Engine swap suggestions for Yz400f chassis for trail bike?

Recently bought a 99 YZ400f with a very damaged engine. The chassis is 100%for complete and in Good shape. I was going to part it but my mind started working and I thought what about lowering the suspension a little and swapping in some sort of old school bulletproof torque monster 4stroke like an XR400, TT500 or even an old twin like a cl360 . I know there will be considerable fabrication and it will be heavier. But im thinking tractor torque with decent suspension.

Well flame away!

I would say TT500. Reliable and a torque monster. If you want to be really cool put a BSA B50 engine in.

I started messing with old hinds twins about a month ago. Might see how much trouble stuffing one in thete

I think you are off the mark here. A 99 WR400 engine is already exactly what you want in there- it's a heavy indestructible torque monster. It is easily capable of making twice the power of an XR400 engine for example and is still very, very reliable. I know several people with badly abused and still great-running early Yamaha YZ/WR-F motors.

You could swap in a 2-stroke YZ or WR engine or even a streetbike motor, but after a ton of work and money what you'll have when you are done won't be worth spit on the sidewalk. Having done more than a few crazy swaps, I try to talk people out of them; there are lots of half-finished morphodite bikes on Craigslist for a reason.

a 426 swap would probably be pretty easy. A 450 swap might not be too hard either.

I wouldn't swap anything old and heavy in there.

I like the XR400 motor.

Air cooled, plenty of power for fooling around.

I wouldn't bother with a modern two stroke motor. What's the gain in that?

An air cooled CR/KX 500 motor would be something to talk about.

Zero resale on hybrids, ya know.

How about a worked over YZ465 or IT465 engine? Reliable, cheap, torquey two stroke. I would get the head cut a little more modern, put a flat slide on it, maybe have the ports touched up a bit with some modern know how, and have a pipe made for it. In stock form though it was very reliable and fairly powerful at around 42hp. I bet you could get it on up to about 55 reliable horsepower and more torque than youll get from any thumper under 600ccs.

TT500 is air cooled, torquey, still a yamaha, super cool swap. But the twin idea is just neat. A honda CL engine would be interesting.

I know a guy who put in a YZ490 motor in a thumper frame. Little fabrication was needed. Two stroke power, lots of torque, air cooled, and now real light. Just a thought!

Recently bought a 99 YZ400f with a very damaged engine. The chassis is 100%for complete and in Good shape. I was going to part it but my mind started working and I thought what about lowering the suspension a little and swapping in some sort of old school bulletproof torque monster 4stroke like an XR400, TT500 or even an old twin like a cl360 . I know there will be considerable fabrication and it will be heavier. But im thinking tractor torque with decent suspension.

Well flame away!

Good thought... but just doesn't sound practical.

The yz400f, will be great when bored out to a 440, higher compression piston and maybe some cams.

Then you can put your welder away before you really mess up something.:busted:

Do you want to ride it, or are you interesting in just building it.

Good thought... but just doesn't sound practical.

The yz400f, will be great when bored out to a 440, higher compression piston and maybe some cams.

Then you can put your welder away before you really mess up something.:busted:

Do you want to ride it, or are you interesting in just building it.

Exactly. You'll basically be guessing your way through the whole project just to find out that Yamaha already had it figured out: buy another 400 motor and trick it out.

Exactly. You'll basically be guessing your way through the whole project just to find out that Yamaha already had it figured out: buy another 400 motor and trick it out.

I figured he wanted to do a swap, not build the bike up.

I thought about the 465/490 2 strokes already they make the best torque of any 2 stroke I've ever ridden. They are like a tractor, 4 ranges (not gears) 1st slow precise, 2nd braap throw 3" rocks at your buddy 100' behind you, 3rd hey watch me do 70mph wheelies, and 4th oh my God I can't believe I'm going so fast I hope the brakes work, maybe I should have bought thoughs new tires. The 400 motor that came with it dropped a valve at probably 13,000 rpm and then sat in someones shop for a year torn apart, and the kick starter won't catch, IT'S JUNK. I have a '95 WR250 that I've completely rebuilt (should have just bought a 300 ktm) it's smooth and torquey and a WR360 Husky that is entirely too powerful for the average rider to use in the woods. I rarely ever sell anything, so resale value doesn't matter. I was trying to think of an engine to put in it that would be smoooth, torquey, climb anything, not transmit every bump through the bars and seat kind of bike. I don't want to do wheelies or roost anyone, I want a full size XR100 w/CR85 suspension kind of bike. If that makes any sense. smooth chassis, non-fatiguing won't stall power.

AFAIK, the 465 is more reliable, less vibes, and the porting more torque focused than the 490. At least that's what google says.

"That's what Google " says Must be true LOL! I've ridden a couple of 490's but never a 465, i'll have to take your work on that, Ur Googles word.

"That's what Google " says Must be true LOL! I've ridden a couple of 490's but never a 465, i'll have to take your work on that, Ur Googles word.

Well, one of the first things that comes up when you start researching the 490 are several "Worst Bikes Ever Created" lists. Not all of it due to the engine, but a lot of it. Meanwhile the 465 is highly praised. I researched it a lot when there was a blaster with a YZ490 engine in it for sale locally a couple years back. Still a lil mad at myself for not buying it, just couldn't picture my self on a quad that small. If only it had been a 250r frame.

I had a couple IT465's back in the day. Awesome, torquey, bulletproof motors for sure.

Stuff a XR600 motor in there. :busted:

Seriously though, the older air cooled motors are physically HUGE compared to the more modern 4T designs. Not sure if you would have room for an XR or TT motor without a lot of frame mods. I'm not sayin it can't be done, but I'd look for whatever is the best fit. An older air cooled 2 smoke would be awesome though. :busted:

The WR500 engine is a YZ490 with proper squish.

Seems like the majority likes the idea of a yz/it465 engine swap.

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