Fit of RGM iso rubbers

i purchased a set of RGM's adjustable iso's for my 73, installed the rear one a while ago with no problems, today i put the front one in. tight as hell getting them in there, now my questions are...

1. the side that went in first, and was pushed through the whole tube isn't sitting flat, but kinda domed like the sides dragged the whole time. No amount of fidgiting seems to resolve it, would this be any issue if left like this?


2. Should the whole thing sit "even" left to right, or should there be any offset either way? no mention in the directions, i'm thinking the threads should protrude equal amounts? the non adjustable side bottoms out when screwed on, i have this small gap, i'm thinking maybe i should push the rubber through until this is flush? (no washer or anything in this pic so it might be closer than it appears)

Wheres the end caps and teflon washers?

pvisseriii said:

Wheres the end caps and teflon washers?

Click to expand...

thats what i meant when i said no washers or anything so i might be there already. I have to clean my end caps tonight after the kid goes to bed then i'll get it all together. just trying to gauge where the rubber should land so to speak.

I'm guessing that these RGM iso sets are one piece units with one piece threaded bushings and attached donuts, kind of like the Norvil sets? I would think that if the donuts are greased on the mounting tubes, they will finally adjust themselves when the vibrating starts? I always wondered about this. But I have the early 71 separate bushes and unconnected donuts with the Hemmings adjuster, so maybe I shouldn't be in this conversation. I would think they all would self center after a while. I used a good amount of silicone lube in the tubes, but some don't recommend that, there is some specific lube that is used there, but I've always had good results with silicone lube on rubber parts and when I took my front mounts apart after 2 years they seem fine and lubed.

Dave
69S

i used the p80 temporary rubber lube that some people on here have talked about before. yes the RGM is as you described, bonded on the tube. The front seemed to be a MUCH tighter fit to get started into the tube than the rear one was. compressing the rubber to get it in there was a real bitch (ask all the neighborhood kids who now know ever curse word under the sun thanks to me) i tried pushing it back about a half inch, then pushing the through again, same result. I'm also wondering if it will work itself out, but don't want to install the motor and then find out it's a problem

Your not wrong about being tight! I fitted the RGM Mk3 iso's earlier in the year. It took much effort and plenty of rubber lube to get the first rubber started. After that the rest kind of followed the first one in with less effort. I ended up using a piece of threaded rod and a couple of big washers to hold the first rubber tight against the mount tube while I levered it in with a small screwdriver. Still plenty of colorful language though. :evil:
Just a thought. Did you have the tube cut down in length?

Might not hurt to call RGM and ask.

Hi boy's,
it is noted within the MKIII manual that the front iso rubber is designed to be a tighter fit than the rear, so things seem normal in that regard.
I'm interested in what the gaiter fit and finish is like. Any photos of the gaiters? I'm completely underwhelmed with the AN gaiter offering.
All the best.

Mark F said:

Your not wrong about being tight! I fitted the RGM Mk3 iso's earlier in the year. It took much effort and plenty of rubber lube to get the first rubber started. After that the rest kind of followed the first one in with less effort. I ended up using a piece of threaded rod and a couple of big washers to hold the first rubber tight against the mount tube while I levered it in with a small screwdriver. Still plenty of colorful language though. :evil:
Just a thought. Did you have the tube cut down in length?

Click to expand...

i did the exact same thing! put the mount in my vise then used a threaded rod with nuts to keep pressure on it while i squeezed it in. i bought these from commando specialties and they say they're a new version that needs no modification to the front tube

I fitted those same isos last week. I too noticed the bowing of the donuts, but didn't worry about that; the bowing seemed to be the same on both sides, so appeared to be equalized.

For the front mount I adjusted the position of the rubbers in the outer tube so that when the fixed cap was screwed down as far as it would go on the inner tube, it just touched the ptfe washer: snug, but not clamping. The adjustable cap was then screwed on until it was just touching its ptfe washer. Then I measured the overall length of the assembled iso unit and it was about 1mm longer than the distance between the mounting lugs on the frame. I measured the original (shim adjusted) parts and decided to take about 0.8mm off the new fixed cap to reduce the overall length without affecting the iso clearances and that should also provide the same across-the-frame location of the mount as the original units.

With the unit set up like that I could get it between the frame lugs but when the mounting bolt was torqued the isos nipped up tight: backing the adjustable cap off 1/8 of a turn and retorqueing the mounting bolt seems to provide a reasonable amount of freedom of movement between the iso housing and frame.

Cheers! ~ Gary

Gary, i remember you posting about having issues with the RGM set, i also cant fit mine between the front mounts without really getting everything tight then giving it a little tap with a mallet. gonna try to email rgm and see what they say

I'm just curious. The MK3 iso are for the 850, no? It was my understanding that the 850 rubbers are stiffer than the 750 ones. Anyone want to comment? The donuts I put in my early bike from the Old Britts early parts list were very easy to install, didn't require any tools, I just pushed them in with my fingers and hands.

Or maybe you all have 850's?

Dave
69S

well the kit i have from RGM is made for pre mk3 commandos as a conversion to vernier. the grunting is al over with, my problem now is just length. once things are all together like RMG's instructions say, with the end caps, PTFE washers, and adjusters, the whole thing is just a bit too wide to fit in between the tabs on the frame. If i REALLY tighten the adjusters down and give it a little tape with a mallet i could get it to go, but that just doesn't seem right. At that point to loosen the adjuster and leave the required clearance i would be basically spreading those tabs apart/out of spec i would think? Sent an email to RGM, waiting to see if i hear anything back from them...

Hate to say it, but I think you should have used the original style rubbers and the Hemmings adjuster. Worked a treat on mine and no machining. Fit between the frame just like original. But you might as well go on with what you have since you've got it.

Dave
69S

DogT said:

Hate to say it, but I think you should have used the original style rubbers and the Hemmings adjuster. Worked a treat on mine and no machining. Fit between the frame just like original. But you might as well go on with what you have since you've got it.

Dave
69S

Click to expand...

i'm starting to think the same thing. I also sent an email to commando specialties whom i bought these kits from. I would MUCH rather take things apart now to fix the problem than later when the motor is in. The rear set wasn't as tight as this, but it was a little bit of a tight fit going into the frame, now i'm starting to question if thats too tight as well. Like i said i don't want to put the whole bike together and find out theres nothing i can do to get the adjustment loose enough. not like i don't have anything else to do with the bike, so i'll set this all aside and see if i get emails back from anyone about it.

an update on this situation. After a few emails with RGM, i have a suspicion that my stock end caps are the problem, as the stainless caps that you can buy from RGM are slimmer by like .029. considering i'm off by .036, and my frame tabs measure 5.982 (very much on the low side of the specs) i'm thinking with the thinner caps, and a tiny bit of flex within specs of the frame things should fit fine. I purchased both front and rear kits from commando specialties, the rear kit came with the stainless caps, the front did not. I wasn't sure what the norm was, but commando specialties have been VERY helpful, and are sending me some parts including the stainless caps to try and resolve the situation. top notch service from those guys!

if anyone cares i finally have a resolution here! The good people at commando specialties sent me a whole new kit that included the stainless end caps from RGM and here's what i found..To get it to fit, I used the new SS end caps(which are thinner than the stock caps), but I had to mix and match the locks and adjusters. Each of the kits had mixed results. The original kit had a lock that measured .575, but the new kits measure .566. But the adjuster was the opposite, the new one measured .577, the old .565. I don’t know if they’re mixing pieces from mk3 and pre mk3 kits at rgm or something? either way, i used all the smallest parts, put it together hand tight and it's under 6" now.