Timing on my 1960 Jubilee

Hello Ian,

My Navigator is also converted to 12 volts and has a Boyer electronic ignition. Boyer has a kit for the Lightweights with a special pick up plate. It is larger than the ones for the Heavyweights or Commandos. I used a timing disc and a pointer attatched to one of the primary cover screws.

 I made some marks on the  Boyer  rotor.

 Also on the pickup plate.

Despite all my markings the ignition was some degrees off , almost TDC which resulted in two sets of seized pistons!

So check, check double check when setting the timing!

Here is a photo of my setup for checking the timing on my Navigator.  The pointer is substantial so it's unaffected by vibration.

I'm using Boyer equipment, a system intended for use with a single cylinder, needed some work to adapt it to fit the timing cover.   

Strobing showed that the initial timing (as described in the Boyer instructions) was some way off being correct, soon corrected.  I was pleased to find that after checking and adjusting the timing on one cylinder, the other was spot-on! 

I check my timing with a strobe, easy with a degree disc and pointer as mentioned above. But following Uli’s experience, I’m going to check it! 
dan 

If you buy an electronic ignition kit (essential in my experience, if you want the engine to last very long), it will come with instructions. Use a strobe, it’s easy enough and guarantees accuracy. That’s how I did mine in 1994 and it’s still running perfectly. That’s the bike described in the Roadholder magazine article. It also has 12V electrics, six-start oil pump worm gears and Superblend main bearings. 

Further to my note yesterday, for anyone who has looked at the letter about the “Achilles Heel” of the lightweights in the latest “Roadholder”, I’ve noticed that at the beginning of paragraph 10, I made the misleading statement that the early Jubilees had a single contact-breaker. They actually did have two, but on a single base-plate, meaning that the cylinders could not be timed separately for accuracy. That offered no advantage over a single contact-breaker. In 1961 they changed to a two-piece base-plate, enabling each cylinder to be timed more accurately. It offered little improvement though, because the automatic timing device wore so rapidly, that it quickly seriously over-advanced the timing and caused major engine problems. As previously mentioned, electronic ignition is the perfect solution for the lightweights.

This is a home made piston stop. It stops a Navi or Electra piston at about plus or minus 32 degrees with this projection from the plug body. M10 tap through plug body then threaded rod. Generous radius where rod touches piston. Locknut and slot on outer end of M10 rod for length adjustment. No great torque required to instal or remove so easier to use screwdriver in slot.

Another picture.

On my navigator I have a Boyer system and use a strobe for precision timing, initially set up with a piston stop and timing disk for TDS. The I machined the timing makes on to the rotor using my milling machine and a rotary table, photo is showing TDS and the other two marks are 24 and 32 deg BTDS.

Roadholder 417 Sept 2022-from Dennis Thompson I quote ';there is no provision for differential timing for each cylinder' excuse me? These electronic ignitions have ONE spark and work on wasted spark as far as the engine is concerned. The pistons are at identical heights 'unless you have dissimilar compression ratios?' So how can the 'ignition timing be a compromise'?

That was me. Guilty as charged. My logic was this. If two contact breakers are provided, as per my original set up, then there is some provision to set either side differently. Since you cannot do that with electronic ignition I was concerned that I was missing some fine adjustment. In fact, having installed electronic ignition, set it up with a timing disc and checked with a strobe, the engine starts easily and reliably.

Dennis

Nice to see you are putting your hands up....the wasted spark is such that both cylinders are fired at the SAME time hence no need for any adjustment, unless of course you are running with unmatched pistons to give you different compression ratios on the two cylinders....

A further thought-why do we have individual settings for each cylinder? Because the points mechanism and the advance retard mechanism is rubbish in manufacture. The engine position for piston height-ignition timing, will always be a constant.

As Peter Holland states above - none of this works UNLESS you establish TDC accurately.

A pencil (or similar) down the plug hole is a waste of time - you may be 5 deg or more out.

A TDC finder (a screwed in device with a plunger) is also useless (I nearly said pointless), as it comes in at an angle. These devices are normally intended for 2-stroke engines, where the spark plug is directly over the piston.

A piston-stopper is the ONLY way to determine TDC. The Norton Twins Manual shows you an example - see below. All you need is an old-type spark plug and a screw/bolt.

The method is simple too. Find TDC (as best you can) with a pencil and set up a WIRE pointer to it. Using the piston stopper, rotate the engine forwards (top gear & using back wheel gently) and backwards until it stops, noting both readings, then BEND the pointer by HALF the difference. Check that you now get the same reading forward & backwards. (Those examples shown above with Rigid Pointers will have trouble bending them at this stage - use a WIRE pointer).

Now set the timing, as per the instructions, at the BTDC Fully advanced setting. - 32 deg Jubilee, 24 deg Navigaor, 30 deg Electra.

Replace the spark plugs, start the engine and check your handiwork with a strobe. On revving the engine, you do not want to see the timing go beyond these settings.

What used to happen with the original set up of two contact breakers on a single plate was that you would set tdc very carefully and fix the timing on one side using a pointer and degree disc. When you rotated the engine to tdc on the other side, you would find the points opening a degree or two earlier or later than on the other, only explicable by manufacturing inaccuracies and wear. The advice then was to split the difference and set one slightly advanced and one slightly retarded by rotating the base plate, so that’s what we used to do. The split base plate from 1961 solved that problem by enabling you to move each contact breaker separately to get the points opening position spot on both sides. As previously mentioned, there wasn’t much point because it didn’t take long before the rapid wear in the rubbish automatic timing device over advanced the lot progressively, wrecking the performance and damaging the engine. Unless you’ve got the engineering ability to make a much better quality ATD, which I’ve never heard of anyone doing, you’re wasting your time with the original set-up. Electronic ignition is the only viable answer. I’ve seen one case of a wrecked engine where the ATD was so bad that the timing was out by 17 degrees. Sometimes they come out in bits.

If the above gubbins is used on a Lightweight (or any engine for that matter), at an angle, the point of 'maximum' will be the same. Only you can't use the numbers as anything useful. A pencil down the plug hole is also very suspect as any wobble will get TDC all over the place. A genuine piston stopper where the centre rise and fall is screwed/adjustable finds TDC from both sides. and you half the distance (degrees).

Getting all this right is essential so that your timing marks (around the alternator) are very precise. The future resetting of electronic ignition for both cylinder at once becomes very easy-strobe.