850 Norton Right Cylinder Misses

Status
Not open for further replies.
B

Blue850

Joined
Nov 21, 2012
Messages
13
Country flag
Easy to start last fall, then it sat for 6 weeks. Since then it's been very difficult to crank up, and when it finally does the right cylinder misses and the exhaust pipe stays barely warm while the left is toasty. I've gone through the carbs, added new condensers, points, coils, plugs (twice).
I've tried swapping the coils and plug wires to no avail. I cleaned all the connections that I can find. Bypassed the ignition switch, and bypassed the wire from the coil to the points, same results.
The only way I can occasionally get it to start is spraying a healthy shot of Quick Start in the cylinders, not something that should be done often, I know!
Valves all adjusted, good compression, timing is correct. I do get 12 volts to each set of points.
I'm really curious why it's just the right side. Any ideas or tips would be greatly appreciated,
Thanks for the help!!
Steve
I
 
Rule out the basics
Is the fuel fresh?
Are you certain that the pilot bush is clear, and a mean poking a wire through it because air/carb cleaner etc won't work, a 16thou drill bit is even better
This has been widely covered on here and is essential
What does the spark look like at the plugs?
Cheers
 
baz said:
Rule out the basics
Is the fuel fresh?
Are you certain that the pilot bush is clear, and a mean poking a wire through it because air/carb cleaner etc won't work, a 16thou drill bit is even better
This has been widely covered on here and is essential
What does the spark look like at the plugs?
Cheers
Click to expand...
 
Yes, I used a tiny thin wire along with carb cleaner and air on the carbs. Fuel is fresh no-ethanol.
Seems like if the carb was clogged, the spray of QuickStart would always fire at least briefly, but this is not the case.
The left plug spark laying on the head is always a bit brighter than the right one, that said, neither looks super hot to me.
The battery checks out fine and I've even tried it hooked to a back up 12 volt spare with jumper cables.
Quite puzzling to me!
 
Once started, if you rev it up will the 'bad' cylinder start firing properly? If so, it's the idle circuit, if not ASSUMing fuel is getting to the bad side, it's ignition.
 
Last edited:
Check the balance tube between the intake manifolds. OEM is a rubber hose but a lot of bikes have been changed over to individual rubber caps.
 
He said he went through the carbs so I ASSumed (!) the balance tube was reinstalled when the carbs were re-assembled/re-installed...;)

Again, will the bad cylinder "catch" and the engine operate satisfactorily as the throttle is increased? Vacuum leaks, which cause major problems at idle/low speed, become less and less noticeable as the throttle is opened. At WOT, they are essentially non-existent as far as any effect on the engine.
 
Have a go from the float chamber end to the back of the pilot jet. I have had a similar problem myself, trying to clean the pilot jet via the adjuster screw just didn't work. I had to come at it the other way that along with carb cleaner and compressed air.......mind your eyes.
 
MexicoMike said:
He said he went through the carbs so I ASSumed (!) the balance tube was reinstalled when the carbs were re-assembled/re-installed...;)

Again, will the bad cylinder "catch" and the engine operate satisfactorily as the throttle is increased? Vacuum leaks, which cause major problems at idle/low speed, become less and less noticeable as the throttle is opened. At WOT, they are essentially non-existent as far as any effect on the engine.
Click to expand...

Very True - but I don' think he said he replaced the hose - maybe a good piece of cheap insurance there!
 
I once had a miss in a motor which I thought was due to tuning. I could not get rid of it. However after I eventually took the head off the motor, I noticed a mark on the piston. I had replaced the valve guides which were originally phosphor bronze with some that I had bought which were cast iron. If a valve touches a piston, sometimes a phosphoir bronze valve guide will simply bell out, but a cast iron one can lose a chip of metal which can ding a valve. I raced for about four meetings with that problem without finding the cause. In my case, there was a dent in the exhaust valve, and the seat. I was interested to see in Paul Dunstall's race book, that he mentions this can happen. I thought I was the only idiot.
 
Well...he said it was running OK until it sat for 6 weeks. Can't imagine that there was some mechanical issue that occurred while the bike was sitting. The only thing that seems likely is the idle circuit, as folks have suggested. Vacuum leaks don't just appear because the engine hasn't been run but modern gas does degrade rapidly absent stabilizer so a clogged idle circuit seems a 'usual' suspect as far as starting/low RPM running.
 
Mine does that quickly with the ethanol if I forget to add the stabilizer.... Like within about 3 weeks it begins to hiccup and get finicky usually resulting in work for me providing the carbs aren't drained prior to sitting... There is no just running it out either once done.
 
Thanks for the advice, issue is still there... Replaced the balance tube, used carb cleaner again in the pilot circuit, it sprays out in the carb airway, so that should indicate that it's clean, I'd think. Doesn't " pick up" and clear that bad cylinder when it's revved.
Just swapped out the new condensers for the old ones just for something to do---no difference, of course.
I used to have the Norton dealership here in my home town back in the early '70's, and never had a problem like this one, 'course they all were shiny and new and started just by looking at them!
The wiring could need to be updated perhaps? Any ideas ?
Thanks again!
 
Each coil fires each set of points separately, and each point is timed separately.
Since one side is brighter than the other, I would start there.
Possible bad coil, bad plug wire or connection at the coil.
First, I would....
Verify all connections.
Confirm point gap and timing on each set of points.
Swap plug wires if you haven't.
Then swap coils.

Just thought of this, if the AAU isn't fully retarding, causes hard starting, posssible kick backs.
Doesn't explain the one side miss though..
 
Blue850 said:
Easy to start last fall, then it sat for 6 weeks. Since then it's been very difficult to crank up, and when it finally does the right cylinder misses and the exhaust pipe stays barely warm while the left is toasty.
Click to expand...

Warm means it's not firing at all. If your spit doesn't bounce off the exhaust pipe with a puff of smoke it's not firing at all. Any time you compress air it gets "warm". An air compressor head and it's exhaust get very warm and there's no combustion going on there. If your cylinder is firing, the exhaust pipe is hot enough to boil off any spit instantly. Yes, spit. That's my preferred simple test to verify if a cylinder is firing. No puff of smoke = not firing

Blue850 said:
I've tried swapping the coils and plug wires to no avail. I cleaned all the connections that I can find. Bypassed the ignition switch, and bypassed the wire from the coil to the points, same results.
Click to expand...

Check the wires to the points on the side that is not firing, there's an insulator on the points wire that has to be assembled correctly or you don't get a spark on that side..

Blue850 said:
The only way I can occasionally get it to start is spraying a healthy shot of Quick Start in the cylinders, not something that should be done often, I know!
Click to expand...

Throw the can of either away. Get a squirt bottle with an internal straw and directional exit tube. (pictured below) Put some fuel in it, remove the air cleaner, and twist the throttle so the throttle bodies rise up. Aim the squirt tube into the intake manifold and give a 2 second squirt of fuel. Give a kick.

A) It roared to life and you have determined your problem is a fuel delivery problem of some sort.

B) It didn't fire your problem is electrical (and possibly the points wire insulator I suggested above)

850 Norton Right Cylinder Misses



Blue850 said:
Valves all adjusted, good compression, timing is correct. I do get 12 volts to each set of points.
I'm really curious why it's just the right side. Any ideas or tips would be greatly appreciated,
Thanks for the help!!
Steve
I
Click to expand...

Right side because it's related to the right set of points if it's an electrical issue. The squirt bottle test will tell you if it's fuel delivery related, but you'll have to figure out why by inspecting the whole system.

You were asked whether the cylinder "kicks in" at higher RPM's. That question implies the idle circuit is the issue, so once you open the throttle enough to dimish the idle circuit effect on overall carburation, if the cylinder begins to fire that would point to the idle circuit as an issue.
 
Blue850 said:
I do get 12 volts to each set of points.
I
Click to expand...

With your positive voltmeter lead connected to the engine (a fin is a good place), with the points open, you should have 12volts on the moving part of the points and 0volts on the stationary part. With the points closed you should have 0volts on both parts.

With the ignition on and the engine turned so one set of points is closed, and with the spark plugs connected and laying on the head, open the points - you should see a spark. Turn the engine so the other set of points is closed and when you open the points, the other plug should spark.
 
Well, finally got back to the Commando...
I reviewed all of the tips and suggestions that were sent in and checked each one out.
Seems the right carb might have had a little something in it perhaps. I think what was the biggest culprit though, was when I checked the auto advance, I marked that secondary timing plate instead of the proper one for correct timing. I had always assumed the timing to be spot on, as it started on the first or second kick. The issue now was that my rotor mark to set the timing via the left side case was missing. It looked as if years ago something was loose in that primary case and it "erased" the timing mark. So, after MUCH guesswork, I got it to start with the left cylinder running fine and right one not so much. So I tried several positions on the timing plate for the right one, eventually finding a spot where it starts first kick and runs sort of ok. Still has a slight miss on the right side that I can't seem to correct, at least it runs now and maybe I can straighten out the miss in the coming days. If you have any ideas on how to statically time this beast without a timing mark I'd love to hear them!
Thanks again!
 
Blue850 said:
Well, finally got back to the Commando...
I reviewed all of the tips and suggestions that were sent in and checked each one out.
Seems the right carb might have had a little something in it perhaps. I think what was the biggest culprit though, was when I checked the auto advance, I marked that secondary timing plate instead of the proper one for correct timing. I had always assumed the timing to be spot on, as it started on the first or second kick. The issue now was that my rotor mark to set the timing via the left side case was missing. It looked as if years ago something was loose in that primary case and it "erased" the timing mark. So, after MUCH guesswork, I got it to start with the left cylinder running fine and right one not so much. So I tried several positions on the timing plate for the right one, eventually finding a spot where it starts first kick and runs sort of ok. Still has a slight miss on the right side that I can't seem to correct, at least it runs now and maybe I can straighten out the miss in the coming days. If you have any ideas on how to statically time this beast without a timing mark I'd love to hear them!
Thanks again!
Click to expand...

The timing scale can be "erased" by the alternator rotor, if the crankshaft shimming is incorrect. A new one can be fitted and the accuracy can be checked with a tool available from Andover Norton. Instead of that, you can find TDC on the compression stroke and with a dial gauge in the spark plug hole back off clockwise until the piston is (SOMEONE PLEASE ENTER THE NUMBER HERE *) inches below TDC for 28°. You can then scribe a mark on the stator with a paint pen or awl for your timing mark, the epoxy scratches easily.

The correct timing mark on the rotor is the one opposite from the keyway slot.

* Someone once posted here the distance below TDC for 28-30 degrees, corrected for the spark plug hole angle. I can't seem to find that post, hopefully someone will fill in that blank.
 
Last edited:
I recall reading such by someone far more capable of concentration over lengthy periods than myself.
 
Status
Not open for further replies.

Similar threads

Kjell
Stuck exhaust lock ring right cylinder 750 Norton Commando 1971
Replies
19
Views
1,754
cliffa
cliffa
S
  • Locked
Oil coming out exhaust on right cylinder
Replies
5
Views
1,440
Torontonian
Torontonian
Kid Thunder
Right cylinder runs hot
Replies
2
Views
1,127
Kid Thunder
Kid Thunder
Lineslinger
  • Locked
Right cylinder smoke
2
Replies
30
Views
6,255
Danno
Danno
K
  • Locked
missing left cylinder
Replies
11
Views
1,706
maylar
maylar
Back
Top