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The new and highly awaited 3.5 cc off-road engine from O'Donnell has finally hit the European shores this week! Here's some pics of its internal parts and in an hour or so I will publish some newly taken shots of it assembled also. :)
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTFobLfIZI/AAAAAAAAByk/iARL1LAIZYk/s400/OdoSS21-carbparts.jpg)
![](//1.bp.blogspot.com/_1EKtN-2yN0w/SlTFk8MX05I/AAAAAAAAByc/PsKeVDA0S7g/s400/OdoSS21-explode.jpg)
![](//2.bp.blogspot.com/_1EKtN-2yN0w/SlTFeQfOjpI/AAAAAAAAByU/pdjxGQuGm7k/s400/OdoSS21-parts.jpg)
![](//2.bp.blogspot.com/_1EKtN-2yN0w/SlTGLbXWPhI/AAAAAAAABzc/3-oe85d3J2c/s400/SS21-cooling-head.jpg)
The cooling head is 60 mm in diameter...!
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTGvTRbQTI/AAAAAAAAB0c/S0q_6J5uYNE/s400/SS21-turbobutton.jpg)
The SS .21 engine comes with a combustion head-button for turbo plugs. There is also a O'Donnell #97T plug included. Also included are a button for normal threaded plugs. As standard are two 0.15 mm brass shims installed for a total of 0.55 mm squish height with the turbo head-button and 0.7 mm with the same shims and the std head-button.
On booth head-buttons the outermost squish is flat (about 50% of the width) and the inner most is slightly angled. The total volume is about 0.18-0.185 cc measured with a O'Donnell plug installed.
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTGrn8eW3I/AAAAAAAAB0U/7wjpKSUfcws/s400/SS21-sleeve-exhaust.jpg)
The brass sleeve is hard-chromed and has a simple and effective designed port layout with three intake ports and nicely (not huge = nice) exhaust port. There is no signs of any chrome burrs - very good. :)
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTGnVkL7zI/AAAAAAAAB0M/1YH0vVK5d0I/s400/SS21-sleeve-transfer.jpg)
The transfer ports are quite wide...
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The booster port.
![](//2.bp.blogspot.com/_1EKtN-2yN0w/SlTGcCJfTdI/AAAAAAAABz8/zdGKg581zR8/s400/SS21-rod-piston.jpg)
Piston and liner. It looks like the piston is not cast but billet type.
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTGX1aZpAI/AAAAAAAABz0/ptU3RbW1aKs/s400/SS21-piston-rod.jpg)
The con-rod is bushed at booth ends of course. Two oil-grooves on the piston. BTW, the piston has a completely flat top.
![](//1.bp.blogspot.com/_1EKtN-2yN0w/SlTGThZslDI/AAAAAAAABzs/mqbKIzHG1A4/s400/SS21-crank.jpg)
The crankshaft is 14 mm in diameter at the thick end and it looks cleanly designed. No silicone-ramp in sight that can come loose - nicers. :)
![](//1.bp.blogspot.com/_1EKtN-2yN0w/SlTGPUZtW2I/AAAAAAAABzk/U1TMKgJjTM0/s400/SS21-crank-b.jpg)
The crankshafts outlet so called "turbo-scoop" has a slightly different flow design then what most engines use.
![](//4.bp.blogspot.com/_1EKtN-2yN0w/SlTGHuJLMzI/AAAAAAAABzU/0kAiq8-_ae4/s400/SS21-case-up.jpg)
Crankcase from above. Booster and one of the transfer channels are seen. The head is fastened with std M3.5x16 mm socket head (hex) screws.
![](//1.bp.blogspot.com/_1EKtN-2yN0w/SlTGDC72rhI/AAAAAAAABzM/fn3OrTlEDF0/s400/SS21-case-rear.jpg)
The exhaust gasket in silicone seems to be of the std size. Thats good as all normal headers like fron Sirio, Nova & Hong Nor etc will fit. The crankshaft bearing fit was really nice on this motor - nice and just the right amount of looseness. Std socket head M2.5x8 mm screws are used at the backplate.
![](//2.bp.blogspot.com/_1EKtN-2yN0w/SlTF5nx5ugI/AAAAAAAABy8/b6RWAbR5-tc/s400/SS21-case-booster.jpg)
The booster channel in the middle flanked by booth transfer channels.
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTF9tD-7vI/AAAAAAAABzE/IeOTVMI53T0/s400/SS21-case-orings.jpg)
Double o-rings in the front box for sealing the carb.
![](//4.bp.blogspot.com/_1EKtN-2yN0w/SlXTK5Ld9qI/AAAAAAAAB00/pDsVrpFZW00/s400/SS21-carb-lock-2220.jpg)
The carb lock (6.9 mm in diameter) is sealed at booth ends with o-rings and is of a "double-squeeze" type.
Tip, if you want to remove it from the case - dont pull/push it out in one piece - you will break the o-rings. Unthread the screw and pull booth parts out at booth ends so to speak - you will save the o-rings.
![](//4.bp.blogspot.com/_1EKtN-2yN0w/SlTF1saDnrI/AAAAAAAABy0/0yCFqoIRXhU/s400/SS21-carb.jpg)
The aluminium carb has a 15 mm throat diameter and an "thermo insolating" sleeve pressed on. As standard there is a 7 mm plastic venturi installed and a separate 8 mm venturi is also included.
![](//3.bp.blogspot.com/_1EKtN-2yN0w/SlTFxZ_b4qI/AAAAAAAABys/G-AaNGNuvBM/s400/SS21-backplate.jpg)
The rear cover with its two funny loocking channel/grooves thaty match the transfer channels in the crankcase.
O'Donnell Racing Products
Distributed in Scandinavia by
Minicars.
You wanna see how the engine looks assembled? Klick
HERE.
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