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View Full Version : 400ex motor in a 300ex?


400in300
03-06-2003, 07:52 PM
Can I put a 400 motor in a 300? This is my first post:D I mean will it fit? I already have the motor with a k&n biggun pipe and jet kit.I already have 400ex a-arms need tie rods and already ordered works tripple rate w/rezzies.
NTPRacing#19
03-06-2003, 08:06 PM
yea a 400ex will fit in a 300ex, ive seen it done in an old dirtwheels magazine. dunno how they did it but it will fit
Scott
03-06-2003, 08:12 PM
I've got two words for ya, frame gussets.

To put a 350X engine in a 300 you had to gusset it or start welding the cracks and breaks, and a 400 has more torque than the 350X.

Have fun and good luck. Might want to order that +2 swingarm right now too. You'll want it later.
400in300
03-06-2003, 08:18 PM
I have a 400 swingarm with durablue will it fit some how? what shock rear? I have a welder I can do some reinforcing on the frame.
Steve-o 400EX
03-06-2003, 08:20 PM
Yea just make sure everything is gunna hold up. The 400 motor has great torque and it'll rip. Good luck!
SpeedBump
03-06-2003, 08:25 PM
Hey, I got a 350X in my 300Ex chassis. I have been running it for almost a year now, it has been ridden hard at times, and I have had no problems. It is basically stock, with a UNI filter, and custom exhaust. It runs about even with a stock 400EX. I haven't reinforced anything on my frame. It seems to be holding up ok. I haven't raced moto-X with it, but I would say for everyday trail riding it is ok.
Scott
03-06-2003, 08:28 PM
I don't know about the 400 swingarm on the 300. If I were you I'd go do some measuring first and see if they're even close to the same width where they mount to the frame. Next would be checking the differences between the top shock mounts between the two, because you definitely don't want the stock 300 shock for the rear.

Break out the tape measure before you go wild with the welder.
Scott
03-06-2003, 08:31 PM
I was going by a friends 300frame/350X engine that he ran moto-X with. It cracked just about every weld on the frame and a couple of the tubes before he gussetted it.
400in300
03-06-2003, 08:41 PM
i will do heavy gussets and powdercoat.Now, do i have to do serious modifications to make the motor fit .
400in300
03-06-2003, 09:17 PM
Will i have to make all new brackets for the 400 mtr
400in300
03-06-2003, 09:17 PM
Will i have to make all new brackets for the 400 mtr:devil
400in300
03-07-2003, 10:09 PM
will i have to make all new brackets for a400ex motor to fit
400in300
03-10-2003, 07:52 PM
btt