Valve adjuster contact geometry

Why? what do you think the "Factory" had that maintained the diamentions...having seen a factory drawing of a head..its not surprising the alignments are a bit errorous!
the vairations in castings just compiled the errors. The guide holes where pilot bored smaller and a check was made..the head was proberly moved on the angle plate to correct matters before final sizing....which ment all the heads where differant.
uote="acotrel"]It looks as though the guide might have been loose in the head and somebody reamed the hole and fitted an oversize guide, and in doing so got the guide out of alignment. If it came from the factory that way, it is pretty disgusting .[/quote]

Yes, that looks awesome. My original issue was that tappet rested on the edge of the valve which was no go, due to poor guide placement.

I would hope that the mushroom tappet would also help with the "scraping" action having it sort of rock over the tip.

Is that Jims Teflon seal down there that required the special tool to seat it? Nice stuff.

A bit late to the party, but what the hell

I had to take off around 0.060" from the push-rods to get the rocker geometry back inline on my Combat.
The head itself was in pretty good shape, but the valve tips showed wear right to the edges, and the guides were probably the worst I've ever seen.
The seats didn't need much re-cutting to clean up after the new guides were fitted, so I was more than happy. It would seem that the wear was worst around the top of the guide.
note that there's about a full thread showing above the rocker - previously it had been about four - it just looked all wrong.

X-file said:

Like I said,the article in Roadholder is completely wrong,and it ignores the fact that tipping the adjuster through 20 degrees causes it to roll on the valve tip.The bigger the radius on the adjuster,the further it will roll IF THE GEOMETRY IS CORRECT.

Holding the adjuster central while it is trying to roll only causes it to skid and create side-thrust.It won't be good for valve guides,and it will cause concentrated wear at the centre of the valve tip.

If anyone were to try that method of adjusting geometry,I would suggest they use a dummy adjuster screw of zero radius (ground to a point where it contacts the valve-tip).The results will be completely different,by about 3/8" in valve length.The results will be more accurate,for reducing scrub/skid and side-thrust on a solid rocker (non-swivel,non-roller).

If the valve length is correct,changing the radius on the adjuster does not affect the amount of scrubbing/skidding.It only afffects the distance that the adjuster rolls across the valve tip.It can roll 0.130",but only skid by about 0.015" in the process.Between 1/2-lift and full-lift,the adjuster is rolling away from the rocker spindle but the skid/side-thrust on the valve-tip is pushing the valve toward the rocker spindle.

ONLY A ROLLER-ROCKER,OR SWIVEL-FOOT (LIKE PORSCHE) ,SHOULD BE SET UP AS DESCRIBED IN THAT ARTICLE.

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As the author of the mentioned article, I wonder if you can explain why my method is wrong when in practice It changed my valve geometry from troughs carved into my valve tips from one end to the other, to the situation I now have were I can watch the valves fitted to the bike, and see the adjusters simply lean throughout their action with no sliding whatsoever?
It has now been many years since I did this, the witness marks on my lash caps are still simply a small circle in the dead centre of my lash caps, I don't even bother checking the valve clearances any more as they never change, with its PW3 cam modern sports bikes riders still feel my Commandos performance is worthy of comment. I have had no issues with wear of any sort.

What should I have done to bring me results better than I have achieved?

This is what you should be looking at

It's actually good for demonstration that this rocker doesn't have the adjuster screw on the valve side. The angle of the adjuster screw often confuses people, and alone it means little.
The middle picture shows the rocker at mid-swing (about 49% lift). Note that the square line taken off the valve tip passes through the rocker spindle centre. Through an accident of geometry, that will minimize the amount of scrub between the rocker tip and valve tip, or at least be a very, very close approximation to that.

Look at the radius on the rocker tip, and picture where the centre of that radius would be. In your case, it would be the radius on the adjuster screw.
Let's just say the actual radius is 0.38823". It will be somewhere close to that and the exact dimension matters little, but that will make the arithmetic and geometry simpler. If the distance from the rocker spindle to the centre of that radius was 1.5" (for convenience) the angle from rocker spindle to radius centre would 15 degrees from the square line at mid swing. Let's say the rocker swings through a total andle of 15 degrees from zero lift to full lift.

The distance that the radius centre would move, relative to the valve stem axis would be 1.5" (cos 7.5 degrees - cos 22.5 degrees) = 0.10135". That's how far the rocker tip would move across the valve.
If you took your adjuster screw (0.38823" radius) and placed it on the valve tip, and then swung it through an angle of 15 degrees (the same angle that the rocker swings through), it would roll across the valve tip if you didn't force it to skid or scrub. How far would it roll ?
2 pi (0.038823" x 15/360) = 0.1016"
That's a very close approximation to 0.10135", and only out by 1/4 thou.

You can try any radius on the adjuster screw, any length of rocker arm, and any angle of swing for the rocker. It will still work out very closely.

I noticed my rockers weren't centered on the valve stems in relation to the rocker axis, so I removed the spindle springs and shimmed the rockers to center over the valve stems. Makes a bit more top end noise, but at least they aren't bearing on one side of the valve stem. Anyone else ever try this?

Danno said:

I noticed my rockers weren't centered on the valve stems in relation to the rocker axis, so I removed the spindle springs and shimmed the rockers to center over the valve stems. Makes a bit more top end noise, but at least they aren't bearing on one side of the valve stem. Anyone else ever try this?

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Yep. Pretty common mod on Commando race engines. You can buy a kit that includes bronze spacers to replace the springs, along with some shims, or you can make up your own to fit. I don't know if it really adds anything compared to keeping the springs and centering the rockers with shims, but I do it on the race engines anyhow.

Ken