kh125, I need help!

[Graeme77]

New coil, plug cap and condensor and a long conversation with some 2 stroke guys and it still wont fire.
deffinately spark though. Pretty sure exciting coil is shot, cant get any resistance from it any more.
Turns out they arent available anymore and all the magnetos on ebay are 3 coil, my bike is 2 coil.

Looks like im going to have to learn to rewind coils!

[matthewmosse]

If you can wait a few weeks I may have a spare... kh bits are way down the pile. Keep watching ebay too.

[Graeme77]

Well, im going to have a stab at rewinding it tomorrow. If that doesnt work ill have no choice than to wait and see what comes up on ebay.
If you do find one, let me know.
Ill update this thread after I try the rewind.

Thanks

[Johnny4428]

Hi Graeme, Just a thought regarding kh125. I know absolutely nothing about these bikes, but have had some experience with two strokes. I have an engine that just would not run and discovered to end up with that there was too much oil and not enough fuel, didn't have to reduce by much but no problem after that.

[Graeme77]

It jad crossed my mind, but it wont even cough on ether. Not even if I squirt it down the plug hole.

[hairygit]

But have you tried ether and a new plug? If excess oil is an issue, it only takes one kick to make a plug wet, once it is, it won't fire.

[Graeme77]

Yes.

anyhow, new coil winding in progress

[Spitfire]

That's one impressive set up

Cheers

Dennis

[Graeme77]

Thanks.

I finished coil. Original was measuring very low on resistance. New coil (I could have done it a bit neater) measured 2 ohm.
Spark is a bit better but bike still wont start.

I compression tested it. One kick gives 110 psi. Checked with 2 testers.
I figured thats good considering the rings arent bedded.

When kicking it over and measuring voltage at the ignition coil I get 0.5v dc or 2v ac, not sure which measurement matters.
Im guessing thats still not enough (been told it should probably be near 6v?)
I guess this means the spark is still too weak to spark undet compression.

Plug is 100% deffinately getting wet.
So, got fuel, timing perfect, got compression, got spark.

[totty]

Do you have a colour tune? It's basically a spark plug with a window used to set the fuel mix, but for your purposes you'd be able to see if it sparked under compression.
The other option is a gap test,  if it'll jump say 3x the normal gap it should spark under compression.
If it sparks it sounds like a timing issue.

[Graeme77]

I have somewhere. Ill see if I can find it.
Timing Is spot on. I set it with the head off too to be sure!

[matthewmosse]

On mine I needed two base gasketts to get the spark at just the right time, going by the crank timing marks I holed pistons from pre ignition. Hence setting timing with a dti gauge mounted into a modified plug, this got it reliable - ie I went further than 4 miles on a piston.

[Woodside]

On mine I needed two base gasketts to get the spark at just the right time, going by the crank timing marks I holed pistons from pre ignition. Hence setting timing with a dti gauge mounted into a modified plug, this got it reliable - ie I went further than 4 miles on a piston.

That rings a bell...I remember a friend of mine rebuilding his large 2 stroke motox bike..and for the life of us it wouldn't run..after speaking to some more knowledgable guys on the subject a thicker gasket was needed ....it fired pretty much first kick with it fitted....I couldn't belive the extra mm or so made so much difference

[Graeme77]

I must say, it didnt look like the timing marks equates to the 20 degrees btdc that I think its supposes to be. Looked more like 10-15 degees.

[Graeme77]

IT RUNS.

I have wound 2 coils but it still wouldnt go.
I found a colour tune kit and put that it to see if ii sparked under compression and it fired right up?

So, whats so special about this colour tune plug?