'57 Huntmaster- Engine running problems - again

[roger.attwood]

I've been moving the carb needle up and down a notch to try to improve the engine running, and taking the bike out for a run of 8 to 10 miles. Each time the engine starts to 'miss' after about 5-6 miles, with the 'miss' getting steadily worse. The 'miss' is irregular, but the engine pulls OK in between. After the first run I adjusted the needle, but couldn't re-start the bike. I had a spark but it appeared weak. I left it until the morning, and it started first kick.

Although the fuel is maybe 6 months old, the engine runs well until the 'missing' starts.

My feeling is it's a heat problem in the mag. Heat from the engine gradually soaks into the mag, perhaps causing a problem with the capacitor. I don't think the mag had been rewound since first fitted, and the capacitor is probably still the original.

I've been toying with the idea of fitting electronic coil ignition - the type that fits into the existing mag body. Has anyone experience of fitting such a system? The Thorspark system says the engine is timed using a timing gun (http://www.sussexmotorcycles.com/thorspark.html) . What part of the engine is the gun pointed at?

Any comments/advice much appreciated.

[Graham.Goral]

My Huntmaster had similar symptoms - cured by an exchange mag armature obtained via eBay and fairly easily fitted. However, on reflection, I wish I'd gone for electronic ignition because the costs are broadly similar and (with the right installation) you can fine-tune the ignition timing without having to faff around removing the the timing chest cover. There's another thread on a Dutch electronic ignition system which will even allow you to re-map the advance curve - and Steve Carter has a system which will accept dry batteries as a get-you-home backup if your charging system fails.

[Steven.Carter]

As Graham says I've got it fitted on two of my Huntmasters. I certainly know that a good mag is the better option as it leaves you free of the charging system. With electronic ignition 12 volts is always needed but again like Graham said it will run for 100 miles on just 8 aa batteries. Also I like the extra discipline relying on my charging systems instills in me. My lights always work, well most of the time
The Thorspark unit is the easiest to install. It uses the existing mechanical auto advance and simply just goes in the end of the mag with the points removed. I've put the twin spark coil under the tank in the triangle formed by the frame rails up near the headstock.

The thorspark instructions allow you to get the bike running but to get it accurate you need to get the strobe out.
My method is to strip the clutch and primary cover off then refit the clutch without the outer primary cover fitted. Then I can get at the engine shock absorber. With the engine running you fire the strobe at the shock absorber. I use a drop of white paint and a piece of wire to mark the correct position at full advance. It's fun to watch as you can see the advance working as the revs increase. It's easy to adjust as you've only got to turn the magnet.
Your not far from me Rodger so if you need a hand just give me a shout.

Steve

[roger.attwood]

Thanks for the info, Graham and Steve. Does it have to be 12 volts? I'm still on 6v, and there is a 6v Thorspark kit. Could you use a step up 6 to 12 volt transformer just to run the electronic ignition if 12v is preferable?

[Steven.Carter]

I've just gone for 12 volts because for me it was easier. I suppose you could use a step up transformer but adding an extra layer of complexity is just looking for another way of breaking down. If you want to stay with 6 volts then I'd get a 6 volt thorspark kit.

[ColinPeck]

One thing worth giving some thought to here. My Huntmaster charges fine under normal circumstances but in 4th gear I need to be doing 35 mph to be actually charging. On a few occasions sitting in heavy traffic with my lights on I have flattened the battery, so sitting at traffic lights I had no lights until I pulled away again. The battery's fine, it just drained with the bike not running fast enough for a long-ish period of time.
I looked at belt drive for the dynamo but ended up fitting LED head and tail light bulbs, these have made a huge difference on battery drain and I haven't had any discharged battery issues since. Fitting an ignition system which relies on battery power to work means if you lose battery power you're stuck, so an upgrade of the charging system might be a good idea?
I realise many people with classic bikes will only use them on high days and holidays so hopefully won't get stuck in situations where the battery could get discharged. However at least with a mag you will always get home, providing it's working of course!
Colin

[Leejm]

Like Colin I have fitted leds everywhere on 6volt I only use 1 amp. I have the short 45 watt dynamo, so running higher wattage bulbs is out of the question and the leds are nice and bright. But the travel from the head light is not as good as a halogen. But still 100 times better than a 25 watt bulb. I have a 13 amp hour battery so no worries about running the battery flat in stand still traffic.

[roger.attwood]

I take note of the possible problems with the battery running flat. I have a 13ah battery also, so hopefully, I'll have no problems. I've been following various threads on LED bulbs, so I may go that route too.

[Leejm]

Leds are a God send on our bikes with poor charging systems. The lights are usable and the draw on the battery is very little. Being stuck in traffic is no issue and no chance of running the battery down. I have spent years riding around in the dark. I had a wm20 at the age of 19. No halogen with bpf Base then. It made no difference if the head light was on or off . I could see bugger all either way! The days of riding in the dark is final over.

[roger.attwood]

Steve, going back to your method of timing the bike with a strobe on the shock absorber. There's got to be a way of doing this without removing covers.

Firstly, why does it have to be at full advance. I'm sure I timed my old Fiat 128, and BSA C15 (side points) with no advance set. Does anyone know where the piston should be at full retard?

Secondly, as I won't be using the mag (if I get the Thorspark system), I won't have HT leads coming from the mag. Under the HT lead connection is the slip ring, and this must surely be synchronized to the speed of the engine. Can I make a mark on the mag body, and a corresponding mark on the slip ring (having first set up the piston etc) as a timing mark?

Am I missing something?