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Boyesen Ports


banshee0509

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I think he is talking about boost ports drilled from the intake port into the transfer ports on each side.

 

Yep I'm sure that must be what he is talking about. 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. However, and I'm not claiming to be a builder, I don't know that those durations etc you were mentioning would be generally classified as a drag port. Also, since I got the impression you are considering porting your own bike, I don't know that this is something I would try first shot out of the hole. Although, you do have to start somewhere. I'm not planning on adding boost ports to my cylinders when I port them in a few weeks, but that is just me. Did you read the link over at PS? Any response on your transfer angle post on PS?

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with the stock cylinders i wouldnt do it.. to make the boost ports big enough to be worth while you will run the risk of cracking the ears off the cylinders.. imo i wouldnt cut them into the stock cylinders...

 

 

 

also drag ported with 190* exhaust duration? that doesnt sound right..

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Ahh...that's what I thought, just wanted to be sure we're on the same page.

I haven't heard 'em called Boysen ports before, just boost ports.

 

Jim at Passion does this, called the Passion 12 port I think, but...he Tig welds extra material there.

 

 

Bingo (and credit to lowriderb too). I understand that you are left will very little cylinder material left, and without additional welding it would certainly crack. Believe some still crack after being welded anyway...

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Thanks guys im just trying to get opinions before i start grinding . Ive been porting and polishing Molding Dies for over six years and want to give these two strokes a try like somebody said I got to start somewhere right. So if those durations don't sound to good for a drag port what might be a good numbers for a drag port on a stock 350 with t5s.......anybody ......thanks. :baseball_wassat:

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From what has been passed along to me, I have heard that T5's really don't work well with port timings much above 194* exhaust duration. Again, not claiming to be a builder, just insight/advice passed to me in my search for porting specs. Wise men have said, you can always take more, but you can't add back on. So, keep that in mind when messing with the port timing. If want a more aggressive grind, take it in incriments. Also, as you change parts, for instance pipes, CPI's and the like will accept more ED more willingly. Also, again, PS has seemed to be the place for the technical discussion. I was amazed at the help and specs I was able to mill through with some (reportedly) reputable sources.

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Two weeks from now. I was going to be porting this month, but I've got a trip planned next weekend (Oct 6th), and rather than risk not getting it done (or rushing it) I decided to put it off until I get back. It will go to the dyno for a baseline the following week, and then tear down, and tear in. After all is done it will go back to the dyno to see what kind of results I was able to pull. I've done all my own tuning, and the bike will be tuned by me before heading to the dyno again, so it will be a true DIY'er. I could not believe how much info they were willing to share, but I hope it pays off. Here is an example of what I am shooting for...

 

Cylinder Pics

 

These were ported by the builder that was forthcoming with all the info. As the discussion followed on PS, notice that the intakes are not huge compared with what many have pics of. I'll keep you updated as my project takes form. Good luck with yours!

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That would be a good start.......I like the exhaust a little higher but no higher than 200*. Boost ports do work but welding is a must!!!!!!

 

 

 

the boost ports in the banshee's would not be big enough to flow enough to be worth the hassle.. they will not be as big as what is built into the cub cylinders.. or what is in the 250R's

 

also for the cost of possibly ripping the ear off of the cylinder i wouldnt waste my time with them.. even if it were welded.. when it rips it will be across the base of the cylinder and through the primary transfers.. pretty much ruining the cylinders.

 

then again both of the motors that ive seen this happen to were 95-109hp motors..

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