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Timing mark - solving for two unknowns!

Classic Norton Commando Motorcycles.

Timing mark - solving for two unknowns!

Postby MexicoMike » Fri Aug 11, 2017 5:14 am

I have done tons of degreeing in camshafts/cranks, etc with a piston stop and my trusty degree wheel. But I'm stumped with the Commando.

I have an Alton E start which, back when I bought it, did not come with a timing mark on the rotor. Frankly, in 2012/13, when I installed the starter, I didn't worry about it. The bike was in time (Trispark) and I figured I'd get around to marking it "someday." Yesterday I decided it was "someday."

But I have to admit that although it seemed very simple starting out I managed to thoroughly confuse myself because there is no engine-mounted reference point to work with. Of course, I can locate TDC as far as the piston is concerned and place a mark or make a pointer to show that. But it then has to align correctly with the scale on the chain case cover for actual timing purposes. I think it's one of those things that's pretty simple but somehow I managed to become quite befuddled! I had flashes of "OH, it's very simple," followed by..."WTF, this makes no sense."

Anybody done this and have some guidance? Again, I have no issue at all using degree wheels/piston stops but I can't seem to come up with how to determine where to mark the rotor once I place the piston at TDC so as to properly align with the chain case scale.


WAIT... just got a flash... does this sound right: Set motor at TDC. Using temporary pointer mounted on the engine, make a sharpie mark on rotor at that point. Rotate crank 30 degrees clockwise (Piston/crank will now be at 30 degrees BTDC) and make "permanant" mark on rotor where it aligns with the 30 degree hashmark on the timing cover scale. (This assumes that the timing cover scale is accurately placed but that's a different issue which I can also check with the degree wheel) Does this sound right?
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Re: Timing mark - solving for two unknowns!

Postby Beach » Fri Aug 11, 2017 5:20 am

Yes, sounds correct...Setting it 30btdc on degree wheel and then either noting which mark on scale is aligned with rotor mark or scribing new mark on rotor..
Bill

1974 850 Commando
1967 Atlas
1966 Atlas
1948 Panhead
1966 BSA Lightning
1965 BSA Lightning Rocket
1971 Honda CB350
1967 Honda Dream
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Re: Timing mark - solving for two unknowns!

Postby o0norton0o » Fri Aug 11, 2017 5:34 am

The place to scribe the timing mark on the rotor is relative to the scale position on the outer primary cover. When you take the cover off, the scale and that relativity disappears. When you find 30 degrees BTDC you want to replace the outer cover and scribe the mark onto the rotor in line with 30 degree mark on the scale.

*If you made your own custom made primary cover, you could make the rotor mark and locate the scale anywhere you want as long as their alignment indicate the correct piston position
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Re: Timing mark - solving for two unknowns!

Postby Holmeslice » Fri Aug 11, 2017 5:45 am

o0norton0o wrote:The place to scribe the timing mark on the rotor is relative to the scale position on the outer primary cover. When you take the cover off, the scale and that relativity disappears. When you find 30 degrees BTDC you want to replace the outer cover and scribe the mark onto the rotor in line with 30 degree mark on the scale.

*If you made your own custom made primary cover, you could make the rotor mark and locate the scale anywhere you want as long as their alignment indicate the correct piston position



This is correct, and the correct way to think about it.
If you set your crank at 30 degree BTDC, that's it... that's the gospel. You can scribe a mark anywhere you like on the rotor, then scribe a matching mark to correspond. In the case of matching it to the Commando timing scale in the primary; you would set the crank to your desired degree, then put on the primary cover and scribe the mark to match the corresponding degree mark on the timing scale. An added bonus: Your timing mark will be much more accurate than most Commandos. We often find timing scale marks to be off several degrees. Some of them even like to move on their own when you're timing the bikes!!

On the race bikes we do we usually scribe marks on the pulley at TDC and the required BTDC timing mark, then put a mark on the case. And usually do it in a location that's easy to see at a busy race track, at 3rd call before your race!!

HTH,

-Kenny
Kenny Cummings / NYC Norton
High Performance Classic Street and Racing Motorcycles
http://www.nycnorton.com
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Re: Timing mark - solving for two unknowns!

Postby NortonMKIIA850 » Fri Aug 11, 2017 6:21 am

Holmeslice wrote:Your timing mark will be much more accurate than most Commandos. We often find timing scale marks to be off several degrees. Some of them even like to move on their own when you're timing the bikes!!

Amen to that – I time with the primary cover off every time, with marks scribed into the side of the (Lucas) stator! I tried removing the timing plug in the cover the other day and it Would. Not. Move. It must've been so long since I took it out ...
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Re: Timing mark - solving for two unknowns!

Postby MexicoMike » Fri Aug 11, 2017 7:59 am

Thanks guys - really appreciate the input. It's marked appropriately now. I'm thinking about making some marks/pointers on the engine case but, as mentioned. That would require timing to be set with the chain case cover removed but, as also mentioned, it would be more accurate anyway. And pulling the cover is no big deal although a bit messy (OEM chain drive). But it's not like I need to do it often with an e-ignition for street riding. The last time I remember timing it was when I rebuilt the engine/ installed the Trispark back around '08. ;)
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