Suzy 600 headache

I have recently been working on a GSX600F (’91 Katana). I am now tearing my hair out!

Originally, the bike would not idle at low speeds (like under 2000 rpm) and would foul out plugs EVERY DAY.

The Bike is “stock” with about 30,000 miles on it. I have no idea what was done to the bike before we got it. The only mod on the bike is a 4 into 1 pipe. The jetting was stock.

First thing we did was dropping the needles (lean out the low speed mix), replace the air filter (with a K&N), and clean out the float bowls.

Same problem. While we were distracted by what seemed other problems, we soon found that simply replacing the plugs “fixed” everything.

Being an OLD rider, I assumed the problem was the coils and wires. (In the OLD days swapping out coils cured a lot of idle/fouling problems)

We ordered in a set of ACCEL coils and wires and installed a new battery.

The stock coils mount to the frame with two bolts going thru the center bar. The hole spacing on the accels is not the same, so we used the Accel supplied adapters. These have two bands that go around the coil and tie into a universal mount. With this mounting, the center bar of the coil is not “grounded” as it would be if the coil was mounted the factory way.

After installing the coils and wires and replacing the plugs (gaped at the Accel recommended .035”) the bike runs great and idles just fine. Unfourtanly the bike only runs a few miles and quits.

We had a screwed up fuel petcock, which had no “prime” position. So we got a new fuel petcocks assembly, flushed out the tank , and when to a richer main jet. Unforutanly when we were “cleaning” the carbs, we used carb cleaner (spray can) and this caused the diaphragms on the carbs to expand. We replaced the diaphragms and set the float bowl level.

Plug chops show the bike to be jetted “about” right- Light tan. While I could go a bit richer, I don’t think jetting is the problem.

Same problem—run a couple of miles- bike dies, wait about 10 min, bike starts and runs just fine- for a couple of miles.

It acts like there is some sort of “thermal cutoff”.

Question one—does anyone know if there is some reason that the center bar of the coil needs to be grounded (I have made an adapter bracket to use the thru center bar mounting- but it’s a lot of work to swap it over- so I thought I’d ask)

Second, I have no idea which wire going to the coil fires which plug. I am assuming that because the bikes starts and runs good (at least for a while) that these wires are going to the right terminals

I have not tried going back to the original coils because the Accel coils required different connectors and the wires are much different. The only way to switch back is to cut off the connectors – I don’t want to keep making these wires shorter and shorter.

Is there any reason that the bigger coils would be somehow “over loading” the electrics up stream of the coils?

Is there any sort of thermal switch that would cause the bike to shut down until it cooled? (the bike does NOT really seem to be overheated, and you can let it idle forever and it won’t cut out)

I certainly don’t want to order a new CDI box (at like $450) just to try it to see if this is the problem.

The other reason I don’t want to put the old coils back in is that I’m assuming that we would be back where we started—fouling out plugs and not idling.

Hopefully someone out there will better understand how the electrics work and be able to give me some kind of answer.

 

Welcome to the boards. Owned quite a few Suzuki's in my time, and while none were Katana's, the GSXR is similar. The only time I ever fouled a plug in my gsxr was at start time, when the choke is open. Otherwise, you should be fine. The bike you have should be oil cooled, and I am not aware of any thermal cutoff. Just make sure you check all fluid levels, keep that oil full and fresh. I used to drag race and on days where it was 100 degrees, none of mine ever locked up. If the coils were bad it wouldn't run at all in my opinion, so replacing the coils might not have solved much. The only thing I can think would be to replace the brain. That bike should run and keep running, it would just run like **** if the carbs were screwed up. If you have a dealer around there, might want to go consult them as well. Sorry, can't help much, but there's my .02.

 

Thanks for the reply.

On coils... As I said- I'm OLD. And in the OLD days, we found quickly that many motorcycles had crap coils. We adaped after market coils to them, and our low RPM spark problems went away-- and as this bike seemed to run just fine except if you tried to run at low RPMs that seemed like a good choice. As it happened, we don't have the idle and low RPM problems with the new coils.

I'm guessing that our only real choice is to go back to the stock coils and see if the "only run 2 miles" problem will go away.

I realy wish i better understood the electrics, I just can't see how changing coils would cause this problem

Thanks!-- hopfuly some others might be able to help