New Norton Owner; tuning questions

desmo said:

i hope you have the straight through peashooters ! a friend had the same bother with baffled silencers
changed them and it was cured

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I believe they are the open pipes. Here is a picture I took earlier.

1up3down said:

well, it may help the revving past 5000rpm thing with advancing the ignition a degree or two as I feel you have some room there

you say you have a Boyer electronic ignition, an older analog or newer digital that probably require resister plugs or wires
like NGK BP"R" 7ES?

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I believe it is the newer digital version; but I will confirm the next time I have the tank off.

My Dad and I were working on the bike this evening and he suggested that the black, sooty plugs may simply be an effect of exhaust leaks on both sides. This explains the dry soot; as the exhaust is being sucked back into the head and onto the spark plugs. The new gaskets arrive tomorrow.

Frankly, it just sounds to me like it's a bit rich jetting-wise. Did you do a plug-chop test to get the spark-plug reading or did you just pull the plugs in the driveway/garage and look at them?

Yes, pulled the plugs after letting it idle, then at half throttle, then at 3/4+ throttle for main jet indication. I'll swap the exhaust gaskets out today and then I feel I'll have more success with adjusting the jetting. I feel like I'm getting close, anyway. A few niggling front end vibration issues to solve next.

There is no way, an exhaust leak will cause a grossly rich condition.

Look elsewhere.

Verify ALL circuits, including air are clear in the carbs. There have been numerous instances of grease in new Premiers, mine included, and it caused problems in some.
Choke slides are properly held open.

Broken wires to the ignition can exhibit this EXACT SAME symptom.

How did it run BEFORE the new Premiers? Or not tested?

The bike would start, but barely idle or rev on the old carbs because the slides were so worn and stuck.

I agree that the leak isn't the mixture issue, but I believe it is the issue causing the popping in the exhaust and lack of power after 5,000 RPM. All I'm saying is, I feel I can address the mixture issue easier after fixing the exhaust gaskets. I guess I have two issues at the moment.

I have cleaned the Premiere's three times now; but I know sometimes it takes even more than that if I've missed something. I do believe my fuel level is also set too low as I experimented with that a week or so ago. I plan on fixing that soon by pulling the float bowls off, adding fuel via external tank, and setting the fluid level to .17" to .24" below the top of the bowl; according to this: http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels

Currently it has 106 needle jet, 17 pilot jet, 3.5 slide (also going to change this back to 3.0)

About the chokes; some people have suggested that the choke plungers should be in the "UP" position. Is this correct? As in, the cable is pulling up on the plunger and compressing the springs. I have never gotten this to work on multiple bikes with old and new AMAL carbs. I would love to be proven wrong about this, but no matter how many tries, the bike runs significantly worse with the chokes raised, all other specs as the manual specified.

I have not inspected any ignition wiring, but did check the advance curve at various RPM and it seemed to be close to the specs I found. Definitely close at full advance.

The choke slides should be all the way up when the choke is turned off
I would raise them further and throw them over the fence
And block off the choke cable entry point in the carb too or it'll pull air in
Your exhaust rose leak is not your problem
I'd stick with the 3.5 slides

I worked on an all original 74 850 that had the Premiers installed. 240 main jets. To get it running properly, I ended up with a 190 main. Runs as sweet as a nut with clean plugs. The newer carbs are so much better, you can use a smaller jet since you no longer have a lot of air leaking around the slides. This bike had the old factory mufflers, swapped them for a new set and it made a huge difference in how it ran. Even though the old factory pipes were straight through, the new ones really let it breathe.

adunham1 said:

The bike would start, but barely idle or rev on the old carbs because the slides were so worn and stuck.

I agree that the leak isn't the mixture issue, but I believe it is the issue causing the popping in the exhaust and lack of power after 5,000 RPM. All I'm saying is, I feel I can address the mixture issue easier after fixing the exhaust gaskets. I guess I have two issues at the moment.

I have cleaned the Premiere's three times now; but I know sometimes it takes even more than that if I've missed something. I do believe my fuel level is also set too low as I experimented with that a week or so ago. I plan on fixing that soon by pulling the float bowls off, adding fuel via external tank, and setting the fluid level to .17" to .24" below the top of the bowl; according to this: http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels

Currently it has 106 needle jet, 17 pilot jet, 3.5 slide (also going to change this back to 3.0)

About the chokes; some people have that the choke plungers should be in the "UP" position. Is this correct? As in, the cable is pulling up on the plunger and compressing the springs. I have never gotten this to work on multiple bikes with old and new AMAL carbs. I would love to be proven wrong about this, but no matter how many tries, the bike runs significantly worse with the chokes raised, all other specs as the manual specified.

I have not inspected any ignition wiring, but did check the advance curve at various RPM and it seemed to be close to the specs I found. Definitely close at full advance.

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“About the chokes; some people have suggested that the choke plungers should be in the "UP" position. Is this correct? As in, the cable is pulling up on the plunger and compressing the springs. I have never gotten this to work on multiple bikes with old and new AMAL carbs.”


There is your problem.

Not “suggest”, but rather, they MUST be pulled up, spring compressed.

Now, pull them up, start working your way back toward normal mixtures.

Some comments...

choke bodies need to be high up in the carb to be OFF. If they hang down then they richen the mixture...

the needle clips sometimes wind up the spring that holds them in their seated position, and that will appear as a rich condition (usually on one side if only one is seated poorly)

Running poor, or loss of power at WOT (wide open throttle) is almost always main jet size... especially if the bike runs well in all other ranges.

Too low of a fuel height level in your float bowl ISN'T going to make your plugs look too rich... If anything they would be leaner, but if you pull the bowl's off, undo the main jet to see if the needles on each carb are hanging down equally inside the needle jet. they should be protruding the same amount when you pull the main jet off.

As concours said, weak spark can also appear as a rich condition, but generally that effects the entire range of carburation, not just WOT. However, odds are in favor of if it runs well everywhere except the top end, that it's not from a weak spark.

Personally, I would pull the bowls and check the needle protrusion, then install the recommende size main jets, reassemble and go for a test ride... making sure the choke slides are UP!

I concur with oOnortonOo, loss of power at WOT is usually related to main jet size. More generally, it is related to fuel flow limitations.

Fuel flow can be limited by clogged screens in fuel taps and fuel banjos, crud inside the taps themselves, and by the orifice size in the needles and seats. If you have 0.100" seat orifice, you might try 0.125".

Slick

How can anyone think that blocking the inlet with the choke slide is normal?

Let’s use our eyes and common sense.

and I will say it again for you tuning wizards, if you don't need the choke than you are to rich and will have poor fuel economy. i ALWAYS keep the chokes . my bike needs them and i also get 55+ MPG US. on a 72 combat with amals. and have seen 60 MPG.

baz said:

I would raise them further and throw them over the fence
And block off the choke cable entry point in the carb too or it'll pull air in
I'd stick with the 3.5 slides

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bill said:

and I will say it again for you tuning wizards, if you don't need the choke than you are to rich and will have poor fuel economy. i ALWAYS keep the chokes . my bike needs them and i also get 55+ MPG US. on a 72 combat with amals. and have seen 60 MPG.

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A choke slide has nothing to do with how the engine runs once the choke is turned off its only used when the engine is started
My bike set up lean because that is where the power is
I spent a fair time getting the mixture spot on on my bike
I use a Koso narrow band 02 air fuel meter and mark off the throttle drum that way it's easy to see what mixture you are at any throttle opening
I tickle my carbs, press the starter button and the bike fires right up
If it's really cold I may need to tickle it again whilst it's running

A mate of mine has a theory that you should always keep the choke slides in a concentric carb because the weight of the slide helps dampen out the engine pulses that wear the slide out

baz said:

A mate of mine has a theory that you should always keep the choke slides in a concentric carb because the weight of the slide helps dampen out the engine pulses that wear the slide out

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Plus, they don’t eat anything.

bill said:

and I will say it again for you tuning wizards, if you don't need the choke than you are to rich and will have poor fuel economy. i ALWAYS keep the chokes . my bike needs them and i also get 55+ MPG US. on a 72 combat with amals. and have seen 60 MPG.

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I never use my chokes bill. I have a starting procedure that doesn't require them. I don't think my bike will idle all that steadily when it's cold, probably because I don't use the chokes, but I've taken heed of some sage advise not to idle the bike very long when I start it up because of the potential accellerated cam/follower wear. I kick it to life, with no chokes, then go..... by the time I've gone any distance it's warm enough not to need choke to idle well... What do you think of that?

i do not try to let it idle when it is cold but it helps for the first little bit when i start it from cold. one issue is unlike an automobile carb the choke does not have a way to raise the idle when on choke so it is a manual job for the rider to increase the idle speed. i also don't leave it on full choke but ease it off as i feel needed by the way it runs and sounds. another thing i have found is idle quality is also a product of the condition of the carbs and the ign. system you are running. an analog ign is not as good at holding a stable idle as a digital with the trispark being one of the best at this. but with my high failure rate i am now using a boyer micro digital and the pazon sure fire was the worse to hold a consistent idle but i blame some of it old carbs.

o0norton0o said:

I never use my chokes bill. I have a starting procedure that doesn't require them. I don't think my bike will idle all that steadily when it's cold, probably because I don't use the chokes, but I've taken heed of some sage advise not to idle the bike very long when I start it up because of the potential accellerated cam/follower wear. I kick it to life, with no chokes, then go..... by the time I've gone any distance it's warm enough not to need choke to idle well... What do you think of that?

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