Forum

[Steve]

How many Ohms should I expect to measure between the kill button post and ground? Should it change if the points are open or closed? Trying to diagnose a starting issue on a 700 twin. Runs like a banshee once it is started. Thanks. Steve

[Adrian]

The kill button and its associated wiring shouldn't be conducting anything if you're not pressing the switch, it just earths the low-tension side of the magneto's coil when you do press it. Is the SR2 the same as the SR1 with the insulated stud on the side of the body?

A.

[Steve]

Thanks Adrian
I believe the SR2 and SR1 are similar except for the cam and cap. I have the side post for grounding the coil. The condenser is also attached to the post. Could you get a chance to measure the ohms for yours, with the points open and closed? I would be very thankful.
Steve

[Adrian]

Sorry, I don't have a meter! I have to use more crude methods. You're not the only one on this forum using one though, so somebody might be able to oblige.

It's possible there could be a condenser issue, but the cut out shouldn't affect it unless the kill switch isn't returning to the open position properly or the wire's shorting somewhere. Does it start more easily with the kill switch disconnected? If so, problem located, if not, new condensers are cheap enough, our hosts list them a £4.40 + the usual.

I seem to recall reading something back in the mists of time about the SR2-fitted twins not being the easiest to start, there is presumably a reason why Redditch abandoned the SR2 for the K2F magneto. Shame, as the rotating magnet design is better and condenser replacement (should it be needed) is MUCH easier.

A.

[mart]

I'm sure you have checked, but I wonder if your mag is not making a big enough spark at kickstart speed? I have a recently refurbed SR1 and that belts out a huge spark when turned by hand. just a thought.

[vince]

Hi, what gap are the plugs set at? I dont know where you get the impression that the SR2 is a bad starter. Normally mine is first kick. Vince

[Adrian]

Usually it's 0.020" plug gap for a mag and 0.025" for coil ignition, according to "the lore". Rex's Speed Shop used to recommend the racing HT lead (the black and yellow covered stuff) with a higher number of copper strands as an aid to curing reluctant starting with a more tired magneto. I had a look among our hosts' ignition accessories but they don't list it.

Also, are you using resistor plugs or suppressor plug caps? They're not recommended for magneto ignition, and could at least make starting harder, even if they're not a problem one you actually have the bike running.

What's the history of your SR2, Steve? Rebuilt? Came with the bike?

A.

[Steve]

The bike is a 1955 700cc Indian Trailblazer (a super Meteor in disguise). It has been upgraded with ~10:1 compression pistons. The magneto is rebuilt by a reputable US shop. The magneto gives a good spark when spun by hand or when kicked over with the plugs removed. The plugs are non resistor, gaped at -025", and are new. I have tried both Champion and NGK plugs. The wires are copper core with non resistor caps. It struggles to start, even with the Doc Z electric starter (my old legs get tired quickly). The carburetor is new, the fuel is 100 octane non-oxygenated. Compression is ~120 psi on both cylinders. I have a second rebuilt magneto, same results. Once started the bike runs quite well, having established a land speed record and improved it three subsequent times. My concern is that perhaps the magneto does not give sufficient spark with the higher compression ratio. Timing has been checked several times. The kill switch works. I have even disconnected it to no avail.
Steve

[vince]

Hi, plug gaps are a bit wide try .020. Vince

[Beezabryan]

Plug gaps .015 - 0.20 I usually use 0.018 for the Flash.

This is interesting -

http://brightsparkmagnetos.com/library/ ... %20SR4.pdf