Rebuilding CB350 Twin. What pistons???

fordmike65

New Member
So, I'm tearing down my 350 twin. Looks like I'm gonna need a rebore,pistons & rings. This will be a street bike, most likely ridden at least a couple days a week,possibly back & forth from work. I want something that is reliable,long-lasting & has decent power. I wanna do this right,the first time. I've seen pistons from several parts suppliers & on eBay. Are some better quality than others? Should I get any particular type of rings? When building my small block Fords, I usually go with forged or hypereutectic pistons & file-fit moly rings. I'm not even sure what is available out there for the 350. Another question, is it practical to go with a Big-Bore kit for a street-driven bike? I know there's "no replacement for displacement", but I'm wondering if it will be worth it for my application. I've seen kits offered by Wiseco,Bore-Tech & possibly others, but these may be more race oriented. I don't mind bumping up the compression a bit, but I definately want to be able to run pump gas. I'm also planning to get a little bumpier custom ground cam,possibly some 30mm Mikunis & a little port work. Again, if these mods won't do much for me, please give some input. I remember reading somewhere about using KZ750 or GPZ750 pistons in the 350's, but will need some valve pocket clearancing. Has anyone attempted this? Is milling the head for a bit more compression a wise thing to do? Thanks in advance for the help guys. I just wanna get all my ducks in a row & my wallet ready for the hit before I start ordering parts-Mike
 
I can't answer your questions specifically, but I will say that if you go with a cam that has more duration, you will need to up the compression a bit. Not too much if you want to be able to run regular, but static compression will go down when valve overlap is increased.
 
I would do a big bore but keep piston domes and compression relatively low. (it's a small combustion chamber so not too many problems)
You can usually run around 210psi cranking pressure with 93 octane (no idea of static CR?)
File to fit rings is an automotive thing, almost unheard of in motorcycle world (at least on modern/Japanese bikes)
Stock cam is fine for a road motor (plenty of people race with stock cams)
Swapping carbs for some 28mm or 30mm Mikuni's is a good idea
 
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