Isolastic Gaiters?

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Mar 9, 2010
Apologies in advance, because I'm sure this is a ridiculous question...

1974 Commando 850

I'm doing some basic work on a running, mostly original condition, low mileage bike that I plan to ride. A lot of sprucing up and a little undoing of the previous owners misdeeds. Mostly minor stuff that I can handle myself at this point.

The isolastics seem fine and I'd rather not get into replacing them at this time. The bike is quite smooth when it's going and the mountings seem tight.

But the gaiters are as brittle as, well, rubber that's nearly 40 years old probably should be.

Question is: It is possible/feasible to just replace the gaiters without banging out the whole isolastic assembly? I'm wondering how the assembly works - Is the central rod, once the securing nuts are loosened, free to move a bit in order to swap out the gaiters (one side at a time) or would that upset the whole assembly? Is it worth the trouble to replace these gaiters, or should I just let them be until I feel a need to bang out the isolastics altogether?

Probably a lame question - but it seems like the gaiters should be easier to replace than they appear to be. I don't want to mess up a functional isolastic system just to satisfy my quirky obsession with soft rubber... Your sage wisdom is, of course, greatly appreciated.
I've done it but too many years ago to remember much but that it is harder on the rear than the Front. The front is best done off the bike, makes the whole job much easier in a vice.
It's certainly possible to replace them without total disassembly. The front bolt needs to come completely out to get to the right side. The left rear will be a challenge to get to. If you're going to go through that effort, I would at least take the time to check the clearances per the workshop manual and be prepared to shim them if needed. The washers, shims, and gaiters should be cleaned and coated with silicone grease while you have them in your hands.
Yep, the front is fairly easy - the rear...not so much. I would suggest you leave it alone until you are ready to go through the isos completely. At that time I would (and did) replace ALL the parts in each iso - metal as well as the rubber stuff. BUT at a minimum, you should replace all the rubber parts. You can be sure that they are in need of it, regardless of how the bike was used because they rubber donuts in the isos are also 40 years old! The metal parts, especially on the front are very likely well rusted and it's not that expensive to replace every item in there, including all new shims. The MK III vernier isos are a popular mod for earlier bikes though I didn't change mine because once the isos are shimmed/adjusted, they stay in adjustment for a long time. However the vernier makes it easy to fool around with the clearance to try different settings for handling/vibration.
Use a solid floor jack (with a bit of plywood on the tongue) and a helper, with some stuff for blocking / chocking the bike up once it and the engine are lifted.

Remove the rear wheel and shocks, then block the chassis carefully. Remove the jack and set it under the tranny cradle, loosen off the rear iso mounting bolt and pull it out. lift the rear of the engine till you have room to work, check PTFE washers, set your clearance, install the new boots, lower and replace through bolt.

Replace rear wheel & shocks.

Set the jack under the crankcase and snug it up. Remove front mount bolt, repeat the servicing done at the rear. Replace the bolt & off you get.
The gaiters were put there by the factory in an effort to keep water away. It rains like hell all the time in England.

I could get banned for saying this:
I believe the opposite is true, that the gaiters just trap moisture inside the rubber.
I have taken them off, cut off with a knife, on all seven of my Commandos through 40 years.
I keep a light coating of grease on the exposed iso parts which stops any rust from developing.
Certainly, many others here would probably disagree.
After all these years on your bike, the studs front and rear are likely galled to the bushings and would be difficult, especially
the rear, to slide back and forth just to put new rubbers on.
My advice only, cut them off, slacken the stud bolts to loosen the clearances, clean and grease what you can get at, snug
it all up and forget about it other than periodic spraying with some lube to stop any rust.
"I believe the opposite is true, that the gaiters just trap moisture inside the rubber."

I totally agree. Most things of this nature that theoretically keep water out primarily serves to prevent it from readily escaping when it does get in...and it WILL get in. So basically what happens is that BECAUSE of the gaiter, you end up with more rust than you would without it. OTOH, the gaiter serves a useful purpose in keeping at least most of the road grit out but the best protection for water is, as noted, plenty of silicone grease on everything, including on the inner surface of the gaiters themselves.
Wouldn't it make more sense, then, to have weep holes in the iso gaiters, exactly as fork gaiters have?
I took mine off and left them off since they are kind of ugly. Nothing a utility knife won't solve.
Sincerely appreciate all the responses and advice! I think for now I will ditch the gaiters altogether and lube the assembly as-is. Southern California and no real desire to ride in the rain anyway... Then I'm sure a complete iso job will be in my future so I'll save my gaiters for that day... On to the next item on my list...
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