56k Posted Thursday at 08:23 PM Report Share Posted Thursday at 08:23 PM I'm a little confused as to what I should run for the ring gap. I'm using an aftermarket wossner forged piston, 71.44mm. Their online ring gap calculator gives the following suggestions: naturally aspirated: 0.29mm (0.0113 in) naturally aspirated racing: 0.32mm (0.0127 in) snow/marine: 0.36mm (0.0141 in) forced induction: 0.39mm (0.0155 in) heavy load/high heat: 0.43mm (0.0169 in) I'm guessing since it's air cooled I should go for 0.43mm (0.0169 in). I've never done this before so I wanted to ask people with more experience than me if this sounds about right. I'm not sure what the oem manual calls for or if it even applies since I'm using aftermarket piston and rings. I just got the case halfs together last night. It's been 15 years since this thing last ran and I'm looking forwards to it, the internals were all original when I took it apart. Quote Link to comment Share on other sites More sharing options...
konrad Posted Thursday at 09:37 PM Report Share Posted Thursday at 09:37 PM Unless you are pinning the throttle and dumping the clutch, trials is one of the least demanding of engine applications. Maybe equivalent a lawn mower. The greater the possible temperature difference between the piston crown and the cylinder, the greater the ring end gap should be. A bigger gap is safer than a smaller gap. But a bigger gap will lose more combustion pressure / performance. The naturally aspirated spec should be fine. If you are a worrier, go with the naturally aspirated, racing spec. As with any engine, always let it come up to operating temperature before going wild with the throttle. The correct piston to cylinder clearance is equally important. Break it in according to Wossner's instructions. Quote Link to comment Share on other sites More sharing options...
lemur Posted Thursday at 09:45 PM Report Share Posted Thursday at 09:45 PM I'd go by the Yamaha service manual and by my read 0.4mm ring gap is within spec 👍 Quote Link to comment Share on other sites More sharing options...
konrad Posted Thursday at 10:52 PM Report Share Posted Thursday at 10:52 PM The thing with the Japanese OEMs is that they sell rings you can just install without any attention. Wossner has chosen a more performance-oriented route. 1 Quote Link to comment Share on other sites More sharing options...
56k Posted Friday at 02:30 AM Author Report Share Posted Friday at 02:30 AM As with any question I ask on forums I always find the answer right after posting the question. Found a .pdf of a service manual and it states top ring: minimum 0.3mm maximum 0.5mm second ring minimum 0.2mm maximum 0.4mm I feel much better now, I don't want to be doing this again for a long while. Thanks guys. 2 Quote Link to comment Share on other sites More sharing options...
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