Runs well then BAM! tries to jolt me off

[thetenthplace]

This problem has been around 2 weeks, been running fine for 6 months prior (since I owned the ZXR400 H2)
I am riding along (singing a song) and the engine seems to cut out and in again sometimes it happens once sometimes multiple times in a row. if the revs are under 4k it just stalls anything above this it will come back in, seems to happen randomly, no set distance or heat. Thinking it was petrol I ran it near empty and went to a different garage, same problem, checked the spark plugs, connections of the IC ignition and the 2 boxes that connect to the spark plugs, all fine. Same problem, next top up I changed petrol station again (just in case) still the same problem.

Can anyone kick me in the right direction? (I have been to a mechanic and was told it was highly likely an electronic problem, but that they could only help with mechanical problems not electrical on the ZXR)

[RedexRobB]

One thing i would say check when this happens, is any lights go off like the clock lights or head light if you can see it at all. That could rule out as to weather the lot is cutting out. Have you checked the fuses? Id be round the entire loom making sure something hasnt chafed through and shorting out on the frame. Would check the earths too, as well as the terminals on the battery, making sure they are clean. Dont forget the main 30Amp fuse on the LHS of subframe, and the connectors.

[thetenthplace]

Haven't seen the lights have only been out in the daytime since the problem started, its been pretty hard to see if the lights cut out. I will check this shortly, and also go over everything else you have mentioned Thank you for the suggestions

[Tirpitz]

How new are your plugs, what is starting like, what is idling like? Mine had a habit of dying below 4K, especially if put under load. New plugs sorted it. It was also a little difficult to start and sounded rough when idling. It could also be slow picking up at low revs say turning into a junction, enough to really unbalance you. Going into roundabouts it would fail to pick up then the power would kick in.

The plugs might give a spark that looks good but they can break down under heat / load in the engine and give a poor spark. At low revs and when picking up from small throttle openings this can give a poor response and give the feeling of the engine bogging.

[thetenthplace]

plugs were put in when I brought the bike, so 8 months roughly
starts fine, idles well once warm, power is good doesn't feel like any drop has appeared. It has only cut while either lowering revs or steady revs. when this first happened I had a thought I was going over bumps and my hand was moving, but has since been proved not to be the case
It doesn't feel like it bogs, it just cuts out and in, then it runs fine again, I cannot replicate this (thus far) without being in gear and moving.

Also the lights don't cut out when the revs drop.

[bendog66]

Check the battery connections like rob said. I had a similar problem and one of the connections on the battery was loose so intermittently lost power

[Tirpitz]

Doesn't sound like plugs then, nor fuel starvation. I agree it sounds more like electrical shenanigans, something loose. While you're hammering along vibration might be enough to keep rattling a connection enough to give a contact. At a steady low revs it might be steady enough to break away long enough to cut out. Plus, if your revs etc are low any slight cut out is going to be more noticeable than a momentary cut when the motor is really spinning.

You could also check your earth connections. If any sign of corrosion remove, clean up and reconnect with a smear of grease.

[gavinfdavies]

you say it cuts out only when lowering revs or cruising? are we to assume here that means steady revs at small throttle opening? if so, it could be carb icing, even with a warm engine. my gpz was doing it at around may last year, turns out the anti-icing circuite (that runs coolant through the carbs via little rubber hoses) was blocked, hence carbs getting cold. might be worth a check - next time it does it, try dropping a gear or two and riding with and open throttle, might sort it. if this does it, it'll be carb icing. try cleaning out the filter (little inline thing on one side of the carbs in that rubber coolant hose) part number 49019 on micro fiche below
http://www.cmsnl.com/kawasaki-1995-l5-z ... E3032.html

that sorted mine out. you might have to blow through the carb coolant lines too clear any gunk.

[thetenthplace]

I had carb icing over the winter, this doesn't feel the same (not saying it isn't carb icing) but the engine when I had carb icing was more a struggle then firing on 3 then started wanting to cut out, this is a sudden cut out and on. I will be lookng over the bike tomorrow and friday depending on how the day goes.
The ZXR400 H2 I have doesn't have the carb heaters (due to being an import is it?)

[thetenthplace]

Right took the bike to bits today, cleaned and put electrics back, no chaffing on cables, battery was well connected, the fuel tap got replaced as the reserve and off weren't working and the fuel pump was cleaned up.

Had my mechanic father around too, who asked if the fuel pump was adjustable (couldn't find it in the manual only instructions on how to remove and replace)
Is it possible that the dirty contacts on the fuel pump that caused this?

Yes it hasn't happened after an hours ride so will watch this space