【SIP PERFORMANCE】 クランクケース SIP，EVO，56mmストローククランクシャフト用

aluminium cast
black
125cc intake，3-hole，LIMA bearing seat 20x47x14mm
Reinforced，large cylinder base sealing surface
TUNING RACE - for professionals

Performance diagramsはこちら

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New SIP EVO Smallframe engine case，precision machined and fly cut in Germany to accept long-stroke-crankshafts as a straight fit.
Our SIP long-stroke engine cases 24311000 and 24321000 are custom made to accept our SIP Performance “Uncle Tom” crankshafts.
Even the largest version with 56mm stroke and 110mm conrod length is a straight fit without a need for any further modifications.
56mm stroke is the absolute maximum that can be used without a dedicated wider crankcase.
The following cranks，among others，are particularly interesting for discerning tuners because of their long conrod：
Crankshaft DRT stroke 53/ conrod 105，art.
no.
45094000
Full circle crank Mazzuchelli 54/105 for Vespa 50，art.
no.
45066000
Full circle crank Mazzuchelli 54/105 for Vespa PK ETS，art.
no.
45068000
Race crank Mazzuchelli Race 54/105，art.
no.
45069000
SIP Performance Uncle Tom 54/105，art.
no.
45029100
SIP Performance Uncle Tom 56/110，art.
no.
45029200
A conrod-length of 105mm and over means the conrod length better correlates to the stroke.
A rule of thumb is twice the stroke for conrod length，and 105mm is much closer than the original 97mm.
As a result engines built with these cranks tend to run more smoothly.
The additional conrod length is compensated with a cylinder spacer.
If，for instance，you use a Polini 133，intended to run with a 97mm conrod，with a crank 105mm conrod the 8mm difference in conrod length is dealt with by an 8mm packing plate (art.
no.
90793910).
The longer stroke of 54mm means engine capacity goes up to 140cc.
More interesting than the gain in capacity though is the option to play with port times and squish clearance without having to machine cylinder and head.
You may of course use other cranks with different specifications by other manufacturers (Falc，Fabbri etc.) in the machined SIP Evo engine cases.
Usually this requires only minimal work on the casings.
Still you MUST ALWAYS make sure the crankshaft and the conrod does not rub anywhere before you do the final engine assembly.
We have the crankcase fly-cut to 89mm where the webs of the crank sit.
Between the webs there is a channel for the conrod with 90.5mm which tapers out towards the barrel，to make sure the angled conrod does not rub.
In the course of the machining the centring lip around the engine case is removed carefully.
The centring of the engine case，as with most modern engines，then comes courtesy of the standard centring sleeve on one of the forward engine bolts and the original centring pin in the rear of the engine case.
Other than that the 24311000 and 24321000 engine cases share the same features as the EVO-engine cases 24301000 and 24302 on which they are based.
That’s the large cylinder base gasket area with no dust lip towards the flywheel and the outside contour of the transfer is not machined where the stator plate sits.
If you decide to use the SIP Performance ignition we recommend to use the Race ignition baseplate art.
no.
51009120.
Attention：The cylinder base bore is not machined or enlarged.
The rotary valve sealing pad is no longer usable after the flycutting.

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