Andrew1234
Active Member
I was wondering how to increase rpm on a jug with a 40mm intake and open transfers and was wondering how to make the most rpm from the port work I’m running no reed valve
How to port for more rpm
- Thread starter Andrew1234
- Start date
GW's Motorized
Well-Known Member
Ask @ImpulseRocket or @Street Ryderz they know a lot about porting
Step one: Purchase yourself a degree wheel and port map the cylinder in question.
Step two: With those numbers as a base, work out a modified port map to suit your desired rpm range. Do that with people here, on your own, etc.
Step three: ????
Step four: Profit.
It's about finding a balance of figures in the port map and the related induction and exhaust side that will all work together to achieve a goal.
This is probably one of the most popular sites for getting an idea of about where you want to get your port timing numbers in relation to the power curve peak of the engine.
martysgarage.info
Step two: With those numbers as a base, work out a modified port map to suit your desired rpm range. Do that with people here, on your own, etc.
Step three: ????
Step four: Profit.
It's about finding a balance of figures in the port map and the related induction and exhaust side that will all work together to achieve a goal.
This is probably one of the most popular sites for getting an idea of about where you want to get your port timing numbers in relation to the power curve peak of the engine.
Two Stroke Port Duration
Port Timing Basics Air/gasoline enters the engine from the carburetor at a ratio close to 15:1. It enters via the intake port (as the piston rises) into the crankcase and then is transferred to the combustion area via the transfer ports (as the piston descends and the piston top uncovers the...
martysgarage.info
Andrew1234
Active Member
Do you essentially want to raise your exhaust port and lower your intake port?Step one: Purchase yourself a degree wheel and port map the cylinder in question.
Step two: With those numbers as a base, work out a modified port map to suit your desired rpm range. Do that with people here, on your own, etc.
Step three: ????
Step four: Profit.
It's about finding a balance of figures in the port map and the related induction and exhaust side that will all work together to achieve a goal.
This is probably one of the most popular sites for getting an idea of about where you want to get your port timing numbers in relation to the power curve peak of the engine.
Two Stroke Port Duration
Port Timing Basics Air/gasoline enters the engine from the carburetor at a ratio close to 15:1. It enters via the intake port (as the piston rises) into the crankcase and then is transferred to the combustion area via the transfer ports (as the piston descends and the piston top uncovers the...
Andrew1234
Active Member
And also make the top of the exhaust port more square?Step one: Purchase yourself a degree wheel and port map the cylinder in question.
Step two: With those numbers as a base, work out a modified port map to suit your desired rpm range. Do that with people here, on your own, etc.
Step three: ????
Step four: Profit.
It's about finding a balance of figures in the port map and the related induction and exhaust side that will all work together to achieve a goal.
This is probably one of the most popular sites for getting an idea of about where you want to get your port timing numbers in relation to the power curve peak of the engine.
Two Stroke Port Duration
Port Timing Basics Air/gasoline enters the engine from the carburetor at a ratio close to 15:1. It enters via the intake port (as the piston rises) into the crankcase and then is transferred to the combustion area via the transfer ports (as the piston descends and the piston top uncovers the...
The simple answer is "yes" to these questions.
The reality is more complicated than that. It's not just raising and lowering, but also shaping. It also depends on what you are starting with. You could get a cylinder that has great intake port timing and needs very little work, but the exhaust needs a ton of work done, or vice versa.
Read through that link I posted, and spend some time watching some YouTube videos on port work to get a feel for things.
Street Ryderz
Well-Known Member
Many people believe that the port timings correlate to the speed/rpm achieved and that's not really true, I've heard so many times that a stock jugs port timing won't allow it to rev past 9k rpm or whatever rpm they believe and that also is not true!
Peak power and rpm are far more influenced by load, pipe and induction type rather than the port timings as the port timings are for filling and expelling the gasses as efficiently as possible with the given time/area.
I or anyone can give you a port map to mimic but that doesn't mean it will work the same on that alone! I can show you three different engines all with the same port map and all have different peak power and rpm due to other factors.
What this means is I can give you a port map suited to the stock carb, pipe and setup that we know works well but then when you change things up with latter mods it will no longer be the optimal timings or area, so we would need to know exactly how you intend to set it up and run it for this to be the best it can be.
You do NOT need to use a degree wheel to find or alter the port timings as this really doesn't tell you much without an understanding of why, so the use of an online calculator is much easier using linear depth measurements with a Vernier Caliper and input the values to Lambretta's port timing calculator, this will give the durations for you to compare and make changes before cutting up the jug.
Give us details as to the setup you intend to run with and we can help steer you in the right direction!
Andrew1234
Active Member
I’m gonna be using a jug with open transfer ports with a nasty jack expansion chamber with a hp carburetor with a Cnc high compression head with a high performance Amazon cdi and ngk spark plug
Andrew1234
Active Member
The jug has a 40mm intake
Andrew1234
Active Member
And I’ll be running a short bilet intake
