Hello, my name is XXXXX XXXXX I will assist you.
The most common failure on this model is the ignition pulse generator. It is located inside the right crankcase cover. Here is a link to a parts diagram for reference: http://partsfinder.onlinemicrofiche.com/wps/showmodel.asp?Type=13&make=hondamc&a=44&b=12&c=0&d=-IGNITION-PULSE-GENERATOR The pulse generator is part #2.
There are two of them inside the engine. They signal the ignition control unit when to fire the plugs on each cylinder.
You will need a multimeter to check them. They should show a couple of hundred ohms of resistance across each coil and they should have no contunity on either wire to ground.
They should also show a pulse of about 0.25 volts ac when the ignition is on and the engine is being cranked with the electric starter.
why does the coil fire the plug when grounded, but not in head?
Have yoy installed a new set of NGK sparkplugs in the rear cylinder ?
Or have you swapped the front cylinder spark plugs to the rear?
I moved frt to rear, also checked plugs for firing on frt coil all four plugs are new
Have you checked compression on both cylinders?
no, I haave a compression gage but need an aadapter for meteric threads
If the compression numbers are about the same on both cylinders then the next thing to check is the carburetors and fuel system. What is the history of the problem? Was any work performed on the bike prior to the onset of the problem?
No work, the bike sat idle for about 6mos. before I got it. I checked the carbs for obstruction and vaccume leaks
aand rear plugs show wet with gas when I pull them
If the rear cylinder is getting too much fuel it can foul the plugs and prevent them from firing. The most likely cause is dirt, rust or old fuel varnish built up on the float needle valve and seat or the choke enrichner is sticking on.
If you need further assistance with this or have additional information to provide just add a reply and I will respond tomorrow morning.
that's possible, I rained tank and carbs, put fresh gas in, but did not pull carbs, chock is stiff, not smooth, but if I put timing light on plug lead from coil it want light on rear coil but will on front coil. let me check choke cables and do compression test and resistance test and then get back to you. can I contact you next time or will I get someone else? You have been very helpful