Dec 5, 2005
My timing marker in the primary case has been damaged, and I need to reset the timing. I am running points for now and wonder if anyone either has worked out the piston height BTDC @ the appropriate timing value. Or daoes someone know a formula. I suppose I could draw the whole thing up and plot it, but I am guessing there must be an easier way?

I plan on making a plug mounted TDC plunger, that I can piggy back a dial gauge onto.

Cheers Richard
Dec 19, 2004
Country flag
primary cover

Hi Richard,
Have you considered picking up a used primary cover. They are frequently listed on Ebay motorcycle parts and accessories (Norton).
If you had to you could pick up a shabby one for cheap then switch it long enough to set your timing.
Or, depending on how your cover's timing mark is damaged you may be able to get a shabby cover and use parts of it to fix your own.

justa thought,
Aug 24, 2005
Richard,I have used a measurement of 5/16" (.312" ) BTDC as the for setting timing,this is the original Norton Co. figure. Good luck.Ride safely. James.
Apr 7, 2004
The tech you speak of goes back to flat head motors with spark plug holes that are straight with piston travel. You need a dead stop tool and a degree wheel for the cam side.
First you need something to stop the piston near the TDC. You can tap a spark plug.
Brake off the ceramic part of the spark plug and remove the electrode wire on that end drill it out with a #29 drill,then tap the hole #8-32. Get a long 8-32 bolt with a 1 1/4 unthreaded shoulder. I used a Socket head cap screw, and loctight the threaded part into the plug the long shoulder should stick out about an inch and one quarter. Cut the the head of the bolt file or sand to a nice bullet shape. File in a drill press or a lathe.
Get the bike up on the centre stand and put her in high gear.Using the rear wheel bump the motor around and get the pistons down. Put the dead stop tool tight as you can by hand. Now gently bring the piston up against it.
Put the degree wheel on the end of the A.A. unit in your case. You need a degree wheel for cam use they only turn at half engine speed you know. It's a 720 degrees and are kind of a figure 8 shape. There on ebay all the time.
Wrap a wire around a couple of jug nuts and make a pointer out of it at around 12 oclock
Set the dial on the wheel to an arbitrary number like 30 BTDC . Now bump the motor around the other way until it stops. In a perfect world it would come out to 30% but it won't.Lets say you get 40% Now you may want to slip the dial a bit to try 5%. Bump the motor back and you should get 30 the other side of TDC
You want to end up with the same number on either side of TDC. The number isn't as important maybe 28 each side maybe 33 each side. Once you have it repeating you can snug up the bolt holding the degree wheel. than recheck again.
Now remove your dead stop tool and you can move the motor around to TDC Zero degees using the pointer and the degree wheel You can now find 28%BTDC for points or31% BTDC for Boyer. Use the rear wheel tuning forward to end up at your mark.
Set it at 28 or 31 see how close your gauge is to true
8/32 was for a reason on Commando's, a thicker bolt can foul the valves because of the angle of movment. It's good to turn your tool down in a lathe to 3/16 dia.on the bolt shoulder to true it up and aviod crashes with the valves.You must be very gentle when touching the probe with the piston not so easy as it sounds.The probe is on an angle and the piston is going straight up and down. Also realize that if you have not taken the trouble to rig your degree wheel with the primary cover on all bets are off there are no dowels on the cover so it dosn't repeat upon re-install. This is one of the reasons it's always off by three degrees all the time anyway.

Now just write down the number that lines up with your damaged gage or make your own mark on the cover boss were the gage used to be. Now you can strobe time the bike per manual or Boyer/Pazon directions.
If you go and remove the primary cover for a clutch tune or whatever you have to re-do this job if you need to restrobe it later.
It's really easy I could have made the tool and timmed the bike in the time it took to write this. Same tool will work for all bikes you can be the expert around town now.


Nov 20, 2004
Country flag
The timing indicator plate 06.0763 (pre-850 MkIII) and hammer drive scews 06.0663 x2 are available spare parts. Although what norbsa has said regarding timing adjustment still applies.
May 23, 2003
I always found that when I retimed my Boyer with the primary indicator that my igntion was off. After using a piston stop tool and a degree wheel (I put mine on the crankshaft) I found the primary indicator to be off by 5 or 6 degrees. Now I always just "translate" the reading on the primary indicator to a more correct starting point when retiming.

I'm thinking of replacing the Boyer with the Pazon and look forward to their simplified timing settings.