Carby Keihin carb clone

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.
 
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.
All post are from my phone, I try my best to make it legible. Sometime I rush through my post to get back to whatever else I'm doing. Sorry for the unconvince.

I did none of the port work, it came that way.

No, why would I.

Exhaust looks widened.

Getting expansion chamber at some point.
 
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yep. at least then you know where you are starting from., without having someone elses failed experiment cluttering up the place.

30 mph is what they do, stock. so what benefits have you reaped?

learn to WALK before you FLY.

get the expansion chamber, and forget about the carb for now. and maybe forever.
 
yep. at least then you know where you are starting from., without having someone elses failed experiment cluttering up the place.

learn to WALK before you FLY.

get the expansion chamber, and forget about the carb for now. and maybe forever.
Have you even read this thread all the way through?

Jeffery gagnon may need to but my bike is fine.
Why would I start with new jug and everything when I just bought the engine.
I just needed help with the carb and tuning it, but I helped myself since I seem to be the first one to buy this engine.
So let's help Jeffery and anyone else with the carb or engine.... gt80 by the way people from... you guessed it gasbike. boooo. Oh well runs great.
 
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I matched everything after reed valve for less turbulence, I haven't run it since matching everything after reed valve tho.


so, in a court of law, you would say that this WASNT your writing?

have you run it since removing the reed valve?
 
All post are from my phone, I try my best to make it legible. Sometime I rush through my post to get back to whatever else I'm doing. Sorry for the unconvince.

I did none of the port work, it came that way.

No, why would I.

Exhaust looks widened.

Getting expansion chamber at some point.


dont worry, that was directed at gagnon that seems to write one big mash of words with no pauses for breath, so to speak.

what you write seems to make sense except i cant figure out if its currently running or not, whether it has reed valves fitted anymore or not, and yep...thats about it.
 
dont worry, that was directed at gagnon that seems to write one big mash of words with no pauses for breath, so to speak.

what you write seems to make sense except i cant figure out if its currently running or not, whether it has reed valves fitted anymore or not, and yep...thats about it.
It is running. It has reed valves fitted. It smoothed everything out shown by the arrows.
PicsArt_05-08-11.14.02.jpg.jpg

I have not even started the engine after this.
What lead to this was I had removed the spacer behind the reed valve (somone mentioned to me that it was of no use and would boosed crank pressure if removed) that cause a leak covered in my other thread. And I had to put the spacer back on.
 
Also if you are running hi compression u really ought to be running hi octane I buy 5 gallon drum of 118 and mix it with a little pump gas you would not believe the difference night and day
 
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