F3 barrels VS Stock well modified Vs R etc etc

[dave32]

After reading up on any F3 article i can find,it seems its still a mystery as to what spec the barrels are ported to,the only article i have found mentions the barrels are raised a mm,thats it.
MJ mentions in an article on here that his own spec barrels are better so im assuming hes seen the F3 spec ones?
Does the R model use F3 spec barrels?
anyone shed some light on this?
Cheers
Dave

[maccas]

This doesn't really help but I read that the KR1-F3 cylinders became the standard cylinders for the KR1S.

I assume the F3 kit cylinders for KR1S were different again.

Dan

[dave32]

Yes it is helpful Maccas
Would be interesting to know for sure if the porting spec was actually different though on the S F3/R models rather than just have to assume they are.
Hopefully MJ can help with the facts,after you cant "do better" if you dont have anything to compare to.

Dave

[dave32]

Well looks like Nobody can help,not even God?
quote MJ,
"Barrels,i can do better"
Must have been a misprint,either that or its all Top secret.

[TwoStroke Institute]

Have you understood pit-lane? What makes the HP is blowdown area or if you don't have area, blowdown time, and lots of blowdown time AND area makes even more HP. Why worry about the mystical F3 stuff when you can transpose from the pinnicle of two stroke design?
With a Stock rod in mm from TDC
Main open 26mm
Sub open 27

A Transfer 40mm
B transfer 39.5mm
C transfer 40.75

Leave the transfer ducts as they are and weld a hump in the exhaust duct.

Done.

[mj43]

So you are saying that the

Main 189° Duration
KIPS 185° Duration
T1 120° Duration
T2 123° Duration
T3 116° Duration

and what to do with the expansion?

On piston speed if the Aprilia peaked at 13,000 the shorter stroke KR will go to 13,300 is this factored in?

[mj43]

Well looks like Nobody can help,not even God?
quote MJ,
"Barrels,i can do better"
Must have been a misprint,either that or its all Top secret.

Dave
I did see the specs and have them somewhere. There was a copy of a Japanese manual floating around. However, the F3 kit was more than barrels including, ignition, power valves, barrels, head, pistons, expansions, radiator - and I think clutch?

I will when I get time do a rubbing of my porting and post it up. From what I remember compared with F3 barrels the transfer area is greater, KIPS and main exhaust are about the same.

From KR-1 to K-1S to KR-1R Kips ports got bigger. They break Jan Thiel's advice of going past the centre line of the bore. I can't say I have done tests to say whether it works better or not going past the centre line but I do and so does the 1S, 1R and from memory the F3/SP barrels.

[mj43]

.... weld a hump in the exhaust duct.....

Like this?

[Luders]

.... weld a hump in the exhaust duct.....

Like this?

What's the idea around that then?

[mj43]

I believe it sends a low pressure pulse back in to the cylinder which ideally arrives at the transfers as they open helping to start the purging/filling process.

TSI can clarify

[KR-1R]

KR250 EXdur (BBDC ABDC) ** SCAVdur (BBDC ABDC)
B. ........186 (93 93) ** 126 (63 63)
C. ........186 (93 93) ** 126 (63 63)
D. ........188° (94° 94°) ** 126° (63° 63°)

KX125 ........EXdur ** SCAVdur
90 (50.6) ......187 (93.5 ..) ** 131 (65.5 ..)
91(50.6) ....... lo187 hi191 (L93.5 H95.5) ** 131 (65.5 ..)

a touch higher exhaust with 5° more scavenging duration (out of the box) is how the MX models evolved different to the KR
on a road bike model they need to be more conservative for emission and fuel economy - its less of an issue on a MXer built for competition - and as MJ said to work in conjunction with other parts

the above figures are a bit like a persons weight - it doesn't indicate how fit or how fat they are - so you won't know the width of the ports or their direction - you won't get direction from any port rub either, or know what is happening beyond the port apertures

I haven't seen any F3 tuning manual ! - for the most part on other kawasaki`s these were thin, basically hand drawn, rough typed up sketches cut and pasted together... However there is a few photos of the Formula 3 kit I've collected if you search our forum on "FORMULA"
the kit pipes look fairly close to standard S pipes dimensions (if not identical stampings) and probably are basically that Except they areHALF the weight and built with springs for ease of serviceability and crash damage

http://blogs.yahoo.co.jp/okatasi2004/9323948.html

http://blogs.yahoo.co.jp/okatasi2004/9464865.html

http://blogs.yahoo.co.jp/okatasi2004/9868738.html

[salty]

In the pictures posted by KR1-R there is a photo of an F3 Piston




I have a very similar piston that I took out of an engine with one Stan Stephens provided barrel - has a similar style cut out - is this the same?



Salty

[KR-1R]

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all the early KR1 pistons came like that (not 100% PTFE coated though like the kit ones were) - yours will have remains of antiscuff coating/stripes down the skirt exhaust port lube holes

...very clean piston, yours - check the ring pegs/pins - they are probably halfway above the ring grooves - a 13001-1354 piston

the skirt port (& tunnel) will PARTIALLY ! expose ! the 2 B (aux/sub) transfer ports ~10mm stroke (~16°) earlier than the piston crown does on the A transfers (MTR), B transfers (STR) and rear Boost port
the 2 transfer ports are partially uncovered much earlier by the tunnel in the piston but nothing will actually flow through 'OPEN' until the crown of the piston (stroke) reaches where the exhaust port starts to open and the whole system can start to move.

BUT I'd say the hole needs to be almost twice as tall to have any real effect (more than a mere couple of degrees) and without the wider width of the KR-1S sub-exhausts doesnt get a chance to bridge/cross flow - see discussion on gudgeon pin plugs (and how two adjacent port might cross contaminate by way of piston hole)
first to open is also last to close

http://www.youtube.com/watch?v=w8sidsux9D0

the skirt port might extend the scavenging duration somewhat and affect the initial direction...
you might have the ability to alter a cylinders timing characteristic - just by changing a piston without altering the barrel
(dont quote me on the fag packet ideas and maths though - and NONE of the magazines actually determined what that HOLE did)
it has the definite potential to leak fresh charge, down a wider sub exhaust port, into the header before being followed by some burning combustion gases - maybe not so flash, think KawasakiAntiLagSystem without a turbo or retarded ignition.

viewtopic.php?t=2701&postdays=0&postorder=asc&start=15

[salty]

Your right - its what I call the "early" pistons with the uncovered peg - its in good nick but can stay on my shelf - don't suppose anyone will want a single unmatched piston.

Had 2 engines both with unmatched pistons - but they had one good pair between them - this is one of the leftovers, but none of the others had the cutout

Thanks

Salty

[KR-1R]

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I have one NOS -1354

I WANT TO INSTALL A (HORIZONTAL) KIPS STYLE SPOOL VALVE IN THE REAR BOOST PORT