Got a problem, plug won't stay one darn color

[Desert Rat]

66C skyhawk
nt carb
48 sprocket
Everything is running great, getting 20 to 30 MPH
but when I ride then let engine cool off and check plug
one time it's a light brown
then the next it's dark chocolate and shiny but not wet
what could be up with this beast?

oh and yesterday boot from cdi came apart replaced it with a spare.

It has been finicky from the start I would think air leak but have tested
for that. I'm using oil at 24 to 1 have carb needle set at richest setting
all this for 1200 ft elevation

 

[maniac57]

Try a magnet swap. Some with iffy timing have been seen lately and it can make a world of difference. Maybe a buddy you can borrow one from to test?
But be aware, sometimes you just get a dog of a motor with chinadolls. I have seen some that just never ran worth a damn no matter what I tried. Sometimes all the bad tolerance parts end up in the same block and it's doomed to be boat anchor.
Jetting makes a big difference too.
I'd trust what makes the engine run happiest, not the plug color.

 

[Desert Rat]

Try a magnet swap. Some with iffy timing have been seen lately and it can make a world of difference. Maybe a buddy you can borrow one from to test?
But be aware, sometimes you just get a dog of a motor with chinadolls. I have seen some that just never ran worth a damn no matter what I tried. Sometimes all the bad tolerance parts end up in the same block and it's doomed to be boat anchor.
Jetting makes a big difference too.
I'd trust what makes the engine run happiest, not the plug color.

Thanks maniac
That's part of the problem, motor runs great and ran great before
but I lost a piston and jug with plug being a light brown, however I chalked it up
to not having the g clip retainer clip on piston wrist pin.
the new motor had the funny u shaped clip o shaped whatever.

let me ask, could the cdi be putting out a variable voltage?

don't have anybody to swap out magneto suppose I'll have to buy another and try it.

 

[Desert Rat]

Finally pulled out the multimeter
and used 2doors giude actual readings at bottom

2door
Default Re: testing a magneto?
If you have an ohm meter, your dad will know how to use it, try this:

Use Low Ohm-Meter Scale About 200 Ohms

Magneto Coil

1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms

As for keeping water/dirt out. Make sure the gasket is good or seal it with a small bead of silicone and fill the hole where the wires exit the case with the same silicone sealer.

Tom

Actual readings




Use Low Ohm-Meter Scale About 200 Ohms

Magneto Coil

1) Check Ohms between BLACK wire and WHITE wire. Reading is around 5.2 Ohms
2) Check ohms between BLUE wire and WHITE wire. is at 350 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity) check
2) Positive lead on BLACK wire and Negative lead on BLUE wire. is at 139.5 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. is at 152 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms
following these instructions its at 6.6 ohms


Beyond taking the readings I don't know what they indicate
please help
Thanks
Ron

 

[crassius]

mag readings look good, but I've never trusted any readings from a CDI since they don't show timing info (that's why I built my tester)

 

[KCvale]

66C skyhawk
I'm using oil at 24:1

Too much oil in the fuel, go to 32:1, (4oz 1/2 cup) of synthetic to a gallon of good fuel.

Are you running an NGK 5944 (BPR7HIX) Iridium plug? They work best and all I use, I even found some NGK Iridiums for the 49cc 4-strokes I build, going to try on this new build today and see if it makes as much difference as the Iridiums do in a 2-stroke.