Project RD250, have RZ350 parts, what to do!

[old-too-smoker]

Hello gents, I have acquired an 1975 RD250 project bike, its rough but complete. Not planning on starting it, just rip apart and redo crank, and whatever else. I have a bunch of RZ350 parts, cylinders etc. I would need to figure the water cooling/ stud spacing, but has any one ever tried to add RZ350 cylinders to an RD250 lower motor. I have mounted RD350 cylinders to the 250???

[Jspooner]

It could be done but lots of work to make it happen. I'd find some 250 or 350 LC cylinders instead, they bolt right on. I think you'd spend more money trying to adapt the RZ stuff than you would spend on LC stuff.

[m in sc]

yeah, not going to happen easily or cost effectively. Joes right. you could probably sell the rz stuff off ad pay for some lc cyls. either way theres still the waterpump and powervalve issue to deal with using the rz cyls after you machine the cases even if you COULD make them fit.  just waterpump on the lc. stuff. + different exhaust stud spacing on the ac vs lc & rz stuff, pipes, and radiator. 

or, find a banshee or rz bottom end and fab up engine mounts.

there was a guy that did it, he made a 5mm plate and then lathed 5mm off the bottom of the rz jug and made it work. seemed like a huge pain in the ass.

Ive done 350 lc cyls on a 250 aircooled bottom end w an electric water pump, was pretty easy.

[motodreams]

Your stuff is worth more as it sits likely.  Sell the RZ bits and the partial RD and buy a well sorted 350 (or a complete project if you want to wrench).  It will be cheaper in the end.

[Jspooner]

Or you could get really crazy and use TZ stuff. Bolts right on and makes gobs of HP. Pretty expensive and getting hard to find some of it but easy to do. Probably would still be cheaper than adapting an RZ top end, but by far easier.

[rodneya]

Or get some banshee cases and internals and use the Rz stuff on that. Not too hard to get it to fit

[Striker1423]

or be like me and just drool over the possibilities and never do any of them... except in dreams after winning the lottery.  :)

[paul1478]

or be like me and just drool over the possibilities and never do any of them... except in dreams after winning the lottery.  :)

HA! my thoughts exactly...

[old-too-smoker]

Thanks for the info guy's, the RZ conversion is too much effort, may do a RD400, the whole engine, not worth the effort to convert. I also have a set of 75 RD350 cylinders, will decide over the holidays what to do... Will keep you posted. I have recently done a RD400 and RZ350 projects that came out really well. This one will a paint job, stickin with the 1975 white USA RD250 colors and decals.

[Striker1423]

Thanks for the info guy's, the RZ conversion is too much effort, may do a RD400, the whole engine, not worth the effort to convert. I also have a set of 75 RD350 cylinders, will decide over the holidays what to do... Will keep you posted. I have recently done a RD400 and RZ350 projects that came out really well. This one will a paint job, stickin with the 1975 white USA RD250 colors and decals.

That's what mine is!
https://i.imgur.com/LcsshqU.jpg

I did the RD350 top end swap and Dave F mod at the suggestion of the fine gents here. Not the hardest job on the planet. I practically HAD to because the 350 cylinders I had were given to me for free! It was like, so wait... heads, gaskets, pistons, and a bore job... I'm out 300 bucks and a few main jets. Sold!

I guess I did do quite a few things to the bike after all.  I really need to take my own advice lol.