Front adjustable Isolastic wont fit

I purchased a new adjustable front Isolastic motor mount and I can get it to fit. I screwed the adjustment all the way in to install it but I can't get it in. The round Isolastic tube hits the front engine case bolt. Am I doing something wrong? The old Isolastic fit just fine. The adjustable end nut is much larger around the the old mount. Also the new Isolastic rubbers are much larger and are difficult to install into the tube. Has anyone else had any problems installing one?

I love it when it ain't me this time. Your description is a bit confusing to me but [as most stuff is] but some adjustable isos need to have ~1/4" milled off the R front engine mount tube end. Set gaps to manual then see how much to remove to allow it to just slip between the frame tabs. Never ran into too big of cushions i couldn't pound in with a violent blow but its my habit to bench grind a bevel on the front big cushions to allow sooner smoohter onset so could also take a bit off the remaining 1/4" wide rim till you can pound em in with one fell swoop, then a few smaller hits to center cushions. I've use bady power to wd40 and a bit soppy water to ease the pounding. Likely less violent ways to ease in the cushions but too much work for me after the diddling to fit metal parts.

I got another front mounting tube and plan to machine it down and installing it with the new Isolastics. The left side of the tube is 5/16" and the right side is 9/16". The left side is where they said to place the adjustable nut on while the right side is locked in place with and allen screw. You said to mill 1/4" off the right side of the tube but wouldn't this cause the tube to be off set leaving a gap between the locking nut and tube? I thought the left side should be milled with the adjustable nut? I thought I would measure the old mount and mill the left side to match the same length as the old mount.

http://www.norvilmotorcycle.co.uk/techtalk03.htm

nortonisthebest said:

The round Isolastic tube hits the front engine case bolt.

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Hitting the lug of the case I could understand, but, hitting the bolt?

nortonisthebest said:

Also the new Isolastic rubbers are much larger

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More likely the old rubbers have shrunk.

Keep in mind two things:

1) the 1/4" is a guideline. On some frames you may find that the 1/4" is too tight and that you can't slip the mount in with the 0.006" clearance desired.

2) on 3 frames I've got, the front mounts are bent from people monkeying around with them. You should make sure they're parallel to each other. You can do this without the tube in, using a feeler gauge on just the adjustable endcaps. Nip them up lightly and use a feeler gauge around them to check for any spots where they're not flat.

I ended up working backwards on mine. Place the isolastic in (no mount), use a feeler gauge and the mount to set the clearance, then measure from mounting lip to mounting lip to get the right C-C distance. Then I just centered it on the mount (ended up with a few thou under 1/4" on each side).

Only side I've seen to remove tube length was on the R on 750's so likely don't apply to mk3's, 4's and 5's. Still mystery on the cushion fit issue. Its tricky to hold mount to mill off sqaure so best wishes finding shop or DIY.

To fit these it is sometime needed to reomve the head steady, remove engine mounting bolts to rock the motor back to squeeze it in.

I said the adjusting screw was on the lift side I was wrong it is on the right side per instructions. I also meant the lug and not the bolt. Also my Norton is a 1973 750 Commando Is this a MK 3 model or ?

There is a retrofit type adjustable kit available for non-MKIII bikes that requires no machining.

Right. If you got just the replacement Mk3 parts it won't work on a non-Mk3 without machining the main tube. Also if you do have the earlier tube machined it must be done squarely. I thought about doing this for a while and decided to just stick with my shims. I have quite an inventory of them collected over the years. They are no big deal to adjust really and with the amount of miles I put on (which is very little these days) it was just not worth doing.

I didn't know about the pre-shorted kit my 1st time around in early 2000's but would be worth returning present too long kit for just bolt on one.

I found out hard way ya can only access the iso adjuster holes if rear on the LH and front on the RH. I carried tools to adjust on road diddling up/dn for best compromise handling vs isolation on Peel till tri-linked to find no compromise gaps, complete early disappearing act and no end of handling extremes I could force myself to attempt. My factory Trixie inherited Ms Peel's off the shelf adjusters but had to take to shop to trim L front tube twice creeping up on trial - error fitting. Now Trixie is so smooth I don't want 1000 mile days to end but I sure don't press her in turns beyond just normal reserve thrill levels or else THE Hinge hits-usually most the way through a nice sweeper as wind &or road surface lumps increased a bit, ugh. No one gets a fully fettered Cdo w/o paying for it in worry time and money.

If it's one of the Norvil ones that doesn't involve machining the tube, as Concours mentions, then they are very difficult to fit. You'll probably have to take the head steady off & the rear ISO main bolt out, while supporting the engine/gearbox unit, so you can either move it back far enough or lift the front far enough to get it fitted.

Ian

You '73 is a NON-MKIII model, they were sold as model year 1975's only in the US. (please fill out your user info, it'll help us help you)

Readily available here: http://www.ebay.com/itm/Norton-Commando ... a8&vxp=mtr

Don't worry your not alone. It won't fit until you have removed all the paint from your frame. At that point it will slot in easily and you will never ever work out how or why.

nortonisthebest said:

Also my Norton is a 1973 750 Commando Is this a MK 3 model or ?

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750 MkV.

I purchased the same Isolastics on ebay from the same guy "racingnorton". The end rubber dampeners are much larger and are difficult to get inside the front Isolastic tube. They are much larger then the stock ones. Because they fit so tight, inside the tube, I'm wondering how effective they are for dampening. Also at this point I'm not to sure how much medal to remove from the front mounting tube before installing the new adjustable Isolastic's. At least I know my 73 Norton is a MKV. Thanks

nortonisthebest said:

I purchased the same Isolastics on ebay from the same guy "racingnorton". The end rubber dampeners are much larger and are difficult to get inside the front Isolastic tube. They are much larger then the stock ones. Because they fit so tight, inside the tube, I'm wondering how effective they are for dampening. Also at this point I'm not to sure how much medal to remove from the front mounting tube before installing the new adjustable Isolastic's. At least I know my 73 Norton is a MKV. Thanks

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On the advice (actually insistence) of Norman White, who said my isolastics (which looked fine to me) were too hard and generally horrid, I fitted new front and rear ISOs from AN. They dropped straight it, were an absolute dodle to adjust and the bike is SO much smoother than it was before.

It seems to prove the point that it is best buying important mechanical components from known sources. Personally, I'd put your current ones back on eBay and buy new from AN !

The conversion kit for the old iso mounts DO fit in the tube and the original longer tube doesn't have to be machined. i went through the same thot processes as you, there was no way in hell it was gonna fit, but, it did. Don't do like i did and buy the conversion, think it aint gonna fit, then buy a $110 Mk III iso tube (see for sale section). it does fit in the original tube. I used so much U.S. Navy-taught profanity and even that didn't get the iso motor mount in the frame. i actually called another member after PM'ing him......sometimes you just need a sympathetic ear and to calm down; which is hard after cussing and f'ing with it for 2 days. Work with putting the mount in the frame, clear of the bolts and work it one side to the other until you can get the through-bolt in the left side to hold it, then line up the other side till bolt goes through. Like my bud from AN told me, you'd swear to god that you need a Frame Spreader to get that mother in there. it'll work. Don't search this site too much either, you'll mess yourself up!

My front tube (1969) also had an almost invisible separate sleeve pressed INSIDE the tube, hard as hell to see; which....has to be cut out. It's in 3 pieces; 1 on each end and a longer middle section sleeve. make sure you can distinguish that they are in fact there first. i took a hack saw blade, nearly level to the inside of the tube until i got an edge, then took a cold chisel to it to get it out. i just did the ones on the ends. as far as the iso's themselves, use real slickery non-petroleum lube. the instructions say you can do it with your thumbs but i must have really weak thumbs; i don't think it's possible. i'm a puss maybe. i took it to a local hot rod shop and had em pressed in. make sure you don't put them in backwards.......adjustment side to the right. SOMEBODY ELSE JUMP IN IF I SAID ANYTHING WRONG. I got so pissed i wanted to sell the dam thing, you'll be happy as when your first child was born when you get it done though!!!

I still haven't done the rear iso yet! shit, i'm gonna be cussing and bleeding again this winter......

and.......the iso conversion kit for old tubes DOES NOT WORK in a Mk III motor mount tube. you run outta threads.

I still haven't done the rear iso yet! shit, i'm gonna be cussing and bleeding again this winter......

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I can hep ya