HeadSmess
Well-Known Member
- Local time
- 8:53 PM
- Joined
- May 17, 2010
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arrrgh, this thread is confusing... certain someone that cant use punctuation or spaces doesnt help much... do you think he ever reads what he has written to make sure its comprehensible?
i now see that YOU are the OP
the port work... the cut out above the intake port should be flush with the transfer ports, or marginally lower. called a boost port. the transfers sort of squirt air/fuel to the back of cylinder, away from exhaust, over the top of the piston, and the boost port then squirts out and pushes the air/fuel to top of cylinder, as exhaust gas is pushed down and out the ex port... it should be very steep, and fairly shallow. its not really a transfer port, more of an assister.
combined with a good expansion chamber that tends to "suck" on the exhaust port, it allows the reeds to open and allow more air/fuel in, rather than rely simply on crankcase induction.
rather pointless if it doesnt have the right exhaust.
problem is that you dont know whats happening inside the cylinder when its running, you need to have a flowbench and smoke-machine, combined with a clear head to really SEE whats happening, and have the engine spinning at operating speed...tricky. theres no point just chopping metal away if you dont know whats happening in operation. its like throwing darts whilst blindfolded. the angle, the depth of notch, the difference between it and the transfer ports...all very critical. guessing doesnt work.
the cut out below the intake port is simply to bypass the piston port closing, allowing air/fuel to enter the crankcase for the maximum amount of time.
have you actually ran it without the reeds with all this port work?
exhaust opened...how? was it only widened or has it been hacked into and raised? edges properly bevelled or just left as machined?
have the transfers had any work such as removing casting flash? any changes in the angles?
probably better off getting a new cylinder and starting it all over from scratch again, go back to stock carb, etc... 35mph (i speak km/h...60 was average) is about what i get with UNMODIFIED 48cc engines. just an expansion chamber. the only bolt on modification that really DOES ANYTHING.
when working on the intake side of things, its best to remove the exhaust ENTIRELY so you know it has no affect on things. then you can make some sort of judgement on results. you then modify the exhaust to compliment the intake.
reedvalves do not improve top end performance. just the mids and lows.
i now see that YOU are the OP
the port work... the cut out above the intake port should be flush with the transfer ports, or marginally lower. called a boost port. the transfers sort of squirt air/fuel to the back of cylinder, away from exhaust, over the top of the piston, and the boost port then squirts out and pushes the air/fuel to top of cylinder, as exhaust gas is pushed down and out the ex port... it should be very steep, and fairly shallow. its not really a transfer port, more of an assister.
combined with a good expansion chamber that tends to "suck" on the exhaust port, it allows the reeds to open and allow more air/fuel in, rather than rely simply on crankcase induction.
rather pointless if it doesnt have the right exhaust.
problem is that you dont know whats happening inside the cylinder when its running, you need to have a flowbench and smoke-machine, combined with a clear head to really SEE whats happening, and have the engine spinning at operating speed...tricky. theres no point just chopping metal away if you dont know whats happening in operation. its like throwing darts whilst blindfolded. the angle, the depth of notch, the difference between it and the transfer ports...all very critical. guessing doesnt work.
the cut out below the intake port is simply to bypass the piston port closing, allowing air/fuel to enter the crankcase for the maximum amount of time.
have you actually ran it without the reeds with all this port work?
exhaust opened...how? was it only widened or has it been hacked into and raised? edges properly bevelled or just left as machined?
have the transfers had any work such as removing casting flash? any changes in the angles?
probably better off getting a new cylinder and starting it all over from scratch again, go back to stock carb, etc... 35mph (i speak km/h...60 was average) is about what i get with UNMODIFIED 48cc engines. just an expansion chamber. the only bolt on modification that really DOES ANYTHING.
when working on the intake side of things, its best to remove the exhaust ENTIRELY so you know it has no affect on things. then you can make some sort of judgement on results. you then modify the exhaust to compliment the intake.
reedvalves do not improve top end performance. just the mids and lows.