xr400 engine in 400ex

[PismoGuy400]

does the xr 400 bolt up, if not what do i have to do to make it fit?

[400exrider707]

I'm pretty sure the bottom end will...

I believe this has been done to eliminate the electric start and convert to kickstart, but for some reason it seems people were only using the XR bottom end.... search for it, I know its been posted before.

[PismoGuy400]

so ive come to find the rear motor mounts are a bit different. thats an easy fix. how bout clutch linkage, will mine bolt up to the xr?

i cant find any threads on the swap really... id like to know exactly what needs to be done

[jeepthing07]

I read somewhere that the 400ex had beefed up bearings to deal with the added stresses of 2 wide ATV tires. I don't think the XR400 would last long in a atv chassis

[400exrider707]

Originally posted by jeepthing07
I read somewhere that the 400ex had beefed up bearings to deal with the added stresses of 2 wide ATV tires. I don't think the XR400 would last long in a atv chassis

It will last, Honda always over engineers things. The XR and EX are both pretty bulletproof motors.

Or look in the case of the CRF450/TRX450. Honda changed which side the load bearing was on between the two and then the quads ended up having a lot of problems in the first couple years because of this.

[PismoGuy400]

so does anyone know what is required for the swap? i want to jump on the deal but not til im sure.

[low70c10]

not much help but i do know youll have to change the way the brake lever is for the kickstarter and grind down the frame where the pivot bolt is to make room for the kicker. atleast thats what i was told. im still debating on doing the same thing or not i can get a complete 96 xr400 for 300 bucks.

[400exrider707]

Search! there is a member on here with an XR bottom end on his quad... he saved a ton of weight and gained good power.

i'd be interested to see if it will fit because i like the way the engine is designed a few bolts and adjustments are in better locations on the XR it has a better cam, more compression and lighter flywheel too

[PismoGuy400]

ive tried, some say 100% bolt up other than the kicker/ brake lever issue some say the rear motor mounts have to be relocated. so im not sure

Mounts dont line up.


I wouldn't put a xr400 engine in it cause you gain so little hp. Only XR engine I would put in a 400ex would be a XR650. If you your self can mount a xr400 engine in a 400ex im sure you could get a xr650 in their.

Originally posted by jeepthing07
I read somewhere that the 400ex had beefed up bearings to deal with the added stresses of 2 wide ATV tires. I don't think the XR400 would last long in a atv chassis

Same thing was said about building yz/crf hybrids. Look at them. Their all holding up fine.

[PismoGuy400]

great, motor mounts line up. howbout factory EX clutch and throttle cables, will they work?

[400exrider707]

Originally posted by Boris The Goat
Mounts dont line up.


I wouldn't put a xr400 engine in it cause you gain so little hp. Only XR engine I would put in a 400ex would be a XR650. If you your self can mount a xr400 engine in a 400ex im sure you could get a xr650 in their.

The 650R motor is too tall to put in without major mods and the 650L motor isn't much more power than a 400ex without major engine mods.

For those wondering about the XR bottom end and too lazy to search...

http://www.exriders.com/vbb/search.php?s=&action=showresults&searchid=2028266&sortby=lastpost&sortorder=descending

Seems like you can convert the 400ex bottom end to kickstart, but no so sure about swapping bottom ends back and forth...