Would it be possible to put a 300Ex head and top and onto my 250X case? would everything bolt right up? a 400Ex head probably wouldn't work, right?

beacuse i want a bigger bore and want it as reliable or as close to reliable as stock...so i figured, instead of going with a 265X or bigger, how about bolt up a 300Ex head, and bore it out to 330cc, and then put all the works into the motor like high compression piston and all that good stuff?

What do you guys think??
Anyone ever try this?

 

A 300ex head will fit perfectl except you won't gain any more cc's. The bore is the same between the ex and x the rod lenght is different.

 

Just for my own knowledge, how can the bore be the same when a X is approx. 246cc and the Ex is 282cc?

do you know anyone that has ever tried this?

thanks

 

When you are talking about the displacement you are talking about the amount of area the piston displaces. If you get a bigger piston, it will displace more, the piston is wider moving more air, fuel, and exhaust per stroke. If the rod and crankshaft are designed to make the piston move further up and down you will also get more displacement. This is what BermBanger is talking about. I don't know all that much about the 250X, so I don't know if the 300EX gets it's extra cc's out of the bore, or the stroke.

One thing that I tried on my old 300EX is I put a vented air box lid on. I had to rejet, but I got more power. The air box is restrictive on this machine, look at the front where it takes in the air, it sucks trough two small tubes in the frame. I read in a 300ex pipe shoot out that you get a 1/2 horse power increase by doing this. I don't know you might have already tried this, but it's an easy cheap power gain.

 

Look the bores and top ends can be the same size cuz the ex has a longer rod in which gives it more cc's.

 

Ahh ok, thanks for explaining that...now i realize what you ment!!

so there would be little or no advantage of putting the 300Ex head on my 250X case?

thanks for your guys help!!

 

Right! No advantage at all. You need the ex rod or an aftermarket one to get yours up to a 330.

 

would there ba enough clearence in the case for this...how about with some machine work?

thanks!

 

Crankshaft needs to be swapped for stroking

 

No you dumbass there is a major difference between the 250x, 250ex, and 300ex. The 250x and the 300ex are virtually the same. They do not make the x anymore. The ex has the recon motor. YOU need to get your facts strait.We are talking about the 250x/300ex not the 250ex.[