WEAK SPARK

[MTrat]

Maybe this is rethrashing an old topic, but can we get some input on causes of a weak spark and what to check for to improve spark..

[racerclam]

that may depend in if its points or CDI

Rich

[MTrat]

Points.

[taber hodaka]

I have seen engines that looked like a weak spark seem to run well. I would say points, condenser, coil.-----Clarence

[racerclam]

Does it run ?

[MTrat]

A current (no pun intended) spark situation on a Wombat prompted the question. It runs but the spark seems pretty anemic when kicked over with the plug out and grounded. A Cycle magazine article from 1975 included some interesting tests and results of different coils.

[racerclam]

you could buy a Hot Wire for it , that will perk it up , check it out on thunder products.com

[Al Harpster]

I thought the same thing about the spark on my Ace. Replaced points, condenser and coil under the tank. No change in spark appearance.

Used one of those adjustable gap spark testers that can be connected with the plug in the head. Seemed to test OK.

Decided on using the Denso Iridium plugs. Supposed to spark hotter with less voltage.

Can't say it really helps, but I do prefer them. Seems like a little more throttle response.

Rock Auto has them at reasonable prices, ships to your door for 3 bucks by USPS.

You may find this helpful and it's rather cheap & easy.

[matt glascock]

Hmm...I've been informed that the iridium plugs were more appropriate for bikes with PVL ignitions and the standard NGK nonresistor plugs worked better with the stock magneto ignition. Interesting.

[Bullfrog]

. . . and don't forget to closely inspect the wiring AND ESPECIALLY the connectors. Corroded connectors can easily cause increased resistance and that is a baaaaad thing in the wiring between the magneto coil and the high tension coil under the tank.
Ed

[Hydraulic Jack]

Wombat specs call for a steady fire across a 7mm gap at 500rpm and 8mm at 5,000rpm. If it will do this, it doesn't matter what the spark looks like. You will need a spark tester for this so you can watch the spark, adjust the gap while the bike is running, and not get zapped.

Plug choice is up to you. The magneto doesn't know or care what kind of plug you use. I stopped using standard NGK back when they came out with the iridium plugs. They don't last any longer, and they will foul just like a B8HS or whatever you use, but I like the way they look, so that's what I use.

The one component no one seems to check anymore is the spark plug lead and cap. Pull the cap and see if the wire is corroded or arcing under the cap. There is an article somewhere, and a video on YouTube, on how to replace the lead. There are lots of solid copper core wires out there to choose from.

[MTrat]

Has anyone here used a non-stock coil and, if so, what one?

[Al Harpster]

Hydraulic jack is right. If you use the test he suggests you've got something you can trust.

Looking at the spark on a plug grounded to the head is like looking at pretty girls.

It's subjective.

[racerclam]

I use iridium and have for years in by bikes and my hot rod truck. The do last longer in my truck been running thsame set since 2003 . But in your bike you will never get to run them long enough to verify before they get muddy . But I'm speaking of electrode wear , most wont ever see that in a regular plug either unless your getting detonation. Iridium is great for high rpm and super charged stuff where cylinder pressure creates more resistance for spark to jump the gap. The fine iridium wire concentrates the voltage making the spark more able to jump .

Rich

[Bill2001]

Harbor Freight carries a spark tester like that. And an auto parts store that sells Lisle tools may have one.