Hi guys, I don't see any suggestions for what I'm about to describe anywhere on here, forgive me if I've missed somthing. Anyway I have a bad stuttering under acceleration on my 07 zx14 with 60k miles. So far I've replaced coils, injectors, tps, (all oem) I did a perfect valve adjustment .007 intake .010 exhaust, fuel pressure holds steady 42psi under load while stuttering, synced throttle body's, new plugs gapped at .30, all grounds are clean, cam position sensor measures 503ohms. Compression test is an even 136 on all four cylinders with plugs out turning the engine with the starter. I did see on here that might get a better reading if I push the bike in gear w plugs out but haven't tried it, kina figure as long as they're the same on all four there shouldn't be any runability issues even though it's kina low. I've had this bike since 2017 it had 20k on it when I got it. I had it dyno tuned at about 45k miles never had any problems, I'm a freak about maintenance change oil kina early etc. A couple months ago it started doing this and I thought ok probably time to do some deeper maintenance so started with a valve adjustment and been kina going in circles since. The bike starts and runs perfectly smooth revs fine doesn't stumble in nutral, it's always used about lil over a half quart oil between changes, hasn't lost any coolant, no FI light,, I'm on the verge of questioning my mechanic manhood over this,, Is there somthing I'm missing?

Fuel filter??

I think your fuel pressure readings rule out a fuel filter issue. When it was "dyno tuned" was it done through the original ECU or with a Power Commander? If you have a PC I'd suggest just disconnecting it back to the ECU only and see what you've got? If that's not the case the next thing I'd look for would be ohming out each coil and injector circuit from the component to the ECU. If they all pass then a load test in the same manner could be helpful?

I'm just the messenger...

Old Honda service books show 153 - 187 Psi as the hi/lo limits of compression. Also I read a Ducati shop manual that showed in caps: POOR next to 150 psi.

So the breakout shows 150 as the abstract to rebuild the top end. Doubt you have a pro compression tool from say Snap-On. I think I have a vid showing 8 pounds off from the manuals highest limit... cold tested.

Someone was nice enough to send me his ECU with a stumble in it. Somewhat like yours. It was an early gen. Sure enough I installed it and it had this nagging stumble.

Useable range for first gen is 149 - 228 psi. Kind of see the 150 is the breakout range? Also you have the subthrottle closed at the comp test.

IF fuel pump is within spec, air cleaner shows daylight thru the pleats, plugs changed every 7,500 miles, ECU is bone stock, i.e., not flashed/PC'd, I'd try to find a used ECU of the first gen and try that.

I assume fuel pressure trumps fuel filter. The tune is on the ecu.. I know the injectors and coils are good, you're saying check each wiring circuit for consistency between ecu and components rite? Elaborate on "load test" please?

BTW, the stuttering seems to get worse as the bike warms up, almost doesn't do it in the first few min of running. The original coils measured fine on the bench but two of them were wildly out when heat soaked so I replaced them, no change, the injectors measured fine on the bench so I wondered if one possibly messing up when heat soaked but of course they aren't a quick remove to check when hot so I replaced em, still no change. Tps sweeped fine on analog meter but I've seen one other tps seem fine and turn out to be bad so I replaced it. Each thing seemed to help a little like the bike really needed everything but the stuttering still creeps in worse and worse. I've been shy about a bad wire or corrosion at a connection assuming the problem would be the same all the time if a bad wire or connection but it wouldn't be the first time I've assumed something couldn't be because somthing else is or isn't....

All the while running fine standing still in nutral as if nothings wrong, it's only under a load..

Thanks Hub I understand.. my compression tool is a cheap one, the secondary Flys are removed heald throttle open for compression test, I'm familiar with 150 ish being the service limit, Guess im having troublw excepting the possibility because 60k miles with good service history (at least since 20k) and haven't really super abused the bike like I would have in my 20's , Im like "really? shouldn't this bike last a lot longer than this? Wouldn't it burn more oil or smoke a lil if it was done?" But I did buy the bike from the president of a ruthless riders chapter so who knows... Im on the hunt for a loner ecu..

Wiring circuits can be affected by heat, with increased heat comes increased resistance. A load test requires the circuit to be isolated on both ends of the circuit. I introduce battery voltage on one end and use a incandescent test light with a voltage meter clipped to the probe. You first verify the voltage at the battery feed end, say it's 12.6v on a fully charged battery then you move the probe to the other end. You've now "loaded" the circuit as the battery voltage has to run through it to get to the test light. The voltage drop should be less than .5v in most cases. If you have a larger gauge wire you use a heavier load like a headlamp or fog lamp. All testing would be inconclusive if using LED's. Hope this is more than "clear as mud"!!

Thanks Fordtech58 I get it!