Help please, ZZR600 missing.

I have a '93 ZZR600 which has been around the block at least once, showing 14,000k, so at least 114,000km. The bike was running fine until I put the bike in for a tune, as the previous owner wasn't very proactive about these things. Anyway when I got the bike back it seemed to be missing badly, which made it very hard to ride at a constant speed, as it kept surging and dying. I spent a good month back in the workshop before the mechanic decided it was beyond him. I took it to another shop and they went through the bike. It is better than it was, but it's still not right. They went through the carbies, compression is down a bit especially on the outer cylinders. I have switched to 95RON, but this hasn't solved the problem. I've had the coils tested and they are OK, one isn't quite 100% but the 1st mechanic tried a replacement to no avail. If I ride at 80km/h and want to accelerate to 100km/h for example, the bike just falls in a whole, and goes nowhere. Any other suggestions would be appreciated as it's really beginning to annoy me.

Hi mate, what exactly was done during this tune that the bike had, prior to the problem showing up?

How far out is the compression? Is it all four that its down on?

Wife's ZZR600 started missing badly (ie really really badly - 2 cylinders only) and it was a loose electrical connection above the carbs that had been disturbed during the service.

If its electrical related, it may be related to connecttions being disturbed as suggested above, or it may possibly only occur at certain revs (think harmonics/vigrations causing contact problems or electrical load issues causing it to give up the ghost).

Alternatively it may be related to fuelling, does it happen at specific throttle openings? i.e. works fine at 1/4 throttle, but the instant it goes 1 degree past that, it goes to shit, and when you roll it back it works fine again? If it is fuelling the issue will be reprodiceable again and again and again, wheras electrical may be a regular issue, or possibly a hit & miss affair as the components phase in & out of being able to function.

Good luck, let us know how it goes.

The bike had the carbies cleaned out and balanced, along with the jets cleaned and new spark plugs. Anyway after the trip to the second mechanic who said the balance was way out and the spark gap was all wrong I have no confidence in the first guys work. It doesn't seem to be at any particular rev's. It is noticed most when I am trying to hold a constant speed, say 80km/h, you can feel it surging and slowing, and there is a different note to the engine. It seems to take off fine, so under hard acceleration it's not as noticeable. The compression was down more on the outer two cylinders. On to the second tank of 95RON now with no change, so doesn't appear to be fuel.

Is it a miss or a surge?

Surging at constant throttle is usually fuel delivery related. Worn needle and seat in one or more carbs? Intake manifolds not sealing properly? Float heights altered when carbs cleaned?

Have you checked out the resistence in the leads, I have a ZZR600 and found that one of the leads was damaged on the plug end, allowing the
spark to escape side ways to the head rather tahn through the plug. The thing ran ok, but didn't go when I squeezed the throttle on.
I'd remove clean and refit ALL the electics first. Then check the Leads, and Coils, and Plugs.
Let us know what you find.

Cheers Mick015

Yeah it might be the resistance in the leads. The irony is that the first mechanic who stuffed it up, sent me on a goose chase to find in line resistors to put in the leads to the outer two cylinders. He said the bike was old and everything had shrunk and tightened up, making it a bit difficult to get the leads from the coil to the outer two cylinders. His solution was to make the leads longer by including an in line resistor, apparently the type that used to be put in leads in the early days of TV (yes we are talking an old mechanic here) which stopped the engine interfering with the TV signal - a bit before my time. My only doubt about this is that the problem arose prior to putting these resistors in. This was his 1st attempt at a solution to the missing. In my opinion it is a missing rather than a surging. It drops power and you put a little more throttle on to compensate to maintain your speed, and the surging sensation I guess is when it clears temporarily.

He said the bike was old and everything had shrunk and tightened up, making it a bit difficult to get the leads from the coil to the outer two cylinders.

He might be onto something there. We've had a similar problem a couple of times when the leads weren't pushed all the way home.

Hi just my 2 cents worth, however
Recently i had the same issue ( altho mine was down low at 2000-3000rpm mark) after doing my gearbox up and found a new set of leads ( 10 bucks for a continuous length and you cut it to suit ) and another set of plugs ( 3 bucks a peice from Bursons), ( the replaced ones, only 40 kilometers old, were also faulty ) fixed my issues. She now is crisp and clean and i have now traveled 250ks and still not hit reserve.
Warm bike up then let sit for 10 mins or so to cool so as to " set " plugs into fault find mode. All plugs should be clean and dry after 10 mins or so of riding.
I feel, Do your leads ( loose the resisters it doesnt need m ) and check your plugs. You have nothing to loose and everthing to gain.
When you remove your plugs do 1 at a time and look at the end with the gap, If it is wet then that is the cylinder that has the fault. Also look at the white part on the plug, it should be obviously white , if it has a black sheen to it the plug is faulty or worn out .
Hope this works out for you as mine did
Regs Mouse_zzr600

Hi,

Where did you get the leads from? Bike shop or Auto.
Thanks

I got hi tension cable from Bursons in Penrith, they had to get it in, but that only took a few hours... I will try to fit them tomorrow, I hope this sorts out the misfire.

A few rules of thumb for the newbies

- If it misses under hard accel --- good chance of faulty HT leads , coils , ignitors , plugs , stator etc.. ie ignition electrical..

- If it surges under constant throttle / cruise --- water in fuel , crap in float bowls , incorrect float levels , carbs out of balance / out of tune air filter waayyyyy blocked..... ie fuel

- Stalling / missing at idle/low rpm only normally points to an air leak from carb to head , blocked low speed / idle jet or if very fuelly , U/S or incorrectly set needle and seat.

Note/Hint;
1.
The HT lead used in most bikes is copper cored 7mm and available by the meter / roll.. (I have 30m of in in the shed)DO NOT ADD INLINE RESISTORS as the plugs ie BR7EVR (the 'R' means resistor inbuilt in plug) so no need. If it needed a resistor in the lead the y would have used carbon core jobbies.
(they may go hard in the insulation but they certainly don't shrink!!! ----I'm suspecting he's stuffed the firing order!!)
2.
Not a great advocate for NGK Iridium plugs - too unreliable I've found.. Platinum gives you similar benifits with far better reliability.(cheaper too)
3.
Fuel RON increase may help with a pre ignition issue / overheating on older bikes but not necessarily a surge / missfire.

Hope it helps peoples

..............Some wise words of wisdom there master

Ok, so that failed......would not start! Backfired. I put the old leads back on, and still no joy. I pulled the plugs out & cleaned them, no go! Then put new plugs in (again) and she runs.......
Any suggestions? Carb balance?
Thanks