no spark why ?

sid1988 · Post by **sid1988** » Sat Mar 16, 2013 11:23 pm

can anoyone help with this conundrum .... put new rectifier on bike started bike checked the charge output got 12.7v at idle 13.7v at 5000rpm an above turned of bike went an had a sellebrity cup of tea went back out went to star it again. nothing just a back fire then nothing. wounded it over some more then it run. then turned it of tryed to start it same all over again . so pulled all 4 plug's out fucked about a bit. found it would only spark on an of sometimes you turn the engine over for a why'll nothing then you stop roll a fag try it again then a spark (it's got a dark purple spark) pulled loom fuse box an every thing to bit's cleaned everything in the loom an fuse box still the same . so checked the pulse generator got 350 ohms thats ok checked primary winding resistance 2.6 ohms thats ok tryed secondary windng's got 15.1 k ohms thats all ok .. so there's me now standing there swearing looking at a 14lb sleghammer ... has it done the worst an fryed the cdi box with the 18 volts it was getting ?

Post by **CMSMJ1** » Sat Mar 16, 2013 11:39 pm

Simple answer.

Started bike, turned bike off wihtout it getting warm = fucked plugs

New plugs and you'll have it sorted.

You can try to clean, dry the plugs on a gas hob and try again, no throttle, full choke.

Dead plugs is no1 cause of a bike refusing to work when all else is right

Post by **Neosophist** » Sun Mar 17, 2013 4:47 am

CMSMJ1 wrote:Simple answer.

Started bike, turned bike off wihtout it getting warm = fucked plugs

New plugs and you'll have it sorted.

You can try to clean, dry the plugs on a gas hob and try again, no throttle, full choke.

Dead plugs is no1 cause of a bike refusing to work when all else is right

Or dead battery.

If you have a weak spark, have you tried charging the battery with a battery charger first?

Overcharging a battery is the easiest way to kill it.

magg · Post by **magg** » Sun Mar 17, 2013 7:47 am

Repeated engine starts without running time to charge the battery is not good for the battery. What is the battery voltage while the engine is cranking, also what is the voltage on the ignition coil terminal with the black/white wire when the engine is cranking?

sid1988 · Post by **sid1988** » Sun Mar 17, 2013 9:28 am

should of put this in last night's post did go out an get 4 new plug's and another battery even though the old one was only a month old charge em both meter tested them both 12.5 volts as thought it be handy to have 2 battery's with all the cranking over so i could swop them over an recharge one why'll the other was in use ... will cheek voltage at coils again to be sure but think it was fine

sid1988 · Post by **sid1988** » Sun Mar 17, 2013 2:28 pm

well so you all know it's definitely the cdi box nothing wrong with rest of bike . i took the cdi box of first thing i could smell burnt electric's so i cut the box open an there's a big round black resister looking thing that's blowen in half need a new one ... thank's for all you help on here gent's bin a great help

magg · Post by **magg** » Sun Mar 17, 2013 9:08 pm

Sid1988, would you be interested in mailing the dud ignition unit to me, happy to cover postage to Australia if reasonable.

sid1988 · Post by **sid1988** » Sun Mar 31, 2013 10:42 pm

hi sorry for the late repley . i took the cdi box to bit's to see what went wrong with it an found that it had blowen the varister which is about the size of a 5 pence peace an black in colour . it is designed to protect the circuit board from high voltage which it did. so brought a new one from good old ebay soldered it in work's fine an back on bike total cost to fix £1.99p . the varister is a znr k220 . but if i hadn't of fixed it i would of posted it to you .... sorry fela

sid1988 · Post by **sid1988** » Sun Mar 31, 2013 10:43 pm

magg wrote:Sid1988, would you be interested in mailing the dud ignition unit to me, happy to cover postage to Australia if reasonable.

hi sorry for the late repley . i took the cdi box to bit's to see what went wrong with it an found that it had blowen the varister which is about the size of a 5 pence peace an black in colour . it is designed to protect the circuit board from high voltage which it did. so brought a new one from good old ebay soldered it in work's fine an back on bike total cost to fix £1.99p . the varister is a znr k220 . but if i hadn't of fixed it i would of posted it to you .... sorry fela

magg · Post by **magg** » Sun Mar 31, 2013 11:44 pm

Not the first time a failed varistor has stopped an NC ignition control unit. It sometimes results in other failed components but quite often all can be repaired. Question is why the varistor failed, a dud rect/reg that over-charges the battery is a possible cause.

The potential battery over-voltage issue is what prompted my other post regarding boost chargers and boost starters, they often supply 24 volts or more to kick the electrical system into life and therefore could stress the ignition control unit varistor, particularly if the boost voltage is applied a number of times.

Although the varistors primary role is to suppress short term voltage spikes, poor electrical system connections can also cause repetitive high voltage spikes that can eventually degrade the varistor to the point that it fails.

Good to hear that you fixed the problem and was cheap into the bargain.

no spark why ?

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