Valve spring insulators on the exhaust side - worth fitting?

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@dynodave says it was a problem skimming the additional head material, but I've already forgotten whether he related that to the MkIII...
I don't know fact certain the heads were cut deeper for the insulators. I am starting to measure the RH4 and RH10 heads VS 750 heads.
Curious of course why so many RH4 are cracked. Did the RH4 heads have a higher roof in the 32mm porting job compared to the "combat" 32mm port job? I have never seen a cracked 32mm port combat head? Did the 1/2" 750 guides VS the 3/4" 850 guides cause the RH4 cracking problem?
Inquiring minds want to know.

I only rebuilt 2 850 heads long ago, and one was for a combat cam and the other for a PW3 cam so, IF there were intake insulators they were definitely left out.

I have searched for "spring heating" among many other search wording, as I believe the springs heat them selves due to the steel flexing and the oil would end up cooling them . I read a lot of discussions though they discussion most of the time concentrates on head and exhaust port over heating the metal. The heat weakens the spring rate. Even a lot of discussion about slowly "aging" the new springs .

spring design wow!
 
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Fast Eddie

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I’m thinking partially about what the factory may or may not have done, but also about what home mechanics have done, especially as the AN diagrams and parts quantities incorrectly show that insulators should be fitted 4 off to all engine types! Surely some (many) people have followed this incorrect advice and bumped up their spring pressures massively ?!
 
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Too much spring pressure was the key reasoning behind Andover Norton’s advice to leave the intake washers out and probably why Norton didn’t wish to install them during assembly. I’m not trying to offer an opinion here other than passing on the detail of my conversation with AN. And agree, a footnote on their website explaining this wouldn't go amiss!
 

grandpaul

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I wonder if original hardcopy parts books, Kim the CD Man digital parts illustrations, and OldBritts' online illustrations are all the same?
 
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To correct things, I said they were not fitted to the the 750's, only to the 850's, why the change there is nothing recorded. I have looked through the drawings and clearly, if fitted with a higher than standard lift cam, there can be a clash of tolerances leading to coil bound, the tolerance is tight even with a standard cam. As the only MK3 rider in the building, I don't fit them under either the exhausts or inlets. How well the insulators work when fitted on exhaust side is debatable as the oil level in the pocket rises over the insulator and contacts the spring cup.
Just because I work there does not mean I follow the parts book verbatim.
I could try asking those few that are left and that worked there in the 70's, but this usually turns up very little of any use.
But from what I see on a daily basis relating back to that period, it looks like it was an attempt to cover up an existing problem they either did not understand or wanted a cheap fudge to keep the administrators happy, I suspect the latter.
 

cliffa

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Is it possible that they are not meant as heat insulators at all, but rather noise insulators? Bikes imported to the U.S. in the 70's had to meet some pretty rigorous noise regulations which included mechanical chatter. These may have helped reduce it.
 
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Cutting the pockets deeper for the insulators only thins and weakens the head - inviting cracks. The insulators don't help much with heat and you don't see them in other engines. Heat buildup occurs from the repeated compressing of the springs. C.R. Axtell once told me that at if there is valve float at peak racing RPM the springs can coil bind and become red hot.
 
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Jim thanks for confirming the spring self heating aspect. In my reading they discuss spring surgeing, which is, I assume a spring resonance that causes some portion of the spring wire to become out of step with the camshaft drive.
In measuring the valve stem above the spring mount area there does not appear to be measurable difference over a 750 which leaves either the port roof being higher or the guide diameter as contributing to port wall cracking. The last possibility was the gorilla "pounding" the guide in with a sledge hammer.
Regardless it is a shame of so many heads being damaged...
 
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I have an 850 RH4 and the gorilla was not there. Still a little timid to crank out the cast iron guides for a rebuild.
 
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Dave,
yes I know and I have access to this test procedure. thanks for your input. We use it in our industry. Nuke power.
Cheers,
T
 
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Time Warp

.......back to the 70's.
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I think you might be better off actually measuring the various installed spring heights (including a FA in my case) over guessing.
You might get a surprise or three.

I think you will find a stock 850 guide is 5/8" OD not 3/4.

I did get JC's advice via PM when I asked the same question regarding insulators (He sent me KW components (valves/springs/retainers/collets/pushrods for the ChinaHead™ including insulators x 2)
 

Mofosheee

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Have been followinig this thread taking in all the chatter regarding the insulators (thank you)
My 850 head has been reworked; bronze exhaust repair, guides, valves........It also came with the insulators described in this thread, so back in they go.
I am in the process of reassembly. Is it recommended to replace with new ?
 
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Just finished My MK 111 RH 4 head rebuild.
New Exhaust bronze guides , new Black diamond valves , all 4 re-cut and seated. New Viton intake seals. New springs.
The heat insulating washers went under the EX. spring cups. The Intake spring cups saw no heat washers installed under them , as per my notes.
Enjoy.
 
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