Coughing, spluttering, losing power @ 60mph/100kph

[Ferret]

Hi Guys,

Got a problem with my ZL1000 ..

Cruising along at about 55mph/90kph, I wind the throttle on and the motor starts to wind up. Get to around 60mph/100kph and it starts to cough & splutter and lacks power. If at that point I give if a fistful, it seems to lag quite noticeably, then seem to clear itself and then pulls like a freight train from there on up.

After a quick burst to say 75mph/120kph or so I let it slow back down to the 60mph/100kph mark it does the cough/splutter/loss of power thing again.

If I stay around 50-55mph/80-90kph it’s fine … no problems at all.

At first I thought it may have been a fuel blockage or similar. So have had the carbs off and cleaned them right out … no sign of any blockages at all.

Just to fill you in .. this motor came out of my “spare bike” .. it has pod filters on it.
Prior to the changeover it had stock mufflers on it with the pods.

As it is at the moment, it has the pod filters on it but now has Cobra F1R mufflers on it, which still use the standard “collector box” underneath the frame.

Am wondering if it’s a jetting thing?? The previous owner said he did muck around with the jetting etc when he fitted the pods and it was a bugger to get running right.

So … am I looking at needing to lift the needles a fraction?? Or is it an electrical problem?? Everywhere else in the rev range it runs fine .. it’s just at around our State limit of 60mph/100kph up to about 75mph/120kph that it does this .. which is both frustrating and dangerous when pulling out to pass a car on the highway.

Any hints/ideas would be helpful …

Thanks
Ross

[zlMark]

sounds electrical to me. Your at that certain speed and the vibes are just right. side stand switch, ignition switch, pick up coils, etc.

[Ferret]

Thanks Mark ...

Yeah I know for a fact the motor was running right when it was in the other bike coz I rode it home and it behaved fine.

Given how specific it is .. is the reason I thought maybe needle position etc because it is such a small range where the problem occurs.

I'm wondering if it might be the igniter?? I doubt it's the coils because it'd be unlikely that both coils would break down simultaneously. Likewise the pick-up coils. It' may be leads, but then again unlikely they'd all play up at the same time.

It seems to occur once the bike has warmed up well and truly .. I mean like 15 mins riding it. Almost like it's temperature related.

Which is why I was thinking igniter?? It is a repeatable and very specific problem. As long as I keep it under that 60mph/100kph mark it's fine ... would and has run all day like that. The moment I go over 60mph/100kph the problem shows up again.

I have a spare igniter here so will swap it over and see if it continues .. basically a process of elimination I guess. Would rather not fiddle with the carbs/jets/neelde position at this stage .. given I've had the carbs apart and there were no signs of probs as far as I could see.

Cheers

[zlMark]

good luck and please post the fix!

[Ferret]

Thanks Mark ...

Thanks for your reply. I replaced the standard fuel tap some time ago with a manual Pingel PowerFlo tap. I have an aftermarket automotive inline fuel filter fitted.

Removing the fuel line at the carby connection and turning the fuel on, there appears to be plenty of fuel flow. At one point, I pulled over and removed the fuel cap, then continued riding. Thinking it may have been a vapour lock issue. Doing that made no difference at all.

In some ways it feels like a fuel starvation issue. Except for the fact that once I am over this speed/rev range it pulls like a freight train on up to 200kph?? It's like there is a pronounced "flat spot" between 100-120kph. After that it's fine. Winding back down to 100kph after a burst it coughs/splutters .. THEN it regains itself as long as I stay below 100kph-ish.

Not knowing much at all about the electrics/igniter side of things I'm wondering if it is in the igniter. Feels a bit like a sticking/faulty "advance/retard mechanism" of the old days, if you get my meaning.

Was basically wondering if anyone else had struck this problem before and could go, "Ahaaah, I've had that problem before .. I know exactly what is is" etc etc

Thanks again ...

Cheers

[zlMark]

i was experiencing fuel starvation a lil while ago with mine. I had the floats set wrong. I raised the floats to .5 mm above stock(16.5mm) and no more surging at highway speeds.

[rammy1500]

Sounds like your going through all the same simptoms by 900 has. And I'm sure you guys have seen my posts on the other website as well. So not to bore you with all the issues I've had here is the condense version. But was only running on three cylinders, try to mess with it myself, took it to a dealership that talked me into a carb rebuild, got the bike back running just a hair better but "flat spotted" at 5K, found they pinched on of the diaphrams in the carb. Also, found they turned the mixture screws out 4.5 turns causing the sparkplugs to foul out. I messed around for another year trying to get the bike to either idle or run right, replaced sparkplug wires and boots, found one of the books was cracked, thus arching out, cleaned all of the switches, found the kickstand switch screws were actually bent and not making good contact. Then found a set of carbs on ebay off of an '04 Concours that I put right on only having to changed the trottle cable bracket, wish I would have figured that out the first time I put them on. I installed an automotive fuel filter, ran fine for a couple of months then acted like it was starving for fuel. Looked at the fuel filter and it wasn't letting enough fuel through although the petcock worked fine by itself, but when I installed the filter and turned it on prime it just didn't let enough fuel through. So I'm back to running without a filter until I find a better way of hooking one up.

So back to your problem, I wouldn't think its electrical since electrical issues are normally they either work or don't work or don't work under load. But having the problem at just a certain range I would think its back to the fuel delivery. Could be the diaphrams are a little worn and won't raise the needle properly at that vacuum but then does raise higher at higher vacuum.

[entoria]

Although this is an old thread, I thought I would just esquire if any of you actually found out what the problem was. My ZL900 has been having the EXACT same problems as being described here to the 'T'. It's uncanny as it is happening in the same speed range (100kms-120kms) as described here.

Did you ever get to the bottom of the problem?