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Re: [turbobike] Compression Ratio

Mon, 8 Nov 1999 08:04:25 -0500

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Hi Steve,

For a street ridden 2 valver on pump gas I would go no higher than 8:1.  Those
Kaws will give you fits with detonation, especially if you want to run any
appreciable boost.  See if you can come up with a 1428 kit to make up for the
reduced compression.  I know the Wiseco catalog only lists up to 1260, but they
do exist.  I like the MTC pistons and their standard thickness hard chrome pins
(even the small 17mm versions for the older Kaws) work well until you really
turn the heat up (like 300 Hp).  The new Wiseco pieces are very good, though.
They solved their problem of wrist pin galling and the pistons have gotten much
better.  Use the heavy wall hard chrome pins from Wiseco if you go that way.

Make sure you take the squish out of the motor.  Run a thick base gasket to put
the piston squish band height at least 0.050" below the cylinder top surface.
You might be able to run the 10.25:1 pistons and use a very thick base gasket to
both reduce the compression and take out the squish.

One option is to go with two plugs per cylinder to reduce the flame travel path.
You can then retard the timing a bunch without losing anything.  The drawback is
that it tends to weaken the head, and you have four coils and eight plugs &
wires to deal with.  It makes a nasty sound when the head splits open down the
center.....trust me.

The oversized valves will help but you'll need porting to go with them.  Your
'83 will make a nice cylinder head.  I have a good source if you are interested.

 Your stock cams will work well.  Several six second funnybikes use those exact

Run a big oil cooler, or else run two smaller ones if they fit better.  Don't
block the airflow to the head and cylinder with the cooler.  I took 40 degrees
out of the running oil temp. on my FJ with the addition of a second cooler, and
gained oil pressure in the process.  I mounted it down on the chin fairing,
right in front of the water injection tank.  You'll need one of those on your
bike for sure as well.

It sounds like others have had good experiences with those thermal barrier
coatings.  I've never tried them myself.

Good luck.

"Steve Leonard" <sleonard@buffnet.net> on 11/05/99 02:20:18 PM

To:   turbobike@natvideo.com
cc:    (bcc: Bob Shammas/EQA/Nsk-Corp)
Fax to:
Subject:  [turbobike] Compression Ratio

I am building a 1983 GPZ1100, with a MoTeC M4 engine management system and a
IHI-RHB5 turbocharger.....

Since this a 2-valve motor and I want it to be some what streetable
(preferabably pump gas), what compression do you recemmend, (1260cc), to reduce
detonation I can retard the timing as boost increases with the MoTec software.
 Also will any great benefit be obtained with 1mm over-size stainless intake and
exhaust valves?
 Is there any advantage to having the combustion chamber and pistons "coated"
with the thermal barrier compounds that are available?( I live about 10miles
from a place that does it)


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