Help I am a long time lurker First time up to bat so to speak. First let me say that this forum is a treasure trove of Commando lore! Wow OK here is the skinny ,While pulling some long overdue maitinence on my 72 Combat I noticed the PFTE washers on the rear mount are falling apart ok no big deal a quick trip to Baxters came home with a sack full of goodies and started in thinking I could drive the rear Iso bolt far enough one direction to pop the vernier adjuster out and replace the washer and rubber gaitor. No such luck upon consulting my Clymers I read that you must pull the motor to do this! Some one please tell me of an easier way. It is prime riding weather here in corn country And do not want scatter her completly if I can avoid it. I have had this bike for 30 years now and she still makes my smile just looking at her let alone riding
Rear Isolastics (2010)
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Holmeslice
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koda said:
Try this, a process I wrote up several years ago, that works with little removal of parts on the bike:
This is my method for rebuilding the Norton Commando Rear Isolastics.
I’ve used this method on a number of bikes with great success each time. It can be done without having to remove any major parts of the bike (other than the power take-off socket). The total time involved is about 1 ½ - 2 hours.
Note: this operation will NOT work for the MK III or Norvil type Isolastic setup. These types use a single, long spacer tube with the bushes and buffers bonded to the tube and long piece like that is not going to fit through the small space we’re working with here. If the MK III/Norvil setup is what you're going for, these instructions don’t apply and a major teardown of the bike will be necessary.
For the rest of us with bikes born before 1975...All you really need beyond a basic set of tools small bottle-jack, a baby-bottle scrub brush, and a patient helper. Here's how it’s done:
Put the bike on the center stand.
Remove the power take-off socket for better access to the Iso mount.
Remove LH side nut from Rear Iso Stud and pound out through the right side; use a drift to get it all the way out.
Remove gaiters, collars, PTFE washers, end caps, and shims.
Now you will have access to the innards of the Iso between the frame and the Iso mount - not much space, but enough to squeeze the rubber bits by.
Dig out the first rubber bush from the RH side.
Pull out the buffer on the spacer.
Dig out the center bush from the RH side.
Dig out the end bush from the LH side
Pull out the 2nd buffer/spacer
Once everything is out, scrape out any old rubber residue that may have bonded to the Iso tube. A screwdriver works fine. Use a baby-bottle brush with some carb cleaner, dousing the inside of the tube and scrubbing it clean. Wipe out the mount by pulling a rag through and making sure it is totally dry.
Then:
Insert a new bush into the edge of the RH side.
Using a drift (a socket works great), push it into the Iso tube so the end of the centerpiece of the bush is just flush with the edge of the Iso tube (flush alignment is IMPORTANT).
Assemble the new gaiter, collar, PTFE washer, and end cap back on the Iso mount on the RH side. (Note: I purchased the Hemmings vernier adjusters from Old Britts, which do not require any shims on either side. If you are using old Norton shimming "technology", I suggest you take note of the shims you initially removed, and replace now with new shims of the same thickness as a starting point).
Pushing the main stud back through as you add new bits will keep everything aligned. Begin driving the stud back through from right to left, through the z-plate and spacer, then into the gaiter/collar/washer/end cap and continuing through the first bush. Have a friend sight through from the left side to tell when the stud has reached the end of the bush and stop there.
Insert a buffer on a spacer from the left side then push the stud through this buffer/spacer.
Insert from the left the center bush, then push the stud.
Insert the 2nd buffer/spacer, then push the stud.
Finally insert the last bush on the end of the LH side and push the stud flush with the edge of the center of the last bush. (In my case, the RH bush center was poking out of the tube about 1/8" so I needed to do a bit of tapping with various drifts to snug all the components together within the Iso tube.)
Once everything is nice and tight, place the end cap over the LH side, then a PTFE washer, and finally the Hemmings adjuster and gaiter. (Again, if you are using shims, this is the time to add them.)
Tap the stud through this whole lot, through the frame spacer and out through the Z-plate.
Torque both nuts down to 25 foot lbs. and set the gap with a feeler gauge (with the bike off the center stand). Voila!…You’re done. Ain't no big thing! (By the way - my old Iso rubbers were almost turning to powder, and were so oblong-shaped it’s a wonder they did any absorption at all!)
A few things to know:
Always lubricate the rubber bits liberally with a silicone-based lube (not petroleum based).
Use anti-seize on the stud and nuts, as well as the inside of all the bushes and buffers.
A small bottle jack can help when placed under a frame tube. This will jack up the frame to match the engine mount/Iso tube and assist on alignment of the stud through the z-plates, etc.
By tugging on the rider's footrests, the frame can be pulled away from the Iso mount by a few crucial thousandths of an inch, which allows easier insertion of gaiters/collars/etc. Again, this is where an assistant is key!
Hope this helps.
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How would you have mark 3 isos if you have a 72 combat?
Anyway, you absolutely do not have to remove the motor to replace anything at all on your isos, does not matter what year or what style, period.
You just take off both big nuts on each end and using a rubber mallet as to not bugger the threads, tap on each side back and forth until you can drive the stud out enough on each end to replace your pieces.
What I suspect you will find is that the stud is galled, stuck, because use of all the years of sitting in place.
I had that problem and it took a small floor Jack placed under the engine cradle plates with just a slight upward pressure to keep the holes lined up because of the downward pull of the motor on the rear iso, and a couple days of patiently driving the stud back and forth a little at a time to get thIngs to loosen up.
Fear not, this can be done entirely in the frame, in fact I replaced all the rubber donuts three months ago on my 73 as I described above.
You are welcome to private message me if you have questions.
Anyway, you absolutely do not have to remove the motor to replace anything at all on your isos, does not matter what year or what style, period.
You just take off both big nuts on each end and using a rubber mallet as to not bugger the threads, tap on each side back and forth until you can drive the stud out enough on each end to replace your pieces.
What I suspect you will find is that the stud is galled, stuck, because use of all the years of sitting in place.
I had that problem and it took a small floor Jack placed under the engine cradle plates with just a slight upward pressure to keep the holes lined up because of the downward pull of the motor on the rear iso, and a couple days of patiently driving the stud back and forth a little at a time to get thIngs to loosen up.
Fear not, this can be done entirely in the frame, in fact I replaced all the rubber donuts three months ago on my 73 as I described above.
You are welcome to private message me if you have questions.
grandpaul
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It's easy to have Mark III isos on a pre-mark III bike, all you have to do is install them at some point in time, MANY people have done it.
You can change them without tearing down the engine, but it involves AMLOST tearing the engine down, removing the rear wheel, and lifting the frame while lowering the isolastic assembly after pulling the long through-bolt. The top head steady assembly needs to be completely removed for clearance, and the front mount needs to be removed as well.
It's not easy, but it can be done without disassembling the engine.
...although maybe disassembling the engine IS easier?
You can change them without tearing down the engine, but it involves AMLOST tearing the engine down, removing the rear wheel, and lifting the frame while lowering the isolastic assembly after pulling the long through-bolt. The top head steady assembly needs to be completely removed for clearance, and the front mount needs to be removed as well.
It's not easy, but it can be done without disassembling the engine.
...although maybe disassembling the engine IS easier?
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So... I installed the isolatics (MkIII style on my 72, so it can be done... :mrgreen: ) and then remembered that I needed to install the gaiters. Luckily the bike as mostly apart but it was ugly.
combat-proddy-build-begins-t4186-90.html#p58200
About halfway down this long post is some horror pictures. Maybe someone could do it easier than I.
combat-proddy-build-begins-t4186-90.html#p58200
About halfway down this long post is some horror pictures. Maybe someone could do it easier than I.
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grandpaul said:
I chose to put them on. If the bike wasn't in the state it was there is no way I'd try knowing what I do now.
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Here is a explanation of how I did mine. I posted it in a earlier thread on replacing the rear iso. As a disclaimer I am pretty new to this stuff and there may be a better way but this worked for me. Good luck!
I recently did this and this is what I had to do to make it work. I first replaced to front Iso. It sounds like you don’t need to do this so I will skip over it. I put the bike on a bike jack that supported it under the frame tubes but was open under the cradle. I then ran a tie-down strap around the rear iso tube and up over the backbone tube. (I had the battery box out at the time, I don't know if you could do this with the box in place, you would have to look). I put tension on the strap to unload the Iso and withdrew the bolt. You can then drop the engine and cradle assembly down, hinging on the front iso, until the inner primary case rests on the frame tube. In this position the rear iso tube will be about 85% clear and you will have enough clearance to remove or replace the old style multi-piece isos. I think this is the position that is referred to in the article you sited. However, you (or at least I) will not be able to get a MKIII style iso in due to it being all one piece. You can get the rubber bonded part in with one abutment installed but you will not be able to get the other abutment on because of the length of the tube. The tube will clear the iso mount flange but you will not be able to screw on the adjustable abutment because the flange will be in the way. If you were to remove the primary you could drop the motor and cradle assembly down a little bit farther and completely clear the rear iso tube. If I had to do it again I would probably do it this way. But, I don't have a puller (yet) and so couldn't remove the whole primary drive. So I ran a second strap around the front iso tube and over the small tube the head steady bolts into. I tensioned the strap and withdrew the front iso bolt. I then tightened the front strap and lifted the front of the motor about 2 or 3 inches. I was then able to shift the whole motor/cradle/swingarm/rear wheel assembly forward in the frame far enough to clear the rear iso. Once the new rear iso was installed I shifted the motor back, lowered the front back down and reinstalled the front iso bolt. I was then able to lift the rear iso into alignment and insert the rear iso bolt. I did have the head off when I did this. I think I would have had the clearance with the head installed but I'm not sure. I was also able to do all of this without any help and without doing anything to the rear suspension. This is just the way I did it, I am fairly inexperienced and there may be a better way.
cdafirefighter
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I recently did this and this is what I had to do to make it work. I first replaced to front Iso. It sounds like you don’t need to do this so I will skip over it. I put the bike on a bike jack that supported it under the frame tubes but was open under the cradle. I then ran a tie-down strap around the rear iso tube and up over the backbone tube. (I had the battery box out at the time, I don't know if you could do this with the box in place, you would have to look). I put tension on the strap to unload the Iso and withdrew the bolt. You can then drop the engine and cradle assembly down, hinging on the front iso, until the inner primary case rests on the frame tube. In this position the rear iso tube will be about 85% clear and you will have enough clearance to remove or replace the old style multi-piece isos. I think this is the position that is referred to in the article you sited. However, you (or at least I) will not be able to get a MKIII style iso in due to it being all one piece. You can get the rubber bonded part in with one abutment installed but you will not be able to get the other abutment on because of the length of the tube. The tube will clear the iso mount flange but you will not be able to screw on the adjustable abutment because the flange will be in the way. If you were to remove the primary you could drop the motor and cradle assembly down a little bit farther and completely clear the rear iso tube. If I had to do it again I would probably do it this way. But, I don't have a puller (yet) and so couldn't remove the whole primary drive. So I ran a second strap around the front iso tube and over the small tube the head steady bolts into. I tensioned the strap and withdrew the front iso bolt. I then tightened the front strap and lifted the front of the motor about 2 or 3 inches. I was then able to shift the whole motor/cradle/swingarm/rear wheel assembly forward in the frame far enough to clear the rear iso. Once the new rear iso was installed I shifted the motor back, lowered the front back down and reinstalled the front iso bolt. I was then able to lift the rear iso into alignment and insert the rear iso bolt. I did have the head off when I did this. I think I would have had the clearance with the head installed but I'm not sure. I was also able to do all of this without any help and without doing anything to the rear suspension. This is just the way I did it, I am fairly inexperienced and there may be a better way.
cdafirefighter
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It is NOT necessary to remove any part of the motor to do anything to the rear iso. Period.
There is also NO need to remove the rear wheel or swing arm, or really almost Nothing at all.
I have replaced all iso parts On four different Commandos entirely in the frame, in just a few hours.
Privately email me if you are serious about replacing your iso parts. It is NOT a big deal.
Count me in the group who lives quite nicely without the rubber gaiters, they serve to trap moisture and rust inside.
There is also NO need to remove the rear wheel or swing arm, or really almost Nothing at all.
I have replaced all iso parts On four different Commandos entirely in the frame, in just a few hours.
Privately email me if you are serious about replacing your iso parts. It is NOT a big deal.
Count me in the group who lives quite nicely without the rubber gaiters, they serve to trap moisture and rust inside.
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highdesert said:
Why don't you just post here how you did it?
You are correct though, for the rear iso to replace just the washers, you may be able to support the cradle, pull the through shaft (assuming it's not stuck), slip out the broken pieces and slip in the new one. That would be the easiest I can think of.
Well let me start by thanking all you for help. I believe I have enough information to proceed. And as far as the late model isos`s on a 72 I first saw my Combat in 1975 when I was 15 my older brother had bought it from the original owner who as I understand it rode it in stock form for about 6 weeks and then proceeded to build a very Seventies Chopper out of it stretched and raked frame,coffintank 8 over tubes ,skinny front tire, a big 16 on the back 6 bend pullbacks sissybar all capped with red and gold metalflake flames very tasteful !! I was in love the first time I heard it 5 years later it was mine!! I rode it like there was no tomorrow. Any how in 1994 after surviving an 79 foot tumble out an oil platform in the North Sea I decided to bring her back to life. It is back in roadster form but there is very little aboard that has not been replaced up graded or tweaked. As soon as I figure out posting pics i will throw some up here. Anyway Thanks so much for the input I will let you know how it worked out.
I did it without removing the motor, but it's not something I would want to do more than once every 10 years.
Both my wheels were off already
I loosened the front iso bolt and removed the bolts that hold the headsteady to the frame so frame or motor could pivot
Put a jack under the motor to support the weight - (engine and cradle stay in the natural parallel)
I took the shock bolts out (I forget whether top or bottom)
Used a 2nd jack under the very rear of the frame, remove rear iso bolt, raise the frame
at this point it was easy
the iso end caps will be lower and more forward - there's already a curve there in the frame
but
You have to be careful because as you lift the frame the centerstand will raise off the ground, your bike will want to slide forward also
Ended up being a balancing act for me- not difficult, but not fun either- As I was doing it alone I was relieved to be done
Both my wheels were off already
I loosened the front iso bolt and removed the bolts that hold the headsteady to the frame so frame or motor could pivot
Put a jack under the motor to support the weight - (engine and cradle stay in the natural parallel)
I took the shock bolts out (I forget whether top or bottom)
Used a 2nd jack under the very rear of the frame, remove rear iso bolt, raise the frame
at this point it was easy
the iso end caps will be lower and more forward - there's already a curve there in the frame
but
You have to be careful because as you lift the frame the centerstand will raise off the ground, your bike will want to slide forward also
Ended up being a balancing act for me- not difficult, but not fun either- As I was doing it alone I was relieved to be done
If Koda just wants to replace the PTFE washers and gaitors can't he get enough room by bottoming out the vernier and removing the endcap? There's enough flex in the frame with the stud removed then if one needed a bit more clearance you could probably get it.
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I may be late on this... but I successfully changed out the front and rear isolastics, plus my head steady on my 73 Commando by following Mike Tyler's videos... here:
His YouTube page is called My Ty Garage
I did exercise some artistic license when I used a car lack to pry open my frame to install the rear isos... but only for 15 minutes... seems to have snapped back into shape just fine.... I think?
PS - I am a complete newbie with this stuff - Mike really saved me.
Good luck
Tornado
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The rear iso R&R is one of the more poorly documented procedures on these bikes. I only know of one video on the tube showing it done in frame...and they used a car engine crane to lift the frame vertically clear, primary inner/outer covers off, rear wheel & fender out I think. Then brute force to drive out old/in new rubbers.
I've seen Mike's video, but he only did the front.
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