- These are the inner bearing spacer(s) that fits between the two driveside main bearings on M30/M40 magnesium crankcase pre-Featherbed crankcases - they are the correct width to ensure the inner roller race of the innermost bearing should just be held off the lipped outer roller bearing race
These spacers are machined from high tensile EN24 steel and CNC machined
Rather than a single piece spacer, I had two slimmer spacers made - if fitted to standard magnesium M30 crankcases they both need to be fitted alongside each other. I made them as a pair, with a view that it may be possible to remove and possibly fit the wider International crank, although I have not tried this yet and cannot confirm conrod will line up in that configuration. They are sold to be fitted as a pair.
When fitted in conjunction with item 0656 (bearing outer spacer oil rings) I have measured and can tell you that with normal RHP lipped C3 roller beairng (standard fitment and the type we have been selling for 10 years) these two inner bearings spacers will hold the inner roller bearing 15 thousandth of an inch from touching the lip of the outer bearing. I believe this lip was provided as a safety measure, in case the left hand mainshaft nut came loose and the crankshaft started forcing against the drive side bearing . . . but better not to be touching against the lip if you dont need to! In addition, providing items 0656 and 0657 are fitted as a matching pair in magnesium crankcases .. . it means you could probably use non-lipped bearings instead of the much harder to find lipped variety . . . which is a consideration as the original bearings get increasingly difficult to find