check my timing check

Out of curiosity I wanted to know how accurate -- or not-- the ignition timing scale inside the primary cover is.I mounted a timing degree wheel on the camshaft -- the wheel is graduated for use on the camshaft,I rocked the engine back and forth to establish accurate T.D.C.,turned the crankshaft back to indicate 28 B.T.D.C. on the degree wheel,looking at the scale inside the primary the line on the rotor lines up with 32 on the scale.My question now is,when strobe timing do I set the timing mark at 28 deg. or 32 deg. on the scale?,I may have confused myself more by trying to be accurate!. Thanks. James.

Your only confused because of the Numbers that came up . Good on ya for checking you will be rewarded later. So OK you degree wheeled to 28 BTOC for points Yes? If you were going to run a boyer you would have degree wheeled to 31BTDC no?Now 28 is really 31 when corrected so to time your points use 31. But if you have a Boyer your going to need some high math. Use 34 degrees.

The timing scale degree position is often slightly inaccurate due to it being made from a piece of thin folded sheet metal which can easily be knocked out of position, and also the primary cover may not go back in exactly the same position each time it is refitted, which can also throw the setting out, so use your timing degree wheel to check the accuracy of the timing scale, and then make an allowance for any apparent inaccuracy of the scale as norbsa has suggested.

If you do run a boyer and time it to 34 we have twins because thats what's scribed inside my timing cover.I wonder how common this is. Poll time LAB.
I have also found that if you take the time to get the magnets just right so that the adjustment slots for the Boyer end up right in the middle of the adjustment as you light time the bike that you can then rotate the coil plate fully and the bike will run with hardly a whimper. It's sickening how forgiving Norton's are not that I recommend this as practice mind you. But if you tried that on a BSA of a Triumph you would hear the ping for miles.
That may be why so few owners really know were the timing is on their bikes and just trust the scale.

I run my 850 at 34° on the Boyer. It's some time since I checked my timing plate but it was right at one time !

I wondered if modern fuels might be allowing / requiring a little more advance . I found the tickover smoother and the pick-up cleaner on 34° and moved the stator to experiment. As Norbsa says, they are very tolerant before they pink.

I have since read here that the engines will run hot if advanced before they pre-ignite. Mine doesn't seem to be....but this summer hasn't been much of a test of an ambient air cooled motor

If your timing marks are correct 34 deg of timing with good compression on modern unleaded, I would think is a little too advanced.
Have a good look at the plug center with a good magnifying glass. If you see any tiny silver blobs, they are blobs of molten piston and head, and the motor is too advanced.

Cash

79X100 if your gage was right on that's the first one I have heard of. You got a good one. On a dyno a bit of retard with a Boyer seems to reduce the 1/4 mile times according to Kenny Dreer. But on the road it may be wiser to look at getting MPG for your rough tunning never discounting the plug reads up inside.

Now you're making me paranoid, chaps...paranoid enough to run to the garage with a magnifying glass. I'm relieved to say that there is nothing winking back at me from the plug tips.

I holed enough two stroke pistons in my formative years to be fairly sure that I would recognise alli particles !

My indicator plate wasn't in the right place, Norbsa so don't start getting worried that Nortons might have let the odd good motor slip through In view of the fact that the plate is slotted and only fixed with self tappers, I assumed that I was supposed to fiddle with it :twisted:

In all honesty, I have had the primary off several (well, lots actually) of times since so I probably ought to put a degree wheel on it again.

I had perhaps naively assumed that if a motor was giving it's smoothest perceived tickover and not pinking under load then the timing must be about right. Is it the forum's opinion that this is a dangerous presumption on an 850 Commando ?

79X100,

If your engine is running strong and there is no detonation under load, then chances are very good that your timing is near spot-on for the fuel you are using.

In the old days, I used to advance the timing until the engine pinged under load and then retard the timing until it just quit pinging. This, I reasoned, was the optimum timing setting for the fuel octane being used.

For the price and time it takes to make a dead stop tool and check it out it's a good fact to know even if you didn't end up changing the timing. The side benefit is to check out the cam timing at the same time they are sometimes found to be out 5 degrees a lot of key ways broached into gears and cut into shafts in the stack up. If you have a mark three you could also double check the 28 degree hole through the timing cover. If you check on the cam timing you will have the one inch travel dial out on one of the valves so you could also check the rocker ratio - cam lift to see if you have good hard cams. Keith at Johnson cams told us that he has never seen a really right stock cam and when a plain old #1 grind is made right it's a perfect cam for a road bike. I have seen the results and it is amazing what a stock cam will do for a machine.

I will check mine again. I am still not certain about the aspect of setting the timing by ear on the basis that I know better than the ignition system manufacturer

If I can cause damage by running a degree of advance which is not causing apparent pre-ignition then perhaps I should stick with the 31° Boyer recommendation. (Just a thought, did their test bike 30 years ago have the plate in the correct place ?)

Well if Boyer's bench mark bike wasn't right they would have no excuse. Les at Norvil has been selling vernier timing sprockets because of this for as long as he's been around. How many years?

Many thanks to all who contributed sage advice,I am running a Boyer unit so 34deg. BTDC it is. I will be double checking as I go. Thanks again.
James.

Do the checks... 34 degrees is just what these two bikes happen to need yours could be the other way.