RZ350/Banshee pistons in RD400s
My experience has been 99% RD250/350/400/Early TZ/RZ so I have rebuilt and modified just a mountain of these engines so of i've seen many many RZ350/Banshee pistons come out of 400’s (and of course installed a mountain of them). These pistons were a absolutely without a doubt a wonderful windfall for the RD400 but you all are right the center tongue which was designed for a bridged intake catches on the RD400’s single intake. Stock and of course even worse with a modified intake. Being aircooled cylinders using more clearance than the watercoolers doesn’t help the issue either. I’ve been called more than once to help someone determine what the noise is after they had some four stroke shop bore their cylinders and give them a set of pistons.. Pull a reedcage and there’s the tang (or tongue).. Of course the other problem is most non 2stroke experienced shops or even those with just modern 2 stroke experience only put what I call micro chamfers on their ports and that doesn’t help… (aircooled cylinders need more chamfer!!) Bottom line from experience and observing piston wear patterns that are always ½ way up to all the way up the “usual” 4-5mm tang when run for any length of time in a 400 if they aren't broken off.. Is cut the tang off and put a chamfer on the cutout it forms, DEFINITELY leave the side “tangs”, and always use a really nice radius and a generous chamfer on the bottom of 400 intakes. Ed
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