Mushroom rockers adjusters clearance issue

Sergio

Sergio

Joined
Jan 17, 2020
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Hi you all,
Is there a way to calculate the exact amount of the skimmed material from head gasket surface. Mine has been refreshed to barely clear the composite markings left from the gasket. Upon installation with new pushrods and mushrooms rockers adjusters from Andover, I'm not satisfied with the rocker clerance issue.

I have read many years ago that machining down the head, would require shorter pushrods???At what measurement of removed material does it apply? Mine is a RH10/850 serial 316801, that has never been machined down, except for the refreshment stated above.

I'm considering to retrofit the standard 06-7546AK rockers adjusters if mushrooms adjusters keeps giving me clearance problems, unless you could propose me a solution.

Finally, what is the appropriate method to check valve springs for coilbound? What tool and procedure to perform this test?



Thank you for your precious advices to help us keeping these old machines on the road.
 
I had the same problem with mushroom valve adjusters with my combat engine. The solution was .060” shorter pushrods which restored the rocker geometry.
With regard to coil bind, if you have a stock camshaft it should not be an issue. Higher lift cam profiles have a potential for coil bind and the manufacturers of those usually have specifications for appropriate springs. For combat engines the factory did not use heat spacers under the intake springs due to this issue.
 
I have not seen any claims made by the manufacturer or the suppliers of the mushroom adjusters as to why it is better than the standard. It seems to be left to the imagination of potential buyers to come to the conclusion that the greater spherical radius of the mushroom head results in less bearing pressure in the contact area and, therefore, less wear and tear.

I did some measuring of both a stock and mushroom adjuster and came to the following conclusions: -

  • The mushroom head has twice the spherical radius of the stock adjuster, so maybe 25% of the contact pressure?
  • From experience, you do not want the point of contact to move onto the cantilevered part of the mushroom head. I’ve had pieces of the rim break off two mushrooms. For this reason the mushroom is a poor choice for the exhaust side, because the exhaust rocker swings through a wider arc.
  • The adjusters move across the tip of the valve and they rotate with the rocker in something approximating a rolling action. The stock adjuster achieves a better approximation than the mushroom when used on the exhaust valve and the mushroom is slightly better on the inlet valve.
For those reasons I’m now using mushrooms on the inlet valves and stock on the exhaust.

Mushroom rockers adjusters clearance issue


 
Thank you for your feed back based on your own experience and measurements. Your included photo is a good demonstration for a potential break. This remember me that some people wrote about that in some threads.This is not a magical/safe solution to the valve train poor geometry. My dream would have been to eliminate the valve tip dent caused by the original adjusters after some mileage...
 
Sergio said:
Thank you for your feed back based on your own experience and measurements. Your included photo is a good demonstration for a potential break. This remember me that some people wrote about that in some threads.This is not a magical/safe solution to the valve train poor geometry. My dream would have been to eliminate the valve tip dent caused by the original adjusters after some mileage...
Click to expand...
You could use lash caps ?
 
ILLF8ED said:
I had the same problem with mushroom valve adjusters with my combat engine. The solution was .060” shorter pushrods which restored the rocker geometry.
With regard to coil bind, if you have a stock camshaft it should not be an issue. Higher lift cam profiles have a potential for coil bind and the manufacturers of those usually have specifications for appropriate springs. For combat engines the factory did not use heat spacers under the intake springs due to this issue.
Click to expand...
Thank you for your advices. A standard cam is in the bike. I put new pusrods and mushroom adjusters from Andover. Now I have clearance issue at the rockers and even coil bind at intake. I can hardly imagine that shaving/rectifying .004''-.005'' from cylinder head, yould require the same reduction on pushrods, considering that the head has never been machined down before. Could the new pusrods be longer? If they are .015''-.020'' longer would be a problem? What is the acurate method to measure them?
 
marinatlas said:
www.rgmnorton.co.uk

VALVE STEM LASH CAP FITS 5/16" STEMS

HARDENED STEEL VALVE STEM LASH CAP
www.rgmnorton.co.uk

that will explain better than I can do, but I had used them with no bad effects , but cannot remenber what was my pushrods lenght !!
Click to expand...
Thanks for that. It states extra 40 thou so presumably the pushrods would have to be 1mm shorter (or whatever, divided by the pivot ratio)?
Can anyone (who knows) describe how these things are actually worth the effort - for a street bike?
Cheers
 
Last edited:
One thing to watch with lash caps is to make sure when fitted they don't make any contact with the valve collets
I have never used them on a Norton but on a BSA I had this issue
 

Lash caps. Any good?

I’m not totally happy with the tappet to valve relationship on the stage 3 Maney head I’m currently playing with. I’m predisposed to being against lash caps as it just seems like an extra thing to go wrong / fail etc. But I’m thinking they would help in my current situation. Anyone on here...
www.accessnorton.com www.accessnorton.com
 
Sergio said:
Thank you for your advices. A standard cam is in the bike. I put new pusrods and mushroom adjusters from Andover. Now I have clearance issue at the rockers and even coil bind at intake. I can hardly imagine that shaving/rectifying .004''-.005'' from cylinder head, yould require the same reduction on pushrods, considering that the head has never been machined down before. Could the new pusrods be longer? If they are .015''-.020'' longer would be a problem? What is the acurate method to measure them?
Click to expand...
Standard cam profile is .330 lift on both intake and exhaust. My combat cam is .390 intake with no coil bind issue using standard valve springs. Unless you have zero tappet clearance it has no effect on coil bind. Binding is entirely a function of cam lift.
 
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