72mm Piston options

[NorthernJordan]

Hi All,

I'm thinking of putting an old rapido 240 barrel I have back into service and I'm looking for piston options.
The bore is 72mm.

AF do Wossner pistons however can someone clarify what's involved with fitting one with a 60mm/110 crank?
Do I still need to trim the skirt?

http://www.afrayspeed.co.uk/index.php?p ... buteID=P25

[Warkton Tornado No.1]

Wiseco (http://www.wiseco.com/Catalogs/Powerspo ... atalog.pdf) make 2 mm oversize (Ø72 mm) pistons for the Suzuki TS or RM250 & Kawasaki KDX250, but you need to check the rest of the geometry for your application. Ebay can often have the odd bargain:

Wisec KDX250.JPG

Wiseco Suzuki RM 250.JPG

[dscscotty]

AF do Wossner pistons however can someone clarify what's involved with fitting one with a 60mm/110 crank?
Do I still need to trim the skirt?

Hi J-sent you an email

[lofty]

Kawasaki H2 was a popular 240 piston (as per DJ tuning manual).. there are wiseco and wossner versions around.. 72mm is probably at the limit.. ive just done a 71mm rapido with a wiseco H2 and theres not a lot of meat left..

[NorthernJordan]

Kawasaki H2 was a popular 240 piston (as per DJ tuning manual).. there are wiseco and wossner versions around.. 72mm is probably at the limit.. ive just done a 71mm rapido with a wiseco H2 and theres not a lot of meat left..

I was under the impression the H2 piston required a 116 rod?

[lofty]

Kawasaki H2 was a popular 240 piston (as per DJ tuning manual).. there are wiseco and wossner versions around.. 72mm is probably at the limit.. ive just done a 71mm rapido with a wiseco H2 and theres not a lot of meat left..

I was under the impression the H2 piston required a 116 rod?

I guess that's arguably the best configuration (or 115 rod).. but you can do it with a 107/110 rod but you would have to shorten the barrel..

[Warkton Tornado No.1]

Post by NorthernJordan » Mon Jan 09, 2017 3:47 pm

lofty wrote:
Kawasaki H2 was a popular 240 piston (as per DJ tuning manual).. there are wiseco and wossner versions around.. 72mm is probably at the limit.. ive just done a 71mm rapido with a wiseco H2 and theres not a lot of meat left..


I was under the impression the H2 piston required a 116 rod?

I think that the Kawasaki conversion became popular ‘back in the day’ due to the gudgeon pin size being identical to Lambretta S3 @ Ø16 mm, whereas the Suzuki piston uses Ø18 mm.

However, with the option of being able to use con-rods with bigger small ends, ‘conversion’ needle roller bearings & the availability of caps for gudgeon pin ‘conversion’ the Suzuki can be a viable selection & very affordable if you shop around for OEM or good quality pattern pistons. I personally have used Mitaka & Wiseco. I have also used gudgeon pin caps with no reservations after experimenting with various types.

Currently, I use a Rapido with a TS 250 piston @ Ø71 mm with a 61 mm stroke & it is very grunty, despite having a Vega/J range flywheel.

The centre to top edge (crown height) of the TS 250 piston is 35 mm so that would appear to place it within a nat’s of your (presumably!) existing crown height of 39 mm with your 110 mm con-rod length.

You might need to have the barrel base skimmed but as you will probably be modifying the cylinder head, you’d be best to see if you’d get away with insetting the head into the bore (no bad thing!) to make the assembly ‘fit’ to your required squish, port timings etc.

I hope all of this helps....