Fuel or Electrical?

[meltroy]

Hi Guys,
Im new to the forum so hope you can help. My 1985 GS 550 EX started cutting out after a mile or so with what i thought could be a fuel problem. I tried everything but all seems ok so I now think it maybe electrical. The bike starts fine and is great or a mile or two, but then starts to lose power and cuts out.

After 10 minutes cool down it starts fine again with rough tick over but then a mile or so later it cuts out agin.

Could this be the coils over heating?

Any help would be much appreciated.

[tom203]

I hope this is not a bad ignitor (fails when it gets warm- cuts out). Members maddog and obsidianghost might be able to offer some clues to this problem.

[Big T]

What's "everything"?

[tom203]

meltroy said....".but then starts to lose power and cuts out.
...After 10 minutes cool down it starts fine again with rough tick over but then a mile or so later it cuts out agin. "

"the starts to lose power" gives me second thoughts...so rule out a fuel delivery problem, like a bad petcock, or a tank that isn't venting right ( building up a vacuum and not letting fuel head to carbs)

[spyug]

Welcome.

On the face of it, your diagnosis about a failing coil is, IMHO, dead on the mark.

With fuel issues, the bike seldom runs right for any length of time, then runs poorly, then clears up in a cycle. Its usually runs properly or hits a stumble at certain ranges, or is hard to start then clears its throat under hard throttle or symptoms like that.

Now, as mentioned it could also be the ignitor but I don't believe they break down like that, they either go or don't.

I have had the exact same situation in one of my earlier bikes a Yammie. It would start and run fine for 15 to 20 minutes then breakdown and eventually quit. Give it 15 minutes to cool down and it would start and repeat itself. As explained to me the coil works fine when cold as the internal windings remain intact. As it heats up, the wire expands and likely pulls apart at a break.

I think new coils are in your future.

Good luck with it and let us know what you determine.

Cheers,
Spyug

[duaneage]

Petcock. Run the bike on PRI and if it goes away there you are.
Might be clogged filter inside the tank on top of the petcock.

Two pairs of coils would not go bad at the same time, not possible. It's most likely a fuel delivery problem. Start with the petcock, then check the floats by draining fuel from each bowl into a cup, should be substantial amounts come out of there and should be the same across the rack.

[spyug]

Two pairs of coils would not go bad at the same time, not possible

True, but you only need one for it to act the way it is. I will be really surprised if it does turn out ot be fuel related.

Spyug

[Killer2600]

True, but you only need one for it to act the way it is. I will be really surprised if it does turn out ot be fuel related.

Spyug

You got one in for electrical

I'm going to put one in on fuel issue

Easy check is to bring along a known good spark plug and do a spark test while your broken down waiting 10 mins - Just pull a plug wire, stick on your good spark plug, lay the plug on the engine, give her a crank, and see. Do this with a wire from each coil and you'll know what you got.

[TheCafeKid]

Need more info:
What's the intake set up? (stock airbox or pod filters)
What's the exhaust system? (stock or aftermarket?)

Have you tried pulling a plug when it gets hot and cuts out to see if there is spark?
Could be a lot of different things including simple over heating because the bike is running too lean. Could be a bad igniter, could be a bad coil, etc etc.

[spyug]

Any further into the diagnosis and testing? I'm interested in seeing what it is.

Good luck,
Spyug