Rear iso conversion with eng & GB in situ?

Tornado said:

Are you saying you can get enough clearance shifting the power plant still in frame to fit the rear MKIII iso or was this only for the rear MKII multi-piece iso assembly? I'm planning out how best to replace my MKII rears....

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I have not tried MK3 but see no difference. I have changed both 750 and 850 Pre-MK3 rear ISO to the AN vernier type. I do nothing with the front ISO when doing it. I do remove the head steady. I shift the frame, not the engine.

I did my '74 850 in situ.

I’m still resisting converting to vernier adjusters. The front is so easy to remove and shim it doesn’t seem worth the expense. The rear is a pain to shim, but then I have had to add a shim two times in 40,000 miles and 25 years. I suppose when I need to replace the buffers I will convert then.

Like Concours,I replaced the rear isos with the engine and trans in situ.Good job for a rainy afternoon.
Mike

As Ying said - good rainy day job. Quite satisfying too.

Found a channel showing this conversion of rear iso to MKIII type with engine in frame:




I like his homemade puller setup for driving out and pulling in the vernier iso. Not sure the amount of disassembly done is strictly needed for this, he was also removing the MKIII air box and other items for his customer so might be overkill for just an iso swap.

I have my MKIII rear iso kit from AN. Checking it over, I found the hole in the fixed collar has not been tapped for the set screw. Luckily I managed to have the correct tap for the supplied set screw (5 x 0.8mm) and put it right.

Decided to go with a full primary removal process and raise the frame enough to have the iso tube clear the frame brackets from below, rather than trying to lift/tilt engine up/forwards significantly further.
Primary now fully off and as I was expecting, noted quite a bit of final drive chain machining against inner primary gb side....due to the deflected gb cradle plates due to the missing thick washer/spacer.

New iso rubber feels quite soft and almost tacky, seems to want to stick to paper if laying against for a few minutes.

Will update this as I progress further....

Now have the iso unit in cradle and will complete reassembly by end of day.

Lifting frame by way of a motorcycle flat type screw jack, with support seats at rear of frame rails. Front wheel held in a floor wheel chock. Front iso bolt loosened. Headsteady off. Hamcan removed. Lifting frame I watched everything for interference and found the horn was limiting further rotation. So was able to remove (Fiamm freeway blaster aftermarket in stocks location) after some wee struggles. Everything else was OK, carbs, throttle cables, wiring, oil lines. Got full clearance to both ends of rear iso tube.

Must say, the mkII rubbers, new a year ago, are approaching hockey puck level of hardness. AN rubber easy to compress and squeeze. They are also about 2-3mm narrower than new mkII ruɓbers (I'm pretty sure these must be Norvil or RGM, my reseller was not able to state what he sent me a few years ago).
This, with the fact there are 3 actual iso bushings with mkII and only 2 on mkIII should make for a dramatic difference in vibration management.

No big issues removing bushes once I recalled needed to twist them in the bore before pushing out. Twisting easy by just knocking a long screw driver against edge of rubber to push it down bore, basically flipping it sideways.
New went in smoothly with good amount of dielectric/silicon grease.

Tornado said:

This is the only video I've found showing the rear iso replacement on a MKII bike with engine in frame:

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Hmm,
Was that Jon Anderson from Yes I heard playing in the background, possibly from the rather ‘old hippy’ album, Olias of Sunhillow?
i suddenly feel very old.
Alan

OK first test ride after hockey pucks removal and the heavy vibrations now gone. Feels like a totally different bike.

I did have an issue with the AN vernier unit, the fixed abutment collar's set screw hole was not tapped. Luckily I had correct drill size and tap handy and sorted it. Perhaps it's too much to expect for a $200+tax/shipping for it to also have quality controls?

Tornado said:

OK first test ride after hockey pucks removal and the heavy vibrations now gone. Feels like a totally different bike.

I did have an issue with the AN vernier unit, the fixed abutment collar's set screw hole was not tapped. Luckily I had correct drill size and tap handy and sorted it. Perhaps it's too much to expect for a $200+tax/shipping for it to also have quality controls?

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I hope you wrote AN about it. I'm certain Simon would want to know, and he will probably check the units on the shelf. They have always been appreciative of the feedback I've given.

marshg246 said:

I hope you wrote AN about it. I'm certain Simon would want to know, and he will probably check the units on the shelf. They have always been appreciative of the feedback I've given.

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Will do. Have let my regional reseller know already.

Tornado said:

OK first test ride after hockey pucks removal and the heavy vibrations now gone. Feels like a totally different bike.

I did have an issue with the AN vernier unit, the fixed abutment collar's set screw hole was not tapped. Luckily I had correct drill size and tap handy and sorted it. Perhaps it's too much to expect for a $200+tax/shipping for it to also have quality controls?

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That's good to hear Tornado (about the lack of vibes I mean). Out of interest where do the vibes stop now?

cliffa said:

That's good to hear Tornado (about the lack of vibes I mean). Out of interest where do the vibes stop now?

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dramatic drop begins around 2800 and pretty much negligible at 3700. Feels like floating on the dead sea! I do have the Dave Taylor HS with springy thingie so there is some further dialing in I can do if wanted.

Tornado said:

dramatic drop begins around 2800 and pretty much negligible at 3700. Feels like floating on the dead sea! I do have the Dave Taylor HS with springy thingie so there is some further dialing in I can do if wanted.

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Once you have the ISOs working right you can tune to your riding style
Generally speaking the looser the ISOs the smoother the ride and the worse the handling/white lining
But it sounds like you have them pretty good
The DT headsteady will transmit a little bit more vibes than the standard set I believe ?

baz said:

Once you have the ISOs working right you can tune to your riding style
Generally speaking the looser the ISOs the smoother the ride and the worse the handling/white lining
But it sounds like you have them pretty good
The DT headsteady will transmit a little bit more vibes than the standard set I believe ?

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The strongest vibes happen when throttling down to idle....passing down from 2k-1k-ish. Seems to give fair bit of mirror shake and the unsupported end of the rear mudguard/tail light bracket waggles significantly. The RGM tech note on setting the suspensory spring unit gives a range of spring extensions and to crank on more spring force to dial out lower rpm vibrations (at the cost of more higher rpm vibes).

Tornado said:

The strongest vibes happen when throttling down to idle....passing down from 2k-1k-ish. Seems to give fair bit of mirror shake and the unsupported end of the rear mudguard/tail light bracket waggles significantly. The RGM tech note on setting the suspensory spring unit gives a range of spring extensions and to crank on more spring force to dial out lower rpm vibrations (at the cost of more higher rpm vibes).

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If you get vibes that low down, may as well pull in the clutch and coast it down before the vibes kick in. (so as not to sacrifice high rev vibes)

grandpaul said:

If you get vibes that low down, may as well pull in the clutch and coast it down before the vibes kick in. (so as not to sacrifice high rev vibes)

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But it still vibes as the engine spools down to 1k, no matter road speed...happens when stopped and I open then close throttle.

Tornado said:

But it still vibes as the engine spools down to 1k, no matter road speed...happens when stopped and I open then close throttle.

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Twiddle the head steady spring until the main front bolt slides in and out with no friction.

If that doesn't cure it, you've probably got too hard of rubber in the isolastics. Every manufacturer is different.

grandpaul said:

Twiddle the head steady spring until the main front bolt slides in and out with no friction.

If that doesn't cure it, you've probably got too hard of rubber in the isolastics. Every manufacturer is different.

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Yup. See my earlier posts re. replacement of hockey puck rear iso rubbers for AN verniers.