[fastbmw]

Okay, for those that are following my saga or those who aren't, here is my dilema. I've got 2 zb50's, one stock and one has an 88cc big valve head. The one with the 88cc head has a horrible case of rod knock, which I'm pretty sure is a blown crank. Here are my choices:



1) buy a stock replacement crank for $39.99



STOCK_REPLACEMENT CRANKSHAFT_ASSY_HD THIS_FITS ALL_XR50_XR70 ALL_CRF50_CRF70 1988_TO_99_Z50R 1982&83_PASSPORT(200067)



2) buy a 108cc crank (51mm) for $175.00



3) (the most convoluted one). I accidently bought a 72cc top end kit for the old short rod cranks.

70cc RESURECTION_Kit FOR OLD DEAD 70'S AND OR 50'S READ DISCRIPTION



Now, dratv sells a 52mm crank for cdi engines intended to make 88cc kits into 108cc.



52MM_MONSTER STROKER_CRANK for_CDI_engines complete_with bearings_&_sprocket (200001)



Can I mate the 52mm crank with the old style 72cc top end to make approx 92cc? This way I don't need to chuck my mistaken purchase and then eventually swap my 88cc kit over to my 2nd zb50.



What would you do?

 

[Kurlon]

I'd swing for the TB 51mm crank and toss it in the 88 motor. You've got to split the cases anyways... it's a drop in at that point.



For the record, yes, you should be able to use that 52mm crank with the 72cc kit you got.

 

[zbnutcase]

Yup go for the 108cc. Do it once and forget about it. 'nutcase