My answer to the 2011 YZ490

The beginnings

So after buying a used frame for a street legal title then finding out that the laws have changed on registering dirt bikes in Wyoming I have a spare frame.

I had a husky 250 1973 area and I thought about putting that into it. But needless to say the backwards kick-starter and odd angles of that engine, and a froze up crank deterred me from pursuing that route. I then thought about my engine that is in a old polaris four-wheeler: my buddy and I happened upon a old IT465 that had been run over by a piece of farm equipment. Frame was pretty busted up but the engine started up and ran fine. So we threw it in the four-wheeler. After going to college it sat and around and ended up with the same fate. except a bail of hay was the culprit.

Then a few weeks back I spotted the YZ490 in the newer frame and loved the idea!! So I talked to my old man and had him pull the engine and bring it out to me as he headed to Virginia.

So hear it is and I set it in the frame to see how far off it will be. Any advice is appreciated. And don't criticize me for wanting to put it in here I have a frame and spare time on my hands so I'm going for it.

Suprisingly it fits pretty snugly, the modifications look like they will be simple if not straight forward :confused:

I'm going to fab up the brackets over the next few weeks and get a swing arm and mount the engine temp and decide how to cut and re-weld the frame.

I'm going to need advice on what parts and years of suspensions, triple clamps and what not would be best to buy. Bit by bit I'll gather up the parts and put this thing together. I'm trying to brainstorm on how to best do the exhaust on the poor thing (it'd be so much simpler if the exhaust came straight out the front!!)

So here are the pics.

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You'll notice this is where the frame mod's will have to happen. exhaust is just a little behind the Y in the frame.

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Should be a fun build. :thumbsup:

Love that huge barrel stuffed into the Al frame.

I hope all goes well. Should be a riot to ride.

Cool. Just a shot in the dark, but since the engine seems to sitting pretty

high above the lower frame tubes, one possibility is to make new front mounts,

tilt the front down and see if another year 400/465/490 cylinder has a straight output.

Have you put a swing arm, rear wheel and rear sprocket on it yet? I'd make sure that chain lines up well before finalizing motor mounts.

Hi there

I think that the lower engine mounts are more important to keep the monster chained. As a side effect it could be that the cylinder get an inch further to the back and you could just dent the pipe around it.

As there is a modern water cooled YZ500 cylinder /Engine design presented in this very forum we are using, you could contact them finding out what they think as they already put some YZ490/500 engine into an alu frame.

I found it best when the engine mounts are not so close that I could get away with just broaden the opening to redo them or weld on new ones. In my case I did the lower engine mounts renewal and filed (dremel) a bigger opening on the front mounts so the upper cylinderhead mounts fit right in.

Good luck

Arnego2

Great idea. I'd redo the frame to accommodate the exhaust, and be sure to notch the fins so the head can be removed in the frame. Or whatever so you can pull the top end. I like the idea. If I could get away with stuffing a big two stroke engine in my WRR frame, it would already be there!

later model yz/wr 490's have a center exhaust port, befroe you do anything with any of the mounts get that swingarm pivot straightened out..... those steel bushings in the engine cases where the swingarm pivot bolts goes through are removable ...... On my yz 426 frame/swingarm those bushing set right in the 465 cases (although the original 465 bushings where a bear to get out) and on the 426 the swingarm/pivot engine chain and sprockets all lined up real well

ps I wouldn't worry too much about having to remove the head .... get that thing running well and the just richen it up one jet and you won't have to worry about it for a couple of years and if you where really worried about having to remove the head take out the studs , loctite some stainless heli coils inthere and use bolts that way you can just slide the head sideways might have a bit of fun lining up a new gasket but it aint that bad

Heat the cases in the kitchen oven, and the swing arm bushings will fall out, just like four stroke cylinder liners.

Hi there

I think that the lower engine mounts are more important to keep the monster chained. As a side effect it could be that the cylinder get an inch further to the back and you could just dent the pipe around it.

As there is a modern water cooled YZ500 cylinder /Engine design presented in this very forum we are using, you could contact them finding out what they think as they already put some YZ490/500 engine into an alu frame.

I found it best when the engine mounts are not so close that I could get away with just broaden the opening to redo them or weld on new ones. In my case I did the lower engine mounts renewal and filed (dremel) a bigger opening on the front mounts so the upper cylinderhead mounts fit right in.

Good luck

Arnego2

I'm planning on modifying the frame around the pipe. When you dent the pipe that close to the header it really affects performance, and I'd like to keep the engine as low as possible in the frame. I'm trying to gain some advantage on my 450 for the woods.

I haven't checked it out yet but I think that I'll be sticking the front mounts off of the WR or YZ on it then making bushings the 465 is way narrower So I have to make up for the width on the front mount.

That new YZ is what my answer is too.

Same thing on top I'm hoping that the YZ WR mounts can be modified and made to work on the top of the head of the IT. On bottom I'm thinking about adding another mounting location right in line with the bottom mount on the engine, then custom fabbing a bracket to hook the them both helping to get rid of engine flex.

As easy as the engine slides in and out I might just pull it out to do work on it. I'm thinking about throwing a new piston in it before I start riding it.

I haven't measured yet but I think (just think) that the YZ pivot is dang close if not spot on. So maybe I'll be able to use it. And yes I'll be getting a swing arm and starting there, that way I don't waste a lot a material's and resources.

"later model yz/wr 490's have a center exhaust port" I thought that I read that the 490 had a different pattern and bore and what not??

Also are there pipes that come out on the right side curve to the left then come back around to the right and along the engine and back??

I'm hoping to find a 500cc or something close to that pipe so it's tuning is close. I may have someone from a performance company make me a pipe at some time. There's a company back east that does custom jobs for sleds.

Another thing I was wondering about what would a good new flat slide carburetor be to try in the bike?

If any of you know of parts that I need IE swing arm, yz linkages, yz shock, yz forks, so on.... basically any body parts. I'll not be buying all at once but I'd like to keep my ears open.

hopefully I can find the stuff for cheap.

And I'm still mulling over water cooling..... trying to come up with a better system.

Cool. Just a shot in the dark, but since the engine seems to sitting pretty

high above the lower frame tubes, one possibility is to make new front mounts,

tilt the front down and see if another year 400/465/490 cylinder has a straight output.

I'd like to if the cylinder has the same pattern and stroke/bore I don't want to start getting into ruining an engine that run's perfectly fine.

And I definitely want to keep the engine as low as possible.

When you dent the pipe that close to the header it really affects performance.

Agreed but to make the cylinder heads engine mount fit that cylinder would drop backwards about an inch, maybe giving you enough space for a decent bend. That would go against the lowest possible engine position.

I would look for a position where most mounts are easily do-able. Like one part a new welding point and the rest Dremel work. I think bending that pipe would be neater than modifying the frame. I personally dislike bent frames :thumbsup:

Anyway put on a sprocket and figure that way up to which point can you move the engine without interfering with anything.

Depending on what pipe you are getting you have to fiddle around with the length of the pipe silencer mounts and all that. Hopefully you have access to mates bikes of different brands so you are able to get a nice measure of each.

Good luck

Arnego2

Agreed but to make the cylinder heads engine mount fit that cylinder would drop backwards about an inch, maybe giving you enough space for a decent bend. That would go against the lowest possible engine position.

I would look for a position where most mounts are easily do-able. Like one part a new welding point and the rest Dremel work. I think bending that pipe would be neater than modifying the frame. I personally dislike bent frames :confused:

Anyway put on a sprocket and figure that way up to which point can you move the engine without interfering with anything.

Depending on what pipe you are getting you have to fiddle around with the length of the pipe silencer mounts and all that. Hopefully you have access to mates bikes of different brands so you are able to get a nice measure of each.

Good luck

Arnego2

Thats true I'd rather bend than dent. :thumbsup: I know people at home with bikes but not here where I'm at at college. We'll see what I can come up with. For sure the first thing is getting a swing arm and lining up sprocket's and what not. I agree with the frame if I can make it work without cutting and rerouting frame that'd be most perfect in my opinion.

It's going to be a long project I'll keep updates as much as possible. I'll be starting my summer internship in 2 1/2 weeks so I'll be pretty busy for the rest of the summer.

Thanks guys

Certainly not an easy task you are going to do. A lot of stuff you have to think through before realizing it.

Great project.

Personnaly I would use a steel framed bike. The exhaust would probably clear the down tubes and steel is alot more forgiving to modify.

That bike will freak people out. I cannto wait to see it finished.

As a bus driver I have a little spare time on my hands now that finals week is over. And since my 450 is tore apart (don't ask I won't yell at you) I decided to put the tank subframe and seat on the 465 frame to do some looking... here's what I got.

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It look's like lining the carb up will be a pain I'll have to make an angled intake, and a custom boot to go to the airbox.

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I'm contemplating building an aluminum fuel tank as well. I could add a lot of capacity by filling up the area's that don't need air movement.

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You'll notice that the bottom mount is a little higher than the frame mounts

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and a little back of it. I'll have to fab a mount to go up and back and I'm thinking as well to make another location on the fram and make the mount a triangle bracket

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This is why I'm bored, after 70 degree weather yesterday it decided to snow.

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Nice pictures, did I see that right or is the engine not balaced? Third picture from the bottom it looks like it is a bit off set.

Regards

Arnego2

Nice pictures, did I see that right or is the engine not balaced? Third picture from the bottom it looks like it is a bit off set.

Regards

Arnego2

Ya I unhooked the one front engine mount and I don't have a swing arm bolt. I just have two bolts shoved into the engine to kind hold it there.

I also noticed that the YZ subframe doesn't fit perfectly on the Wr frame and I might just make a new mount on the frame rather than getting a WR subframe, airbox, and different side covers and the whole shi-bane

Best would be if you could compare, what you have to change to make the new mounts, vs the air box configuration. I think you could go around and measure from the outside, the position of the airbox, the thickness of each mount, how wide is the subframe. Also there is the seat, which has to connect nicely on the tank.

Have you got a carb? And what kind of ignition you would like to use?

You defenitely have a greater challenge ahead then me.

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