Please need advice asap!

I have a chance to get either a yzf400 or 426 motor to put in my 400ex frame. Which one would beb better for an atv or is there much difference? Whats the biggest bore that a 400 can go to and be reliable?

The later the better.

Why is that, I need some info.

More cc's and a better clutch. Bigger radiators too if you are getting them with the motor.

But cant a 400 be bored out just as much as a 426?

But cant a 400 be bored out just as much as a 426?

But you asked:

"I have a chance to get either a yzf400 or 426 motor to put in my 400ex frame".

Why would you then chose 400 and bore it up if u can have 426? :cry:

Heres the deal. I have a 250r and a 400ex rolling chassis. I can get a 250r frame with a yzf400 motor already modded and ready to roll, or can get a good deal on just a yzf426 motor and have to mod my 400ex to fit and buy some other things.So please help me out!

What year 426 motor? The 2001 and later has a splined crankshaft snout, whereas the 2000 and earlier have a keyway for the counter balancer gear, Yes a 426 jug and piston will fit a 400. Better carb on a 2000 and later model too.

OK, will a 2001 and later carb bolt directly onto a 98-00? Also I see a wiseco 444 kit on ebay that comes with the cylinder, piston and all for the 426, will that bolt directly onto a 400

I think the rods changed at some point, but I don't remember what year?

Anyone else, I need some info.

426 gets the larger id rod small end.

426 rod less prone to shed its small end than a well used 400.

400 has a closer first and second gear which results in a closer ratio gearset for the 400 which might be adventageous for the 4wheeler.

Upgrade the rod to a failcon for a stroker cr-f and get the bushed small end.

A 97 mm kit will require fittment of the 426 rod, or the above falicon choice.

I would rebuild any motor before fittment, as there is no gaurantees.

SFO - What's the end cubic capacity after the CR-F stroker and 97 mm overbore? Thanks.

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