Strobing a Jubilee

You’ll need to make your own marks & pointer on the alternator rotor - do a “search” on here for lightweight timing, one of the responses will give the details of setting TDC & Ignition point - example in my photo

Bruce

I printed a timing disc of the Internet, glued it to some stiff card and undid the flywheel nut fitted the disc and tightened it up. I made  a pointer like above. Set the pointer to TDC with a dial gauge and bobs your uncle. I ran the engine fairly fast to set it on full advance. You can mark the flywheel if you like or just use a disc when you want to check it.

dan 

Disc's can slip in use,  better to mark the alternator .

Hi John,

There are no marks, you have to create them.

First find Top Dead Centre (TDC):-

Fit a pointer of some sort as shown on the picture earlier.

I push a short screwdriver down the bore such that the piston pushes it up from first contact to TDC by about an inch.

Now back it off and bring back up again until it just touches the screwdriver. Mark the alternator where the pointer is pointing.

Now rotate backwards until it again just touches the screwdriver, mark again.

Measure between the two and this is TDC. 

You now need to measure / calculate how far before TDC to mark the appropriate line to strobe. This is usually quoted as 24 degrees before TDC.

Print out a degree disk scaled to fit the alternator is one way.

Hope this helps.

Tony

John, 

Ignition timing is very critical on the Jubilee if you want to avoid seizure / piston damage and must be set at 32 degs before TDC (fully advanced) and NOT 24 degrees which is the Navigator setting.

Cheers

Nick

The photo shows my setup for timing my Navigator.  I made a new crank shaft nut with a male threaded extension so I could fit the timing disc to the crank.  I also made a substantial pointer that does not move while the engine is running.  Found TDC using the positive stop method.   There is plenty of room inside the case so the extended nut stays on the crank.

Not sure about marking the alternator rotor, a timing disc is still needed to do that or am I missing something here?

I'm using Boyer ignition.  Set up initially to the instructions. Then ran the engine to strobe and adjusted until right.

Incidentally, does anyone know why there is such a big difference between Jubilee and Navigator timing?

I would always recommend using a dial gauge rather than the stop method, they are only a few quid, although you have to be a bit inventive to get the gauge vertical to the piston.  

Dan 

I do apologise for getting the timing wrong, I had been answering a Navigator question and forgot to change thinking heads. Thanks for correcting.

Tony

I would strongly suggest that using a dial gauge is not the way to find TDC.  Try it and it will be found that when the piston stops at " a TDC" the crank shaft will rock backwards and forwards a little, even on an engine that is in good condition.  Might as well guess where TDC is with a bit of wire poked down the plug hole!

The positive stop method as described in the Norton workshop manual is by far the best way to find TDC.  This method will take in to account any slack in the system and find TDC accurately.

Attached is a photo of my stop tools, an old spark plug with the insulator removed and a bolt of suitable length welded in to the plug body.  Also a photo of the crank shaft with the male thread for securing the timing disc.

Point it at the disc pointer, you should see the timing advance as the engine revs, it should stop at 32 btdc. If it doesn’t adjust the timing until it does! 

Dan

Nick

Thank you for pointing out my misassumption! I hurriedly just copied the figure from the post above - , you are right its 32 at full advance and important to get it right.

dan 

Using a Piston Stopper is THE ONLY WAY to get an accurate TDC.

You need an accurate TDC on these bikes, as, being ultra short stroke (esp Jubilee) the timing is VERY critical. 32deg BTDC = Jubilee; 24deg = Navigator; 30deg = Electra

I use a piston stopper like the attached. Its an old spark plug that unscrewed for maintenance - just fit a short bolt instead of the electrode.

I find that a timing disk fits snugly on the end of the crank, if I invert the large washer below the nut for support.

As explained above, set up timing disc and a pointer with your best guess for TDC, using a pencil down the plughole. Then wind the piston down the bore, fit the piston stopper & gently bring the engine up (using back wheel & 4th gear) till it touches. Note the reading. rotate the engine backwards down through bottom dead centre and up the other side until it touches again. Note the reading again. If the two are the same, you are a genius & you got TDC by dead reckoning! Normally the two readings will be a little different. Subtract one from the other & halve the answer - move the pointer by that amount. Recheck to make sure you moved the pointer the right way!!

Example - one side reads 32deg, the other reads 36deg. Thats 4deg difference, half that is 2deg - move the pointer back 2deg to 34. Check again to make sure....

Congrats - you now have TDC! - Bit long winded - but worth it to get a smooth running engine.

Andy is absolutely right! Timing is VERY critical on Lightweights! I thought I got the timing right and made some marks on the stator and rotor on my Navigator. The result was a seized engine- twice!

The timing was off towards TDC. I got I right after strobing the engine.

So check-check-double check!