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hi all new to yamahas always been honda xl just brought what i thought was a 1976 xt500c (the frame is) when i get it home and look at engine nos it begins 2j4 which i think is a sr 500 engine looking in the manual it says the sr 500 does not have points this engine does. any ideas? do you think someone has just changed the crank cases would these two engines be interchangable as said never worked on yams before know nothing about xts sr my idea was to restore the xt so could i just buy some xt500 crank cases 1n5,1e6 and change the whole lot over i was planning on full engine rebuild anyway (when ive finished the xls) any ideas you xt men please