No, 67.5mm pistons 901,75 cc when calculate bore 67.5mm, stroke 63mm. This size is possible with the "tapered" sleeves, OD 70mm into the case. My case needed to be grinded really much to ensure clearance.
I need one (or 2) more bike(s) for my old 836 and growing pile of parts
so you must have a new piston kit?with higher compression?billp
Yes, new for me but used.
Cyl block + Wiseco 67.5mm pistons, std 10.25:1 Used just a little, pistons looked like new. Bores with a fresh light hone. Mike Rieck helped me to get it.
I'm not sure about the resulting CR since the chambers are a little bit opened for old RC 65mm pistons. Head decked some.
I'll check with my compression tester to compare with my old 836 with RC295 cam copy that had around 180-190PSI. DP315 will leak.
The engine runs very well so the compression is good enough today. MLS head gasket Cometic 0.040" 68mm is in now.
I have a used thinner 0.030" as spare to be used if I need more CR and open the head.
I did not realize that the DP315 cam should behave so good as it does. Smooth constant power from the beginning to top which I have not tried yet. The new crank and rods bearings might need some break in first.
I got a happy low wheelie when twisting the throttle on 2:nd gear. TMR32 carbs react very quick, full throttle in less of a 1/4 turn. Stable hand when driving slowly or take off.
I understand why guys on the forum praise the RC315 (RC315 type 2 as DP315 is if I have got it correct thanks to this forum).
I'm sure that my CX-7, RC295 copy, 125-20 will give more torque, hp with higher lift and less duration. I like the smooth DP315 behavior and it's sound, not that loud.
Engine runs very well with APE lightened, balanced crank and Carillos. Prim hub cush rubbers new, CCC HD prim chains (tighter) as used before, new OEM prim tensioner, all metal cam chain tensioner possible to hear buzzing inside. Head got a little bit more port job when installing 5mm conv kit to adapt to the new guides/valves. 34/28 as I used before but with slimmer stems plus hopefully no more problems with mushrooming F2 Inlet valves. Not even lash caps helped when the adj screw started to dig into the end of the shorter F2 stem.
Again one more reason to not have highest lift. DP315 measured to 0.368 lift -0.10 lash must be good for the long run.
My RC295 copy had 0.398" lift-0.004 lash, AF SS-1: 0.361"-0.004 lash, 125-20: .0377" lift -0.004 lash, CX-7: 0.393" lift-0.004 lash. All measured in my engine.
I'll see what the Dyno will say about power and A/F ratio. 4-4 will stay, 4-1 might give more power but the sound from the HM300 replicas with no diffusers is very nice, especially when closing the throttle. I like the classic look too.
I wish +95 rwhp, minimum +85rwhp. (836 had +80 with + SS-1, +83 with 125-20)