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boost ports


t.spraker

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yeah we need better pics ,it looks like to me that the lower boysens are very smallish and up against and too close to the liner . it is pretty choppy no doubt, but it doesnt look to me like its gonna cause trouble ,i can see the sleeve is intact and hole doesnt protrude through it .you might be okay IMO , the upper auxilairy ports (baby holes) were done in vain IMO ,where are they going? and there size is so small,that i doubt they have much of any functional purpose. looks like this builder(aka capt.caveman ) opted to widen the intake alot, but didnt manipulate the duration of the intake port much if any..id throw em back on ebay . :D

Edited by rocketboy
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The rings don't even go that far down anyway guys. The lower ring stops above the top of the intake ports. From the angle of the wannabe boost ports it looks like they feed the transfer ports as well (more boyesen ports). Those ports look so small that any flow through them will probably be insignificant.

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They are a little closer than I would like to see but should be ok. The lower boysen or whatever YOU wish to call them are too small though to even be there, they can be made quite a bit bigger without cutting through if you watch what you are doing. I usually end up with one about double that size. The other boosts are definately too small to be of any use. I have seen that tried on honda cylinders before but not on banshee's. Both seemed like a waste of time. You are not increasing the SA of the tranfer port and are if anything screwing up the turbulance of the port even if they flow anything.

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  • 5 years later...

Sounds like the cylinders he is buying have 2 boyesen ports and 2 boost ports per cylinder.

 

Do Boost ports really do anything?

 

I think they do because if u look at how a stock 250r runs they run hella good for stock and they have boost ports and ive put them in every two stroke i have ever had,but i hjave never just done that i awlays do all my porting at once.but i think it would help because ur more in ur transfers faster there does like tiny intake ports.

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I think they do because if u look at how a stock 250r runs they run hella good for stock and they have boost ports and ive put them in every two stroke i have ever had,but i hjave never just done that i awlays do all my porting at once.but i think it would help because ur more in ur transfers faster there does like tiny intake ports.

way to bump a 6 year old post

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at least its interesting!!!

 

lets keep it going??

 

if i could post pics i ahve been working on some "boyesen boost ports" on some welded stockers.. i'll be getting them bored next week and start reassemble the motor for testing in a month or so.

 

the boost ports on dirtbikes, and hondas are there to help with low end and midrange on TT bikes and some circle burners the old skewl builders actually fill in the boost ports ( even eric goor does, suggest this) to help with top end powa.. the CUBS on the other hand are so large that they must help feed the trasfers also the bridges are far enough UP that they must blwo across almoat all the ports.. ofcourse this is what i THINK is going on as i have to envision it in my head..

 

in my opinion cause i only know of a very select few sofar that can use computer programs or a wet flow bench to simulate flow in the engine at diff speeds those top port probably did mess up flow through the rear trans port BUT i have to again.. envision it in my head. and think about how the fuel/air mix coming throught that small hole under pressure from the down stroke is at a high turbulence and blowing the incoming charge to the other wall of the inner trans tunnel port.. i personally like a VERY large boost port BUT only on lower powerbanded motors. engine with peaks in the 9000 rpm range and useable lowerend HP.. of course i havent personally ran a set fully welded and boost ported with holes big enough for my thumb to fit through BUT this "test" set of cyls is going to be my first attempt..

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