Yamaha G1 Charge Coil questions

[Contrary1]

We have a 1984 G1 Gas that developed ignition troubles. It runs just fine in forward. However, we have no spark in reverse. Checked all the connections and followed the service manual diagnosis instructions. In doing so, it appears that the issue is with the charge coil. Across the brown and black wires I am supposed to have 350 ohms resistance. I have an open circuit across these leads. I have verified that the black does go to ground like it is supposed to so the black wire appears to be fine. HOWEVER, If I check the resistance of the charge coil while rotating the engine slowly by hand, I do get intermittent resistance (nothing consistent and extremely brief). So my questions are, 1) if I am having issues with the charge coil, why does it still run fine in forward. 2) how hard is it to replace the charge coil. 3) If I need a charge coil, where do I find one. Any assistance, advice, or info would be greatly appreciated. Thanks.

[1989Marathon]

Welcome to BGW!
Keep everything wired up, and with the keyswitch in the reverse position install a jumper from the white green wire coming from the CDI magneto, to battery ground. See if you get spark. If you do, it is a bad keyswitch.
If the CDI charging coil was bad, it wouldn't run either direction.

[Contrary1]

I have been a long time lurker at BGW but never signed up to post as I always have found the answers in other posts/replies.

I did check the switch with a meter per the service manual and it all appeared good (I checked all three positions and connections since I had it accessible at the time). When the switch is in reverse, the buzzer buzzes and it cranks over, just doesn't have any spark. That's why I moved on to checking the pulsar coil (had 14.9 ohms) and the charging coil (which had an open circuit except some intermittent resistance as you rotated the crank by hand). I agree, I didn't think it should run in forward but not reverse if the charging coil was bad but that was the only thing that tested wrong based on the service manual I have. Which is why I'm here looking for advice.

I'll give your idea a try tomorrow when I'm out in the shop.

[1989Marathon]

The switch can be bad and the starter will still turn over. The buzzer can still buzz. The ignition is on it's own set of contacts.
If you find that it fires with the jumper installed, check the connection of the W/G wire from the magneto, all the way to the keyswitch.

[Contrary1]

OK. Put a jumper on the white/green wire coming out of the engine and ran it to the negative terminal on the battery. No dice. It still had no spark in reverse. Using the connectors down by the engine, I checked the resistance across the pulser coil which was 14.9 ohms. I checked the resistance across the charge coil and it was 390 ohms (yesterday I showed an open circuit but I didn't have the ohm meter on the correct range so it wouldn't read it as it was out of scale....might be an excuse to get a new autogranging one). Both the Ignition coil and CDI Mag grounds test good as well.

Could the CDI unit up by the relays cause the cart to run in forward but not reverse?

[1989Marathon]

Remove the jumper from the W/G. In the reverse position, run a jumper from the W/R from the magneto to the W/R at the CDI and try again.

[Contrary1]

No dice. Ran a jumper from the W/R coming off the CDI mag on the engine and ran it up to the W/R on the CDI Unit by the relays. Still no spark in reverse.

[1989Marathon]

Remove the jumper. With the switch in reverse, measure resistance from W/G to battery ground, and W/R to battery ground. Put the switch in forward, and repeat the measurements. It turns over right? Just no spark?
Did you leave all the stock wiring intact when you installed the jumpers?

[Contrary1]

So far stock wiring has ben left intact on the tests. The motor spins over just fine, just no spark so it won't fire up.

Here is the latest test
W/G Forward 15.5 ohms
W/G Reverse 0.8 ohms

W/R Forward 0.6 ohms
W/R Reverse 13.9 ohms

I certainly appreciate your time and help. I'm a decent backyard mechanic and can fix most things but this one has me stumped.

[1989Marathon]

That's good.
Is the B/W on the CDI only connected to battery ground when the switch is OFF?
Is the Black wire at the CDI connected to battery ground in all key positions?
Swap the W/G and W/R at the CDI and see if it only has spark in reverse. It probably won't start, but check for spark.