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Old 05-16-2010, 12:36 AM
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Default MVVS 12

I just bought (stole actually) a NEW MVVS 12 engine from the eBay "Buy It Now" feature for only $60.00. Received the engine today and it is sure enough a NEW condition engine .... it has the number 12 machined into a smallish circle on the left side of the lower crankcase, will this denote the vintage or age of this big bad boy?!

Can someone tell me the bore of this engine particularly in comparison to the .60 size MVVS? You can likely guess my next question as follows: Will the MVVS .60ci factory diesel head option work in this MVVS 12 (.77ci) engine? And is this MVVS 12 engine indeed STOUT enough to handle diesel operation? Last question: Is there a website or other source where I can fetch up the paper-work (manual / instructions, etc.) on this engine? I have been a Small-Bore (mostly .15s) MVVS Engine Fan for a long time and have always desired a nice Big-Bore MVVS and sure enough one has finally "Fell In My Lap", so to speak!

Thanks to any and all who might comment, offer hints / advise on operation, return feedback, etc. on this engine and my related questions. Sincerely, Donald Garry
Old 05-16-2010, 02:18 AM
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Default RE: MVVS 12


This engine has a 12.7 cc displacement and is indeed the .77 cid model.
Later versions of this engines used a black-on-red 'plaque' pasted onto the side of the crankcase; printed '13', to more correctly denote its displacement.

The bore of this engine is 25 mm and the stroke is 26 mm.

It shares its crankshaft with the 15 cc .91, which in turn uses a 27 mm diameter piston, making the .91 the sole 'over-square' engine, in this MVVS class of engines.

The 12.7GFS/R is 'under-square' (what has become popularly known as 'long-stroke'); but it shares neither of its smaller, 10 cc sibling's bore and stroke dimensions (23x24 mm, like the OS.61SF engines).

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