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Recent comparison new power arc vs tri spark

Classic Norton Commando Motorcycles.

Recent comparison new power arc vs tri spark

Postby Joe Schlaberdowski » Wed Mar 15, 2017 5:33 pm

Has anyone heard anything about the new (this year I think) power arc vs tri spark. I looked and the last comparison I saw was at least 4 years old. I know there is a new power arc that has either come out or is about to come out. I'd like to replace an old Boyer. Are there any good (new) magnetos with an advance unit, centrifugal or otherwise. Had an old Lucas mag (centrifugal advance if I recall) on a Matchless Norton in the '60s and it started easy. No battery, no battery worries. Well, maybe the passage of time has made it look better tban it was. I dunno.

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Re: Recent comparison new power arc vs tri spark

Postby dynodave » Wed Mar 15, 2017 6:33 pm

Not heard of much on comparisons, but as wanting the programmable version of trispark... I'm building a 11:1 combat cam atlas and I'll need to custom rein in the advance curve, to run our crappy USA EPA E-10.
I have only a little curiousity on the street products, such as the advance curve...
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Re: Recent comparison new power arc vs tri spark

Postby ashman » Thu Mar 16, 2017 3:23 pm

New Joe Hunts don't need advance unit to get them to run, they start first kick every time and will keep full spark till your motor goes bang, I have been running my JH for over 6 years now on my hot 850 and will never go back to any other ignition system ever, they are so good and the best thing no need for a battery to run your bike and if others say they need advance units then they have never owned or run a JH before, I have run them on my old Triumphs without any problems with advancing them, the faster they spin the bigger the spark and they idle great.

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Re: Recent comparison new power arc vs tri spark

Postby Joe Schlaberdowski » Thu Mar 16, 2017 3:46 pm

Well I'd like to ask the magneto guys: Anybody have problems with those? Nice even tickover at idle? Or slow cruise? Pull strong from a reasonably low rpm without knocking? I guess it's true they cost a lot. I think I could put up with one hanging off the side if it was an easy install and just ran -- like ran forever (at my age forever is probably not too far off).

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Re: Recent comparison new power arc vs tri spark

Postby JimNH » Thu Mar 16, 2017 6:34 pm

ashman wrote:New Joe Hunts don't need advance unit to get them to run, they start first kick every time and will keep full spark till your motor goes bang, I have been running my JH for over 6 years now on my hot 850 and will never go back to any other ignition system ever, they are so good and the best thing no need for a battery to run your bike and if others say they need advance units then they have never owned or run a JH before, I have run them on my old Triumphs without any problems with advancing them, the faster they spin the bigger the spark and they idle great.

Ashley


Are you saying that there's no centrifugal advance and that they're running at full advance all the time?

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Re: Recent comparison new power arc vs tri spark

Postby Triton Thrasher » Thu Mar 16, 2017 11:39 pm

JimNH wrote:Are you saying that there's no centrifugal advance and that they're running at full advance all the time?


He is. He says it quite a lot.
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Re: Recent comparison new power arc vs tri spark

Postby gripper » Fri Mar 17, 2017 2:24 am

Makes you wonder why all other ignition systems bother with an advance/retard system.

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Re: Recent comparison new power arc vs tri spark

Postby eskasteve » Fri Mar 17, 2017 8:03 am

Joe Hunt magneto advance curve. Never had one, but a friend that has used one for years sent me this link.

http://www.jcna.com/library/tech/images/tech0015i.jpg

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Re: Recent comparison new power arc vs tri spark

Postby kommando » Fri Mar 17, 2017 9:04 am

But thats a curve for a BMC Mini engine which has a distributor with vacuum advance and bob weights.
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Re: Recent comparison new power arc vs tri spark

Postby lcrken » Fri Mar 17, 2017 9:56 am

The Joe Hunt Magneto for Nortons does not have an advance mechanism. When used as a replacement for a Lucas mag at the rear of the engine (Atlas, converted Commando, etc.) the stock Norton mechanical advance mechanism is used to provide an advance curve. When used on a Commando and driven off the end of the cam, it has no advance mechanism, and is timed at full advance all the time. I've used that system on a race bike with no issues, but only had a brief experience with it on a street bike. When trying to kick start a high compression 920 with fixed advance ignition, I did have serious problems with kick-back, enough to break the mainshaft first gear on a Quaife gearbox.

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Re: Recent comparison new power arc vs tri spark

Postby jseng1 » Fri Mar 17, 2017 12:15 pm

You can have your cake and eat it too. You can set up the Joe Hunt magneto for a Commando with a lever arm that retards the ignition 20 degrees for starting. No kickback. Then flip it back when you're ready to fly. Ashman is right about the advantages of a magneto. I have the Atlas type with the auto centrifugal advance and it starts very easily.

Here's the retard lever assembly for the Commando type magneto (aluminum arm lower right).

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Re: Recent comparison new power arc vs tri spark

Postby lcrken » Fri Mar 17, 2017 12:30 pm

That's a clever mod, and should really help with starting.

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Re: Recent comparison new power arc vs tri spark

Postby grandpaul » Fri Mar 17, 2017 4:26 pm

I've gotta get me one of those starter advance covers for the JH mag on my '69 Triumph...
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Re: Recent comparison new power arc vs tri spark

Postby ashman » Sun Mar 19, 2017 12:19 am

In all the years of running Joe Hunt maggies on my Triumph for over 9 years and just coming up to 7 years on my Norton I have never had any problems with kick back while starting, when I set up the JH on the Norton I static time at 28 d and if I get any kick back I just retard it till no kick back you don't have to move it much at all, I have never used a timing light but normaly static timing is pretty close, my Norton takes one big kick when cold but once started for the day it will start with just a 1/2 swing on the kicker first kick every time.

As for any maintenance I have all my timing marks scribed inside the mounting plate, I set the timing marks at 28 d unbolt the maggie from its mounts and work on it on the bench then when I put it back on in the same position the timing is still set without retiming it, but in nearly 7 years I have only pulled it off for maintenance once, every oil change I pull the front cover off to put a few drops of STP on the felt to lube the points cam, but with the JH the plugs are set at 18thu instead of 25thu as standard.

One day I was coming home from work I was just down the road from home when my Norton got a slite misfire, I looked down to see one plug lead had come out of the maggie cover and the lead was hanging about 2" from the cove but the spark was jumping from the cover to the lead, the bike was still firing on both plugs with just a misfire on the plug that came out, I could see the spark clear as anything jumping, I didn't stop till I got home, I was very impress, it happened the first week of putting it on my Norton.

The new JHs have 4 rare earth magnets where the older ones were 2 rare earth magnets, I have been zapped with my old Triumph JH and I can tell you it friggen hurts, I don't even want to think about getting zapped by the one on my Norton.

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Re: Recent comparison new power arc vs tri spark

Postby o0norton0o » Sun Mar 19, 2017 10:11 am

I've done a lot of reading up about magnetos. Obviously, the retard lever which a few magnetos have is there to cure a design fault in magnetos, which is not having an advance mechanism. Some older magneto designs had an advance mechanism, but for some reason that design wasn't carried forward into most modern magneto designs. (although I did find some which have an advance mechanism)

Not having an advance mechanism doesn't lend itself to stop and go engine use as much as it does to power up and stay powered up engine use. This later type of engine use minimizes the need to have an advance mechanism and it's why a magneto's simple, more reliable design has no real disadvantage in engines on an airplane, some race vehicles or a lawn mower.

On a vehicle that has to stop and start, I want an advance mechanism. If it was an advance mechanism on a magneto that would be ok too.

When my dad was a kid, he learned to drive on a car that had an advance lever on the steering wheel, so as the engine sped up, you advanced the spark timing. To start the car, you retarded the lever or the car would backfire.

So,.... my question is,..... IF an advance curve is a good thing, (but obviously not essential) why don't modern magneto incorporate an advance mechanism into them? Look at some of the 70's and 80's car distributors. Many of them have a simple vacuum advance or bob weights. Why don't magnetos have that simple advance mechanism of some sort??
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