Norton Commando 1969 timing issues

Status
Not open for further replies.
M

Migsan

Joined
Dec 9, 2020
Messages
88
Country flag
Hi everyone

I am working on a 1969 S type commando.
Just reaching the end of the restoration and it was time to fire it up. It´s running the Boyer MK3 with good spark. Already tried setting the timming from 28 to 31 degrees using the counter-clockwise hole with no success. Checked the degrees scale and it seemed in place. So far I only got backfire and some smoke out of the airfilter box. It really seems to be related with the timming.
Also worth mentioning replaced the floaters and needle valve for stay ups and viton tips. Set the fuel level to 4.5mm from the top of the bowl.
Any ideas of what I might be missing?

Thank you very much!
Cheers
Miguel
 
The procedure you described is good.

However.

If your cam is out of time that would produce the symptoms you describe. The cam chain should have 10 pins between the marks on the cam sprocket and the intermediate sprocket while the gear section in the intermediate mark is aligned with the crank mounted pinion gear. Worth checking.

Best.
 
Migsan said:
Hi everyone

I am working on a 1969 S type commando.
Just reaching the end of the restoration and it was time to fire it up. It´s running the Boyer MK3 with good spark. Already tried setting the timming from 28 to 31 degrees using the counter-clockwise hole with no success. Checked the degrees scale and it seemed in place. So far I only got backfire and some smoke out of the airfilter box. It really seems to be related with the timming.
Click to expand...

Are there two timing marks on the alternator rotor (as a '69 rotor could still have only one)?

If there are two rotor marks 180 degrees apart then a common mistake is to set the timing to the wrong mark so the sparks will occur 180 degrees out.

acotrel said:
If you have got compression, swap the plug leads.
Click to expand...

The Boyer ignition is 'wasted spark' so swapping the plug leads won't do anything.
 
RoadScholar said:
The procedure you described is good.

However.

If your cam is out of time that would produce the symptoms you describe. The cam chain should have 10 pins between the marks on the cam sprocket and the intermediate sprocket while the gear section in the intermediate mark is aligned with the crank mounted pinion gear. Worth checking.

Best.
Click to expand...
I will check that just in case. thanks
 
L.A.B. said:
Are there two timing marks on the alternator rotor (as a '69 rotor could still have only one)?

If there are two rotor marks 180 degrees apart then a common mistake is to set the timing to the wrong mark so the sparks will occur 180 degrees out.



The Boyer ignition is 'wasted spark' so swapping the plug leads won't do anything.
Click to expand...
I have good spark on both sides. What I have done is without the sparks check for top dead center on the compression stroke and once I am there I put in 4th gear and back up the wheel the opposite direction until I hit my mark. The rotor has two marks but I and almost 100% sure it´s the right one I am using.
I didn't open the engine. just checked transmission chain. At least the top engine was done it has clean pistons. I was told it was a Norton guy that rebuild the engine but don't know any details. I rebuilt the wiring harness and everything on that end seems to be doing it's intended job. But it just resembles the symptoms I had with my t140 when the timming was off.
 
Last edited:
Crossing-over
Migsan said:
I have good spark on both sides. What I have done is without the sparks check for top dead center on the compression stroke and once I am there I put in 4th gear and back up the wheel the opposite direction until I hit my mark. The rotor has to marks but I and almost 100% sure it´s the right one I am using.
Click to expand...
You seem to have it correct.

Check the wires aren't crossed over between the pickup and the Boyer box.
 
If the MkIII Boyer is not kicking back when it backfires, it could still be a little retarded.

My motor will backfire if there is not enough fuel in the combustion chamber, and I'm not kicking it over hard enough starting the kick with the pistons in the wrong part of the stroke. It lights right up when there's enough fuel in the combustion chamber and I kick it over correctly.

What do the plugs look like when it won't start? Are they soaking wet or still dry?
 
Enough fuel? Yes, I always tickle my carbs until I see fuel coming from them. Push it over compression a time or two, not a full stroke, just enough to make sure when I do the final thrust I'm just before compression or at the top, make sure the clutch is free and then it usually starts 1 or 2 hits. Assuming you have Amal carbs.
If I don't start the kick at just before or right at compression, I can't always get through the second compression stroke with the same kick and it won't start. But I'm using Pazon. Make sure enough battery voltage too.
 
Schwany said:
If the MkIII Boyer is not kicking back when it backfires, it could still be a little retarded.

My motor will backfire if there is not enough fuel in the combustion chamber, and I'm not kicking it over hard enough starting the kick with the pistons in the wrong part of the stroke. It lights right up when there's enough fuel in the combustion chamber and I kick it over correctly.

What do the plugs look like when it won't start? Are they soaking wet or still dry?
Click to expand...
Just removed the new spark plugs I installed yesterday and they were smelling like gas and I could see the valve bed was wet as well butnot soaked though. I set the fuel level to 4.5 mm from the top of the bowl on the carbs.
Also I followed all the engine cycle through the plug hole and it all seems correct so I don't believe the cams are set wrong either.
 
DogT said:
Enough fuel? Yes, I always tickle my carbs until I see fuel coming from them. Push it over compression a time or two, not a full stroke, just enough to make sure when I do the final thrust I'm just before compression or at the top, make sure the clutch is free and then it usually starts 1 or 2 hits. Assuming you have Amal carbs.
If I don't start the kick at just before or right at compression, I can't always get through the second compression stroke with the same kick and it won't start. But I'm using Pazon. Make sure enough battery voltage too.
Click to expand...
Battery is new and measured 11.7 volts. Again tickle the carbs and start kicking. Only get backfire, gas smell and a bit of smoke coming both from the pipes and the air filter. Getting really frustrated
 
Migsan said:
Just removed the new spark plugs I installed yesterday and they were smelling like gas and I could see the valve bed was wet as well butnot soaked though. I set the fuel level to 4.5 mm from the top of the bowl on the carbs.
Also I followed all the engine cycle through the plug hole and it all seems correct so I don't believe the cams are set wrong either.
Click to expand...
A big V8 will do similar when timing is 180 degrees out. Difference is it's really obvious and loud backfire.

I think I'm having a brain fart. Can a Norton wasted spark ignition be 180 out? Ya know like a broken clock is right twice a day. Sorry I went off the rails.

Have you taken the valve covers off and checked where the valves are when you are at what you think is TDC compression stroke. You can do it through the spark plug holes too, but with the valve covers off, you'll know for sure what is happening.

In my limited experience when the Boyer ignition is set up statically according to the instructions, it's usually fairly close, and the motor should start.

I don't want to sound like a smart guy, cuz I'm not, but are the carburetors synced up and using the right jetting, needle, slide, and so on?

Kommando has a good point. If the battery is showing 11.7V with the key Off, the battery is probably too low for a Boyer MkIII with the key On. Did the bike have the Boyer on it before the rebuild?
 
Status
Not open for further replies.
Back
Top