1984 gs550es sarts cold, runs well, then won't start

[Guest]

Hey all, I just bought the title machine and its driving me crazy. I can start it cold and run it for a ride, but when I shut it off it will not restart. It tries to run, but won't catch. If I do get it started, it will die at low RPMs. I have cleaned the carbs (I work at a powersports dealer as a tech, so I have access to great stuff), checked compression, valve clearance etc. I do have spark, but it seems weak. The plugs are dry when it won't run, if I give it a hotshot it still won't run. I did measure voltage at the coils and got around battery voltage, but when cranking, the coils drop to about 8 volts. I am thinking that the ignitor is bad, but the low voltage at the coils concerns me. I do have a brand new battery in it and the float bowls are full, so I know its getting fuel. Can I run voltage to the coils using the O/W wires as a signal wire through a relay from the battery? Is there any way to see if the ignitor is producing the ground, or is it switching too fast? Really want this machine to run as my daughter just passed her MC driving test and class. Thanks, Chris

[Steve]

Yes, you can do what is commonly referred to as the "coil relay mod", but it would make more sense to find out WHY your coil voltage is only 8 volts when cranking.

By the way, the ignitor doesn't really "produce" a ground to fire the plugs, it actually LIFTS the ground. If you know about ignition systems with points, you can think of the ignitor simply as "electronic points". There is nothing magical inside the box, it's just a bunch of transistors that break the connection (like points opening) when the trigger on the crank tells them to.

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[Cipher]

Check primary and secondary coil resistance.

My coils always loolk weak but run fine quite a sickly spark but runs great.

Could it be the petcock vacuum not keeping up resulting in a starved set of carbs?

[tackwest]

I thought of the vacuum petcock, but tried it on prime to bypass. Didn't leave it on too long, didn't want to override floats. Carbs seem full of fuel and it should fire with a hotshot of carb cleaner, but doesn't. also wouldn't explain why it runs great, until you shut it off. I would assume that it would continue to have enough fuel to even hiccup? as far as the coil having only 8 volts when cranking, is that too low? Not familiar with these machines. It really feels like electrical the way it simply won't start ten seconds after you shut it off. Thanks for the responses! I really want to like this bike.

[Cipher]

heat soak in pulsar coils? Pop the cover off the crank end and check the resistance.

[Cipher]

I have never checked voltage to coils but that seems a bit saggy. A few years ago I replaced my wireharness and got quite a surprise in one of the connectors there was nothing but a wad of verdigris at what should have been contacts.

[tackwest]

Thanks cipher. I will try tomorrow. Had to walk away today. I am going to try and setup the relays tomorrow. Do you think I will need a relay for each coil, or can I wire them through a single relay and split the outgoing power? Anyone know what the resistance should be for the coils and the pulse coils?. Thanks so much for the help

[Cipher]

please dont do a coil relay mod it only masks the root cause of your problems.
Get the service manual from the basscliff website

oh and the shot youre using is that ether? Ive had my bike not start on ether only when the battery was beyond repair.

[tackwest]

Ok, so I tore it down today. Checked pulse coils, both had 343 Ohms, I think (don'tremember now), all the connections I could find were ok. I did rig up the relay as a temperary indicator, but saw no difference. When running the coils are at about 12 vdc, so I'm thinking voltage drop from starter. I'm wondering if this is a carb problem afterall as i have spark always. I did tear them out and checked them. I can't see any markings on any of the jets, so I'm wondering if someone has been in there. I also notice that the plugs are always dry. If no spark, then wouldn't plugs be wet? This bike is making me feel very dumb.

[tom203]

Ok so it cold starts fine, but won't hot restart.. Dry plugs stuff. have you tried using the "choke" during a hot restart? Maybe your pilot circuits ain't delivering enough during cranking.

[tackwest]

I did try the choke, but it didn't work. I did discover that it will start immediately after shutting off, but after a few minutes it won't start. Would it be worth pulling the wiring harness out at this point, or am I barking up the wrong tree and need to focus on fuel delivery? Thanks guys, its nice to have help.

[Cipher]

I recall mine is awlays hard as hell to start after shut down on hot dys
as if the bowels evap all thrir fuel and as if evn on prime the bowels wont fill

[Cipher]

does it crank super fast? in cold and hot conditions?

[tom203]

When you attempt a hot restart, do you leave the throttle alone?

[Cipher]

oh and you do have the airbox and filter on and everything tight?