Norton Dominator 99 with K2F magneto

texasSlick said:

Before setting the timing, report back on point gap on both ramps. I cannot over emphasize how important it is to have both gaps equal. Your bike will run so much better if equal.

Slick

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Hello, i will do so, i know for sure that they are not equal, when i was talking about the arcing/sparking you could see bigger arc/spark on other side than the other thus bigger arc/spark = bigger points cap on other ramp.

13 degrees BTDC fully advanced would explain your symptoms.

Many engines wouldn’t start easily at the associated retarded static timing, which must be about 8 degrees after TDC.

texasSlick said:

Before setting the timing, report back on point gap on both ramps. I cannot over emphasize how important it is to have both gaps equal. Your bike will run so much better if equal.

Slick

Click to expand...

And check timing on both cylinders.

I will do that.

Probably going to try to equalize the caps on both ramps with the Slicks tutorial, even though it would be easier to buy new cnc machined one. On my cam ring there is deep scores at both ramps(alot of wear?) I would add pic if i could.

Those new points have huge offset to each other which i dont like that much ole one did not have, should the whole plate come out of the mag after the long screw has been removed? It would be easier to disasemble point set if i had the plate in my hand.

Yes the points plate is on a keyed taper. Wiggle it a bit with a screwdriver and it will come out.

You can bend the “stationary” point to mate squarely with the pivoting point.

Triton Thrasher said:

You can bend the “stationary” point to mate squarely with the pivoting point.

Click to expand...

I will remove the whole plate tomorror and fix the "aligment" between stationary and pivotin point before i check the cap differences.

I am greatly bothered by these facts:

1) your bike ran well before this problem suddenly happened.
2) your timing is now very late
3) the AAU is "stuck" on the magneto taper
4) your bike has remnants of a manual retard system

A "slipped" AAU does not fit the facts! If the AAU slipped on the taper, it would be easy to remove.

I propose the cam ring has slipped inside the cam ring housing. There is a threaded stud at the 6:00 position on the magneto housing (about 7:00 as the mag sits on the bike) which prevents rotation of the cam ring. This stud is present on magnetos fitted with AAU. I do not know for sure, but I think early magnetos with the manual system did not have the stud. The manual cable rotated the cam ring to retard timing ... thus no stud needed or desired.

If a PO retrofitted the AAU, he would need to put in a grub screw somewhere to prevent rotation. I suggest this grub screw came loose, the cam ring slipped, and you suddenly had late timing. This fits all the facts.

Next step:

Remove cam ring ... see my tutorial for how to do it.
Inspect cam ring housing for a stud or grub screw.

Report back

Slick

The threaded grub screw with eccentric peg that is used to time points opening to correct armature position relative to the magnets, is present on automatic and manual magnetos.

Mags for use with an ATD use a cam ring with a notch that fits closely on the grub screw peg, so the cam ring cannot rotate.

The cam ring in a manual mag has a wide slot fitting over
the eccentric peg, that allows the cam ring to rotate to retard. The eccentric peg holds the cam ring at the right armature/magnet position for best spark at full advance.

Thanks for the clarification on the grub screw, Triton.

I still think a slipped cam ring best fits the facts. If the cam ring has indeed slipped, the problem must be related to the grub screw .... n'es pas?

A correct cam ring for use with an auto advance can’t slip.

A manual advance cam ring will retard itself unless something (like the manual timing plunger and spring) stops it.

Triton Thrasher said:

A correct cam ring for use with an auto advance can’t slip.

A manual advance cam ring will retard itself unless something (like the manual timing plunger and spring) stops it.

Click to expand...

I am thinking the grub screw has come loose far enough to allow the cam ring to rotate approx 32 minus 18 degrees. It is a possibility that should be investigated ... otherwise KuusistoNorton might properly time the magneto, only to have the ring slip again. Moreover, if the ring has rotated, the points will not be breaking at the maximum magnetic flux.

I am just flubbergasted that the AAU slipped ... they just don't, especially if they require a great deal of persuasion to pop loose.

Slick

I’ve had auto advance and solid mag pinions slip.

One auto type late last year.

A manual cam ring in a mag with no manual control has to be somehow jammed in one place.

Auto cam ring.

Manual cam ring. The narrow slot is for the mushroom ended plunger that moves the cam. The wide slot goes over the eccentric peg on the grub screw.

Don't want to seem like I'm OCD, but wondering why a mag that seems to have suddenly developed bad timing also has arcing points? The arcing alone would be a cause of bad running. Do two separate problems exist at the same time? Possible but.... Very curious to see what develops.

Bodger said:

Don't want to seem like I'm OCD, but wondering why a mag that seems to have suddenly developed bad timing also has arcing points? The arcing alone would be a cause of bad running. Do two separate problems exist at the same time? Possible but.... Very curious to see what develops.

Click to expand...

Bodger, I think two issues here. Excessive arcing at the points is a capacitor issue ..... that will burn out points early, but I cannot see how it can cause the sympoms described by the OP.

Second issue is late timing as verified by KuusistoNorton who measured 18 BTDC full advance. This value is consistent with the problems he has described.

I think first step is to resolve second issue, then address the first.

Agree! ..... "very curious to see what develops"

Slick

texasSlick said:

Bodger, I think two issues here. Excessive arcing at the points is a capacitor issue ..... that will burn out points early, but I cannot see how it can cause the sympoms described by the OP.

Second issue is late timing as verified by KuusistoNorton who measured 18 BTDC full advance. This value is consistent with the problems he has described.

I think first step is to resolve second issue, then address the first.

Agree! ..... "very curious to see what develops"

Slick

Click to expand...

I agree about the correlation between the over retarded timing and the poor running including banging ignition in exhaust. I have made that mistake. Just weird that it slipped all of a sudden, but you and Triton are probably on to something with the cam ring. Interesting puzzle.

Hello,

The manual retard cable is removed from the handle bar but cable sit intact since there is small spring inside that returns the cam ring to full advance whenever cable is not pulled.

In principle when the rubbing shoe starts to climb up the ramp it could rotate the cam ring with it if the forces are greater than needed to compress the spring itself, but i tested it out by pushing the cable towards mag while it was running to be sure that it was in advanced position and it didnt help.

Anyway thanks for the ideas, i will investigate cam ring, points, gaps etc. Before retiming it. I was also thinking if i would have ditched cable since its not in use anyway and just jammed the ring to advanced position for sure so it could not slip. (Was thinking of an bolt with same type plunger in the end and you could screw the cam ring to advance position and then lock to bolt in place with nut.)

I didint believe that the AAU could have slipped either, sounds impossible to me, like usually if you taper it just sits there. But now after checking the timing it seems to be that its just whats happened.

After i've got all thing above good shape i will re check timing and if no changes then retime it.

What comes to the arcing/sparking between points, i would remember that it was doing it already when i bought the bike last year, and i've got about 5000km so far without any issues with the ignition until now.

I'll keep you updated.

Okay,

Points gaps were set wrong, they were too small.

I set them again to 0,30mm and find that the other one is 0,10-0,15mm bigger.

I set smaller gap to 0,25mm precily so the other one is 0,35mm to 0,40mm.

Checked the timing full advance and left cyl was about 35° BTDC and right cyl was about 40° BTDC.

Could the too small gaps affect the overall timing so bad? I started it to try it out but its still running the same..

Expect that i turned the engine off and get my strobe lamp and started it up to see if its advancing and wtf moment came by all suddenly since it really was advancing and i could rev it.. And i let it come down back to idle and its suddenly acting like before, not advancing and spitting flames.

So the problem started to be kinda on/off type.. and i think that the timing has not slipped but either the cam ring is slipping or AAU is not advancing everytime.

Edit: Fixed some typos..