Piston. 47mm 48mm & 48.5mm Higher compression ideal for tuning C90 engines

Piston. 47mm 48mm & 48.5mm Higher compression ideal for tuning C90 engines
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£44.99 £37.49 ExVAT


Product Code: 5736

Piston. 47mm Higher compression ideal for tuning C90 12v CDI engines

Standard 47mm = 85cc 1mm over size = 89cc

New version with extra valve pocket clearnce inacse of an over rev!

Rather than the stock dish topped piston this has a crown.

1 X RK ring set to suite size

1 X piston custom top with wider valve cut outs

1 X pin and clips. 13mm

We have now modified these pistons to work directly with the stock 90 heads and E22 heads saves on the hassle with incorrect cam chain tension.

Piston to valve clearance we haven’t got to alter the pockets for the stock C90 and E22 heads so all good there for stock cams worth checking if you’re using over 7mm lifts.
At the moment piston to valve clearance at 12 degrees before and after is 4mm so safe; you can run them as close as 2mm but no less.

Also check you have 2mm on rocking stroke TDC 2mm min incase of and over rev.


Closet point to the head .70mm using stock 1mm gaskets any less you are at risk with piston to head contact resulting in the top lan failing.

Sadly price is high as these have been air freighted from Japan and we have had to invest in setting up to machine them all.

This is the very last standard pistons we could get..

Made in Japan

This piston don’t just expect to put it in and ride it, as it almost 11 to one compression ratio you have no room for error with ignition or fuelling, before you will end up melting the crown or sizing up.

List f don’ts

1 Don’t use stock C90 CDI units you need one that will advance and retard verses revs.

2 Don’t use a CR7HSA only use a C7HSA unless you’re running D/C ignition.

3 Don’t just copy your mates jetting as there are a number of different cabs and needles that look the same, also main jet numbers don’t always mean the same thing. Some are flow rate some are in MM and some are just unknown!

4 Make sure you get it dyno set up, best results around 11 to 12% AFR one acceleration and no weaker that 13% flat out.

5 We recommend for endurance you run and oil cooler as they will start to burn the oil when it’s getting to hot.

6 Valve timing, if you want the best possible performance then set the LCA equal, inlet and exhaust.

 

We have set up and dynode 11 bikes with this set up non of them have failed only the ones without oil coolers have lost their oil.

Worth running 20/50 if the ambient tamp is over 20c

Pistion kit only photo shows relation to cylinder

MODEL

CUSTOM

OEM No.

 

BORE(mm) :A

47

LENGTH(mm) :B

47.00

PIN DIA (mm) :C

13

COMPRESSION HIGHT① (mm):D

23.00

COMPRESSION HIGHT② (mm):E

19.5

PIN LENGTH (mm) :F

38.5

  

STROKE

4

Product Code5736
ConditionNew
Weight0.2Kg

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