hard start when cold

[DimitriT]

This is a 1982 GS550.

I recently updated the top end and it has great compression and runs strong.

But it seems to suffer from an electrical issue.

During my top end work I pulled the headlamp fuse (the 10A fuse for the headlights) so I could save the battery while I was working on the bike.

I noticed that when the headlight was off, the bike would start up right away. But when I put the fuse back in the bike would have difficulty starting.

It would still crank strong but it would just spin and eventually stumble to life. Once it has run up to temp I can start the bike without a problem until the next day.

This problem is easily reproducible.

I'm guessing the problem is either in the coils or with some wiring going to the coils. Removing the headlights allows a bit more voltage to reach the coils and allows the ignition to work.

I've heard of people doing a bypass to the coils and I was thinking of doing something similar. I would tap into the ignition switch (which goes to the starter relay) and add another relay which would turn off the headlight while the ignition switch was on. This is actually a common thing for most cars.

Seems like a nice solution to the problem, rather than replacing expensive stuff.

Thoughts?

 

[Burque73]

Have you checked the voltage and connectors at the coils?

The wires to my coils were nearly severed because the factory had them pulled too tight. While fixing the bad connections, I decided to go the extra mile and install an ignition relay.

http://gsarchive.bwringer.com/bikecliff/images/coil_relay_mod.html

Not sorry I did either. Starting is a breeze and I swear it runs better, smoother idle.

These were the stock connectors going to the coils.

20200412_164301 by Roger, on Flickr

The inline fuse from the battery to the relay

20200412_164711 by Roger, on Flickr

The relay is bolted to the frame right behind the coil.

20200412_162806 by Roger, on Flickr

(The blue goop is rather ugly on the coils I know, it's high temp RTV sealant. After replacing the spark plug wires, I didn't trust the epoxy to keep water out.)

 

[Gorminrider]

yes, first Do check your ignition wiring for good connections (including kill switch) and lowest voltage drop....also the battery.

The trouble I have with relays on the ignition is that you rely on them for the bike to run. It's very bad if the relay fails...
If the commonly used NO (normally open) relay is used, you are relying on the relay's contact points AND it's electro magnets' windings...so you'd better use a really good one. BUT-

If you want a little more juice for the coils when the starter is spinning, I think you would be better off to use a headlamp relay that is NC (normally closed) but opens when the start button is pressed...ie the relay is tapped to the solenoid' wire. Or just install a manual headlamp on-off switch.

 

[DimitriT]

If you want a little more juice for the coils when the starter is spinning, I think you would be better off to use a headlamp relay that is NC (normally closed) but opens when the start button is pressed...ie the relay is tapped to the solenoid' wire. Or just install a manual headlamp on-off switch.

That's sort of the idea I was going with. A manual switch might be fine too but I'd have to find a place for it. Although a switch like that might be useful in other situations (like a dead battery or a failed charging system). The 8616 mini relay that amazon sells for less than $10 has an NC and an NO connector.

 

[Gorminrider]

Yes , sorry, you did say that. Best way I think, if the bike has that kind of personality. One "newer" bike I have has a relay and two have real on/off switches as OEM, but I always seem to end up putting one on if they don't come with them.

just a thought, but If using a plain switch, if it's "sprung" you won't forget to turn your headlamp on while riding. Microswitches and buttons are normally "sprung", while the usual toggle type is not, if you get my meaning.