Valve adjuster contact geometry

pete.v · Feb 12, 2013

I have some slight concerns on how my adjuster is contacting my valve tip.
Any input from the pro's? Pictures of yours?

Although you cannot see from here, the adjuster in making contact just inside the edge.

Fully Open seems proper

Here is the other side. Not nearly as pronounced.

comnoz · Feb 12, 2013

It is not optimum but it will run. If the wear mark goes all the way to the edge of the valve it will wear out faster
.
Either the guide is bored crooked or the guide hole is not where it should be. Jim

rpatton · Feb 12, 2013

Is it possible to go with a longer pushrod, pull the adjuster in to the extent you can, and bring the arc of contact more toward the center?

ntst8 · Feb 12, 2013

i'm not near a scanner at the moment but there is an article in this months Roadholder (NOC UK magazine) on just this subject, someone else may be able to post?

Matt Spencer · Feb 12, 2013

Heres a picture of ' another ' make .

The dreaded ' side thrust ' is notorious for giveing valve guide wear .

Ideally the contact should be center at 1/4 & 3/4 travle , give or take .
So the contact slides though centre , on average , so side thrusts even.
( unless you allow for side thrust effects of gas flow in ports . :lol: )

The ideas that the load averages straight down the valve , rather than cocking it over . Hence ' side thrust ' from offset causes premature wear .

You can see this suckers Dead Centre - ish . :?

Matt Spencer · Feb 12, 2013

By Golly ,

This is sortta wot Yr looking at .

from here , they seem to have a bit of usefull Injun Info . http://www.circletrack.com/techarticles ... ewall.html

Matt Spencer · Feb 12, 2013

HAVE A LOOK , Here , valve-seat-rocker-question-t12930.html Same Dilema for seuth .
E R " the Wonders of Modern Tecnology " .

peugeot 1914 dohc , 8 valve twin

splatt · Feb 12, 2013

The top of the valve looks short and the adjuster is backed right up, is the valve seat totaly shot ?

marinatlas · Feb 12, 2013

Hi , could valves caps improve the seating area , ( not the geometry!)............?

stockie2 · Feb 13, 2013

Yes compared to mine the valve stem looks short, especially with mushroom head adjusters, I have some hardened lash caps, but there is not enough clearance for them to work on mine, maybe your angles could be improved with them? Where does the rocker line up at half lift?
If want the caps PM me

Richard

Keith1069 · Feb 13, 2013

It is not optimum but it will run. If the wear mark goes all the way to the edge of the valve it will wear out faster.Either the guide is bored crooked or the guide hole is not where it should be. Jim

Just like mine. I also read the article in the last Roadholder but apparently the last section is missing and has been posted on the website by Tony Ripley. However and due it seems to a continuous conflict between and among posters the section where it appears; 'News & views', is forever being pulled. I don't claim to understand the maths but its interesting. The article explains with the 'improved' rocker angle through valve shortening and extending the adjuster, then the 'wipe' length is reduced to a small contact area, like a dimple. Here is my LH EXH with new valve from a couple of years ago, with old valve after maybe 9,000 miles which had already been rotated 180 deg. to even out wear. Just in process of replacing both exhausts now. I can see how winding in the adjuster would change the attack angle on the valve tip (and after valve shortening and addition of lash caps). Trouble is I need new OE length adjusters since the ones now in use are the lightweight (dont laugh - minus 2grams) RGM parts which are .13" short.

pete.v · Feb 13, 2013

splatt said:
The top of the valve looks short and the adjuster is backed right up, is the valve seat totaly shot ?

These valve are new and the reason they look short is that they have the JS beehive valve spring kit.
The tips are machined at the retainer area to compensate for the longer spring. (See the JS web site.)

Although the seat were cut a few years back, there is plenty meat there and have been freshly lapped.

My original valve showed wear there but the new valves have stellite tips.

pommie john · Feb 13, 2013

Welcome to Norton valve geometry.
here's mine:

Left

Right

I got someone to grind off half a mm from the valve tip and it is just adequate, if not ideal.

Bernhard · Feb 13, 2013

Probably the reason why Doug Helne went over to eccentric valve adjusters on the original 500 Domiracer with its high lift race cam, the rockers could be ground to stay in contact with the valve tip.

john robert bould · Feb 13, 2013

Error's in the machining, in the early-late seventies Norton had no C.N.C just a pile of jigs and fixtures, all the machine errors add up.
Some differances in the basic casting and slight mis-alignments "threw" hole's and dim's in differant directions.
It's called the best of British!

marinatlas · Feb 13, 2013

hi, would shorter pushrods make the things better ??

pete.v · Feb 13, 2013

marinatlas said:
hi, would shorter pushrods make the things better ??

I might think that it would exagerate the angle even more. As seen here, when the valve is fully opened, the angle seems quite proper passing perpendicular. As mentioned by a couple of you, I tend to agree with the fact that it may have been machined a little off.

I do not know why I hadn't noticed before or why I am giving it a second thought now. I guess I'm giving myself reasons to justify a new head. The mushroom adjusters and the stellite tipped valve stems should help with longevity. I have not had any running issues in the past and adjustment seem to stay just fine.

rvich · Feb 13, 2013

Was the geometry improved on the Fullauto heads? Or just more accurate machining?

Russ

pete.v · Feb 13, 2013

rvich said:
Was the geometry improved on the Fullauto heads? Or just more accurate machining? know.

Russ

At an updated price of 2695.00, I will never know.

JRD · Feb 13, 2013

One of the reason of change in geometry is the seat recess.
When guide are changed , the seat is usually recut . Then the valve seat is a bit deeper in the head, the valve sits higher and the rocker arm is no longer in the middle of the valve stem.
Solution is to change seats , and avoid to recut seats when guide are changed (if possible)

Valve adjuster contact geometry

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