Sep 3, 2023 · To take advantage of the larger ,smoother boyesen ports the cases can be altered to remove the flow restriction across the transfer tunnels. If you put the cylinder back on the cases without a piston in and reed block in you can see the area that can be changed.

Jan 7, 2012 · It doesn't change your port timing at all, but it does give the intake path more window space when the piston is down in the stroke.

Apr 23, 2024 · Yes shaving the bottom of the cylinder could be an option but it depends on current (stock) exhaust port height. If it's already on the limit, lowering the cylinder could put the bottom edge of the port lower than the piston's crown when at BDC.

Jun 25, 2014 · Boyesen power reeds probably won't transform your bike, it just isn't a dramatic enough mod in order to do that. Eric Gorr recommends a 12 tooth front sprocket and vforce reeds on your model year CR80 (I'm assuming to give it more low end): http://www.goforwardmotion.com/tech.php.

Jan 7, 2005 · According to the book there should be two ports that connect the main intake port to the rear transfer ports on either side. Eric also states that these ports should be about 1/2 inch in diameter. What i want to know is has anyone done this before? and does it work well?

Nov 9, 2001 · The Boyesen ports only work on cylinders that have reed valves bolted to the cylinder. In a case-reed engine like your 89KX125, having the reed valve bolted to the crankcase provides the clear passagways needed to transfer mixture gasses up into the cylinder when the piston starts its upstroke.

Apr 17, 2014 · These are 2 different pots on one cylinder. The boyesen ported side is an aggressive trail port and the other is a dune/light drag port. Not everything I do is shown, only the constants that I've found. If the area looks rough or untouched, that's because I haven't researched that area.

Mar 8, 2012 · Boyesen ports as they're called, short circuit the crankcase and allow charge directly into the transfer port. They also give the charge somewhere to go when the piston covers the intake ports instead of the charge "backing up" towards the reeds.

Apr 27, 2010 · What the Elsinore lacked was top end power and the YZ had gobs of it. However, don't think you have a slug. The Elsinore out handled everything in it's class that year and the suspension was almost perfect as it was from the dealer. A little port work was a lot cheaper than suspension work which the YZ badly needed.

Sep 26, 2006 · Back when boost ports first came about, some of the first to start doing this with any noteriety was Boyesen. Or so legend has it. To answer your question, banshee0509, boost ports are used in conjuction with drag style porting by many users.