TheSamba.com :: View topic - What Are the Symptoms of a Bad Ignition Coil?

Sat Oct 25, 2008 11:32 am

I have a stock 1600DP, new Hot Spark 009, new H30/31 carb. I can't seems to tune the rich out of it. The only thing not new is the coil so I was wondering if a bad coil could cause persistant richness.

Sat Oct 25, 2008 11:37 am

donmac wrote: I have a stock 1600DP, new Hot Spark 009, new H30/31 carb. I can't seems to tune the rich out of it. The only thing not new is the coil so I was wondering if a bad coil could cause persistant richness.

These have a bad rap.

It could, but it would be unusual.. usually ignition problems show up under load, with cutting out and such.

It's probably the carb or fuel pressure.

Sat Oct 25, 2008 11:58 am

Replacing the stock Bosch coil or Bosch Blue coil can certainly improve your performance, but it's not going to affect your fuel mixture problem.

It's unlikely that your ignition coil is the problem. But if you have another ignition coil laying around, it only takes a few minutes to swap it in to assure yourself that the ignition coil is not your main problem.

The condition of the highest fuel mixture density will be the hardest to fire the spark plug. Full throttle will produce a high fuel mixture density and your ignition system voltage will be dropping at high RPM. So High RPM Full throttle conditions are usually the worst case, and when missing usually occurs with a weak ignition system.

Scott Novak

Sat Oct 25, 2008 12:07 pm

When they get hot, it will miss. At high RPM's it'll miss. You'll have a weak spark, and go through a lot of plugs. It'll get physically hot to the touch...

But before you accuse the coil of being bad, ohm out the poles and see if it is wired up backwards. (The labels aren't always on the same side as the old ones...)

If I were you, I'd check my float level as well as main jet size, and fuel pressure. If all that is in spec, see if the pilot and power jets jets are reversed. Lastly... make sure your choke isn't stuck.

Go ahead and install some new plugs right from the start... no sense trying to tune her up if she's full of goo.

A lot of these beasts are hugely over-jetted because folks think they "Run cooler" with a big jet. They'll also foul up plugs, spit soot... The reason so many end up with rich jets:

If it has gotten real cold suddenly... it is possible your heat riser is plugged up and your intake is icing up. It'll smell stinky rich, run poorly and not return to idle worth a darn when the choke is off. You can get around without the heat riser working, by going up a few sizes on the main jet... horrible gas mileage, but at least she'll run till you clean out the exhaust. It makes no sense, but without manifold heat she has a lean condition... even though your dumping gas in by the gallon.

Good luck.

Sat Oct 25, 2008 1:49 pm

Swap in a new coil (or a friends) and, if the problem persists, it is not the coil.

Sat Oct 25, 2008 1:59 pm

"you cant tune the rich out of it"

Do you mean you cant get the idle screw in a position where its not running rich?

Or you cant jet it to not run rich?

Sat Oct 25, 2008 2:17 pm

krusher wrote: "you cant tune the rich out of it"

Do you mean you cant get the idle screw in a position where its not running rich?

Or you cant jet it to not run rich?

Turning the idle screw in till it dies, turning it back out seems too rich. White smoke on startup.

Sat Oct 25, 2008 2:20 pm

Rocknrod wrote: If it has gotten real cold suddenly... it is possible your heat riser is plugged up and your intake is icing up. It'll smell stinky rich, run poorly and not return to idle worth a darn when the choke is off. You can get around without the heat riser working, by going up a few sizes on the main jet... horrible gas mileage, but at least she'll run till you clean out the exhaust. It makes no sense, but without manifold heat she has a lean condition... even though your dumping gas in by the gallon.

Good luck.

Yes, it smells stinky rich and interestingly my heat risers are blocked off by design (aftermarket exhaust). Maybe I should drill them out? The temps are in the 70's though.

Sat Oct 25, 2008 2:46 pm

Without heat risers it takes more fuel to keep the correct mixture in suspension in the air.. more drops out along the runner and when you snap the throttle open, that all gets pulled in and PEWEE! Rich!

Heat risers - GOOD.