No Spark until I turn the key off

I have a 74 850. That usually always starts second kick. I tried to ride it today and nothing. I haven't ride it in about a month. Work got real busy. Anyway I checked gas it was flowing great then checked the plugs a bit sooty. Cleaned them and kick nothing. Then I grabbed the plug with key on and got a shock. Then turned the key off and tried again nothing. Then shut off the key and spark. It has a Boyer I never had any problems with spark any ideas?

Thanks,
Guy

Check the pickup wires.

From memory with Boyer, it is normal to get a spark when you switch off ignition.
if you haven’t used the bike for a while my first suspect would be a pilot chamber blockage on the carb.

I should have said. Standard test for Boyer is to disconnect the two rotor wires (usually easiest done at the control box end) and touch the wires together. If you get a spark then the box is probably ok.

Battery on tender while bike not in use .....

Like SteveC said probably OK.

I was farting around flipping my ignition switch off an on real quick the other day and got fire on the left cylinder and little puff of smoke out of the air cleaner on that side. It's a Boyer MkIII and still works fine. I am swapping it up to a MkIV for he heck of it though.

Something that I am telling myself I have run into since resurrecting my old desert sled is the fuel I'm buying now seems to completely evaporate in the combustion chambers and in the intake tract much quicker than it did 30 years ago. If I let my bike sit more than 4 days, it is a PITA to start. It takes considerably more than 2 kicks to get fuel back into the combustion chambers. In my case the issue is fuel related, and has nothing to do with spark. I'm using Mikuni carburetion. Amals probably wouldn't have exactly the same issue because of the tickler feature. However, if your plugs show dry soot and have no odor of fuel, there may not be enough fuel getting into the combustion chamber to light a fire.

I know how the Mikuni choke is supposed to work for anyone that has the need to tell me how it works. I have low vacuum for a variety of reasons so it does take some extra kicking. Plus my right leg is not 18 years old anymore, so my kicks are kind of whimpy.

photoguy_43420 said:

I have a 74 850. That usually always starts second kick. I tried to ride it today and nothing. I haven't ride it in about a month. Work got real busy. Anyway I checked gas it was flowing great then checked the plugs a bit sooty. Cleaned them and kick nothing. Then I grabbed the plug with key on and got a shock. Then turned the key off and tried again nothing. Then shut off the key and spark. It has a Boyer I never had any problems with spark any ideas?

Thanks,
Guy

Click to expand...

On any coil ignition (other than energy transfer), the coil sparks when voltage is removed. So, if you mean that it sparked one time when you turned the ignition off, that's fine. If you mean that with the key off and you kick it you gets sparks, then you have a wiring or switch problem.

No I didn't kick it just switched the key off then spark. Thought it was wired that when I moved one of the spark plugs leads that I got a shock. This only happens with the key on. No I was not kicking it at the same time. If anyone one wonders. Just odd to me that it would spark after the key was off and no spark when kicking.
The battery was on a tender.

Simple test: pull a spark plug and ground it on the head. Turn the key on and hit the kill switch rapidly a bunch of times. If the plug sparks, your black box is fine (Because it sparked when you turned off the key I expect this test will show your box is working). Next test is key on and kick the bike. If no sparks, then something is wrong with your ignition stator or wiring from the stator. From there I’d leave the key on and start shaking the wires up from the stator and also under the tank. If there’s an intermittent short it will start sparking like mad when you find it.

when the trigger wire test no longer works,,,
If the triggering portion of the box has failed, it my not work as expected . The output transistor fails in two modes initially SHORTED and finally burned OPEN.
When shorted the manual on-off control acts like the points in a points coil system and it sparks. In the shorted transistor EI mode it acts the same way and will spark.
However if powered on all the time, the transistor will almost always eventually burn open and the power on/off test no longer gives false indication.