WOW!!! what a difference a little grinding can make.

GoldenMotor.com
Jul 27, 2015
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R.I.
This is my first motorized bike build and I didn't want to go crazy right out of the box. I did your basic port and polishing and gasket matching on both the intake and exhaust. I rode the bike for about 50 miles and then had a funny little mechanical problem where a foreign object jammed the clutch and crank gear, no major damage. I had the engine apart so I figured I would take the internal modifications one step further and notch the intake side of the piston. Wow!
I'm still running about 14 and a half - 15 to 1 ratio on the fuel mixture so she tends to be a little sluggish but the low end torque coming out of a turn now is at least 15 to 20% better with this one modification. Without a doubt if you buy one of these kits notching the intake side of the piston is a must.
 

YesImLDS

Member
Jun 29, 2013
960
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18
Columbia, Missouri
The modifications help a bit, but holy crap 15:1.... 32:1 is completely safe and not drowning in oil. You would probably get better performance too.
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
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63
Littleton, Colorado
The modifications help a bit, but holy crap 15:1.... 32:1 is completely safe and not drowning in oil. You would probably get better performance too.
Yep. Drop that oil ratio and you'll feel a differenece right away. Excessive lubrication isn't necessary and will only slow the break-in process and make a mess.

Drop down to to 32:1 and feel the difference and report back. I think you'll be impressed.

Tom
 
Jul 27, 2015
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R.I.
Will do Tom. Thanks for the input. I got the motor bolted pretty tight no oil leaking out of the gaskets or anything yet nothing from around the exhaust gasket but when I put it away it leaves a nice little puddle of pure oil under the exhaust tip. Also it smells more like an Evinrude outboard. There's a quick little picture of it. I'll finish up getting the rear rim painted up and everything but I just wanted to ride it before the winter came.
 

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Kioshk

Active Member
Oct 21, 2012
1,152
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Connecticut
Could you describe this "notching"? I agree that you're using too much oil. Also, since this is your first build, you may only be experiencing the performance improvement of "break-in". I wouldn't be too hasty attributing the improvement to your modification.
 
Jul 27, 2015
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R.I.
The "notch" is on the bottom intake side of piston. This makes the intake port about 15% greater by area when the piston is at t.d.c. I had about 50 miles on the motor then I had to fully disassemble it because I had a foreign piece of debris jam up the crank and clutch gear. I didn't want to touch the piston initially. I ported and polished and gasket matched the top end but I left the piston stock for the break in. I had it all apart because of the Little jam up with the gears and lost my patience and said the heck with it I'm going to cut the piston now. I noticed the difference in power the first time I got back into the gas going around a corner. The throttle response is significantly better as well but if I had to guess I probably increase my low end torque by 8 to 12%. You don't have to remove too much just remove your intake bring the piston to top dead center and you can see that the piston skirt reduces the area of the intake opening.
 
Dec 11, 2014
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Tucson
Nice build! I happen to have a curved file that matches the intake port exactly so I put the piston at TDC Mark it thru the port, file it to the mark and I have a perfect port match. Again, compliments on the build.
 
Jul 27, 2015
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Thank you very much for the kind words sir. I wasn't so gentle with my piston. I just made the mark and shoved it in the my bench grinder then cleaned it up with a nice find file.