Porting for 66cc flying horse 2 stroke engine. Do's and dont's please help.

[Pixelcreator1]

I run a 66cc flying horse 2 stroke with a FM80 con rod (38mm stroke) I run a knockoff mz65 pipe with an added smaller pipe as a stinger g2 reed valve and a mikuini vm18 carb with a large windowed piston and a shark racing cylinder head. Im not good at understanding porting or the timing of the exhaust powerband and port timing like exhaust port timing and transfer port timing. If anybody knows what port for my engine specs or any information to help me learn porting would be greatly appreciated! my speed goal is 50mph yet my engine currently cruises at around 35-38mph.

 

[mark20]

read up, should help you understand porting.

http://www.amrca.com/tech/tuners.pdf

 

[Street Ryderz]

I run a 66cc flying horse 2 stroke with a FM80 con rod (38mm stroke) I run a knockoff mz65 pipe with an added smaller pipe as a stinger g2 reed valve and a mikuini vm18 carb with a large windowed piston and a shark racing cylinder head. Im not good at understanding porting or the timing of the exhaust powerband and port timing like exhaust port timing and transfer port timing. If anybody knows what port for my engine specs or any information to help me learn porting would be greatly appreciated! my speed goal is 50mph yet my engine currently cruises at around 35-38mph.

Hey, is 35-38 your cruise speed or top speed ? if your goal is 50 mph is that for cruise or top speed (big difference) a top speed of 50 is not that hard but a cruise speed of 50 takes some knowledge and ability to set it up right. TBH what you have even with the stock port timing should produce 50 as a top speed and probably best to work on that first but there are many here whom can help you along the way!

 

[Pixelcreator1]

Hey, is 35-38 your cruise speed or top speed ? if your goal is 50 mph is that for cruise or top speed (big difference) a top speed of 50 is not that hard but a cruise speed of 50 takes some knowledge and ability to set it up right. TBH what you have even with the stock port timing should produce 50 as a top speed and probably best to work on that first but there are many here whom can help you along the way!

It tops out about around 37mph my goal is for it to cruise (WOT) at 50mph ive also learned my port timings and blow by ive gotten these numbers by sloping the piston in the exhaust and transfer areas the cylinder jug is untouched.

• exhaust: 135°
• transfer: 104°
• blow-by: 31°
• intake (always open)

 

[Street Ryderz]

It tops out about around 37mph my goal is for it to cruise (WOT) at 50mph ive also learned my port timings and blow by ive gotten these numbers by sloping the piston in the exhaust and transfer areas the cylinder jug is untouched.

• exhaust: 135°
• transfer: 104°
• blow-by: 31°
• intake (always open)

Daniel these timings need adjustments made to suit your goals, Blow down is actually 15.5 degrees and the intake can not be always open or you're engine wouldn't run. You will need 160 exh, 120 transfer, which will give 20 degrees blow down, intake only has 180 degrees available (up stroke) but because there is 4 degrees top and bottom dwell (no piston movement) that only leaves 172 degrees and the piston has to climb some before it actually starts to create any vac so realistically it's like 160 with the use of the reed valve. Ramping the piston is a temporary way of making slight timing changes but is not intended for permanent use, these ramps effect the squish and make it non existent, squish is important as it cools the piston crown and controls detonation so that you don't melt a piston trying to make more power!

 

[Pixelcreator1]

So can you raise your transfer port timing by adding more base gaskets rather than raising the transfer ports of sloping the piston?

 

[Chainlube]

You can add a thicker or second base gasket only if you're willing to chop off the top of the jug. If the gasket is 1mm thicker then your squish area is 1mm bigger, if you had a squish area of .7 mm before, then now it will be 1.7mm which is way to big.