Norton Commando
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riddle me this

 
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Chris Barrett



Joined: 23 May 2003
Posts: 36
Location: Chicago

PostPosted: Thu Sep 09, 2004 3:12 pm    Post subject: riddle me this Reply with quote

Backfires and sputters on right cylinder. Standard 850 with Boyer analog, dyna dual output coil, Keihin FCR carbs.

This is a spare engine I have in while rebuilding my high compression 880 unit. The backfires being confined to the right cylinder rule out timing or anything else eletrical as plugs and coil routing alternation cause no changes.

I've rebuilt the carbs, confirmed that there are no intake leaks....stumped...

She starts easy enough, but will die if not revved to 2k.

Just bought a compression gauge and will check the jugs tomorrow. The only thing left I can think of is a compression leak.

That, or she's just jealous of the newly acquired CB400f.

Head scratchin...

-Chris
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mkiii 850
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PostPosted: Thu Sep 09, 2004 5:35 pm    Post subject: Reply with quote

Chris,
Have you looked at the valve adjustment, too tight or too loose, or the guides worn to the point the valves won't even seat (don't ask me how I know that one) also check the "lift" of the pushrod compared to the left side,maybe the cam has worn round.

A comperssion gauge is ok but kinda hard to read on a slowly revolving two cylinder motor, what woiuld really tell more is a cylinder leak down test. Most good garages have one I don't think they would charge too much, it would be pretty easy on a Norton.

Good luck.

Ride On
Dave
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Chris Barrett



Joined: 23 May 2003
Posts: 36
Location: Chicago

PostPosted: Thu Sep 09, 2004 5:49 pm    Post subject: Reply with quote

I was hoping it would be a valve adjustment. This was a "professionally rebuilt" engine I picked up off ebay in the spring......the valve adjustments were spot on. Also noticed that the tach drive had the o ring seal done which raised my confidence in the rebuild. Time and fettling will tell.....
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Derek Wilson



Joined: 25 Jun 2004
Posts: 86
Location: The Great White North

PostPosted: Thu Sep 09, 2004 7:21 pm    Post subject: Reply with quote

Sounds like carburation to me.
I had one doing a similar thing when it showed up at my shop, turned out that who ever put slides back in the carbs was not careful when lining up the needle with the needle jet and managed to drive the needle up into the slide. It would start up and idle fine, back fired and spit back through the carb when revved.
Of course, that was with Amal carbs, I don't have any experience with Kiehins on a Norton, but it's something to check.

Cheers,

Derek
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illf8ed



Joined: 30 Dec 2003
Posts: 474

PostPosted: Fri Sep 10, 2004 4:58 am    Post subject: misfire Reply with quote

My lack of trust of Boyer low tension wires makes me add a suggestion to check these at the magnetic pickup plate. It's possible for only one of these to break inside the insulation. There's no visible indication. You have to do some type of continuity check. Often there is weak contact until the wire is pulled on.
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Chris Barrett



Joined: 23 May 2003
Posts: 36
Location: Chicago

PostPosted: Sat Sep 11, 2004 3:46 pm    Post subject: Reply with quote

Bingo Derek!

I happened to have a single Mikuni setup that came with the bike (never tried it). I switched my fancy flatslides for the Mikuni and the bike started right up and dropped into perfect idle. As I've already cleaned all the jets in that Keihin, I must have either some deep internal blockage or some really nasty air leak.

So, I've lost a little top end and acceleration until I get the Keihins in order but at least I've got a runnin Norton....wooHoo!
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The Unapproachable Norton Commando

At the end of 1967 the Norton Commando was announced.

The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.

It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.

Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.

It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.

The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.