I have just been pulling a 998 motor apart. It's a 9YATAH thin flange block, yet it has press fit gudgeons. I though only the A+ motors were thus fitted. The part numbers on the rods appear to be press fit type rods (12G127 & 12G124) yet it's an early engine. I believe it is standard bore size as well, but the pistons are marked AYA009 and are 3 ring pistons, which strike me as being a later piston.

Any ideas? I can only think somebody has put A+ rods and pistons into an early block, which strikes me as odd since it's still standard bore (I think, don't have my calipers handy).

I think it was at least 1980? or later that those rods appeared, in the A+ 998 (not ever sold here in Oz), so I agree someone has stuck `em in an early block.
One of the few A+ 998 improvements... no circlips to fall to bits when you give it the big rev.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

In the late 1960's these pistons were used for a very short time in the 998 engine. Pistons were made by Repco and had a 3/4" gudgeon pin.

These pistons are now unavailable - all you can do if you need pistons is to fit the earlier rods and the normal 998 pistons. Hope this helps

Well then I've learned something. It did strike me as odd that somebody would have retrofitted A+ rods to an otherwise standard 998 motor.

Shame pistons are NLA for these rods, as I liked the idea of press fit gudgeons. I take it 998 A+ pistons will not suit? Not that I have much use for a 998 motor at the moment, I was just tinkering!