to LH to gain tire/chain clearance. D/t rear chain pull skewing power unit in frame, shims tend to wear more on LH front and RH rear and best to shim those places or tends to skew/bind in frame to point vibration less isolated. .018" is on loose side which should isolate nicely but extra slack to build up bouncing till Hinging wobble/weave so beware crossing paint lines and lumpy or windy spots till ya know what lurks. I test this a fairy low/safe speeds zig zags to sense a twitch taking up slack and narrow gap till no twitch sensed. Check head steady mount amd set to neutral undistorted cushions. Its can take a few 100 miles for iso's to settle in and tire condition and pressure feed back alot on isolastic sense of smoothness so don't judge yours till new broke in tires on and air balanced.

Ugh ok only skewed in my loose swing arms before attented too. I've been told there is a skew force from drive that wears iso's assymetric, so is there a perfered side to shim front or rear? Worse worn everything was my buddy Wes '71 when he was my guru [15 yr ago] and watched him finnaly get around to front iso with like 1/4" [no kidding] gap so gave him a big thick washer + some shims and by golly it handled good and isolated good too, a few years, then back to vibes and twitchy taking up slack, I'm sure Wes will get around to again.

Thanks guys,


I have noticed the wobble/weave changing direction as the iso's take up the slack. Should i be ironing this out so there is no slack when dipping into a corner. Seems to be more prevalent on left hand bends than right ones. Definatly better than it was though.

Regards

Connie,

that feeling of looseness you describe when transitioning could very likely be your head steady is too weak, instead of an iso problem

the entire motor tends to fall from side to side with the stock head steady, I noticed a big difference when I switched to a DaveTaylor
and later now to the CNW head steady, both prevent side to side movement much better than the stocker, still have that on?

Yeh i definatly still am rocking the stock one at the moment. Head steady that is.
Is it worth the money upgrading it?
Also wondered if its worth putting in the dollars to get the vernier iso's but cant justify the 200 odd dollars when i may only need to check and adjust shims every couple of months.
Any other mods anyone would suggest.?
Thanks 1up3down

Regards

Am I wrong to slightly alter the recommended torque on the front isolastic bolt in order to alter the shimmed clearance?

Seems that less torque on the nut will open up the clearance, and tightening will decrease clearance.
I have played with my original shim style isolastics by trying to manually turn by hand the end caps. If I can just turn it by hand the operating
clearance is pretty good.

I now run without the hard plastic isolastic gaiters and give the PTFE washers a spray of silicon lube occasionally.

Yeh i definatly still am rocking the stock one at the moment. Head steady that is.
Is it worth the money upgrading it?

Click to expand...

Connie, maybe your head steady rubber snubbers are cracked and flexing too much, time to pull the tank and replace

is it worth throwing the stocker away and replacing with a rod type that stops side to side movement?

yes, twas for me and lots of other folks

" Vibration up to 3000 RPM - Rear tight, Front OK
Vibration 3000-5000 RPM - Front tight, Rear OK
Vibration up to 5000 RPM - Both tight"

Connie73 said:

Yeh i definatly still am rocking the stock one at the moment. Head steady that is.
Is it worth the money upgrading it?
Also wondered if its worth putting in the dollars to get the vernier iso's but cant justify the 200 odd dollars when i may only need to check and adjust shims every couple of months.
Any other mods anyone would suggest.?
Thanks 1up3down

Regards

Click to expand...

There is nothing wrong with a stock headsteady although the newer boxed type should be employed. I prefer it over the DT type solution. The Norvil PR headsteady is my ultimate preference. But that's another thread and has been debated in length if you choose to search.
Anyhow, here is a few things to concider as you tune your handling. These things should not be under estimated nor overlooked.
1. Check front to rear wheel alignment.
2. Check to make sure your front and rear wheel hub offset is correct.
3. Although this may or may not be snake oilish, pull the gas tank and loosen the 3 fastener on the headsteady to head. Sit on the bike, off the stands, and while offering your full weight(as if riding), snug the three fasteners back up to set the headsteady to a "home" position.

Factory head steady even if perfect does compress and spring back side/side to build up w/w upset, so a rod head steady [IF rod radius lenght long enough] will both isolate better and allow higher oscillating load tolerance than just rubber lords mounts. Still once factory steady diddled to neutral with pilot on its fine for me to kick up heels 'some' in turn loads on factory Trixie but if trying to go around fast as sports bikers out for fun it can go nutz on either side of apex so should pick choose test area to find out limits on purpose - not surprised w/o space/time to recover. You can not really tell what is doing what on handling until both tires are in great shape and air balanced to least steering effort as decades long reports of sweetness returning just replacing tires. I am so depressed disappointed and scared of unlinked Cdo antics on Trixie - smoothness is my main desire so after head steady rubbers set neutral I also bench grinder waisted them ~1/3 depth for very pleasant all day long isolation and decent handling. If ya can stay on high corner loads on smooth surface calm wind, so nil oscillations slack build up, an un-tammed Cdo can break rear loose for a scare/twitch/step out but if ya can't keep high loads on taking up all slack - such as lumpy surface &/or wind gusts or easing up/braking before apex or the automatically easing loads leaving apex climax >>> all hell can break loose. Only one way I know to get beyond rubber babby buggy handling and embrass fatso rigids but who'd believe it w/o experiencing it.

I like eailer fracture prone headsteady mount better than the ugly big ole boxed version - after the earlier version flexure braced.

Bob Z. said:

Am I wrong to slightly alter the recommended torque on the front isolastic bolt in order to alter the shimmed clearance?

Seems that less torque on the nut will open up the clearance, and tightening will decrease clearance.
I have played with my original shim style isolastics by trying to manually turn by hand the end caps. If I can just turn it by hand the operating
clearance is pretty good.

I now run without the hard plastic isolastic gaiters and give the PTFE washers a spray of silicon lube occasionally.

Click to expand...

no it wont make any difference if you over torque the isolastc bolts the clearance is controlled by shimming unless you have mk3 isos ,they have a fine adjustment thread but are still not adjusted by the tightness of the iso bolts ,,,,,,,,,baz

Righto, so i have adjusted the iso's last night, pushing the engine over to get the 10 thou on one side. Left on the front and right on the rear. I have also adjusted the head steady pushing the bike off the centre stand sitting on it and tightening the nuts. Will see how these adjustments have affected the handling if any on friday, weather permitting.

Cheers
Baz
Hobot
pete.v
1up3down

How's the swing arm? IMO, that's the biggest issue with handling. New swing arm bushings and swing arm clamps made my commando corner like it's on rails. I keep my Isos (vernier in rear, shims in front) at .005- .006 and the bike will handle with anything around. But the swing arm bushings/clamps were the major (by far) factor in excellent handling.

I think the swingarm is ok. I did the push/pull test on the rear rim/tyre to see if there was much movement but didnt notice any considerable amount. I tried to pull it apart but got as far as trying to pull the threaded pivot out. Coudlnt find a suitable bolt with the right thread to pull it out so i checked for play side to side, put some 140w oil in it as it had none and sealed it back up.
I have now set the clearances at the front and rear to about 10 and 14thou respectively with the engine pushed over

Any ideas on the right bolt to pull the pivot out.?

Regards