www.zxrworld.co.uk

Ok Guys,
The forged kit pistons that Rob (toecutter on the board here) has been patiently developing are finally done.
They are made by Omega who are one of the best in the buisness, far superior to Weisco or JE. They manufacture for F1, WSB & Moto GP.

Crown shape has been taken from the set of Kit pistons that were sent to Rob (see thread viewtopic.php?f=117&t=10108)
The kit piston has a higher compression ratio (13.0:1), slightly higher compression height (for increased squish) with deeper valve pockets.
These are a CNC machined forged piston not a cast piston, lightweight & incredibly strong. They are available in 57.5mm (0.5mm oversize)
& 58.0mm (1.0mm oversize), Rob has both sizes in stock now.

Ok thats enough of the sales pitch please see some photo's below. Rob can be contacted here on the board,
memberlist.php?mode=viewprofile&u=3096
PM him if you are interested.
I have ordered a couple of sets already.
Regards,
Michael

Posting some Kit & Standard pistons to compare to, kit piston is on the left.

Nice !

Not wanting to upset anyone but surely they are cast that have been CNC machined rather than cut out of a solid billet - the photos clearly show granular casting rather than the tell tale milling marks you would ecpect to see on all surfaces

But I know there are two types of casting and the one using dropped molt and pressed (that right) is reffered to as forged rather than slow pour into a mould for regular cast.

If I blow up my BEET engine I may have to drop the hammer on a set for the next build

MM!

Mori thanks for the reply,
However they are a forged piston, grain structure is off the die, check the lack of separation lines on the underside of the piston & uniformity & size of grain structure. Cast pistons are generally die cast not sand cast, the die needs to be disassembled to remove from underside of piston from contraction after casting, hence separation lines. A Cast piston will have a larger unhomogeneous grain structure whereas a forged one will have finer grain structure.....
toad it may be time to break out the old text books.. been a long time since I ran through this stuff.
For this type of piston a blank is forged then the finale shape is CNC machined. There is alot of technology in these pistons, check the bridge design on the underside.
Regards,
MB

how much are they

what i'd give for a 3mm oversize kit (444cc!)

price wise I suspect that if I have to ask, I can't afford them?

I've been waiting awhile for these, I've got a motor apart right now. Hopefully we can get the motor back together for the first races in March.

Ok a few more details
Weights for the piston assemblies are,
57.5mm dia piston 92.7g
Rings 4.1g
Pin 27g

58mm dia piston 99.5g
rings & pin the same.
The pin is supplied by Omega.

Std Kawasaki 57.0mm dia piston is 101g
Std Kawasaki Rings are 7g
Std Kawasaki Pin is 28g

0.5mm oversize Kawasaki Piston (57.5mm) weighs 104g
So you will be able to have the befit of increased torque in the 58mm piston without sacrificing the RPM ceiling.
Regards,
MB

AFM I am in exactly the same boat as you & looking forward to see what the motor can do.

Ok my batch of pistons have arrived, ready to stuff into a motor

Photos taken on phone, any details wanted I can get a higher res pic, also scales are postal scales to weight is prob +/- 1g
I will post some build photo's & dyno graphs when I get to it.
The quality in these things are amazing.
Regards,
MB

hey you got them then
glad you like em and the extra rings will be on their way soon sorry for the delay hope it wasa worth the wait
told you they are the nuts
rob

Rob,
Not wrong, engine is ready to assemble. I will let you know how it goes.
May have to twist your arm for a 2mm os set for the 750
MB

Ok bit of an update, had time to do ab bit of a dry assembly to check all clearances.
Strip the engine, linish the little ends to fit the new pistons & reassemble with used gaskets.
Lay some moddleing clay. Assemble, crank by hand & disassemble for inspection. Everything good to back together with some soft resin solder. crank by hand disassemble & measure either end & average.
Assemble head with checking spring & reassemble motor. Degree in TCD & dial in cams. All checked pistons came in,
Piston to head 0.67mm
Inlet valve to piston 0.72mm
Exhaust valve to piston 1.20mm
This was at 12deg btdc & atdc as per kit manual, cams at 105 inlet & 100 exhaust. Head was skimmed 0.5mm.
All in all pretty much spot on, could skim head another 0.1mm for exact piston to valve clearance but I am already into the seats. Going to rev to 15500rpm so a touch more will not hurt. I will get the burette out later to check but estimate compression to be about 14.2:1. Very happy with no need to pocket the pistons, the guys at Omega did their homework.
Regards,
MB

A few pics of the rest of the engine, head done with alloy/bronze seats as the sintered ones were starting to work harden & chew up valves at high rpm. Is cheaper to cut the seats than replace valves. Crank & rods out to re balance now that piston weight has been reduced.