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Discussion Starter #1
I've ported several cylinders in the past, but never a 250R cylinder. The guy wants the widest powerband possible, with a focus on low end and lower midrange.

My thoughts are:

EX: 188
Main: 130
Secondary:132, 2 degree angle
Boost port: 128, angle undecided
Mains and secondaries will be aimed as far back as possible and will have the outside radii increased, with the inside radii just cleaned up so as to increase the time for the charge to be straightened before it enters the cylinder. I will be following the port/time method, but will choose more conservative numbers.

The pipe will be a Pro Circuit with a 22cc dome, carb is a 36mm Keihin, UNI w/o airbox lid. Rider weighs 170lbs, bore is on 67mm.

Thoughts?

*if any top end builders have any ideas that they don't want to share with the public, I gladly accept PMs :D*
 

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Hello 86LT; Are you going to accurately grind the ports by hand?? Good Luck. I can only hit that kind of porting from the outside while making a new liner. I’m not one of those Hot Shoe porting guys. If anyone else has figured all of this out, I doubt that they would be willing to pass along their Trade Secrets. Running one of the small angle grinders is a PAIN, I’ll bet your Dentist could do a good job. I’m not trying to be funny, the guys who are good have scrapped more than a few while learning this skill.

I just pulled the liners from an old piston port 250 Yamaha twin. We recut the ports to Yamaha factory racing specs. The job was done on our vertical mill. After slipping the liners back in we ground the aluminum to match the recut sleeves. I’m not yet good enough to make the transfers look very respectable. No pictures this time, my camera fried a battery.
JT
 

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Discussion Starter #3
Haha, I know about that pain. It's good to speak to you again, T. Porting is quite the killer sometimes, but I always have fun doing it. The CCs grinder makes everything much easier and the 250R cylinder is cake to work on. Compared to a Blaster or a Banshee, the 250R ports are massive. This isn't my first or even tenth porting job, either. Matter of fact, I've had 2 other port jobs this week. TTR125 and Banshee. Having a really good set of carbides, a lot of light, and some gloves tucked into some sleeves all make the job night and day easier as well.

This is my recent post (as tfaith08) on Blaster Forum: http://www.blasterforum.com/threads/porting-101.58962/

But I do understand where any pro builder would be reluctant to give numbers because I would too. However, a semi-pro builder may very well know much more than I do and may also be willing to give a few (or a thousand) pointers, haha. To be honest, I don't care who gives me some ideas so long as they're good ones.

-Tyler

Last thought: Maybe if I post something completely erroneous, Flotek will chime in to correct me and spill some knowledge by accident...
 

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back in the old days they must have used files and other stone age equipment. today electric hand tools seems to be more efficient :Secret:
 

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The Blaster & larger cylinders are a piece of cake to grind transfers with the cute little offset grinders. What gets tricky for me is the 56mm & smaller cylinders. It’s so easy to slip & cut pecker tracks up the side of a 100cc 48-50mm bore cylinders.
Whoever is good at small bore cylinders, show us your work. It would be nice to know where to send the little ones.
 

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the real small cylinders arent as easy to work with as bigger ones. they make smaller than normal tools for that stuff
 
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