Hi, I have a Polini Evolution 3 70cc kit "Bolt on" mounted on my Minarelli Horizontal block (Aerox). When I bought the kit I decided NOT to align the port transfers from the case to the cilinder because of the crankshaft that was allready mounted.. At this point I am wondering if disassembling the engine is worth the gain from the port matching? Full Setup (mina hori LC): - Polini EVO 3 (stock) - Polini Digital Ignition - Doppler Endurance Crankshaft - Yasuni C21 Carbon - Stage 6 21mm Black edition - Stage 6 V-Force - Malossi Overrange 2006 - Stage 6 13-43 gears Here is a picture I took from an old engine block to give an idea about how the ports of the cilinder differ from the engine case.
Of course. Take the block apart, push the crankshaft out of the bearings. It is important to leave the bearings inside the crank case. Clean the whole block, start drilling only one case at a time, constantly putting the cylinder holding screws in and out while checking the cylinder and case. After all that drilling, take the cases to the nearest sandblaster. With your configuration this modification when done right could mean 3-4 Bhp more, and smoother performance curve. Or if You would like, I can do it professionally for 90 GBP.
Thanks for the reply! Woah! I was expecting a maximum gain of 1 Bhp but aiming at 3-4 Bhp makes it definitely worth taking the engine apart... I have the tools to drill and sandblast the cases, but I was wondering if there anything more besides aligning the ports? I have read about "Flowing" the crankcase but found mixed opinions about it... With my current setup, this engine has reached 13.4Hp at the rear wheel, so a nice increase in engine power looks realistic to you? Thanks!
Well, I'm not going to lay out all the cards! But basically, it's worth it, your ride could make 16 Bhp at rear wheel with ease, if set up correctly, cleaning out everything, etc. I heard the new generation Polini cylinders have a lot of potential
Haha I understand it could be a secret black magic I would gladly like you to take care of my engine, but unfortunately I live overseas in Belgium so considering shipping risks and shipping costs.... I'm not going to take that course :-( Anyway, I would like to thank you for the advice!
when you take your cases apart, look at the course the fuel mix takes, from the carb to the exhaust port, any sharp edges can be carefully removed, but dont make anything smooth, smooth intake tracts cause the fuel to "bead". cant be bothered to go into the physics of it. think of it as being like the exhaust restrictor, stopping the pressure from moving smoothly. i would take the bearings out the cases myself, but i work in a bike shop and have the tools to put them back in easy (we hve a minerelli bearing punch!). im guessing that you know tis already but make sure you use plenty of oil when reassembling, and take it easy on first start up. while you have the engine apart check all your bearings and parts for wear.
its just a big punch that matches minerelli bearings, wouldnt know which it is without having a bearing to match it to if that makes sense? (we have a draw full of punches)
