I've been having issues running properly for a while now. I thought it was fuel related, so I replaced all the lines, had the carbs (Mikuni 38s) cleaned, replaced the vacuum fuel pump with a Mikuni unit, tested the coils, the plugs & wires, the compression, checked the valves - all good. I'm at a loss, the shop that has it is at a loss. The only thing they can't test are the Kokusan ignition units. I don't know what else it could be. The shop suggested deleting the excess fuel line (the "Y" in between the pump & carbs that returns fuel to the tank), because they didn't think the vacuum system would send that so fuel that it'd be necessary.

What happens is it feels like the engine would start drowning; it wouldn't rev as quick as usual, it needed a lot of fuel and clutch feathering just to get moving from a stop. And then, every once ina while, there would be a brief flash of proper combustion. "Brief" like a snap of the fingers. Which makes me think it's electrical.

I was considering replacing the coils with the high output offering that California Cycleworks sells, but now I wonder if it's really the Kokusan unit I should replace? Is there any way to test that properly, or can anyone confirm if just replacing the coils with those HO coils would eliminate the Kokusan unit altogether?

At this point, I'll try anything, because even the shop is shrugging its shoulders at me. Thanks in advance, folks.

Hi,

Question: (how) did you test the ignition coils?
Coils can (only) be tested properly with special testing equipment most motorcycle workshops have, they sometimes stop working but most of the times they still give some output (spark) but just not enough for the engine to run properly under all circumstances.
If not available, you could try to test it by "making" a sparkplug with a gap of roughly 3/8 of an inch and it should still spark without hesitation.
On the other hand if you could exchange it with another (working) coil it is easy to feel possible differences.
This last method is easy snd can also be used for the kokusan units, but in that case you need someone who is willing to lend it yo you for a brief moment .....

Anyone near you who owns a Paso with kokusan units?

Hope it helps you somewhat.

Frank

I would almost bet it's not the Kokusan units. They rarely break down. However you have a Monster so you can try its units.
In what condition are the membranes in the Mikuni? Are they still soft or are they stiff? The throttle slider is vacuum operated and if the membranes become dry over the years the carb won't work properly. Worth checking. If you want to check be careful when removing the round covers as on the bottom there's a small O-Ring.
The fuel return line is not required with the vacuum pump but if you had that also before when the bike still worked properly it's not the issue.

@Frank - the shop tested the coils, not me. The shop owner actually used to have a Paso, so he's familiar with them (and possibly therefore more sympathetic to me?). The tech was convinced it was jetting - although it had been running fine for years prior. So that's why we've moved into electrical.

Gerhard - you raised a good point with the Monster. I'll actually pulling the engine from mine because the output shaft bearing grenaded, so it won't miss its ignition. I'll bring that stuff to the shop, see if that fixes the problem. If that's the case, then in the meantime, I'll just look for a replacement while the Monster is a basket case.

Thanks, fellas - I appreciate the objective viewpoint. I'll keep you posted!

there are a couple of things that are often overlooked...

a are the fuel hoses OK? dont say they are new, have you actually checked them ? sometimes they come "defective" but because you think they are new " and therefore must be OK" then you do not check if they actually deliver fuel.

another thing is the fuel cap, are you sure the tank is properly vented? if the tank is not vented properly after a short wile it will create vaccum and starve the engine; when it starves try opening the cap, maybe it is just that simple.

as for the electrical side, the ignition key switch and the kill switch on the handlebar are also something that need to be checked, I had a Paso 750 with both issues and they were driving me nuts. You can disassemble clean and refurbish them, it takes patience but is feaseable.

Check for a voltage drop to the coils. Sounds like how mine ran when there was, due to a fouled on/off/on switch. Dyna coils helped for a while, as they fired better under the lower voltage, but eventually the switch was found to have its contacts fouled so badly, even the Dyna coils couldn’t keep up. Cleaning the switch contscts corrected the regualar plug fouling of the forward cylinder, and intermittent stumbling from running on one cylinder.

angelix & streetsurfer - you guys might be onto something.

I know the new fuel lines are ok, because I put them on and I put clear ones on because the first couple things I tried didn't fix the issue - and I specifically wanted to see what was going through the lines.

But the ignition/kill switch ... for a while now, I've had this problem with my start switch: unless the battery was just fully charged, the starter wouldn't trigger when the switch was in the 'run' position. However, you can make the starter turn in the 'off' position - but the cylinders won't ignite. So I would turn the dial to off, hold the starter, and then flick the dial to run, and voila! Ignition!

So I wonder if that isn't causing some kind of issues when it's actually running? Luckily, I have a Monster that isn't running and doesn't need its right hand controls at the moment either ... (sigh)

More as it happens - thank you for input, folks!