KZ1000 MK2 detonation problems

Hello

I'm struggling with detonation from around 3000-6000rpm on my KZ1000

It has:
Stock head with bigger valves
K410 cams
MTC 1075cc cylinder kits
DynaS ignition
Dynatek 3ohms coils
Tayler cables and Iridium plugs

Head seemed okay and same with cylinder high etc...
Im runing good 95 or 99 octane fuel

Ive adjusted the ignition 1000times giving a little more or less - ive played with the advance system - tighten spring - runing only one spring and also taken it form a runing sock bikes....

racing people says as long as the piston is only called 10.25 - 10.5 it shouldnt be the compression

what to do??
Im thinking the DynaS ????

I'd try richening up the mixture. Can you lift the needles and bump mains one step?

larslykkegaard wrote: Hello

I'm struggling with detonation from around 3000-6000rpm on my KZ1000

It has:
Stock head with bigger valves
K410 cams
MTC 1075cc cylinder kits
DynaS ignition
Dynatek 3ohms coils
Tayler cables and Iridium plugs

Head seemed okay and same with cylinder high etc...
Im runing good 95 or 99 octane fuel

Ive adjusted the ignition 1000times giving a little more or less - ive played with the advance system - tighten spring - runing only one spring and also taken it form a runing sock bikes....

racing people says as long as the piston is only called 10.25 - 10.5 it shouldnt be the compression

what to do??
Im thinking the DynaS ????

Recent problem or since engine /bike was built? When did it start - as in what happened just before that could have changed things?

Which year of 1000 is it? (I'll assume its 1980 here). What carbs?

I'm guessing under large engine load and large throttle openings, too.

I've had problems with contaminated fuels occasionally.

Have you checked the pistons (not just no. 1 - all of them) for TDC matching the marks on the timing plate (using a degree wheel and piston stop)?

On top of raising needle and / or increasing needle jet and mains, how many turns out on the pilot screw (or turns in on the pilot air screw - depends on what carb you have)? I would try maybe 1 1/2 to 2 turns out or 1 1/4 turns out, respectively.

Ruling out a batch of bad fuel, If it isn't happening after 6000, my strong guess is carburetion, ignition advance too much too soon is next suspect.

Well? new pistons or used? Reliable machine shop? Cast or forged pistons?
I'd hate to say if pistons are used or boring was not correct.
You have loose tolerance between cylinder wall and piston skirt. That's your knocking under a load.

Cast pistons are bored nice and tight.
Forged pistons with high silicone content are bored .002 or .003 looser.
They expand with heat to seal.

z1kzonly wrote: Well? new pistons or used? Reliable machine shop? Cast or forged pistons?
I'd hate to say if pistons are used or boring was not correct.
You have loose tolerance between cylinder wall and piston skirt. That's your knocking under a load.

Cast pistons are bored nice and tight.
Forged pistons with high silicone content are bored .002 or .003 looser.
They expand with heat to seal.

Off topic a bit but my cam ground, forged pistons rattle like crazy when dead cold but I can hear them quiet down in just a few mins.
Depending on where the clearances are measured before final assembly, tight areas were right at +.003"
However the wide clearence areas around the skirts....really startled and concerned me at first!!
But the engine runs super strong, uses no oil to speak of after close to 4500 miles now and when changing the oil and filter, the oil is still looks nearly new, clear and relatively carbon free when I do....(which has been about every 1800-2000 miles after break in.)

My KZ1000MKII always detonated under load even using premium fuel. It is dead stock. I made the mistake of installing a 10.25 to 1 piston kit in a GPZ1100 and it was not even ridable from detonation. They are a design that doesn't fare well with heat and high compression, or even heat and low compression. If your MTC kit is 10 to 1 compression or higher you will never get rid of the detonation most likely. Just my experience, others run 12 to 1. Sure they do.

Try standard plugs. What carbs?
Steve

Ive top dead center the engine with a degree wheel and the "T" adjusted so it was spot on (when i squeezed it the way i tighten the bolt it matched perfect
The Dyna S was adjusted at around 2-3000rpm/full advance and set to the advanced marks - also tried to just adjust with the "F" mark but no difference
I've tried stock spark plugs and no difference

The Pistons are 'standard' MTC 1075cc/72mm and the company who did it usually do dragcars and also old Ferrari, porsche due to their machining skills - the piston fit seems very nice compared to my 1200cc REC piston kit which was done by a german company (dont buy from them)

I haven't done anything really to the carbs due to i wanted to go for a dyno run when the engine had some KM on it (and when i got rid of the detonation) - have done around 1000km but only more or less with a soft throttlein the middle rpm due to the detonation

Carbs are Mikuni 32mm TMR's with KN-filters and im running with 145 main jet and if i remember correct the needle was around the middle but will try to lift it just to see any difference

I have a Dyna 2000 system on my bike, and occasionally get minimal detonation when pulling away from dead stops. It occurs mostly when it is hot (90+ degrees F.) outside, and/or when carrying a passenger.

Can this detonation be eliminated by adjusting the engine timing?

larslykkegaard wrote: Ive top dead center the engine with a degree wheel and the "T" adjusted so it was spot on (when i squeezed it the way i tighten the bolt it matched perfect
The Dyna S was adjusted at around 2-3000rpm/full advance and set to the advanced marks - also tried to just adjust with the "F" mark but no difference
I've tried stock spark plugs and no difference

The Pistons are 'standard' MTC 1075cc/72mm and the company who did it usually do dragcars and also old Ferrari, porsche due to their machining skills - the piston fit seems very nice compared to my 1200cc REC piston kit which was done by a german company (dont buy from them)

I haven't done anything really to the carbs due to i wanted to go for a dyno run when the engine had some KM on it (and when i got rid of the detonation) - have done around 1000km but only more or less with a soft throttlein the middle rpm due to the detonation

Carbs are Mikuni 32mm TMR's with KN-filters and im running with 145 main jet and if i remember correct the needle was around the middle but will try to lift it just to see any difference

I had that problem with my 33's. Had a lean spot just off idle and had to step over it. The bike would get hot and the throttle was all on or all off. Turned out the PO of the carbs drilled the emulsion tubes. I soldered the extra holes he drilled in them, the bike ran like with the stock 28's. I'm not saying someone did that to yours but you might try a smaller air jet or different tubes/nozzles. Raising the needles might help but if it does, that might be your problem. Don't forget to sync the carbs anytime you disturb the slides.
Steve

z1kzonly wrote: Cast pistons are bored nice and tight.
Forged pistons with high silicone content are bored .002 or .003 looser.
They expand with heat to seal.

Weisco forged pistons use something like .0025-.0030" clearance total. OEM cast pistons are about .002-,0025" so not that much different.

Nessism wrote:

z1kzonly wrote: Cast pistons are bored nice and tight.
Forged pistons with high silicone content are bored .002 or .003 looser.
They expand with heat to seal.

Weisco forged pistons use something like .0025-.0030" clearance total. OEM cast pistons are about .002-,0025" so not that much different.

All the Wiseco's I've put in lately wanted (instructions) really tight piston to cylinder clearances - 0.0015", which seems like asking for piston seizure.

I don't do that - I like to set at 0.002" for street engines and trail machines. Racing stuff gets 0.0025" NA, Turbo / NOS 0.0025-.0035". Blown / injected Fuel (when I do my ultimate statement TF KZ engine someday) will be 0.004 - 0.005"......