What's the difference? Why would you pick one over the other. I would imagine the 440 would be the fastest and best... but I've seen so many people with a 416 that it makes me wonder....

 

i've been looking around for a while and all the post i read basically note that the 416 would be better then the 440 since it can rev higher and faster since the piston is lighter then the 440 but I believe that the 440 pumps more HP and torque... just ask around and see what people tell ya

 

Yes, the piston is lighter.

It's also cheaper & easier to go the 416 route since the stock sleeve can simply be bored to accept the piston - where with the "440 kit"), you need to get a sleeve & piston and have your machinist install the sleeve.

 

what about 426? can u keep a stock sleeve and order a piston to get 426?

and how can you run an 11:1 compression on a 416 and a 440? does it have to do with the shape of the head that allows you to run regular feul and the size that makes the power difference?

sorry i am still foggy on some aspects of big bore. any help is appreciated.

 

...actually- I'm clueless to the whole aspect of the big-bore topic. What needs to be done specifically. Can someone please explain this in laymen terms? I'm already wanting more power- and want to bump up the engine. Can the 440 run on high octane fuel... or does a special alcohol blend need to be run?

Has anyone raced a 440 agains a 416? or even the size mentioned above?

 

The key to the EX's power is higher compression. I chose to bore mine to a 426, which means a machine shop bores the cylinder .120 over. I thought that since a 440 is only a 435, there would be know difference in power. But, for some reason when I race my buddies 440 I always come out on top, we have pretty much the same mods. The best set-up is by far to start out with is 416 10:5:1 or 10:8:1 compression. The reason I chose 11:1 is because there is race gas handy here and I run half and half. It all breaks down to want kind of power band you want, 440 lots of torque smooth power band, 416/426 fast reving almost like a two-stroke. Also the cam you choose plays a big part in your compression choice. I have heard awesome things about the GT Thunder cam, I am switching to that cam as soon as the cash comes in.

 

Yes it can be done, but the cylinder's getting pretty thin at 87mm (416) - I believe GT Thunder recommends that you re-sleeve for anything larger (that would include the 88mm 426cc setup).

I don't think I'd be comfortable taking my cylinder beyond 87mm after seeing how thin it currently is. Maybe if it was liquid cooled...

The compression is increased by using a "domed" piston instead of the stock "flat top" piston. Combustion chamber design, bore size, camshaft profile, and altitude is what determines the compression ratio can be used with various octane fuels. 11:1 seems to be the magic number for most 400EX's that draws the line between premium fuel or race fuel. Keep in mind that bikes like the Yamaha YZ426F run 12.5:1 comression on pump gas with no trouble at all...

 

LDJ,

What two octane gases do you run in your 50/50 mix? How long have you run this combination? Any problems? Does sea level have any affect on how much octane I'll need to run with my 11:1 Wiseco? Thanks. Anyone is open to help me, and it's greatly appreciated.