86 GS450L lost spark on one side

[Headspin]

OK.. this thing is driving me nuts!

Now I lost a spark to one pot. It starts on two, but when it warms up it drops off.

I don't know where to start? Would it work at all if it was the ignighter?

I'm reading about signal generators going bad too... that seems likely.
I guess I can test the coils... not sure if they would fail when they got warm?

The rectifier does get warm.. but I'm guessing that's normal, judging it by the heatsink fins.

So, if anyone has any experience of the most probable cause, please let me know.

Thanks.

[Headspin]

OK.. I took some meter tests.

Book says the signal generating unit should read 6- - 80 ohms
Mine reads 66 ohms - which is a good thing

Secondary coils should be 23 - 25 K ohms
Mine read 22.4 so that's on the low side

Primary coils should be 3.5 - 4.5 ohms
Mine read 4 and the problematic side reads 4.7

Is this really enough to cause my issues?

It's still intermittent.. happens when it gets warm. So.. does anyone think it could be the coils?

[Headspin]

...Anyone??

[suzukibuck]

I had the same problem with my 450, except no spark at all on right side. I found a couple of ignition coils on ebay. I bought both (one for a spare), and installed one and it fired right up.

[Headspin]

THANK you for the reply.... I just swapped the coils over and once warmed up the other pot dropped out...

For a while I wasn't sure what I had proved, until I realised I also swapped the plug leads over... meaning the same coil is giving the issue no matter what I do so it HAS to be that.

Great to get a reply and confirmation though

[Headspin]

For future reference.. and anyone else searching on this issue.. It was the coil.
eBay saved the day and I'm up and running again..

I have a 87 GS450 and my coils came from an 81 model.. they are very different. I had to use an angle grinder to widen the gap and also grind the bracket to get it closer to the frame as the older ones are fatter. After that, the tank wouldn't fit on as the fuel sender was catching on it. I had to cut 3/8th of the mount post and grind down the bolt to get it to fit. It's only held on by one post. I had to have it angled away from the frame at the front a little so the HT lead would reach the plug...

Thanks all..