dies/ no start after rain

My 83 750 has an electrical problem somewhere. For a day or 2 after a rain it will start then die and not restart. If I wiggle the wire harness under the seat I can sometimes get it running again. It is always a crank and no start condition, leading me to believe the problem is in the ignition circuit somewhere. But, I haven't been able to narrow it down any more than that. Anyone have any ideas??

 

alot of these old yamaha coils have cracks in them and if they are the stockers the plug wires themselves are quite old. THe other issue if you haven't updated your fuse box under the seat it is probably the time to do it. It isn't too expensive or hard it just takes some time to do and make things right. Chacal i believe sells a nice replacement box that take the automotive style blade fuses rather than the glass fuses.

 

+1 what MaximXX said.

 

I don't have a fuse box, just a few inline fuses. and I have replaced all the fuse holders with covered ones, and I haven't been able to find any cracks in either the coils or the wires. Whatever the problem is it is shutting down the ignition entirely because it won't fire at all when it acts up.

 

Next time it is dry and it is running fine take an spray bottle(like a old window cleaner bottle) fill it with water set the nozzle to mist and start misting things down. Personally I would start with the coils on min eyou couln't see the cracks untill I removed the coild and looked at them from the bottom side they were cracked inbetween where the wires go in. THen work your way out to the plug wires and boots. If you are still good then work your way back towards the seat. It could be a number of connectors that have just enough corrosion in them that the moisture complets a circuit and is gorunding something out. I guess one could unplug the connectors one by one and make sure they are all clean then lube them up with some di-electric grease to help keep moisture out.

 

I'll bet dollars to doughnuts that it's either your coils as said above, or it's the TCI module.

Both are known to develop age cracks, and they can be just hairline cracks and still short out your ignition. The TCI can be especially aggravating as even a humid, foggy night can cause it to stop functioning.

Try the spray bottle trick - that'll be an excellent way to track down which is the culprit.

Short of replacing the parts, there's a couple of things you can do. For the coils, the most effective I've heard of is smear them with a coating of liquid electrical tape or silicone. The TCI is a harder one - you can disassemble it, and coat it with a layer of dielectric grease to stave off electrical woes.