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Author Topic: Cylinder porting and transfer ports  (Read 271 times)

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Offline iranana

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Cylinder porting and transfer ports
« on: October 26, 2013, 04:47:09 PM »
Hey everyone, I came across a pair of ported cylinders for my RD250E, but the seller on eBay isn't very helpful in explaining exactly what's been done. From the photos, I can see that the transfer ports are massive, and it looks like they've gone all the way down to the steel liner. He said that the exhaust port has been lowered, which I find strange unless the piston moves below the exhaust port in a stock engine. I know these photos aren't the best and don't show the intake or exhaust, but does this look like a bad porting job? The intake looks to have be widened as the intake window on the piston looks rather large. There's something about those transfer ports that look kinda weird. Can someone explain what effect enlarging the transfer ports has?
« Last Edit: October 26, 2013, 05:43:50 PM by iranana »

Offline Yamaha179

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Re: Cylinder porting and transfer ports
« Reply #1 on: October 26, 2013, 06:42:16 PM »
I don't see where you can show where the transfer ports have been lowered.  I can see where the dividers have been knife edged but the top edges are stock and the bottoms of the liner haven't been raised.  I don't know why the guy modified those pistons; they are only good for the trash bin.  If you try to run them they will break.  (I speak from experience.  That is an old, bad, trick.)
You would have to look at the cylinders, have them in your hand, to know if the timing has been changed.  Be careful.
Lyn Garland

Offline iranana

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Re: Cylinder porting and transfer ports
« Reply #2 on: October 26, 2013, 07:40:50 PM »
Thanks Lynn, I was looking for a pair of stock cylinders in the first place, but came across these and they piqued my interest. I don't really remember what the transfers look like in a stock cylinder, but thought these looked larger. Might keep looking for a pair of unmolested cylinders, or I'll try and get some more info on these.