need a new coil?????

[norman]

On my KZ750 am only getting spark on plug when touched to engine about 7 out of ten.

Points OK

Plugs and HT leads ok

Any suggestions Please

😕 😕

[norman]

The coil on it appears to be an aftermarket unit it is japanese in origin

If i need a new one any good sources please.

💡

[norman]

Hi

have both plugs out of engine attached to ht leads and touchinh engine

one plugs sparks every time and the other 7 out of 10 this is with freshly charged battery on electric start

[Kaptainkwak]

right thats a clearer picture.

Firstly if one plug is sparking 10 out of 10 then the coil itself is fine as its the same one for both plugs so that can only be the Lead, Plug Cap or Plug itself.

Have you tried swapping the plugs round to see if the problem switches sides? that would confirm/eliminate the plugs.

Next try the same with the Plug caps and finally, as you think its an aftermarket coil, will the HT leads unscrew at the coil end? If they do and neither of the above 2 ideas give results i would fit new HT leads.

Let us know

KK

[BiqueToast]

norman wrote:

..one plugs sparks every time and the other 7 out of 10 this is with freshly charged battery on electric start

I’m one of those people that believes in replacing the coil without hesitation. You’re going to need them sooner or later anyway…

Both the stock coils on my 750s were crap – and I didn’t know this until I got new ones and got to see the difference! They were misfiring just like you describe. When under heavy acceleration, I always felt this sort-of… hesitation… stammering…

Anyway, I got a 5 Ohm Dyna (for bike with points) and wires from z1enterprises.com… with the current exchange rate, that should be pretty affordable for you chaps, I’d imagine.

[norman]

Thanks kaptain and Bique

I’ll try a combination of both

Regards

BPH

[Kaptainkwak]

I cant disagree with biquetoast as i havent had that problem.

If you want a new coil i have one here. Its a 3 ohm as opposed to the standard 2.2 ohm that is stock. Will send it for ?30 inc P&P if yer interested mate, thats what it cost me.

[Laudanum]

I can get new coils for ?25 2.2 ohm, although to be honest I’d buy kap’s as you get a better spark with 3 ohm, just make sure your points and condensors alright.
Another thing to consider on a twin is that the spark goes from earth through the plug then the coil and back out through the other spark plug. So if one sides got a better spark than the other the chances are its either the leads, plug caps or spark plugs.
If the windings were breaking down the spark would be going down on both plugs.
One last thing is to check the polarity of the coil, if the leads are arse about tit the spark is trying to jump against the impedance of the charging circuit.

[BiqueToast]

kaptainkwak wrote:

… the standard 2.2 ohm that is stock…..

Was that Ohm rating for the later models with electronic ignition?

[norman]

Thanks all for the advice.

However just to keer things going would it be better to strip the lot out and put in electronic ignition and if so any reccomendations.

Regards

BPH

[norman]

And kaptain I’ll take up your kind offer of thet coil as i have another rather crappy Z750 which one day may roll again.

can you let me have your address and i’ll send funds to you asap.

regards

BPH

[Kaptainkwak]

Quote:

kaptainkwak wrote:
… the standard 2.2 ohm that is stock…..

Was that Ohm rating for the later models with electronic ignition?

Good question biquetoast. I got that from my manual and assumed it applied accross the board. I will have a look tonight.

[whipkwakaway]

one question norman …
what model are you talking about ??

[norman]

Hello Whip she is a 1978 Z750 B 2 or 3 I suppose.

Regards

bph 😕

[whipkwakaway]

no problem sir ,
a b2 should have …
the front caliper forward of the fork leg ,
three screws on the front left hand engine cover for the coil field ,
a seperate regulator and rectifier ,
and the engine and chassis numbers between 016101 and 025700 .
hope that helps !!

[Author]

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