Greg's 73 Commando

I have managed to put a couple of miles on the bike and it was running great up until friday. The idle was rock solid and it was a first kick starter every time. Coming home it started to develop a bit of a missfire at about 1/8 to 1/4 throttle. I had a look at the plugs when I got home and they were both sooty. Since the bike was still running perfect at idle and when cruising I decided to try leaning out the needle one notch but it still missed and fouled the plugs. Last night I lowered the needle another notch but didn't have time to test it. This afternoon I started it up after a couple of kicks and it just stalled and ran like a pig. I never even got it to the street. Since the plugs were fouled again I thought that maybe it was idling a bit rich so I swapped the smaller 38 pilot jets back in. Now the bike won't idle and the left cylinder won't even run on its own and the plug is coming out with oil on it.

Obviously, if the changes I made caused it to run worse then I have been going the wrong way. I still don't know why the plugs became so sooty at normal freeway speeds if it wasn't running rich but it now appears that the needle jets weren't it.
I have been following the normal procedure that I learn with the Amals but must be misreading things.

Somewhere I believe you said you are running a Boyer. When you mentioned the misfire at 1/8 to 1/4 throttle, Boyer problems sprung to my mind. They have a nasty habit of breaking the wires from the pickup coils on the plate. You won't see the broken wire. It's parted inside the insulation. Also, it's not continually open. It seems to separate at low rpm then make contact again as you coax it to run faster. I assume the vibrations at the certain low rpm range cause this. As for oil on the plug, that doesn't sound good. Probably not carb or ignition related. I do know that 90% of carburetor problems are indeed electrical.

Oil on the left plug - are you running it on the centerstand, or letting it idle on the sidestand.

If the bike is leaning over on the left side, oil can pool around the exhaust valve guide and dribble into the cylinder.

BillT said:

Oil on the left plug - are you running it on the centerstand, or letting it idle on the sidestand.

If the bike is leaning over on the left side, oil can pool around the exhaust valve guide and dribble into the cylinder.

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Bingo! It never even occured to me until I read your post. I had the same issue once before with another bike and completely forgot about it. Thanks.

JimC said:

Somewhere I believe you said you are running a Boyer. When you mentioned the misfire at 1/8 to 1/4 throttle, Boyer problems sprung to my mind. They have a nasty habit of breaking the wires from the pickup coils on the plate. You won't see the broken wire. It's parted inside the insulation. Also, it's not continually open. It seems to separate at low rpm then make contact again as you coax it to run faster. I assume the vibrations at the certain low rpm range cause this. As for oil on the plug, that doesn't sound good. Probably not carb or ignition related. I do know that 90% of carburetor problems are indeed electrical.

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I hadn't even thought about it being the Boyer unit. I did notice yesterday when I had the bike idling on one cylinder with the other lead attached to a spark plug wired to the head that the spark was very weak. Hopefully I will get some time tonight to pull the carbs off and put them back to the way that they were and then check the Boyer wires as well.
Thanks for the suggestion.

I'm just starting to get along with my Kehin copies also.

Hopefully I will get some time tonight to pull the carbs off and put them back to the way that they were and then check the Boyer wires as well.

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The best way to check the Boyer wires is to replace them. Unsolder the old ones. Since you are at it, drill out the holes where you removed the old wires. Attach some new ones by using a ring lug crimp connector and a 4-40 screw and nut. Do not solder the lugs. The solder is what's causing the problem. It wicks up the wire making the wire solid. The vibration causes the wire to flex, eventually breaking. Since the insulation covers the break, it's not obvious. Evidently the wires are still making contact and only seperate at low rpm. Somewhere between 1500-3000 rpm. It will idle fine, but once it hits the critical rpm it separates causing the miss. Usually, it's just one wire, hence the one cylinder missing.

I finally got some time to work on the bike.
First order of the day was to remove the carbs from the bike so that I could fit the 40 pilot jets back in and move the needle back to the middle groove.


I have found that the easiest way to remove the throttle spring to get to the needle jet is to twist it out.


Once the needle was out I put the clip back into the centre groove.


Next was to remove the float bowl so that I could get to the Pilot Jet.


Here are the 40 Pilot jets that are now fitted.


Once that was done I reset the float level to 19mm. I think that I must have snagged one of the floats when I removed the float bowl last week without removing the carbs from the bike.


Once the carbs were back on it was time to check out the Ignition.
I tested the black box which checked out fine and also tested the pickup plate and that came up fine.

When testing the ignition by unplugging and plugging in the wires to the pickup plate the right spark plug was firing but the left one wasn't.
I checked the power to the coils and it was fine. It looks like maybe the left coil isn't working properly.
I rang around to get a new 6v coil but the local norton parts dealer only had one in stock and suggested that I should really buy them in pairs. I am inclined to agree with him.
Since I was up for $120 for the two "old style" coils I figured I may as well look into something a bit more modern and neater.
I found an Accel coil at Supercycles that is meant for a Harley Davidson. According to the salesman it is a 3 Ohm which should be perfect for the Boyer, especially as the output is about double what the old style PVL or Lucas coils put out.


Before going too far I thought I would just test the coil before I went any further. Unfortunately it measured 2.8 Ohm's.
So, I took it back and Supercycles are going to see if they can get me the next one in line which is supposed to be 4.7 Ohms.

Because I am removing the old coils and the coil bracket which I had my Boyer black box mounted to I had to find another place to mount it.
I decided to mount it vertically up against the frame under the tank. There wasn't anything to actually mount the box to so I decided to drill a couple of holes through the gusset and use cable ties to hold the black box to the frame.


This it the black box trial fitted with a temporary foam backing between it and the frame to reduce vibrations.


A friend of mine is going to source some angle iron for me to make a mounting bracket for the new coil when it gets in. Once I have the angle and the coil it should be a pretty simple job to fit it all and get the bike up and running again.

Then I will only need tyres since the ones on it have a LOT of radial cracks in them.

Rather than start a new thread, what are peoples opinions of the Avon AM23's 3.60 front and 4.10 rear?
I was looking at the AM18 and AM20 but was told by the local reseller that they are no longer available.

Veefore,
From the last close-up pictures of your frame, the gusset and front fuel tank mounts are non-standard. Did you add those? Could be repair from an accident, but if not, the gusset isn't necessary for a street machine and the space it occupies is where I normally mount the electronic ignition box.

Ron L said:

Veefore,
From the last close-up pictures of your frame, the gusset and front fuel tank mounts are non-standard. Did you add those? Could be repair from an accident, but if not, the gusset isn't necessary for a street machine and the space it occupies is where I normally mount the electronic ignition box.

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No I didn't add them. I just assumed they were standard. I know this bike has been in at least one crash judging by the dents I found in the fuel tank and the the damage that was even underneath the tank. I think that this bike has had a pretty hard life before I got it. It is no wonder I am having so many issues with it. Not only was it poorly treated but it was just left outside to rust for at least 10 years before my father and I got hold of it and got it running again.

It's hard to see at first, but those bikes left outdoors are very expensive to own. Even if you are given one, it's usually cheaper to buy a bike that has been garaged and has at least rudimentary maintenance. That free bike will cost you way more than the one you paid $4000 for.

Clever idea on that spring. I compressed mine on a wire tie and then cut it after installation, your idea looks easier.
My bike is idling on the pilot jets the PWKs shipped with so I think they will work for me. I also need to upgrade my spark, but I'm going with two individual coils just because I've limped back home on one cyl when a coil failed in the past. On one of my BMWs that was running a single combined coil I got a good walk carrying my helmet, so I kind of like the two coil idea.

JimC said:

It's hard to see at first, but those bikes left outdoors are very expensive to own. Even if you are given one, it's usually cheaper to buy a bike that has been garaged and has at least rudimentary maintenance. That free bike will cost you way more than the one you paid $4000 for.

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As I am rapidly finding out. On the other hand, I kind of feel like I have "saved" one from an undignified death. Anyway, I don't really see myself ever selling it so I have got plenty of time to eventually get it right.

[quote'"Cookie"] Clever idea on that spring. I compressed mine on a wire tie and then cut it after installation, your idea looks easier.
My bike is idling on the pilot jets the PWKs shipped with so I think they will work for me. I also need to upgrade my spark, but I'm going with two individual coils just because I've limped back home on one cyl when a coil failed in the past. On one of my BMWs that was running a single combined coil I got a good walk carrying my helmet, so I kind of like the two coil idea.[/quote]

I have just noticed on the instructions with my Boyer that this model will take 12v coils if they are in good condition. I wish I had noticed that before. Since I have already paid for it if Supercycles don't find me a suitable dualfire one I might just head down to Supercheap and get a couple of Bosch GT40's. I must admit that I am getting a little sick of pushing my bike. 5km in Bunbury at the Indian Harley club rally, 2km at Kellerberrin after it nipped up while testing it after the rebuild and the longest 500m ever pushing it up the bloody steep hill at the end of my street.

JimC said:

It's hard to see at first, but those bikes left outdoors are very expensive to own. Even if you are given one, it's usually cheaper to buy a bike that has been garaged and has at least rudimentary maintenance. That free bike will cost you way more than the one you paid $4000 for.

Click to expand...

As I am rapidly finding out. On the other hand, I kind of feel like I have "saved" one from an undignified death. Anyway, I don't really see myself ever selling it so I have got plenty of time to eventually get it right.

Cookie said:

Clever idea on that spring. I compressed mine on a wire tie and then cut it after installation, your idea looks easier.
My bike is idling on the pilot jets the PWKs shipped with so I think they will work for me. I also need to upgrade my spark, but I'm going with two individual coils just because I've limped back home on one cyl when a coil failed in the past. On one of my BMWs that was running a single combined coil I got a good walk carrying my helmet, so I kind of like the two coil idea.

Click to expand...

I have just noticed on the instructions with my Boyer that this model will take 12v coils if they are in good condition. I wish I had noticed that before. Since I have already paid for it if Supercycles don't find me a suitable dualfire one I might just head down to Supercheap and get a couple of Bosch GT40's. I must admit that I am getting a little sick of pushing my bike. 5km in Bunbury at the Indian Harley club rally, 2km at Kellerberrin after it nipped up while testing it after the rebuild and the longest 500m ever pushing it up the bloody steep hill at the end of my street.

That's kind of the way I feel about my current Norton. I wish I had both the ones I let go so why sell this one? I have other bikes to ride so plenty of time to sort the old dog is fine. It's just a hobby anyway.
On the good side she has not made me walk back yet. I do have plenty of tools with me though.

Update time!

I have been a little busy lately but managed to get a little done after work the last few days.
This is the bracket that I made for the coil.



Here is a picture of the coil that I bought mounted to the bike.




And here is a view of the Boyer now fitted and the coil.



And finally with it all back together.




I took it out for a test ride and it started out great but as I got a little more "spirited" there was a HUGE flat spot develop. If I continued to push it the bike got worse until it nearly stopped. Once I slowed down and just tootled along just above idle it seemed to clear up a little. After a short time at idle it would go ok for a few seconds with lots of throttle but would then die again.
Here is a picture of the spark plug that I pulled out of the right cylinder.




This shot is a little washed out but shows inside the plug better.



I have tried the pilot jets and the needles so my next guess is that it is the main jet that is causing my problem. It currently has a 140 main jet in it and I am thinking about going down two sizes and see if that clears it up. I will keep a close eye on it to make sure it isn't too lean and if it is I will grab some in between those and what I have now.

I hope I am on the right track here, otherwise I guess it is just another step in learning to be a Commando owner.



Also, while I am at it, My gearbox is leaking oil from these two bolts on the front



Can I remove these and replace the O rings without upsetting anything inside the box?

If so, what size are the O rings that I need to get?

Also, it is leaking from the gearlever.
What is involved in replacing the O ring there?

Thanks for your help everyone.

Your coil mounting setup is very similar to mine except I have a different Accel coil model (140402). I had problems in the rain (bike would die) and had to goop up inside the spark plug boots at the coil with clear silicone sealer. It was arcing from the HV terminals to the low voltage connections on the coil right thru the boots when it rained or after a trip to the carwash.

Russ

ludwig said:

I see you have the old type of head steady . These tend to crack . You should replace it with the later , box type ( or by something better)

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yeah, the rubbers are cracked and it doesn't look like there is much life left in it but it is just one of the many things on the list to do. I was thinking about having a go at making one of the rod-end type eventually. I want to also convert the rest of the iso's to vernier style and try and get some of that "bend in the middle" feeling that the bike has.

Sunday.


I spent yesterday morning driving around the bike shops trying to find some 135 main jets and finally found them at the last place I went to, Motorcycle Masters.
Fitted them this morning then took the bike for a ride. MASSIVE difference. The bike now runs great and after a wash at the local car wash and some bits and pieces like cleaning and oiling the chain, checking and topping up the oils, a bit of polish on the tank I took it out for a ride. I managed to get it up to about 90mph and it seemed to do it pretty easy though it didn't have much left in it so I think I might have a bit more fine tuning to do. After the ride, I stopped in to get some air in the rear tyre as it was a bit low. I was then reminded why I should buy some new tyres before going 90mph again.

Here is the front tyre.



Here is the rear tyre sidewall




And here is the rear tyre tread



I am going to try and get some time to polish the rims this week and then I will take them in to the Bike Doctor and get some new Avon AM26's.

The new tyres are fantastic. AM 26 Roadrider 90/90-19 front and 100/90-19 rear.

I only have about 50 miles on them so far but the handling has really sharpened up and the ride has improved.

The only things that I really need to get sorted now before Bunbury are the oil leaks. There are three from the gearbox, two from the engine and one from the Primary cover.

I fixed one of the engine ones simply by tighten the plates on the end of the rocker spindles. The exhaust ones on both cylinders were loose with the right side leaking enough oil to douse my trouser leg in a 20 mile ride.

The engine is also leaking from the sump plug which doesn't have any kind of washer on it at the moment so should be a simple fix with a new fibre washer.

The gearbox is leaking from the quadrant bolt and the selector cam bolt as well as the gear lever.

This is the gearbox leak that I mentioned in a previous post and my first point of attack.



If you look closely, you can see a small stream of oil running down from the quadrant bolt. What you can't see is another one running down from the camplate bolt below and to the right of it.

To my dismay, I found that none of my spanners fit either of these bolts so it was off to the shops for a 3/16 whitworth spanner.
I was a little shocked when I saw the price but I needed it.



Yes, that does say $48.85 for one spanner. I also bought a 1/4 whitworth which was $53.20.

First job was to get the bolts out and remove the old O-rings. Not an easy task when they had gone hard and appeared to be siliconed into place. I managed after some effort to get a scriber in and pry them out.
Looking a the washers that the O-rings sealed against it is no real suprise that they were leaking. There was a shallow groove worn into the steel washers by the rubber O-rings. I am always amazed when something made of a soft material manages to cause more wear into a hard material than on itself.




I took out my combination sharpening stone and used that for facing the washers to get them nice and flat so that they would make a good seal with the O-rings.



After the stone I used some of the 2000 grit wet/dry to "polish" the washers.




Below are the two new O-rings and one of the old ones.



It all seems to be holding tight now.

Next on the list will be the leak from the gear lever.