jonnienumberfive
Scoot Member
just found this 1970 2 cylinder 2 stroke yamaha in a barn,been there since 1980
Posts: 87
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Post by jonnienumberfive on May 5, 2012 17:52:09 GMT -5
I was removing my factory"tuned pipe" and noticed the exhaust port in the head is shaped like a D, its not round...any body had one of these apart and seen the same thing?? wondering if this is a restriction, or the way its made..... :stars:
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Post by Fox on May 5, 2012 18:15:37 GMT -5
That's the way it's made. Mine is the same way. I thought about grinding (porting) it with a Dremel tool but I didn't because it runs pretty good the way it is and grinding away at it could leave metal shavings in the cylinder that can screw up the rings.
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jonnienumberfive
Scoot Member
just found this 1970 2 cylinder 2 stroke yamaha in a barn,been there since 1980
Posts: 87
|
Post by jonnienumberfive on May 5, 2012 19:00:52 GMT -5
Thanks Dave for the info
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Post by Fox on May 5, 2012 22:43:53 GMT -5
I wonder if opening that port up would help or hinder a stock setup?
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Post by jmkjr72 on May 5, 2012 22:52:03 GMT -5
it will help
i did it on my zuma with the stock bore and an after market pipe
with an oem pipe it wont do squat
and while you are in there raise the port about 1mm and widen it just a bit
but for the work that you put into it unless you have a high compresion head your better off buying a bbk
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Post by dude on May 5, 2012 23:49:45 GMT -5
I just rounded the port the best I could and didnt raise or widen the port. With a Stage6 Street pipe I didnt like it. It may of worked better if changed the CVT springs. It seem to kill my low end. I did like changing the hump style head to a flat squish style head.
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Post by jmkjr72 on May 5, 2012 23:53:09 GMT -5
yeah you have to retune every thing for a higher rpm
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