Author Topic: kh125, I need help!  (Read 10751 times)

Offline Graeme77

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Re: kh125, I need help!
« Reply #30 on: December 02, 2015, 06:41:22 PM »
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!

Offline matthewmosse

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Re: kh125, I need help!
« Reply #31 on: December 02, 2015, 09:38:34 PM »
If you can wait a few weeks I may have a spare... kh bits are way down the pile. Keep watching ebay too.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline Graeme77

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Re: kh125, I need help!
« Reply #32 on: December 02, 2015, 09:53:02 PM »
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 :)

Online Johnny4428

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Re: kh125, I need help!
« Reply #33 on: December 03, 2015, 08:33:15 AM »
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.
1952 Cymoto on Triumph bicycle.
1961 Matchless G3
1974 Honda CB550K1. Running resto,
1978 Honda CB550K3.
1999 ST1100 Pan European 50th Anniversary.
1975,1980,1984,1986 Honda C90’s
1973 Honda CB750K3

Offline Graeme77

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Re: kh125, I need help!
« Reply #34 on: December 03, 2015, 04:00:43 PM »
It jad crossed my mind, but it wont even cough on ether. Not even if I squirt it down the plug hole.

Offline hairygit

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Re: kh125, I need help!
« Reply #35 on: December 03, 2015, 04:16:39 PM »
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.
If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline Graeme77

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Re: kh125, I need help!
« Reply #36 on: December 03, 2015, 05:17:07 PM »
Yes.

anyhow, new coil winding in progress :)

Offline Spitfire

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Re: kh125, I need help!
« Reply #37 on: December 03, 2015, 06:46:00 PM »
That's one impressive set up

Cheers

Dennis
1976 CB750F

1977 CB750F2 In bits

1964 BSA A65R In bits

Offline Graeme77

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Re: kh125, I need help!
« Reply #38 on: December 03, 2015, 07:05:25 PM »
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.


Offline totty

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Re: kh125, I need help!
« Reply #39 on: December 03, 2015, 07:15:46 PM »
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.

Offline Graeme77

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Re: kh125, I need help!
« Reply #40 on: December 03, 2015, 07:30:05 PM »
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!

Offline matthewmosse

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Re: kh125, I need help!
« Reply #41 on: December 03, 2015, 07:57:38 PM »
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.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline Woodside

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Re: kh125, I need help!
« Reply #42 on: December 03, 2015, 09:11:41 PM »
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

Offline Graeme77

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Re: kh125, I need help!
« Reply #43 on: December 03, 2015, 09:24:36 PM »
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.

Offline Graeme77

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Re: kh125, I need help!
« Reply #44 on: December 05, 2015, 03:18:50 PM »
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?

 

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