Help.. Poor spark *(weak yellow with new plug) wont start occational backfire when cranking. Fully charged battery. Have checked coils primary 3.2 Ohms (2-3.5 range ok) * these are general specs for RR Secondary 23.2 k Ohms (23-37k ok) Pulse coil 427 ohms (range 340-420) No shorts to earth anywhere between all test points and earth. MC-19 j should be 2.52-3.08 primary and 11.7-14.3k secondary. Pulse 315-385. Looks like my number pass RRL specs but are wrong for MC19 maybe RR coils and Pulsars. Have Taken the guts out of the CDI and it looks undamaged (no burns corrosion or obvious damage. (i have ordered a replacement anyway) Leads and cap are ok. Was running fine in the workshop before I took it outside and tried to start for a ride. Any thoughts on any thing else I should check, I cant do a peak value as only have a std multimeter.
Will get some cable and make up some new ones, the existing ones are already too short for a trim. My brother said "Use some Start uBastard' works every time as the spark is always shite and slight fowling of the plugs and curtains.
MC 19's did NOT use resistor type spark plugs, rather, their plug caps had a resistor in them (removable), running resistor plugs & cap resistors together will kill the spark intensity. Non resistor plugs are hard to come by these days.
Yes cant find non resistor plugs, have ordered a CDI (wont hurt to keep a spare someone will need one one day), ordered std ngk resistor plugs as that was what t was running prior to the problem. Also replacing leads and lots of start ya bastard. It was giving slightly low voltage (10.9v ) to the coil so cleaned up all connections now its 12.7) Removed cover and checked pulsers, someone had used silicone instead of a gasket and daggs from it were floating around inside so cleaned it and fitted a new gasket. Will fire it up again tomorrow and try to get a peak voltage read on the feed to the coil.
These little bikes have weak batteries, so the voltage at the coil when cranking sucks. My friend had an MC-19 that always started once you stopped cranking.
Thanks mate I have ordered one from China but my brother owns a wreckers and has some there and will bring one down to Sydney on the weekend for me to try. Yes tried a good battery 12.8 volts static and 10v while cranking. Pulsar coils pass test 422 and 424 ohms. Just finished Peak current tests output from pulse generator 1.14 and 0.90 (both seem in spec >0.91 read time can effect the 0.9 instead 0.91 so not sure if I should read anything into the 0.01 difference) Output from spark unit to coils should be greater than 128volts Mine read 142 an 90 volts so that looks bad. Should have a 2nd hand KY1 CDI to try on the weekend. Thanks for the help from everyone since the start of this drama, going back to play with my 1951 500 single Ariel, magnetos I do understand less complexity and crank speed is directly related to downward force on the right leg on kickstarter.
Getting new battery and plugs today, the CDI is out of speck so will be replaced as it was playing up at about 8-10k before. I had cleaned and rebuilt carbs as I thought that could have been the problem but with underlying CDI problem coil 1 may have been giving poor spark. Will keep you posted with the battery, cdi not here till weekend.
Well new battery been on charge all day 13.2 volts and tests as 155 CCA on load tester its a gel 12v 7ah from xcite, still drops to 10volts during cranking, the old battery was reading 115 CCA. Not sure if the tacho was reading as I was concentrating on multi meter and probes, have tested all wires and connections plus new plug wires. Didn't try to start as was running with dry carby so as not to wet the new plugs, awaiting CDI tomorrow, fingers crossed. May have to spin it with no plugs and see if it was the compression contributing to the high draw from starter motor or dodgy starter/relays/wiring.
10 volts with the starter motor is normal in my experience on bikes. That said, you will want to voltage drop test the large positive leads from battery to starter solenoid, and from solenoid to starter motor to make sure there is no excessive voltage drop. And then check all the earth leads and clean the fuse points.
Well finally got the 2nd hand CDI from my brother found out there are actually two different CDIs on the MC19 one has the yellow label and one red the yellow one (J 1988) has 5 pins on connector the 1989 K has 6 wires the extra is probably for speed limiter. This replacement unit has peak voltage to the coils of >150 volts gives a good spark on both 1-4 2-3, finished syncronising and started to put it together again, seems battery doesn't matter when it starts first touch. The moral is that if you have access to a peak voltage adapter and a multimeter trouble shooting electrical (wont start problems) are much easier. You will have coil and pulser resistances from your multimeter (mine passed) and peak voltage output from spark unit and pulsers. (mine passed pulser but failed signal to coils) Thanks to all that followed me through this experience I hope this information will help someone else.
