Fortunately we have some good people out here, a fellow motorcyclist stopped to check out the bike while I was trying to get it fired up, he went and got his van and gave me a ride home.

The first symptom was what seemed like spark cutting in and out while coasting down. Once on the throttle it was fine, cruising was fine, it ran good enough to get me pretty far from home before it just died. I suspected a fouled plug since I had forgotten to reconnect the spark plug lead for the first few kicks and I assumed it was a little loaded up. Pulling the spark plug cap and testing with a spare plug on the side of the road revealed no spark. Removing the plug cap from the plug wire revealed pretty strong and consistent spark from the wire to the head. I assumed a new cap would get it going.

Once I got it home and installed a new plug and new cap, I did have spark but the bike still would not run. I got a few hits, it ran very briefly but nothing more. At the present time, spark is intermittent and the bike is inoperative. This sucks, it's been running quite well lately since the last round of motor work.

I suspect the pulser has given up. I swapped out the CDI box with a spare, no change. I do get better spark directly from the plug wire than I do through the old or new plug cap. This seems odd. Do these things require a low resistance cap? I'm also wondering it something electrical was damaged while kicking with the plug lead disconnected. It seems likely since the bike ran great last time I rode it on Saturday.

First i'd pull the flywheel & check the crank key, although it should still spark--just in the wrong place. Then push the bare lead onto the plug thread, just wriggle it around & it'll go on & hopefully stay there. Not sure after that without testing resistances of stator source coil & pulser. I did have a faulty pulser on mine & came up with a dodgy plan to run it solely on the advance half which worked--30 or so years ago.

Just be a bit careful when kicking a bike over . CDI's can produce very high output voltages
and without a sparkplug connected , to earth out the charge , they can actually do
internal damage to the CDI Box . Always have a plug installed on the HT lead, and earthed
out to the motor .

If the cap is the original there is a resistor and a compression spring that is removable after unscrewing the female brass terminal that slips over the male spark plug terminal. On one of my dt360s the resistor was an open circuit. There was a carbon trail on one side of it where the spark was apparantly jumping to get to ground through the spark plug. The bike would run but would misfire under light acceleration.

From what I scratched up about the cap it was a 5K resistor. New caps can be purchased through Yamaha and they will be the hard plastic with rubber boots type and not the chunky all rubber type.

The new caps are NGK and can be purchased for about $4 at an autoparts store in the US.

Since the B9 plugs were discontinued through my local source I started using the BR9 ones and replaced the open resistor in the OEM cap with a solid rod of 0 ohms resistance.

The flywheel key is good, it's all timed up properly relative to TDC.

I'll try to take my plug cap apart just for kicks, I believe it is original. I don't have much hope that will solve the issue since it is present with a new cap as well. Perhaps if I do the same as you did, eliminate the resistor in the cap and run a resistor plug, it might work.

I have a coil on the way. The highest voltage by far is generated in the secondary winding of the coil, I'm hoping that the coil has broken down and is not sending all of the juice through the plug. If that doesn't do it I'll have to order up a new ignition system. NOS parts for this are very scarce to nonexistent, and if you do find something like a pulser coil it going to cost damn near as much as a whole modern 12v system.

I have a Kawasaki 350 Bighorn I just picked up and my hopped up KE250 to ride until this Yamaha gets sorted out. I'll be alright.

I went ahead and ordered up a Rex's full race 12v kit. Further prodding and screwing around with the stock CDI system has produced nothing but a few very loud blasts out of the exhaust.

I did learn a bit about the stock design through this process. The two staggered grooves machined in the inner hub of the flywheel seemed odd, now I understand that the pulser contains two separate coils and reads each groove separately. One provides a delayed signal for starting and the other is used to run the CDI at normal engine speeds. I don't know if these pulses are read separately or in series but I suspect that without both pulses the engine cannot run. Perhaps with only one of two it is only firing every other revolution and way off of TDC.

There are zero NOS pulser coils available and I figured if I did find one it would be damn expensive. Rex's kit was about $450, comes with an advance/retard curve and increased spark and lighting output. I expect a significant improvement in overall performance over the stock CDI, which as far as I know only retards timing during starting and maintains the same advance from around 1500 RPM all the way up.

Turns out it was the ignition coil. The 20 dollar yz80 coil from ebay got this thing going in two kicks. At least I know all of the other components are good. Perhaps I'll sell the stuff when the rex kit gets here.

I also found it very surprising that my spare stator works. I had left it on the bike after I had thrown in the towel and it fired right up with a good coil. The thing looks like it has been under water for several years, pulser and all. Apparently its fine.