Valve Clearance

I always set the valve clearances , oposite ( side ) fully open .

dunno if any of these modern ignitions have a built in adjustable ' rev limiter / cut off ' . the THING would go STRAIGHT PAST ( or wouldve ) If you let it . Caugt 7200 once or twice .
But is there Tach Lag .

If we assume the MASS of the Valve is about that of the Follower , with the larger clearance , the acceleration of the followers already commenced , allowing it to ' throw ' the valve .

If your oil pumps any good ( Not Slack & wet sumping , at all ) there should be plenty of oil CUSHION in the mechanism . Al. has compresability , elasticity , and ' resonance ' ,
Therefore , if the pushrod absorbs liniarlythe initial force , and releases ( springs it ) in unison with the follower , the whole characteristics can be enhanced .

Which would explain a few things . SO AS , if your inable to try BOTH the .016 & the Std . theres no hope for mankind . by a ticket to Mars .

" I think that the increased valve clearance on the combat engine had more to do with how hot it was going to get and the rpm it was to be run at than it did to the shape of the cam shaft, If advancing that cam puts you into a lower rpm power band and your intension is to run the engine more normally then I think you could put the clearance back down the .002" to the original spec. "

maybe . If you never get out of town . And dont ride in summer . As its a Two Stage cam ( powerband ) If its past 3500 continuous - its not hanging about . Oil temperature will be past 90 ( Touchable for 3 sec ) .
So we will start on about orrible little oil tanks , next .



If you look at it as one of these , that they forgot to put the rest of it on ,
youll see that nothing less than the best , should be accepted or tolerated .

You say advanced it , about 3 degrees . IF its the center of the ovelap 3 degrees early , fine . But would be nice to know atually wot it is / measures .
with mine I had the choice of overlap 2 late or three early ,with stock parts . but if yours was already say 2 early 7 you added 5 , that'd be 7 .
Be intresting to see how it goes . If it dosnt hiccup & blowback into the intakes , or loose all top end go , and bottom end .


NOTE : These figures could be advanced a maximum of THREE DEGREES , for the COMBAT Camshaft . ( below )


IF you dont know EXACTLY where it is , And you shouldve checked , anyway :
40 thou. piston clearance .
Nip the adjusters down , no slack . wind in ONE full turn . this has them 40 ' up '
Plugs Out carefully & judiciously turn it over . fingertippy . If it C L A N G S you
Get a six foot lever & push it thru . Thatll bend everything so it'll go over . Or Better
STOP immediately , re check ( on mainstand in third , but better a spanner on crank nut )

Should turn over No Sweat - this is to check 40 tho piston to valve . If the cams way off
theyll both try'n occupy the same space at the same time . Which Einstien says is impossable.
He may well be right .

Might pay to loosen off a few times round , prior to putting the valves down 40 . As you ' feel your way ' for clearance .

( Id been given stiffer A Adv Springs , Tames it , But the wheelspin if careless with Std is better . In Hindsight .

That 65 degree BTDC inlet opening of the $S Commando cam is what I would use on any long stroke four-stroke motor, regardless of the cam shape and exhaust opening and the closing points. I think it determines the size of the gulp the motor takes, and where the power bump begins. The exhaust system needs to be optimised to suit. My cam is probably 650SS. Normal inlet opening is 53 degrees BTDC - I have added 12 degrees. My exhaust system is two into one. Exhaust opening is around 92 BBDC

Dan1950 said:

You don't have to be exact.

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In my case inexact would be guaranteed.

I actually got out a spare cam to see if your suggestion made sense, and I can see the base circle has room for my inexact skill set.

Schwany said:

In my case inexact would be guaranteed.

I actually got out a spare cam to see if your suggestion made sense, and I can see the base circle has room for my inexact skill set.

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Jist watch the exhaust rocker. As the exhaust valve closes, the intake will start to open. That will be within a few degrees of TDC.

Dan1950 said:

Jist watch the exhaust rocker. As the exhaust valve closes, the intake will start to open. That will be within a few degrees of TDC.

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I was going to do it as you suggested to see how it went but I went to TDC on the compression stroke and did the int and ext on the cylinder on the compression stroke as rob suggested. I did not use a straw to find TDC though. I have an old tool that screws into the spark plug hole for finding TDC. Easier than watching the rockers move for me.

Lash measurements were exactly the same as they were when I did it the old Haynes manual way a month ago. I feel like a dope doing it the Haynes way for 50+ years.

Schwany said:

I was going to do it as you suggested to see how it went but I went to TDC on the compression stroke and did the int and ext on the cylinder on the compression stroke as rob suggested. I did not use a straw to find TDC though. I have an old tool that screws into the spark plug hole for finding TDC. Easier than watching the rockers move for me.

Lash measurements were exactly the same as they were when I did it the old Haynes manual way a month ago. I feel like a dope doing it the Haynes way for 50+ years.

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By observing the valves at overlap on one cylinder, you are placing the other at the top of the compression stroke.

Same result without straws or other means.

Dan1950 said:

By observing the valves at overlap on one cylinder, you are placing the other at the top of the compression stroke.

Dame result without straws or other means.

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Yeah I get that. It would be easier if I had x-Ray vision though.

I had another reason for checking the valve adjust procedure the way I did. I wanted to mark my rotor for TDC because the Molnar crank I'm using has the rotor keyway in a different position from the earlier crank I had been using previously. The factory Lucas marks were 90 degrees out. The old tool I use makes finding TDC easy.

Schwany said:

Yeah I get that. It would be easier if I had x-Ray vision though.

I had another reason for checking the valve adjust procedure the way I did. I wanted to mark my rotor for TDC because the Molnar crank I'm using has the rotor keyway in a different position from the earlier crank I had been using previously. The factory Lucas marks were 90 degrees out. The old tool I use makes finding TDC easy.

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Use a piston stop. Mark the rotor when you encounter the stop, then rotate in the opposite direction until you again encounter the stop. Mark the rotor again. TDC will be midway between the marks.

Dan1950 said:

Use a piston stop. Mark the rotor when you encounter the stop, then rotate in the opposite direction until you again encounter the stop. Mark the rotor again. TDC will be midway between the marks.

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Alrighty that's a popular way to do it.

I get it close enough and 100% repeatable without a piston stop with the head on. I use a degree wheel and pointer along with the gizmo shown below for cam and ignition shenanigans initially. Then just use the gizmo after it is marked. The two thin shiny marks on the side of that sliding shaft are TDC and 28.5 degrees before TDC. Been doing it that way on the Norton since 1973.