Nambotin's reed block

[Keg]

What is going on here with Nambotin's 2007 ISDE bike?

http://www.gasgasonly.com/index.php/...ike-close-look

[GMP]

Is that Robby's (Boomhauer) bike?

[gasgasman]

Originally Posted by GMP

Is that Robby's (Boomhauer) bike?

Yes.
It has some crazy port modifications.

[Keg]

It was a New Zealand ISDE bike that was then sold into Australia with the rest of those bikes after the event.

I assume the plates help flow but does anyone have any other suggestions what it is for?

[GMP]

Is it still a VForce? Doesn't look like it. If not, and the new reed is more narrow, they may be there to take up volume. Also, the cases are very clean in the area of potential reed contact. The stock cases are rough and uneven. If the reed block is different, I would say these mods are to fit the reed properly. I fit a VForce to an '03 and had to do a lot of case cleanup, that was of no issue with the stock RAD valve.

[Berkyboy]

The French built race bikes have all kinds of internal case modifications. My nephew has one of them, from the North American '06 WEC rounds, and we have yet to have to tear it down for anything other than a couple top ends.

At one point we thought we had to convert it to a 250 for a weekend (we were out of 300 pistons) and we discoverd that the cylinders would not swap out due to the case modifications.

One of these days we'll get around to it and document some of the changes.

They mostly modify the case volume and flow characteristics yet still keep compression about the same as the bike he has never really needs race gas other than good fresh premium pump gas.

They also remap the CDI and block off the small compression relief hole, found on the PV side of cylinder that helps lower compression for starting, to raise compression slightly at lower rpms.

Power delivery on that 300 motor is sweet. Hasslebri was the original US owner where he had it for a year and has dibs on it if it ever comes up for sale again. Hopefully I can beat him to it

[GMP]

If I remember, Robby's bike was a 275cc version. What did they do there, bore a 250 or de-stroke a 300?

[gasgasman]

Robby just called it a "275".
It was the 300 bottom end with the 250 cylinder.

[Berkyboy]

As far as I know Robbie's bike may be a 250, stock the 300 and 250 both use the same crank only the cylinder, head and piston are different.

Unless the French relocated the crank pin and/or used a different connecting rod and/or/and modified the cylinde/head nobody's 100% sure as we never had to go inside the motor and I don't know if Robbie did either.

Stock 250/300 and 200 cranks all use the same connecting rod, mainly the crank pin location is the difference which obviously changes the stroke.

All we know for sure is Robbie's motorcycle's paperwork (vin number and engine number) indicate it started life as a EC300 and during the "French" buildup they used a stock 250 piston as well as a 250 cylinder and head.

I believe his bike was Nambotin's when Nambo' rode in the WEC Junior Enduro class, where displacement was not a factor and for those races they may have thought they needed a 250 instead of a 300. Or it indeed could be a hybrid (275) not really sure.

[coopernicus]

Okay, that's pretty much confirming what I thought as even though Robby called it a 275 I pretty much thought it was a 250. I was thinking of freshening up the top end soon so I will check the stroke just to confirm (Robby said it used a 250 piston). I will say it does run much better than a 250 should at altitude with my weight! At sea level I would say it was the sweetest 250 I ever rode...It's a keeper!