Joe Hunt mag. Pro’s and Con’s for a tuned motor...

998cc said:

Loctite is the moral of this post!

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Or crank balancing ?

A good trick is to add a few drops of red locktite to the timing side mount magneto adapter plate where it fits into the timing cover. You can always remove it with heat but its not going to fall off.

Fast Eddie - I'm curious about the Electrex self generating EI and kind of disappointed you've ruled it out.

Accurately balancing a motor with std pistons will shake X amount.
Accurately balancing the same motor with heavier pistons will always shake worse because the vertical twin is inherently out of balance.

Funny you mention Fairbanks Morse magneto as I have one on my Wisconsin twin cylinder on my Howard Gem Rotivator. I was going to mention, despite having no experience with bike mags, the mag on the tiller has funtioned flawlessly since I went through the engine some 30 years ago. I cannot even remember what the thing looked like inside. However, the Wisconsin engine will light off first revolution of the hand crank after sitting for a year or more. I remove a threaded 1/8 plug from the intake manifold and give it a squirt of lighter fuel. Latch up the hand crank, give her one good umph, and chug a chug chug the old Wisconsin comes to life. If you want the finest tiller ever built, get youself an old British made Howard Gem. We have quite a lot of them around the Bay area as there was a lot of agriculture here in the early years. This one currently listed is a steal at that price. Get one if you like digging the dirt.
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My brother uses Electrex self-generating EI on both his 750cc and 500cc methanol fuelled Kawasaki two stroke sidecar outfits, which he uses on speedway. For racing two strokes, they are the only way to go. With four-strokes, finding a way to trigger and power them might be difficult. The power and triggering part of the system usually fits on the end of the crank. But at $600, they are almost cheap.

For a road race bike, a JH would be pretty good. But it looks completely out of character. With my own bike, I try to make it resemble something which existed back in the 60s and 70s. But that is just me. One of the things I really like doing at historic road race meetings, is having a look at old racing bikes which are genuine. Often you see things and think 'so that is how they did that ?'. I don't like Velocettes. But a few years ago I saw a Thruxton at Phillip Island which was nut and bolt perfect. It was a joy to behold. Historic racing has destroyed a lot of good bikes in Australia. Most guys these days would not know what an original Manx Norton looks like. Every one of them has something which is wrong on it. Even if it is only Japanese brake levers.

jseng1 said:

Fast Eddie - I'm curious about the Electrex self generating EI and kind of disappointed you've ruled it out

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Jim, fair point, allow me to explain...

When I was racing (mainly Triumph and Nourish engines) I spent a huge amount of time and money on fancy ignitions always believing there was a better way than the off the shelf stuff.

One was called “Runtronic” and was designed for model aircraft. Hence it was tiny and weighed nothing.

Then in one closed season reviewing the ‘lessons learnt’ from the year, I realised just how much agro and DNFs I had due to my fancy f***ing ignitions.

So, I bought an Interspan kit, huge and heavy by comparison, but wow, super easy starting, better running, although I didn’t compare it on the Dyno I believe it gave more power, and best of all... zero issues, ever!

Later on, I did some Dyno testing and learnt that these old bikes of our benefit greatly from super big fat sparks. I got 5 bhp more out of a 988cc BSA triple just by fitting a better ign with high voltage Dyna coils. Modern engines, especially those with smaller combustion chambers, do not need this. So something that works great on a little Japanese two stroke may well perform poorly on a great big 920 Norton.

All of that history has made me averse to being the front runner in this kind of stuff, I’m happy to follow others and go with the most proven route !

Fast Eddie - I'm with you on being averse to experimental ignitions. A racer once wanted me to try/test out a new EI. I called the maker and he tried to tell me the Norton would run great with 42 deg advance - he was generally full of BS. The racer wanted to market it but I refused to get involved. The EI maker must have sold him on the over-advanced timing because he ran 36 deg ignition advance with high compression. In his words "the more advance the better". He didn't seem to understand the basic requirements of Norton ignition timing and he was lucky not to blow up his motor. He ended up having a miserable year on the track including a filmed event where his ignition died on the starting line - embarrassing. Another tuner and I convinced him to bring his timing down to 28 deg advance and his motor survived.

There are three things which interact affect combustion temperatures - comp. ratio, fuel mixture and ignition advance. Normal practice is to set the ignition advance to suit the comp.ratio, then adjust the mixture. However the mixture is affected by the vacuum in the inlet tract, so the needles in the carbs are tapered. If the ignition system has a programmable advance curve, it is possible to keep the balance between those three factors better optimised. With high comp. you use more fuel and less ignition advance. Overall you should get more power, but probably don't in most cases.

With methanol in a low comp. motor you can run a lot if ignition advance,- at 9 to 1, I use an extra 4 degrees advance - but at 12 to 1 comp. standard petrol timing is normal when using methanol. At 14 to 1 it is wise the retard the ignition by about 4 degrees. With petrol as fuel, you do not have unlimited antiknock, so you are pretty much buggered when you further advance the ignition timing. If you added two degrees in a standard motor on petrol, it would probably be too much.
With some Harleys, the Dynatek ignition system drops to a less aggressive advance curve when the switch in the inlet tract senses loss of vacuum. However I have never had an engine detonate when using methanol fuel, even two-strokes usually seize or burn a piston first.

With Elf racing fuel , you might be able to use more ignition advance. The antiknock rating is probably higher. What is lean jetting at 9 to 1 comp. uses more fuel if there is more ignition advance. But the engine wear rate is higher.