Boyesen ports..
- Thread starter jus_me
- Start date
To be honest every single race bike cylinder that I have seen minus case reed engines all have boyesen ports.Now bare in mind that race bike need to get 0-60 70mph very quickly there for they need a good amount of torque so I've came to the conclusion that's why they have boyesen ports for the extra torque. As far as blasters go there is none because they leave the factory intended for trail riding not racing.In my opinion without getting all scientific if you want more torque then try it and see if it helps and report back to give us all a good idea to what can come from these ports.Just remember to not go to big because the stud ear on the cylinder could be weakened from the internal material taken from the aluminum cylinder.
Every professionaly ported aggressive trail cylinder ive seen an used has boyesen ports, the ones in my cylinders appear to be about 3/8 in diameter, my one was ported when I got it an had aluminum welded to the outside corners orange jug as the port are drilled through that welded portion, but Denny at flotek looked at that jug and said its ok but looks like it was done by a blind man, the jug he did for me dont have any material addedto the ooutside, an the ports are tighter to the intake port allowing plenty of meat between the intake ports and the the outside edge also, buy the ports appear to be about the same size in both those jugs, but flotek's cylinder performs substantially better then the other cylinder I have that was ported by unknown person, my flotek engine even sounds different idling then everyone else's blasters around here, it sounds like its "cammed" and it runs Damn good
I did my brothers boyesen ports over two years ago and since then he's had it bored to the next size twice and he's never had an issue bud.I went a little less then 3/8" though, trust me you'll know when you've went to far because you will see it break through the outside lmao lol jk jk.Now when I drill them I have a jig that I made to get it as close to perfect as I can and I must be honest I aim them for the transfer port deviders bud but then again everyone has different ways.Also try and keep them close to the sleeve so that away it leaves plenty of material.We couldn't really tell any significant improvement but I will tell you this much we sure pretend it does because we've done it and its to late to go back lol.
oh also I as well did not add any material.I'm also doing this to a new cylinder that I have.If you need some pics bud just let me know and I'd be glad to send you some.
Aiming of the boyesen ports is very important. I'll tap on that tomorrow if anyone is interested in what this guy has to say 
I recently rode 2 blasters that a good friend of mine ported. Both ran FMF pipes and both had a UNI filter with the airbox. Both had identical timings and widths, but the boyesen ports we're different.
The first was aimed from higher along the intake walls, down to a steeper angle into the transfer areas. He said he only did minimal radiusing and that the port was around 7mm. He described it as a smaller 250r boyesen setup. It produced a good bit of bottom end power and had a nice wide range.
The second had boyesens that were angled more at the divider wall and were a bit larger at 8mm. He used a slightly rounded taper from the intake, but left the corners very square. With the same pipe, it made more midrange than the first and had a stronger hit when it came on the power.
Our theories for these is that the effects are based off of two things: where the port is aimed and where the charge will end up with its trajectory at different amounts of time (different rpm ranges).
I've found that a median between these two works very well. At lower rpm ranges, the charge falls short of the divider and helps the secondaries purge the cylinder. At higher rpm, it overshoots the divider and gets divided evenly when the charge flows upward.
I also like to make it easy for the AFM to flow into the boyesen ports very easily, but hard for the charge to revert.
I don't have any Blaster pics, but I do have these if my banshee templates.
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.
The first was aimed from higher along the intake walls, down to a steeper angle into the transfer areas. He said he only did minimal radiusing and that the port was around 7mm. He described it as a smaller 250r boyesen setup. It produced a good bit of bottom end power and had a nice wide range.
The second had boyesens that were angled more at the divider wall and were a bit larger at 8mm. He used a slightly rounded taper from the intake, but left the corners very square. With the same pipe, it made more midrange than the first and had a stronger hit when it came on the power.
Our theories for these is that the effects are based off of two things: where the port is aimed and where the charge will end up with its trajectory at different amounts of time (different rpm ranges).
I've found that a median between these two works very well. At lower rpm ranges, the charge falls short of the divider and helps the secondaries purge the cylinder. At higher rpm, it overshoots the divider and gets divided evenly when the charge flows upward.
I also like to make it easy for the AFM to flow into the boyesen ports very easily, but hard for the charge to revert.
I don't have any Blaster pics, but I do have these if my banshee templates.
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.
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