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Hi, I would be interested on member's thoughts on my SOHC rebuild. I'm having a set of Wiseco 836cc pistons fitted along with a copper gasket. The head is also being flowed, although the valves will remain standard size and I am sticking with the original carbs. Since I'm having the engine apart to this extent would it be a good idea to go to a different cam, along with stringer valve springs etc, or could I just have the existing cam re-profiled or left alone? Some of what I'm reading suggests a cam is necessary to get much benefit from the slight displacement increase, but there are plenty of builds where the standard item is retained.Many thanks
Because I modified the standard 750F2 frame I could work on the top end easier. So for riding abroad I used a standard cam to go with the fitted Yoshi 823 pistons I bought from Dixon Racing. At the time 812 pistons wern't available hence the reason I got the 823 kit. As far as I remember the 836 kit is 0.5mm up on the kit I had. This was the furthest you could safely go with the standard liners. For a 900 kit new liners needed to be pressed into place.I polished the ports but didn't remove much metal. I fitted ally/bronze valve guides, S&W valve springs, had the seats recut, had the crank & conrods polished, balanced & lightened, fitted a 750K0 solid cam sprocket & degreed in the reprofiled cam I used for fast road use. The base circle of a standard F2 cam was ground to give slightly more duration & lift. This worked perfectly with the F2 carbs & Andrews high output coils, gold plugs & Boyer-Bransden ignition. The standard exhaust was welded up & a CG exhaust bolted up. Worked a treat My bike was in a CB750 feature in Superbike magazine back in 1982
RE BHP I used a big bore kit on my my DOHC 750, taking out to 823cc + cams + flowed head and carb mods. Gave 95 BHP at rear wheel after proper dyno set up at TTS. Big percentage gain over 78 BHP ish (at crank) for stock I think? Keeping in mind you are talking SOHC / 8v, therefore poorer breathing and less output to start with, something less than the 95? Not very scientific I know....It did transform my bike both in terms torque and top end but yes to get all the bits working together it is a big expense to consider....