Frustrated Beyond Measure

I am very disappointed with myself and with my Norton. It has never been right and it seems that I can't make it right. Every time I gear up for a ride I spend the day jacking with it. Bear in mind that this is Debby's old bike and it was built with care. According to my notes from Debby, the engine is a 1974 840 and has been rebored to first oversize with new JCC pistons. The head was rebuild by Jim Comstock and included exhaust thread repair and new exhaust valves. Plugs are Autolite AP64.

Running analysis: The bike runs great in mid range. It pulls hard on acceleration and runs great at speed. I have had the bike up to 70mph on the highway. It may be my imagination but it seems to take a lot of throttle and some time to get there. It has always been hard to start when hot. It is an issue that even Debby couldn't seem to remedy. I live in fear of a flame-out in traffic. Stops are the worse. It's not like I expect it to idle but it pops and farts, stumbles just as I am coasting to a stop. The fear of hard starting makes the bike un-fun to ride in any kind of traffic.

Some History: Debby used non-ethonol gas. I have no access to non-ethonol gas so I use the highest octane ethonol gas. The gas usage does not effect the running or starting issues. The only changes I made, in the beginning, were installing bigger jetting for Texas flat lands. I am running a 240 main, needles at mid position. Debby was running 180 mains and the needle was set one notch lower in Colorado. It uses two Amal 932s. These carbs have the brass sleeves. I just got through tearing both carbs down. I drilled factory plugs for a straight and open pilot circuit. I then cleaned the pilot circuits (clear and open with carb cleaner clearly squirting through every orifice.) I checked needle heights, jet sizes, float height settings, the carb balance and everything else I could think of. Timing is Pazon Electronic Ignition set at 28* at 3000 rpm. (Today, I retarded the timing by 1 degree to see if this made a difference. It maybe made it worse but that's hard to tell.) Plugs are new and have no color. The old plugs were light ash brown in color.

Note 1: I had an issue with the left side farting and popping but the right side seemed to be fine. After writing this screed, I installed new plugs. No change. I swapped plug wires side to side and the popping and farting stopped. Strange. Road test today indicted that the popping and farting is worse. It acts like you would expect a bike to act if it were cold.

Note 2: In the recent past I have been able the start the bike consistently by holding maybe 1/3 throttle.

Note 3: Tickling the carb in hot starts does not help at all. Pulling the choke on does seem to help.

I have been considering replacing the Pazon EI unit with a Wassel unit. I am running a Wassel on my Triumph which works fine. I have also considered replacing the dual lead coil and the plug wires but I hate firing a parts canon at a problem when I do not know what the problem is. (I am starting to think it is ignition related.)

Any help or thoughts would be greatly appreciated. I really want to ride and not wrench.

How do you set the pilot air screws?

"Pulling the choke on"? You pull the choke off on a commando.

How did you decide on 240 main, if it had been running ok (I suppose) for Debby with 180?

Slow to rev? Could the cam timing be off a tooth? (don't ask how I know) If your going to change ignition get a Tri Spark

In my experience it makes little difference on the main jet unless you are really wringing it's neck

My 74 850 came from the factory with 260 mains jets and I run 270 in it with the work my motor has, bike runs great starts first kick every time I think the M111 had 220 main jets standard, so maybe your jets are too small and slow to get up and go, what size pilot jets you running.

What silencers are you using? Stock air filter? Take a temp reading with an infrared off the
pipes and head?
I had similar issues. Usually is careful sync of throttles and adjustment of the air screws.

B+Bogus said:

How do you set the pilot air screws?

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Pilot screws are set one and 1/2 turns out. It seems that turning them further or less makes no difference of because of a lack of consistency, in the first place, has little effect.

Tornado said:

"Pulling the choke on"? You pull the choke off on a commando.

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By "pulling the choke on" I meant pulling the choke lever around to raise the choke plates and render them off.

Big_Jim59 said:

Pilot screws are set one and 1/2 turns out. It seems that turning them further or less makes no difference of because of a lack of consistency, in the first place, has little effect.

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I know you’re not gonna like this after what you’ve done, but those are symptoms of a partially blocked pilot circuit.

Spraying carb cleaner through only proves they’re not 100% blocked, they can still be partially blocked and pass plenty of carb cleaner through !

Personally I’d say your best bet is to ring Greg Marsh and buy a pair of Amal Premiers already checked, tested and set up for your bike …

Issues like this are difficult to solve over the internet because many things can contribute.

If I had been going at it for this long without success I would go back to basics.

1. Pops and backfires are often due th leaking either in the inlet or exhaust manifold system. Check your header pipes are tight and sealed.

2. Take the tank off and inspect all the wires and connections carefully. I had similar issues with a wire which been trapped by the fork stops and partially cut. At random times it would cut off the ignition. I had a similar symptom from the ignition trigger wire blowing back in the wind and melting against the exhaust balance pipe.

3 check the ignition switch. They can get bad connections inside. Even if the key ring has too much weight from other keys it can turn off.

4 Of course check the kill button or switch if still fitted.

5 check the coils. You should have 3.5 ohm. With a Pazon you should have either resister plugs or resister plug caps. Not both. Check the HT leads and if fitted resister cap for 5 k ohms. Forget the resister plug or cap and you will get popping and backfiring just like you describe.

6 check the tappet clearances. This will also answer the question if one of the cam lobs are badly worn.

7 Now we come to the carbs. First off I'd look at the cables. Check how the choke works and how off and on works. There are still people getting it the wrong way around. Using 1/3 lift to start suggests to me the carb sync and cables are badly out. Next I'd clean the carbs in an ultrasonic bath and check the two tiny holes into the throat infront and behind the rear of the slide are open. If it were me I'd also check float heights. Follow the Amal or Bushman carb instructions and I'd put all settings as per the book. I'd only look to change if the aircleaner or mufflers were different of I was a high elevations.

8 You sound like your timing is OK. It can be worthwhile checking that the timing marks are accurate. Mine were 1.5 degree out. Static time at 28 deg and around 30 at 3000 rpm plus shoukd be OK for normal compression. 28 to 29 for 10 CR.

9 as I said above. When you put the carbs back on check for inlet tract air leaks and use petrol proof sealant. Check the balance pipe tube for leaks too..

ashman said:

My 74 850 came from the factory with 260 mains jets and I run 270 in it with the work my motor has, bike runs great starts first kick every time I think the M111 had 220 main jets standard, so maybe your jets are too small and slow to get up and go, what size pilot jets you running.

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My bike is running the 260 mains and needle jet is 106. Pilot jet is what ever came with a Amal 932.

Ethanol fuel can cause carb problems of all sorts.

 Glen

I just reread you post. What does this part nean?

"It uses two Amal 932s. These carbs have the brass sleeves. I just got through tearing both carbs down. I drilled factory plugs for a straight and open pilot circuit. "

I don't understand the brass sleaves or what you drilled.

Maybe a new pair of premiers would solve the issues but rather expensive.

If not carbs, I think Mean Gene is right to raise timing. Those are symptoms of being over-retarded. If the EI is timed correctly, the valve timing could still cause the same, if a tooth out. More than that and I'd guess you'd hear the pistons hitting the valves?!

johnm said:

I just reread you post. What does this part nean?

"It uses two Amal 932s. These carbs have the brass sleeves. I just got through tearing both carbs down. I drilled factory plugs for a straight and open pilot circuit. "

I don't understand the brass sleaves or what you drilled.

Maybe a new pair of premiers would solve the issues but rather expensive.

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The Amal Premiers come with a removable pilot jet. The off side plug is drilled and taped for a threaded plug to allow full and total cleaning of the pilot jet and passages. (You can actually look through the pilot jet and see light!) By "off side plug" I mean the blanked off area opposite the air screw.

The "brass sleeve" means the the slides are not the original pot-metal aluminum slides but are brass sleeved. This is the first time I have seen this but I understand that it is done to allow the old carbs to idle. And yes, I am thinking that a new pair of Premiums would do the trick but I have to be willing to touch off the fuse on the parts canon.

Big_Jim59 said:

I just got through tearing both carbs down. I drilled factory plugs for a straight and open pilot circuit.

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Does this mean you no longer have pilot jets?

johnm said:

Issues like this are difficult to solve over the internet because many things can contribute.

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Thanks Johnm! I am going to put the bike in the shop and go through your list. Some of them are not applicable since I am running a toggle switch for ignition but I get the point.

Big_Jim59 said:

The Amal Premiers come with a removable pilot jet. The off side plug is drilled and taped for a threaded plug to allow full and total cleaning of the pilot jet and passages. (You can actually look through the pilot jet and see light!) By "off side plug" I mean the blanked off area opposite the air screw.

The "brass sleeve" means the the slides are not the original pot-metal aluminum slides but are brass sleeved. This is the first time I have seen this but I understand that it is done to allow the old carbs to idle. And yes, I am thinking that a new pair of Premiums would do the trick but I have to be willing to touch off the fuse on the parts canon.

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Possible to borrow a pair you know are working, first?