G.E.M. reed valve on 250

[rob w]

Has it ever been truely determined, if there are any significant advantages in using a G.E.M. reed valve on the 250 engine.
I have one, never used it, guess I could find out for myself, but would like to hear from someone experienced with the modification. (Kent comes to mind).
Would use with stock 36 Bing.
Also, if anyone has, or knows where I can get some new petals for it, I would appreciate that.
Thanks
Bob Wardlow
Grand Rapids, Michigan

[Larry Perkins]

Bob,

I raced one with a reed that JP Morgan did that had a Mikuni.  It had the broadest powerband of any of the Penton 250s I have ridden. Loved that bike and have tried to buy it back numerous times to no avail. Won at Mid-Ohio on that bike in Over 40 one year. JP has done several reeds on Pentons and is a brilliant tuning mind to pick. He is a whiz at using modern available things on these old bikes.  There is some Boysen reed that I think fits those but not positive.

Larry P

[rd400pi]

Rob,
  I have the mentioned bike and rode it many times years ago.  It has awesome power and even awesomer grunt factor.  Also have a Bing flavored non-reed bike for comparison.  Both have Jemco pipes.  The stocker will require some clutch work down low on occasion whereas the reed bike doesn't.  The Mikuni is actually a 34mm unit bored to 35.5 due to case clearance issues.  Cheers.

  Mike H.
  Tulsa POG

[rd400pi]

Rob,
  Also must add that this reed unit is not a GEM but something with no name on it.  

  Mike

[JP Morgen]

I used the Yamaha six petal reed cages from early 70's Yamaha 250/360's on the 250 and 400 motors I built, vintage legal and very "modern" in their design, and you can get carbon petals for them as well. The G.E.M. reeds are a little small to provide a large boost in performance throughout the rev range. I used 38mm Mikunis, Penton aftermarket(Carl Cranke?) pipe on the 250, along with the porting specs., a 420 pipe on one of the 400's, a Honda 1984 CR250R pipe on the other. I also have done 175's with similar set ups.

[brian kirby]

The GEM reed just bolts on to the stock manifold flange and they do not work very well. JP does it the correct way which is to graft an actual reed intake to the cylinder.

Brian