2-stroke IT490 motor swap

[Mathius]

well went online and typed in engine numbers 23x and found out thATS its a 1983 yz490k, has a 465 jug but looks bored out to the 490 piston, and its a 4 speed

I don't think you can take a 465 out to 87mm? The stock bore on a 465 is 85mm, I think the biggest you can go is 86.5.. But don't quote me on that.

The 465 YZ motor has better porting, and a closer squish than the 490. The IT motors have mild trail porting, and don't make the same power as a YZ motor. (It's also been said that the 465's don't vibrate near as bad as the 490)
So the 465 will run smoother, and cooler. Just make sure you keep an eye on your head temps. They shouldn't get any higher than 230 degrees.. Running higher octane fuel helps that out a lot.

If you wanna run that motor, I say go for it..
Just gear it 14/40, maybe 13/40 if your running a bigger rear tire.. (The 4 speed has a high first gear)
Make sure you swap out some heavy duty clutch springs, and never run motor oil in your case. Use a good trans lube, or ATF.

 

[357warrior]

could u post some pix of ur swingarm up close and take some measurements of the swing arm so i know how much to cut out. and also maybe take a pic of ur kicker for me to. thanx

 

[Mathius]

could u post some pix of ur swingarm up close and take some measurements of the swing arm so i know how much to cut out. and also maybe take a pic of ur kicker for me to. thanx

I tried to take some pics of my swinger using my phone the other day, they didn't turn out so great.. But I'll try again tomorrow.

Also the 465 kicker is way different than a 490 kicker.

 

[357warrior]

i got a 490 bottom end so r u using the 465 kicker. i know they give u a mile to kick. got a 94 kx250 here and the kicker is no where near that long.

 

[Mathius]

i got a 490 bottom end so r u using the 465 kicker. i know they give u a mile to kick. got a 94 kx250 here and the kicker is no where near that long.

Oh yah.. I forgot about that. Sorry.

Measure the diameter in the splines on the input?

 

[357warrior]

well good luck wth your build mine took an unexpected turn found out ill be makin right hand turns my frame is bent, so this is to all if someone got a donor frame (straight) for free or really cheap mine build will be on pause.

 

[Gen1Pat]

Check with Yamahauler, he is parting out a 92. Idk if he will ship the frame or what he wants for it.

 

[Mathius]

well good luck wth your build mine took an unexpected turn found out ill be makin right hand turns my frame is bent, so this is to all if someone got a donor frame (straight) for free or really cheap mine build will be on pause.

Well that just plain out sucks..

I did some research this morning, and found out that the kicker on the 5 speed motor is different that the 4 speeds.. Your kicker would have a smaller input shaft, and is a way different angle. It almost goes strait up, and down.
You could always cut, and reweld the stock kicker to get the proper clearance, and angle you need. But you might be better off swapping out that input shaft to the bigger one (which is a pretty simple swap. The shaft is the same size as the one in your motor now, it's just a different spline count) http://www.ebay.com/itm/KICK-START-...Parts_Accessories&vxp=mtr&hash=item588acedd72 , and try using a newer YZ250 kicker. I've been thinking of getting one for myself.
It has the same size input as the later 490 motors, and it comes out at more of an angle to clear your frame. Plus it's aluminum.
http://cgi.ebay.com/ws/eBayISAPI.dl...akeTrack=true&ssPageName=VIP:watchlink:top:en

But if you ever get another frame, and decide to swap that smoker into it. I'll gladly help you in any way I can. :iagree:
:atv:

 

[357warrior]

i still wanna c pix of ur swinger i figure i can still use this frame as mockup to do all the motor mounts because its just the front end that is twisted. wats more powerful it or yz

 

[Mathius]

So here's a few pics of the swinger I did..
I would just use mine as a base line where to start.
I could give you some measurements but I think because my frame is a first gen, you would be better off taking you own measurements to make sure your sprockets line up..

I just used a strait edge to line up the sprockets, and mocked up the motor just sitting on the swinger bolt, and a 2x4 under the motor (It made it easier to slide back and forth) A little grease on the swinger bolt helped to.. lol
Then just held the swingarm up the the back of the motor, marked it, and started cutting.. lol

The swinger, and my mounts before I stripped it, and sprayed it with primer.

Here's an older picture of where my kicker sits. I don't have the kicker right now, so I will update it on the next round of pictures

 

[Rhyno]

IT haha looks great, I'm excited to see IT haha run......

-Rhyno

 

[Mathius]

So I got my head pipe made.. It's not as long as I wanted it to be, and it doesn't look very pretty. But it should do the trick.

But as an unexpected catch, now my kicker doesn't frick'n fit..
I might have to go back to the drawing board with that?

 

[Mathius]

But as an unexpected catch, now my kicker doesn't frick'n fit..
I might have to go back to the drawing board with that?

So heres a quick update.

I found a kicker, and kicker shaft off a 465 that I had lay'n around..
I'm going to cut about 2 inches off of it (About an inch before the splines start), and extend my kick start outward. I'll just machine a hole into the shaft, and tap some threads into it so it screws onto the existing shaft.
The 465 kicker is a little bit shorter, and sits more vertical. But extended outward it clears the pipe better because of a recessed bend. (It'll also sit closer to the frame in the neutral position)

Then I'm going to make a mount off the swingarm bolt to hold a bushing, it'll help keep the kicker shaft from breaking with the extra length.
It should work??

:tup:

 

[bones]

MAN i love this thing .... lol... it needs yz490 graphics white plastics and a red seat cover

 

[Gen1Pat]

Doin a great job on the build, man.

 

[gawarrior]

So heres a quick update.

I found a kicker, and kicker shaft off a 465 that I had lay'n around..
I'm going to cut about 2 inches off of it (About an inch before the splines start), and extend my kick start outward. I'll just machine a hole into the shaft, and tap some threads into it so it screws onto the existing shaft.
The 465 kicker is a little bit shorter, and sits more vertical. But extended outward it clears the pipe better because of a recessed bend. (It'll also sit closer to the frame in the neutral position)

Then I'm going to make a mount off the swingarm bolt to hold a bushing, it'll help keep the kicker shaft from breaking with the extra length.
It should work??

:tup:

Yeah, that was kinda my thought when I originally asked you about the kicker. If you extended the shaft and made a mount on the frame to steady the shaft. Can't see why structurally that wouldn't work... If you're anything like me, I tend to over engineer the hell out of anything I build, anyway...

 

[Mathius]

Yeah, that was kinda my thought when I originally asked you about the kicker. If you extended the shaft and made a mount on the frame to steady the shaft. Can't see why structurally that wouldn't work... If you're anything like me, I tend to over engineer the hell out of anything I build, anyway...

Yah thats where I got the idea for that. (Thanx man)

I kinda wasn't thinking though, about threading it on.. It would back off when you kicked it.. lol
I'll have to weld it.
But that shaft is made from some kind of chromium shiznit, that is tuff as snake crap!! Rolled in sand, and dried in the sun.

I'm also kinda worried about the extra stress on the clutch case, and kicker gears.. Even with some kind of mount, and steady bushing?

But if I extend it, it'll work way better than the bent kicker.
That 465 kicker, sitting out about 1,1/2" inches... Clears the frame, and the rear brake cylinder way better than the 490 kicker did.
The 465 kicker also clears the pipe way nicer in the neutral position.

 

[gawarrior]

The right way to do it would be to find a hollow shaft of the right diameter, cut it to length, and have the inside machined to fit the splines of the original shaft, then have the other side machined on the outside so the kicker would fit over. I would use a tube about 1-1/2 to 2 inches long for the sleeve, if you want to get fancy, throw some needle bearings and a grease fitting on it. It'll look funny, cuz the only way to brace it is to come from both the bottom of the frame and back nearest the starter. As long as the alignment is good and it's well braced, it'll last forever.

 

[YAMAHAULER]

I can't wait to see and hear some video of that sucker looks like it'll be a freekin screamer man nice work

 

[bones]

Me to man love this threAd just wish it was updated more