Valve lash w/o feeler gauage adjuster turns (2012)

Valve lash w/o feeler gauage adjuster turns if stems dimpled or no feeler handy.

Commando adjusters are 9/32" - 26 tpi BS Cycle thread. ( 1 turn = 0.0385")
5/16" UNF is 24 tpi. (1 turn = 0.0417")

Based on 26TPI 1 turn = 0.0385in.
0.006in~ 0.15 turns or 54°
0.008in~ 0.20 turns or 72°
0.010in~ 0.25 turns or 90°

C'mon Steve, just get out the feelers.

Dave
69S

Amen.

Amen. But what if a .0005 sized piece of grit got between two threads???

Well when he is doing some emergency repair without feelers then he will be one up on everyone else. Most people don't think of stuff like this because they are not as serious about riding as he is, and will not get into the situations he does.

hobot said:

Valve lash w/o feeler gauage adjuster turns if stems dimpled or no feeler handy.

Commando adjusters are 9/32" - 26 tpi BS Cycle thread. ( 1 turn = 0.0385")
5/16" UNF is 24 tpi. (1 turn = 0.0417")

Based on 26TPI 1 turn = 0.0385in.
0.006in~ 0.15 turns or 54°
0.008in~ 0.20 turns or 72°
0.010in~ 0.25 turns or 90°

Click to expand...

I've used this quick calc method for years in machinery repair (because many times clearance isn't designed to be measured), and it's shockingly accurate when done by experienced hands. A great field repair tool to get you in off the road.

beng said:

Well when he is doing some emergency repair without feelers then he will be one up on everyone else. Most people don't think of stuff like this because they are not as serious about riding as he is, and will not get into the situations he does.

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Hence the old saying: "Chance favors the prepared mind" :idea: :lol:

When this happened, my riding buds were laughing, "let's see you fix THIS ONE with wire ties MacGyver!" Track exploded while doing the ton, BTW :shock:

The thread turn method is faster, easier and more accurate than feelers blades for a number of reasons. I should scribble the amounts on back side of rocker covers as I forget them between each valve lash check. I love your 99 miles of caution avatar concuours.

Steve, maths is right, But if the lock nut "pulls up" the adjuster when nipped, and how often! then the clearance will be wrong.
How many time have you found the clearance slightly out when the nuts fully tightened? Plus if the valve end or tappet is worn..then this doe's not work due to dents and flats.

LAB, think through your last remark, as the tpi method is self compensating for dings dents and dimples, while the blade drag/snag method is definitely prone to some error from these. If the lock nut moves/shifts the adjustor bolt clearance on snug down then there is SERIOUS dangerous fault lurking in the rocker or adjustor thread integrity. Thankgoodness our crude craft can get away with errors short of the extremes of too tight or lose. Still its a bit sweeter running and sounding the closer to spec ya get lash.

Sunday, I was getting my bike ready for the SoCal Norton club's Hansen Dam ride on November 4 and I was feeling guilty about not adjusting my valves . . . .

Foolishly, I didn't check and record the existing clearances. I just felt them, decided they were loose and got to it.

I pulled the lash screws out and found that all four tips were galled. But, in looking down through the rocker arms' screw holes I could see that the tops of the Kibblewhite stems were polished where the screws "wipe" but none were dimpled.

Hmmm . . . I need some new lash screws . . . . it's Sunday . . . there used to be a Norton dealer . . . . but . . I don't want to wait . . . I wonder if I can dress these things into shape? I wonder, are they hardened? Hmmm, a file easily cuts them, uh wait, not really . . .

Chucked one up in the drill press, gently touched it with a fine file, cleaned them all up partly, retained the profile, followed with 600 sandpaper . . . the galling was too deep to eliminate entirely but I could eliminate the high spot on either side of the "wipe" that prevents precise adjustment when the screw turns up onto that high spot.

It looks like they have a dot of hardened material at the center that is inlayed into the softer steel of the screw.


Now, back to this thread - thanks Hobot.

The book calls for 6 & 8 standard, and 8 & 10 for Combats, intake and exhaust.
26 Threads Per Inch
1/26 =.03846/turn
26/6 flats = .00433/flat

So - for my standard:
0.0043 = 1/6th turn, one corner
0.0065 = 1/6th plus to the center of the flat, between corners, or 1 1/2 corners
0.0087 = 2/6th turns, to the second corner

That's where I set them, but then I read another thread on here and since my head was skimmed at least 20 thousandths I have to take Jim Comnoz’ advice -

https://www.accessnorton.com/NortonCommando/valve-clearances-why-so-different.9994/#post-133470


- so I have to go back and do it again at a tight 8 & an even 10, or
almost 2 corners and 2 1/2 corners.
.0086 and .0099

But, since my lash screws have smooth domed tips, I'll use the feeler gauge.

Ah . . . nuts, I'll order some new lash screws. They'll be here before November 4.

What a load of time wasting BS for the price of a set of feeler gauges......Too much time on your hands?

Not a total waste, IMO: as the adjusters wear, are they not prone to develop a cup shape underneath, for which a feeler gauge will not compensate?

Correct!!. And too small clearances are known to cause overheated valves and burnout,even when there is still some clearance when fully hot.

Mr. Rick said:

Not a total waste, IMO: as the adjusters wear, are they not prone to develop a cup shape underneath, for which a feeler gauge will not compensate?

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Well, it seems to me that when that wear occurs, it is time to replace the worn parts with new ones!

A noted in an earlier post, when you set the lash, tightening the locking nut changes the clearance. Using feeler gauges you can do the necessary re-setting/re-tightening to ensure the clearance is correct. I don't see how you can do that by eye looking at the adjuster flats.

Admittedly, we probably all have a different "feel" for the "correct" resistance of the gauge as it slides between the clearance points. So there is some slight variation inherent in the process. So maybe the screw-turn method does just as well. These aren't F1 engines anyway...

With practice it’s easy, quick and accurate.

MexicoMike said:

Well, it seems to me that when that wear occurs, it is time to replace the worn parts with new ones!

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Sensible riders don’t tear their bike to bits to replace useable parts.

when you set the lash, tightening the locking nut changes the clearance.

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The adjuster is held up against the threads when you screw it down onto the valve: it’s held up against the threads again when you tighten the locknut.

I guess we have a different view of the term, "sensible." I would replace or, if appropriate, resurface the parts since, IMO, they are excessively worn if the clearance cannot be set with a feeler gauge. That wear then causes additional, more rapid wear of the relevant parts.

Re clearance changing when tightening - I have found on every car/bike I have owned/worked on with adjustable valves that the same thing happens. The clearance changes slightly as the lock nut is tightened even though I am holding the adjuster with the appropriate tool. Typically I have to niggle the adjuster and lock nut a bit to end up with the clearance I am looking for. Admittedly, the difference that occurs is probably not more than what a tighter or looser version - depending on the mechanic's preference - of the feeler gauge "drag" as you slide it in/out of the parts.

I ordered new adjuster screws but by re-finishing the tips of the old ones I was able to adjust by feeler gauge and ride my bike in the meantime.

The point of the “count the corners” method is just that. If you have dimplied stems, then short of rebuilding the head, that’s how you have t do it. Gauges won’t work if the tops of your valve stems are dimpled

Re clearance changing when tightening - I have found on every car/bike I have owned/worked on with adjustable valves that the same thing happens. The clearance changes slightly as the lock nut is tightened even though I am holding the adjuster with the appropriate tool. Typically I have to niggle the adjuster and lock nut a bit to end up with the clearance

Click to expand...

Keep a slight tightening strain on the locknut when you’re adjusting.

I must be getting old. I have never used feeler gauges to set tappet clearances on any motorcycle. I've always used the fact that most Brit bikes have 26 TPI threads on their adjusters and one turn is 40 thou. If you don't jet too lean, you will never burn a valve regardless of the tappet clearance. Too little clearance and you lose compression - if you did not detect it, you would have to ride a million miles to burn a valve that way. However it seems that some people have 'no sense, no feeling' when they are riding their bikes, so don't know when it is not performing.