ZRX Misfiring problem update - Aaaaargh!!!

[seiko1]

Is the timing chain in the correct position?

[MAXUMIS]

Just out to help but if you have a miss on the dyno it can alter the 'real' AFR's buy a long way,all i mean is the AFR's can look rich or vise verser depending on the problem.When you find the prob as it can be hard to find without actualy seening what is happening your best bet is to get it run up again just to make shore your AFR's are write.

Yeah absolutely mate that's the plan. The bike is still sitting on the Dyno at C and M so we'll plug the hole in the airbox tomorrow and run it and see if that does it. If not then I'll take it home and just keep fiddling till I find it. Once I do then it'll be straight back on the Dyno again.

Fingers crossed for tomorrow.

Mate i hope it all work's but if your trying to use the dyno to find the problem you may be chasing your tail,been there and done that.A dyno is a tuning tool not a diagnostic one.

[Disco]

Well guess what we've found. The twat who worked on the bike for the previous owner in an attempt to presumably make it run better did a few dodgeys.

I thought you got it with only 1,000k's on it?...Seem's like a lot of mod's for a bike that he never rode

[Glen]

Just out to help but if you have a miss on the dyno it can alter the 'real' AFR's buy a long way,all i mean is the AFR's can look rich or vise verser depending on the problem.When you find the prob as it can be hard to find without actualy seening what is happening your best bet is to get it run up again just to make shore your AFR's are write.

Yeah absolutely mate that's the plan. The bike is still sitting on the Dyno at C and M so we'll plug the hole in the airbox tomorrow and run it and see if that does it. If not then I'll take it home and just keep fiddling till I find it. Once I do then it'll be straight back on the Dyno again.

Fingers crossed for tomorrow.

Mate i hope it all work's but if your trying to use the dyno to find the problem you may be chasing your tail,been there and done that.A dyno is a tuning tool not a diagnostic one.

He's only using the dyno to run it right through the rev range without having to do 200km/h around the block. The problem is that it only misses when you get on the throttle hard.

Waiting for my envelope to turn up.

[Glen]

Well guess what we've found. The twat who worked on the bike for the previous owner in an attempt to presumably make it run better did a few dodgeys.

I thought you got it with only 1,000k's on it?...Seem's like a lot of mod's for a bike that he never rode

1,467 to be precise. I think after he bought it he's taken it to a bike/lawnmower shop and asked them to tune it for him. The shop's had an old bolt on left around which didn't fit so they made it fit by cutting the pipe off and shortening it, then gave it a heap of fuel (ie changed the needles but left the jets stock)and thought he then just needed to give it a heap of air as well (so put a K and N on and ripped the snorkel off). They probably then run it on the Bum Dyno and because it made more noise it was going awesome.

Remember the owner lived about 200 meters from the Black Spur and did 1,467 klm's in 2 years so I'm thinking he maybe didn't know a real lot about bikes.

Anyway, life would be boring if you didn't have challenges.

[bonester]

Removing the snorkel is one the common mods done to ZRXs. I didn't remove mine, but I did remove the foam thingo inside it, which was worth 1hp on the dyno.
I reckon I could raise you in previous bike owners who shouldn't touch bikes- my last GN250 that I bought for my school was an ebay purchase and the biggest pile of shit I have worked on. The previous wanker pulled the engine top-end down, and reassembled it with silicone and reused the gaskets even though large sections were missing! It pissed oil and ran like a dog. (he couldn't get it to run properly) He didn't tighten the cam sprocket bolts. Told me it had a new cam and rockers in it- it had what looked like a hand welded cam and rockers with hand-filed surfaces. He broke two head fins off, assumedly coz he missed the two little nuts under the head that hold the head on. Pulled the oil screen out and it was full of plastic and a small amount of metal. Wonder where that was from? Been a rattling noise on deceleration- turned out that someone (I don't believe the previous owner would be capable of doing this) had replaced the stator and starter clutch, and damaged the gasket surface for the stator cover AND left one of the stator bolts loose - it was hitting on the rotor....hmmmmm. Makes your ZRX look good huh!

[JetPilot]

Glen I seen ya bike there over Xmass and was talking to them about it. Have ya got an ignition advancer? Is this in the right spot? They only replaced 1 coil, maybe it needs 2 new ones or 2 off a running bike to check it out. They tested yours but they can be stuffed and test okay. High tension leads could be arcing on the engine somewhere. Could you be running out of fuel at high rpm hence the missfire at full thottle. These are just some thoughts to help, well I hope they do. Good luck mate.
By the way it looks bloody good. Luv the silver Muzzy.

[Glen]

Glen I seen ya bike there over Xmass and was talking to them about it. Have ya got an ignition advancer? Is this in the right spot? They only replaced 1 coil, maybe it needs 2 new ones or 2 off a running bike to check it out. They tested yours but they can be stuffed and test okay. High tension leads could be arcing on the engine somewhere. Could you be running out of fuel at high rpm hence the missfire at full thottle. These are just some thoughts to help, well I hope they do. Good luck mate.
By the way it looks bloody good. Luv the silver Muzzy.

Yeah mate Phil mentioned you'd been out there, so did Craig. I'm going to try this out and then if it doesn't fix it get it home and just work over it myself with all of the above. If the airbox doesn't fix it I'm going to chuck $500 at it and replace both coils, leads and plug caps. It's got an ELS 4 deg advancer on it but we tried taking it off and putting the stocker back on but no diff.

I'm glad I went the Muzzy, it looks and sounds pretty sensational, just got to get it running right.

[Glen]

Removing the snorkel is one the common mods done to ZRXs. I didn't remove mine, but I did remove the foam thingo inside it, which was worth 1hp on the dyno.
I reckon I could raise you in previous bike owners who shouldn't touch bikes- my last GN250 that I bought for my school was an ebay purchase and the biggest pile of shit I have worked on. The previous wanker pulled the engine top-end down, and reassembled it with silicone and reused the gaskets even though large sections were missing! It pissed oil and ran like a dog. (he couldn't get it to run properly) He didn't tighten the cam sprocket bolts. Told me it had a new cam and rockers in it- it had what looked like a hand welded cam and rockers with hand-filed surfaces. He broke two head fins off, assumedly coz he missed the two little nuts under the head that hold the head on. Pulled the oil screen out and it was full of plastic and a small amount of metal. Wonder where that was from? Been a rattling noise on deceleration- turned out that someone (I don't believe the previous owner would be capable of doing this) had replaced the stator and starter clutch, and damaged the gasket surface for the stator cover AND left one of the stator bolts loose - it was hitting on the rotor....hmmmmm. Makes your ZRX look good huh!

I think I'll stop whingeing now, that's a shocker.

[hoffy]

1hp gain with modified snorkel! Id be all over that Glenno..

[JetPilot]

I gain 3hp after removing mine on the Motard... go figure.

[Glen]

Ok so the snorkel went back on and the misfire off the bottom has gone. Now you crack the throttle and it pulls cleanly to 5000 rpm but then breaks down badly from then on. It sounds like it's missing everywhere and its crackling and carrying on. Talking to Phil and reading Marty's first post it's sounding like I've had a combination of issues but now I think we've narrowed it down to what sounds like electrickery.

This may sound stupid but at least now it's doing it all the time, not at random so I'll know when it's fixed.

Next step is get it home and go over all the minor stuff everyone has suggested then if that all checks out I think it might be time for new coils, leads and plug caps.

[Benno]

That definitely sounds like the logical place to start mate. I've actually had leads on a car that would break down after a certain RPM.

Great to see you're making progress though.

[Strika]

Pull the leads out from the plug ends and have a look. As the Rex has one achilles heel being the No1 plug can get wet a bit when parked. The plug well fills with water, the plug lead ends corrode around where the press into teh plug cap. Check them for that. Have you checked the leads for spark interruption? You can pop a device on them which tells you if a lead is breaking down......

I still reckon based on what you are saying that it's jetting related. I know my first thoughts were electrical, but if putting a snorkel back on half fixed it, is suggestive of a fueling issue not a spark issue. I could be wrong, but what jetting and needles are in there now???

[hoffy]

Glenno, ill bring my hammer over tomoz...