KZ1000 MK2 detonation problems

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

Couple of things - Do we know what year it is yet or did I miss that?

The reason I say check TDC marks on all cylinders is because of the possibility the crank shaft might be twisted - it is a pressed together crank, right? I know that is unlikely if no. 1 lines up, but that isn't a guarantee, either. If I'm serious about tuning a particular engine, I check all cylinders and make my own accurate TDC marks.

Maybe try backing the ignition off a bit and see what happens. Get a good timing light that allows for setting and adjusting the advance. Here those are about $175 CAN. for the least expensive ones.

APE did my 700cc Weisco's right at .002 to be run on the street..... if I remember right I asked him to bore em leaning toward the tight side (that he felt comfortable with)

These are their specs.
Steve

Oh, yes, with unleaded fuels, the KZ chamber design does promote detonation....hemi is not the best chamber from an efficient and even mixture burning perspective, and the KZ makes it even worse by having the spark plug way off to one side instead of dead center.....

One day when I have the time and some extra large chunks of billet 6061 alloy just lying around, I want to machine what I think would make a better, 4 valve, central spark plug, multi piece, KZ cylinder head design to work with an 85 mm flat top piston design. It would also feature straight in and straight out fully machined high "D" ports and runners, oil cooled intake runners and valve pockets / combustion chamber domes.....and a target of 16:1 or higher compression ratio (for anyone who doubts that number - research what CR the top pro stock bikes are using these days.....).

Until that grand day...see picture at left for what twin plugs in a J head look like. If you can see, both plugs are machined straight down, and are 10 mm dual ground electrode plugs. Picture was taken shortly after the head was welded and the new plug holes were machined in. It has seen many more refinements since the picture was taken. I'm going to run actual 12.7:1 compression on that one, 1394 cc, and target is no detonation with a special ignition system using the Dyna 2000 as the core component with 8 deg. initial ign. advance, with full 32 deg. advance at 3600 rpm. Of course, those are my theoretical numbers....major revisions might be necessary when I get to testing those theories

Kray-Z wrote:

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"......

I've discussed this at length with a lot of very knowledgeable people, both here in Aus and in the US, the general consensus is NOT to compare modern forged pistons to those of the "good old days", After years of testing and making forged pistons, modern alloys used to make them are far superior to those used in the past, hence the tighter clearances, expansion rates aren't what they used to be...

What was my best local parts guy (until he got tired of all the BS he was putting up with here and moved away, damn it...) stopped recommending Wiseco pistons (aren't all of Wiseco's performance pistons forged - BTW?) completely.

I asked him about that, as I have never had any quality issue with any Wiseco piston; in fact I'm an ardent promoter of the drag racing KZ1260 super-lights (out of production now). He said too many customers were complaining of seized pistons when they were installed by his mechanics. I asked what cylinder clearances they were using. He said "whatever is on the box label". I said "that is why you are having problems"....

I wonder what type of alloy Weisco are using now and its silicone content.? The last 2 sets of forged pistons I bought were JE pistons made to a custom order bulk buy, but in saying that, Weisco 836 kits are very common in Honda 4's and I haven't heard of many seizures in them recently..?
4032 and 2618 seem to be the common alloys used in forgies, 4032 has far less thermal expansion than 2168 and is better suited to road applications...4032 has about 11% silicon, the older "rattling" forgies were closer to 7% silicone and therefore had more thermal expansion....

No doubt the alloys are getting better, along with the obvious leaps and bounds of progress in CNC manufacturing, but I'm going to theorize, with some knowledge behind my idea, that CAD (Computer Aided Design - not just drawings) also has a big influence on the newer stuff being better designed for controlled and predictable thermal expansion and thus able to run tighter clearances. But I still say 0.0015" is just a little too tight to account / allow for variations in cylinder and piston manufacturing / machining and engine dynamics....

Kray-Z wrote: No doubt the alloys are getting better, along with the obvious leaps and bounds of progress in CNC manufacturing, but I'm going to theorize, with some knowledge behind my idea, that CAD (Computer Aided Design - not just drawings) also has a big influence on the newer stuff being better designed for controlled and predictable thermal expansion and thus able to run tighter clearances. But I still say 0.0015" is just a little too tight to account / allow for variations in cylinder and piston manufacturing / machining and engine dynamics....

Or, do what I did and buy a billet aluminium block with similar expansion properties, also running Nikasil bores, so no conflict with the cast sleeves.....
I agree, run a bit more clearance but, it still shouldn't knock...

Ended up mounting a Dyna2000 - adjusted it to 40" advance and was running great in 2 program


- Thanks for all the inputs

larslykkegaard wrote: Ended up mounting a Dyna2000 - adjusted it to 40" advance and was running great in 2 program


- Thanks for all the inputs

Nice move on the ignition.
My engine runs good in setting 2 as well. Dynatek (tech) suggested to set timing set at 36-38 degrees, but I'm not clear why since the spec in our FSM is 40. Mine is set at 38+/- based on the tech recommendation.

Thanks in advance to anyone who would care to describe the reasoning of that.

38 Deg provides best power for 2 valve heads.