TOPIC:

hey guys i'm currently in the process of building a turbo motor for a kz. i have a kz1000 block bored to accept forged 1075 10.25:1 wiseco pistons, i'm using a fresh j head to get the compression ratio down to the low 8's, i have a welded crank, planning on using a hobb switch tied into a dyna 4000 to retard timing upon boost. i assume heavy duty cylinder studs, back cut trans, and mls head gasket would be a good investment as well? i will be using stock cams as i dont see a big cost justification for using different grinds. the turbo kit is a mr turbo with an f25. i plan to run 12 psi or so normally with the occasional 20 psi run with some higher octane fuel. ill probably eventually get an f40 turbo as well if the f25 back pressure gets too high. 

am i missing anything here? what would you guys recommend. open to all suggestions, thank you. 

What is your budget ?
APE    Lower end studs , Top studs and  new hd  nuts.
O ring cylinder  with one pc copper head gasket.   ( cometic )
HD clutch pieces   , shift bushing 
If you want more advise  just ask  
Dave

I'm currently building this.
It's pretty much the same spec you are considering with J head and 10.25 pistons but with zero deck height you will only drop the comp to around 9 to 1 with just the J head so will need a barrel spacer to get down to around 8 to 1 or slightly under.
The mls head gaskets are good for the increased pressure and will negate the need for piano wiring as long as the head and barrel surfaces are clean and  free from any deep pitting.

Quick spec of mine.
Rajay f40, Mikuni HSR42 carb,  HD case and barrel studs, back cut trans, billet 2nd gear, welded MK2 crank, 10.25 wisecos, MLS head gasket ( no O,rings ) , Ported J head with larger stainless valves, APE guides, hd valve springs, HD camchain, Manual camchain tensioner, Solid idler sprockets,  GPZ1100 Unitrack cams on slotted sprockets , lock up clutch with roller pusher and Bill Hahn boost retard ign.



 
 

Rob that looks outrageous !!   will you need to "heat-shield" the underside of the tank so it doesn't vaporise the fuel with the header running under the tank??

Wookie58 wrote:

Rob that looks outrageous !! 

 will you need to "heat-shield" the underside of the tank so it doesn't vaporise the fuel with the header running under the tank??

Thanks, Should be fun when it's finished..
Yes! The link pipe will be wrapped with an insulation blanket that cuts down up to 96% of the radiant heat , The underside of the tank will be lined with reflective insulated adhesive mat that does the same and for proper belt and braces there will a heat shield that bolts to the redundant coil brackets.
The underside of the tank will probably experience less heat than it normally would..

the barrels are unmodified except for them being bored out- so you think i should get a spacer to lower it further? i thought putting a j head on kz pistons lowered compression 2 points not one? thanks for the response!!

since ive already put so much into it i would say there isnt really a budget, trying to make it last is all im truthfully concerned about, now that being said i dont want to put another 5k into it haha. i wont be driving it too much as i have 7 motorcycles at this point but maybe 2 times a month or so. picking up a turbo for my cbx in the next few weeks 

QUESTION: Since the 1100 (KZ-B1 etc) has the same CR as the 1000J&K is it fair to assume the 1100 has a larger combustion chamber (everything else seems the same) if that is the case then a 1000 head on 1100 barrels would give a CR of approx 10:1 and in reverse would an 1100 head not give a reduction of 1 point on a 1000 ???   (fag packet maths here)

Wookie58 wrote:

QUESTION: Since the 1100 (KZ-B1 etc) has the same CR as the 1000J&K is it fair to assume the 1100 has a larger combustion chamber (everything else seems the same) if that is the case then a 1000 head on 1100 barrels would give a CR of approx 10:1 and in reverse would an 1100 head not give a reduction of 1 point on a 1000 ??? 

 (fag packet maths here)

All the 998cc /1089cc J type non kickstart engines have a 40cc chamber volume ( including the GPZ1100A Unitrack bathtub head )
All the 903cc/1015cc kickstart engines have a 36cc chamber volume.
Any compression ratio differences between models of either type is due to the piston dome volume not the chamber volume.. ( unless you are fitting a J/GPZ head on an earlier motor )..
 

turbodarnell wrote:

the barrels are unmodified except for them being bored out- so you think i should get a spacer to lower it further? i thought putting a j head on kz pistons lowered compression 2 points not one? thanks for the response!!

The statement often quoted that the J head drops the comp of an earlier engine by 2 points is a sweeping generalisation that is not actually accurate in all applications.
The drop varies depending on bore size, deck height, compressed head gasket thickness, actual chamber volume ( which can vary slightly due to valve recession etc)  and the stated compression ( dome volume ) of the pistons being used.
In actual fact the comp drop is closer to 1.5 points with the 1075cc - 10.25 -1 pistons which will put the comp closer to 8.75 -1 with zero deck height so will need a spacer of a calculated thickness to achieve the 8-1 or thereabouts you need.


 

gotcha because the bore size changes then the compression ratio also changes. i ran the numbers on summits compression ratio calculator came up with 9.1:1 after changing cylinder head volume from 36cc to 40cc so i guess i will need a spacer under the jug.. makes sense. i appreciate the help. anything else you can think of that im missing? looks like ill need about .06 of compressed gasket thickness to get my comp down in the low 8's like i want 

zed1015 wrote:

Wookie58 wrote:

QUESTION: Since the 1100 (KZ-B1 etc) has the same CR as the 1000J&K is it fair to assume the 1100 has a larger combustion chamber (everything else seems the same) if that is the case then a 1000 head on 1100 barrels would give a CR of approx 10:1 and in reverse would an 1100 head not give a reduction of 1 point on a 1000 ??? 

 (fag packet maths here)

All the 998cc /1089cc J type non kickstart engines have a 40cc chamber volume ( including the GPZ1100A Unitrack bathtub head )
All the 903cc/1015cc kickstart engines have a 36cc chamber volume.
Any compression ratio differences between models of either type is due to the piston dome volume not the chamber volume.. ( unless you are fitting a J/GPZ head on an earlier motor )..


 

The bath tub heads are 37.5cc from the factory. And that is what my Uni-Track head still measures. My LTD head is at 35cc after I milled it .025.