Tuning Duration

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Jan 18, 2006
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How long does your Norton stay in tune?
With standard 73 interstate, points & k&N pod air filter. I can tune mine up and be happy with the performance for five or six rides. during this time the edge goes off performance and smoothness, vibration of engine deteriorates. So a week or two later back to the tuning process. I think this must be normal. Is this due to points and plug burn in & deterioration?
How long has your machine been holding its tune?
Will electronic ignition hold the tune longer?
A Commando with electronic ignition and carbs in good condition shouldn't need constant fiddling with and I rarely touch spark plugs. What is it that you're having to do ?

The only thing that really makes mine feel rough quickly is a long ride in the rain. guaranteed to introduce roughness from the final drive chain and make the cables feel graunchy.

Weather conditions make a difference to mine. Late evenings or early mornings in the summer seem to be worth a few bhp

I have to say that I don't like K&Ns on Commandos. Despite playing with mains, needle positions and slide cutaways, I always seemed to be chasing a flat spot up and down the rev range. I had a single filter which fitted on both carbs.

I know that there are people who swear by points and I am quite fond of old singles with magnetos, but I wouldn't consider running a Commando without electronic ignition.
1974 850

This past year I pulled the single Mikuni off (first time in 10 years) had it ultrasonically cleaned and rebuilt it. only last year after nine years did it start acting strange......the boyer has been performing flawlessly for 10 years and other than having left the choke on for a minute too long here and there and fouling the plugs, they rarely get touched. I did a ride 1000 mile ride with 6 modern BMW GS's, 2 modern Ducati's and another 850 Commando this past summer and other than having the battery lead become loose, it was dream ride. the two of us on Nortons were constantly on the tail end of the pack, but who cares. It never rained and the air temp was constant but in the upper 80's to mid 90's daytime(mid 50's at night), elevation was from below sea level to +2500 ft. The other Norton (a 1973 850) had an Amal/Boyer combo.
SpitfireRick aka Eric
DG - I'll second the recommendation to go Boyer. Mine's been faultless for 20 years (it was pretty much the first mod I did after buying the bike) and as long as the connectors are sound, they are "fit and forget". This only then generally leaves the carb setup to fiddle with as there shouldn't be an issue running the recommended NGK plugs or a good quality equivalent. My 73 850 is my daily ride-to-work transport involving a brief blast over some hills and then into town for the other 15 minutes of the journey; about 10 miles in total each way. I got fed up with the recently fitted new dual MK1 Amals not holding their tune on idle and just-off-idle and was resynching them about once a week. Going to a single MK1 has eradicated this weekly chore entirely, and I can't remember the last time I touched the carb. So, go electronic ignition first and then see how it goes.........
G'day DG,

I bought my bike about 12 months ago it has Boyer and a single Amal after fiddling with it to sort a few problems out I haven't had to touch it since, it's stayed in tune, starts second kick and once warm runs pretty sweet.

Regards Mike.
This is good information to know since I am brand spanking new to Commandos. I bought an all new Sparx electronic ignition for my MkIII and it has a single Mikuni on it right now. Glad to know I won't be fiddling with carb adjustments every week once I bust this thing out in the Spring.

Your ignition points should go 15,000 miles without touching them. I currently have some 12,000 miles on a set of points and they're still going strong!

Thanks for all the input.
When the engine performance fades i normally go for the idle and air mixture screws on the carby's to try and smooth the engine running out abit. This mostly always works ok. If not I start checking the tappit clearence, points and then carby's again. This would generally get the performance up to scratch again.
I haven't checked the chain tension in under the timing cover, ever! If this chain drives the points then it may need looking at! If it only drives the oil pump then its not going to affect the engine running. I must have a look in the Clymers manual.
I think that you need to analyse what you are doing and why. Worn carbs will cause fluctuation and it might be worth checking the condition of the O rings on the adjuster screws. A smear of gasket goo won't hurt. Are you having to enrichen or weaken ? Faster or slower tickover ?

Before tuning the carbs, you should make sure that the timing is spot on. Are you using a strobe ? If so, is it advancing progressively ?

The timing chain doesn't drive the oil pump (a worm from the crank does that) but it does affect both ignition and camshaft timing. If your cam chain is slack or has tight spots, it will give the bob weight advance-retard a harder time and your timing will be all over the place.

Most of us went the electronic route because the cost of new points and back plate to replace the notchy original was not much cheaper than electronic. It is well worth taking the assembly off and making sure that it is clean and can turn easily if you gently move the weights

Do you have to adjust the tappets everytime ? Loose tappets will cause noise but have to be quite bad to affect performance. If they're closing up constantly, this will cause problems and suggests valve seat recession.

I would say that the timing chain meeds looking at. although timing was not all over the place.
Tappits are generally ok, keeping their settings.
Carbys are only 12 months old.
Motor recently strobed but needs checking.
Advance seemed to snap over to 28deg at 3000revs maybe springs need changing it did not seem progressive.
I think that the advance - retard may well be your biggest problem. It is certainly worth stripping it completely, cleaning and polishing the spindle and making sure that everything moves smoothly. It is a mechanical component and if it is over 30 years old, there is bound to be some wear.

I found that the smooth advancing and retarding was one of the biggest improvements of going electronic. The old bob weight system used to fly on to full advance and would retard just as abruptly, usually at just the wrong moment.
My bike's AAU still seems to be functioning perfectly after all these years. I think the leaky points seal the DPO was too cheap to replace kept it well lubricated! :lol:

72 semi-Combat
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