Exhaust Popping and Wet Plugs

[Saskzuki]

Hi all,

I've got a 94 Katana 750(f?). Bought it from a lady who's son stored it in her garage for 12 years without running it. Apparently it ran before he stored it but when I bought it two of the ignition wires as well as the choke cable were melted to the valve cover. so I replaced those and cleaned the carbs, tank, clutch plates (they were stuck together).

Got it running but the left two cylinders are not working how they should. I have spark on all cylinders, and the right two cylinders heat right up but the left two stay virtually cold even after 10-12 mins of running. I pulled all the plugs (which are brand new) and the two on the left are wet with gas but the two on the right are a nice golden brown colour.

The bike sounds like it's running on all four except for a loud popping out the exhaust at low rpm. In fact I can't get it to run at all below 2000 rpm without stalling and popping like crazy. I am certain all four cylinders are firing to some extent because if I unplug one of the spark plug wires on the left while it's running it wants to die.

All parts are stock, new fuel. Wondering if this is a compression/valve problem? All help is appreciated!

[kdo58]

How did you clean the carbs?

[Kreylyn]

Agreed, lets discuss carb prep for this. Many times what one would assume is enough... isn't.

2nd... double check the wiring to the coils, and the plug wires are in the correct order. Don't assume, no telling what someone before you did for example.

Krey

[Slofuze]

Agreed, lets discuss carb prep for this. Many times what one would assume is enough... isn't.

2nd... double check the wiring to the coils, and the plug wires are in the correct order. Don't assume, no telling what someone before you did for example.

Krey

Knows his shit.

[dano68]

Knows his shit.

Enuff said

[Saskzuki]

Wow, thanks for the responses guys.

I took all the bowls off and pulled the jets, tubes, floats and sprayed some nose hair-curling carb cleaner in all the holes and tried to get any crap out with q-tips dental picks and rags. I thought that should do it but now that it's run a bit it might have nocked some stuff loose that I couldn't get before. I'd be willing to try cleaning the carbies again.

As far as the ignition wires: Cyl 1 is from the lower part of the right coil. Cyl 2 is from upper left. Cyl 3 is upper right. Cyl 4 is Lower left.

I'm sure I wouldn't have had the bike running the way it was if the wires were in the wrong order.

I guess for now I'll be cleaning the carbs again. However do you think that a plugged/dirty carb would cause that kind of extra gas build up in the cylinder?

Unfortunately I won't be able to try that for another month. I'll let ya know how it goes!

[92xjunker]

left coil 1-4 doesn't matter which wire, the length will dictate. right 2-3 same scenario. honestly you need to use a carb dip on the bodies. see Carbs 101

[Kreylyn]

As far as the ignition wires: Cyl 1 is from the lower part of the right coil. Cyl 2 is from upper left. Cyl 3 is upper right. Cyl 4 is Lower left.

I'm sure I wouldn't have had the bike running the way it was if the wires were in the wrong order.

um... about that...


Yes, it will run on 2 cylinders... and some people don't even realize it's only on 2 when it is.

Krey

[COLDSTEELE]

Idk Brother The plugs are wet cause the carbs are doing their thing I mean unless they are dumping fuel I'd leave them alone. They are wet due to there being no spark to ignite the fuel air mixture.That's also why those cylinders arnt getting warm remember when you do get it straight to change the oil even if you have already Idk how much fuel has been sent into the crank case and it's not good for the viscosity of the oil The big clue is the melted ignition wires he found at the start something happen there and I'm sure it's the same cylinders that are wet that those wires went to There was some kinda break down in the ignition system there. Also idk but I'll ask have you checked all your fuses I'm betting you may also find a few blown fuses I may be way wrong just the melted wires tells me that was the problem the other owner had. Check the bowls if they have fuel and they arent flooding dumping alot of gas I think you can hold off on them check your coils for spark please make sure there is no wet fuel spilt before you start checking for spark

[Saskzuki]

Well kreylyn you got me there. I was totally convinced it was running on all four but it turns out that it is running only on the right two, that would explain why it won't idle under 2000 and why it pops all the time.

The carbs are clean and delivering fuel as they should (I believe). The float needles seem to be sealing well cause I left the bike for three weeks and there was still fuel in the hoses so it hadn't drained down into the cylinders.

What about bad coils? Does electronic ignition ever get messed up timing? Any way to check electronic ignition timing? I have spark on all ignition wires but I also don't know if it is strong enough.

Also a point of interest, it looks like the bike has been running hotter on the right two cylinders for a long time judging by the condition of the crossover on the right side (flaky and rusted compared to no rust on the other side). Ive been trying to track down a compression tester cause bad compression could equal unburnt gas I believe?

Oh and the melted ignition wires when I first got the bike were because they were resting on the valve cover not because of electronic failure. It was just the insolation that was melted. Fuses are all good. I tried swapping the wires going into the left coil (controlling cyl 2 and 4) and it ran about the same as it did before! What?????

[92xjunker]

. Ok, if you have spark, the ignition is working. Week spark is a low + feed to the coils. Measure the voltage at the coils while trying to start. You need 11+v for a good spark.
Coils left coil is 1 and 4 cylinder. obviously, right is 2 and 3 cylinder.

[shpielers]

If you swapped wires and the same 2 cylinders were not firing, it's probably a carb issue. Trouble idling is usually because the pilot circut is clogged. Dissassemble and soak in cleaner overnight, chase circut with fishing line to make sure it's clear, and reassemble. (read carbs 101 on the wiki)

[Kreylyn]

I tried swapping the wires going into the left coil (controlling cyl 2 and 4) and it ran about the same as it did before! What?????

Left coil is 1 and 4....

It's a wasted spark, so both plug wires fire. If you only swapped the single coil wires, it would normally make no difference. They both fire each time.

So what I was saying... check your coils are plugged to the correct # cylinder. As sitting on the bike, left side is 1.

Left coil is 1 & 4.

Right coil is 2 & 3

Each coil has an orange wire for constant power. Each coil will have a colored wire for the signal. Of that colored wire...

Left coil is whiteish/tan.

Right coil signal wire is black / white stripe

Krey

[Saskzuki]

Ugh...I must apologize. I had the ignition wires hooked up to the wrong cylinders ): Swapped them around and it runs great! I guess I didn't understand that two cylinders are always in sync therefore a coil is sending a spark to two cylinders at the same time. Got the bike running like a top now. THANK YOU GUYS FOR ALL THE HELP!!!!!!!