positive stop for ignition timing verification (2017)

Can a positive stop down the spark plug hole be made to work in an assembled, runnning engine- to verify TDC, then 28 degrees BTDC, without the stop hitting the valves? Wondering if the pointer is accurate
Thanks
Doug

I don't know what might have been done to your motor, but I just did this recently on my stock engine bored .020 over, and found that the valves did indeed touch the stop as I brought the motor around.
So I pulled the stop out temporarily and put it back in after passing the "danger zone". Found my mark was within half a degree of correct.
Here's the thread:
timing-disk-t26711.html

I made one for mine but i make sure it is only fitted once you can see the inlet valve has gone back past the plug hole (an only fitted in RH side it was made for). As Mr. Rick said "past the danger point" my engine has a big valve head an PW3 cam fit so things would certainly contact if it was left in a wrong point in the engine's cycle.
As you ask for 28º i would guess you have points setup. I have Boyer so run 31º an only use the stop to check the marks on rota line up correctly if i have removed to primary cases or done something that may affect the pointer alignment. But timing with EI needs little on no maintenance after that unlike points so its not really an issue in my case.
Another point you may or may not have considered is depending on what set up you have the distance between the piston an plug hole face may change. If for example you used my tool as i run no head or base gasket the position it would stop your engine in would be wrong.

Toppy
A mild and momentary deviation from OP but...
Joe Craig was my Granddad - died the year before I was born.
Where did you get the quotation you attribute to him?
Regards
Rob

robs ss said:

Toppy
A mild and momentary deviation from OP but...
Joe Craig was my Granddad - died the year before I was born.
Where did you get the quotation you attribute to him?
Regards
Rob

Click to expand...

I read it once in a magazine article about him and his work at Norton. It was apparently his reply when being told that in theory the Norton machines would not be competitive against mpre advanced multi cylinder machines but at the time they atill were.
I can't remember which magazine (probably Classic Bike Guide) it was fews years ago now. But i liked it an the articles writer quoted it to him an said it was typical of his character.

Ta Toppy!

a rod , old pencil , etc . Needs to be THIN so its truely concentric / vertical - To BORE .
Tri a old hacksaw blade across / stuck in fins . On Centerstand nudgeing rear wheel in 2nd ,
To get T D C Very Carefully . Then scribe ? line on vertical thing .

Seem to recall 31 is 3/8 in , same distance as whateve on Tri Magneto . So a D T I & Extn Rod , 3/8 of the top , is Yr 31 .

But TDC on ' the disc ' is best verified as half distance between same ' to T D C ' both sides of top of stroke .

A clapped out engine would have ' take up ' , rotationally . Also .

I made my stop by knocking the ceramic out of an old spark plug, then I epoxied in an 8-32 brass nut, ran in a 8-32 screw with a locking nut on it and it is narrow enough to miss the valve on rotation. It works on my 850 and my Combat motor, both with standard valves.



It is defenitely worth finding out if your timing marker is accurate. Check to see how much movement your primary cover has on its dowels. In my experience they tend to want to rotate clockwise against the pins after some road time.

Russ

Douglass Harroun said:

Can a positive stop down the spark plug hole be made to work in an assembled, runnning engine- to verify TDC, then 28 degrees BTDC, without the stop hitting the valves? Wondering if the pointer is accurate
Thanks
Doug

Click to expand...

its fine as long as your on compression stroke before fitting it