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Old 05-03-2015, 09:25 PM
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Davezilla Davezilla is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: Best engine kit?

As far as porting goes, here are a few basic guidelines to get a very noticeable improvement without worrying about all the math and science in it all... it wont make you a 10hp screamer but it will give a nice torque increase with better power and rpm up top...

Start with a new engine or cylinder
go in and nremove all the overhanging nikasil from the intake, exhaust, and transfers
take a sharpie marker and mark 1mm on both sides of the intake and exhaust port, and mark 1mm on the exhaust roof.
now take your dremel and carefully cut to these marks using a carbide rotary file if you got one.. the high speed steel ones also work well on the aluminum but the nikasil can wear them out quickly...
Once you got the ports opened up 1mm on each side of the intake and exhaust, and raised the exhaust roof by 1mm,use a sanding roll to smooth everything out but don't cut any more into the openings.
next. Mark your piston crown where the transfers and exhaust openings are and ramp down about 1mm in these 3 places. At the bottom of the piston skirt on the intake side, cut 5mm off the bottom of the skirt and smooth it out.
Clean everything up and reassemble everything.
Now your engine will have better torque down low but capable of reving up at least 1000 more rpm on top.
You can also boost your compression for even more torque by lapping off about 1mm or so by placing a sheet of sandpaper on a flat surface and rubbing the head over the sandpaper in a circular motion until about 1mm is shaved off...start with about 120grit paper and smooth out with 240 grit paper.
You will have a noticeable increase in acceleration and speed just from this simple mod... to cut any further this is where you'll need to learn the math and science behind it all and use a degree wheel to ensure you don't go too far and mess up the jug and or the piston.
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