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Discussion Starter · #1 ·
The bike is a Norton Atlas with a K2FC magneto. On the compression stroke I found top dead center with a screwdriver and tried to get right int he middle of the dwell. I inserted the tool into the plug hole which reads at 1/8 increments. I bumped the back whell back whiel in gear to move the timing 3/8ths back. With the timing cam locked in full advance i brought the points in the mag to a point where i was just able to slip celophane out of the points. At this point the auto-advance cam/cog was locked down and everything was buttoned up. The plug wires on the mag when looking at it from the timing side are the top one to the left cylinder and the bottom one/one toward the back to the right cylinder. Upon kicking i get either puffs of mist/light smoke out of the carbs or with teh plugs switched a loud backfire. After ripping the bike down and reassembling three times i never got it right. At this point can i just unloosen the point plate in the mag and bump it either direction slightly so i dont have to take the exhast and timing cover off and the plugs out etc? Thanks in advance
 

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timing a Lucas mag can be frustrating, it takes me about 45 minutes to get it right on most times. but I couldn't imagine doing it without a degree wheel on the engine. I would pull the primary cover and attach it to the crank there. then start with the timing procedure, we also use a timing gun and check it with the plugs outside of the head and clamped on the fins of the head. you need to check both cylinders because often times the points cam is often worn on the bottom and it will fire that cylinder in as much as 4 degrees off the setting so you need to do a average timing of the top and bottom setting trying to stay around 38 degrees. check it by just kicking the motor over and watching where it fires, most times you need to flip the pickup lead of the timing gun because it each wire fires the opposite polarity, we also use a small chunk of fuel to lock the advance unit in the full advance position. when you are all done don't freak out if it won't run and just pops, then you just switch the plug wires around.
 

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Discussion Starter · #3 ·
Tony - I just had the mag rebuilt by Doug Wood so I woudl think (could be wrong) that the cam and all poins are new and there shouldn't be much variance. I was just talking to a friend and it seems maybe its operator error. I was turning the points counter clockwise to look for when the points gap opened up - he said I should be turning it clockwise to see when the points are opening. Does that sound right?
 

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Doug knows what he's doing so you should be ok there,and yes it should turn the same as Triumph which is clockwise when you are looking at the points.
 

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This is spooky. I'm just finishing-up an Atlas Cafe Racer project and I'm in exactly the same boat. Did you ever figure this out?

I've found TDC using a dial gauge down the spark plug hole. Setup a degree wheel. Cranked it back to 32 degrees before TDC. Then I installed a buzz box on the points. Loosened the Mag auto advance using the self extracting bolt.
Moved the mag until the points just open, lock down the mag. Oh yeah, I propped the auto advance open with a bit of plug wire. Afterwards I verified the timing by turning the engine back and forth to verify the points opening and it's spot-on.

When I try to start the bike I either get a spit-back in the carb, or a loud backfire in the mufflers (depending on the plug wire orientation). I suspect the spitting back is the closest to correct because my 71 Commando did this occasionally and it would start.

I bought this bike as a rolling basket case, so I've never had it running.
Did a total restoration on it.

I've triple checked the basics.
At TDC my cam drive sprocket indicator is at around 11 o'clock.
Intermediate sprocket mark is the same.
10 chain pins between both marks.

Crank pinion and intermediate pinion yellow paint marks all line-up.

My K2FC magneto was rebuilt by Mark Seibert in California.
Any ideas?

Mark Schmitz
http://www-cdf.fnal.gov/~schmitz/Atlas.html
http://s646.photobucket.com/albums/uu188/mschmitz57/Atlas/
 

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If you are "backing off" from TDC, make sure that you go past the setting and then bring it back in the direction of travel, to eliminate any backlash.

A simple check to ensure that you are not 180 degrees out ( ie. the plug lead is going to the correct cylinder) is to put your thumb over the plug hole and crank the bike over. Your thumb being blown off the hole by the compression should correspond with the spark you see from the plug, which should be earthed to the head.
 

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Don't fuck around, get a degree whell and use that. You can even photo copy one, glue it to a flat peice of plastic and use that (I made my own.)

28 degrees BTDC with mag at full advance. At 28 BTDC the points should jst start to open. You can use a piece a piece of tinfoil. As soon as you can pull it out of the contact points, fix the timing gear. Crank engine over, recheck your timing.
You're done.
 

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sorry for starting a shit-storm guys, I thought we were talking about a Triumph :)

but no matter what the setting should be I always check it with a strobe light by clamping the plugs to the fins on the head and kicking it over with it locked in full advance and watching where it fires on a degree wheel,
Other wise it is all just a guess at where it timed.
 

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No storms on my end. This is interesting.
My information comes from the Genuine Norton Maintenance Manuals.
You can download the pdf file if you want. Good reading.

http://www.eurooldtimers.com/eng/manual/93-norton-all-models-1968.html

The Atlas ran a lower compression ratio (7.5 to 1) so timing was more advanced (32°).

Mark
OK, I seem to recall the lower compression running a few degrees more. Whne I built my Atlas/Commando hybrid engine I put 9:1 pistons in as it was all I could find in standard bore.
 

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I'm running Commando pistons as well. This was my problem.
I reset the timing to 28° and it started right up and settled into a nice idle.
I suspect this was "The Dewd's" original problem as well. I imagine every Atlas rebuild
uses Commando pistons as new dished pistons are probably not available.
I was reading Paul Dunstalls "Tuning for Speed" and noticed the compression ratio vs ignition timing chart and realized this was my problem.

http://s646.photobucket.com/albums/uu188/mschmitz57/Atlas/?action=view&current=976c1962.mp4

Thanks for the help,
Mark
 

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that's interesting, it must be something with Norton's, most Triumphs run 9.5/1 and 10/1 pistons at 38 degrees BTC.
That's a full 10 degrees more advance.
 

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that's interesting, it must be something with Norton's, most Triumphs run 9.5/1 and 10/1 pistons at 38 degrees BTC.
That's a full 10 degrees more advance.
I think BSA's are similar too, as in about 10Deg more than a Norton. My 750 Atlas/Commando engine runs perfect at 28 BTC with a 32 mm Mikuni and Hunt mag. Starts easy and pulls hard enough to wheelie with ease.
 

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I've got a Triumph T110 with a magneto and 6v electrics.Never used a strobe light before to check when the magneto fires,if I buy a 12v strobe light will I have to use a 12v external battery?...and does the strobe need a xenon light and not a neon?
 
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