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monster2stroke 11-26-2011 11:16 PM

it465 big bore 2stroke
Hi,I'm new to this site,would appreciate if you guys can help me I sold my kdx200,bought a old it465 2stroke(said2be very powerful and grunty).took4ever2start,but once it came 2life it sounded good.didn't ride it,heard it could be crank seals,replaced them,BUT,the seals that came out was a double seal,and I only fitted single seals,what is the difference,and would this seals be as good as the double seals.what can I do 2make this big bore2stroke start easier,as u have 2jump on kickstarter coz compression is hectic.they say 3rd and 4th gear whEelys r common 4 a it465,I can't wait.would appreciate it if you guys can give me info/tips/comments on this ancient 2stroke.can't wait2hear from you guys.tnx

photomd 11-27-2011 04:56 AM

The one I used to ride was a hoot. However, starting it was a chore when cold. We always used starter fluid when it was cold. Once warm, it would fire right up. Make sure your plug is good and the correct one. Also make sure your air filter is clean. If you're worried about the crank seals, I would test them with propane or WD-40. Cool bike.

concours 11-27-2011 03:26 PM

My IT490 was a bastard to start.

anotherguy 11-27-2011 03:29 PM

After re-jetting my YZ465 is 1-3 kick starter cold and 1 kick hot. Yamaha jets 'em really fat for some reason. It took replacing everything but the slide to get it there.

What are your jets now? What fuel/oil ratio are you running?

Helmet_Hair 11-27-2011 03:53 PM

The big IT's were known to be hard to start. Lots of compression, and a big old piston. Kick it like a big-bore 4T; hard from TDC all the way through. No little dabs at the lever.

exoff-roadgoat 12-01-2011 06:06 PM


Originally Posted by Helmet_Hair (Post 17393758)
The big IT's were known to be hard to start. Lots of compression, and a big old piston. Kick it like a big-bore 4T; hard from TDC all the way through. No little dabs at the lever.

My friends IT 400s were puppy dogs to start....Just a little off topic...there is a nice looking IT 250 on the Grand Rapids Craigslist that has just come up for sale cheap. If I wasn't so far from home I would snap it up myself.... I'm on my friends netbook and for some reason I can't figure out how to put up a link so your going to have to Google it yourself. Sorry for all the extra work.:cry

bmoto54 12-02-2011 09:42 AM

You have to kick like you mean it - my 84 IT 490 takes 3-4 kicks cold and typically 1 warmed up. Sometimes she can be stubborn but I just lean it over till gas pours from the overflow and then will usually fire first kick. Tons of fun but make sure you don't have any loose nuts, bolts, or fillings cause they'll vibrate out in no time!

FJ_Kevin 12-02-2011 03:04 PM

Oh yeah... the mighty big bore 2-stroke yamahas.

I completed my '83 IT490 in the early fall. My bike was also initially hard to start. I had a couple of problems, first problem was a clogged pilot jet. The other problem was a leaking base gasket.

These bikes are noisy and I was unable to hear the base gasket leak while the bike was running. I noticed it when I was running my fingers around the base gasket area. With the bike running, I could feel leaking around the transfer port area on the left side. This is a fairly common problem. Consider using a factory Yamaha base gasket as it has a sealent round it that the aftermarket gaskets do not have. I checked the base of my cylinder for flatness and it was fine.

Once I fixed these problems I then spent some time jetting it. They come rich from the factory so blubber in the low to mid range area. The fix for me was to change the slide, the jet needle and the needle jet. Do not try and solve this by going too low on the main jet or you will ping. The main jet is ineffective in tuning the low end and mid range.

The stock slide is a 2.0. I replaced this with a yz slide which is a 3.0. The trick is then to file the slide to a 3.5 (no longer available). The slide modification can be found on the yahoo yz490 group. The needle I used is fatter towards the point, this makes it leaner on the bottom 1/3rd throttle. I tried pilot jets of 35, 37.5 and 40. It starts well with the 37.5 and 40. I have the 40 in it now. I think the yz465 came with pj=50.

I will post the jetting that worked for me tonight as I do not have that information now.

These are nice bikes once fully sorted. You get the jetting right and this bike will haul the mail.

I raced it in a hare scrambles (after 30 years away). I was kind of worried as it was a dead engine start. It fired 1st kick. Went from 5th or 6th at the start to 2nd within the 1st lap. And I started with a flat front tire!

There was a nice section coming out of the woods where you could really wack the throttle. Whoa momma!

But unfortunately I am an old man now and my conditioning is just not up to snuff (yet?). I wore myself out and was unable to finish! Figured I better stop before I hurt myself, didnt want to give my wife a reason to shut me down!

So yeah, keep working on it, these bikes can really kick some a$$:evil. Or at least it kicked my a$$!:eek1

Here is a link to some photos of mine as I worked to get it in shape. Have fun but dont hurt yourself!


FJ_Kevin 12-03-2011 11:57 AM

Alright, here is current jetting for my '83 IT490 runnning a yz piston and a DG IT490 pipe.

Main jet= 380 (it pinged with a 370)
Pilot jet = 40
Jet needle = 6DH4 with clip in center position ( the standard needle an 6F8 needle did not work as well)
Needle jet = RO, 247 series (you must specify the series when ordering)
40:1 premix

The best place I found for ordering mikuni jets is from Pats small engine parts. They have good stock, ship fast and prices are low.

The standard carb slide is a 2.0. The YZ465 slide is a 3.0. You should at least try the 3.0 slide, I think this is important. A common modification is to open up the 3.0 slide to a 3.5. You can do this with a file if careful. Search the yz490 group of yahoo for details on how to do this.

I did the needle jet, jet needle and slide modification pretty much together. My bike ran much better with these jetting changes. It now pulls cleanly off the bottom end and hammers right to the top. It is also easy to start so long as you kick hard from the top of the stroke.

While I am here, I will offer an opinion of gearing. I found the stock 44 tooth rear sprocket too small for tight woods. I went to a 48 tooth and found this to be more suitable. I was still able to use the same chain with this change but not with a 50 tooth.

The 48 let me get through very tight areas without needing to clutch it to avoid a stall. These things do not have the lightest pull clutch in the world, so this helps save energy over a longer event. In fact, replace all the cables if they are not fresh. Also check and lube the brake actuators in the brake plate. You really want all the controls to work as smooth and as lightly as possible.

Good luck!

D.T. 01-21-2012 02:52 PM

Did these bikes come in white? I have seen one, but I was wondering if white is an aftermarket color.

Nice bikes. I like to look at them, owning one is another matter. I do have a 85' XT600 though. I had a 1978 DT 125 growing up. I remember that thing had a huge flat spot in the midrange.

I heard the IT 200 is a pretty sweet bike too.

Cordless 01-21-2012 03:13 PM

The '81 model came in white. I have two of them I am combining into one running IT465. I prefer the blue color but the white is a nice clean bike when the plastic is spiffed up.

I have a new piston in a rebuilt top end and lots of new cables and other parts. Just need to clean up the frame, paint it, and put it all back together.

My good friend Agitator took the tranny apart several years ago, promising to put it back together when I had installed all new bearings and seals. I rudely moved from New England to New Mexico and he doesn't want to fly in for a weekend to put it all back together. I have not reassembled a tranny like this before so when I get to that point I will seek the chiding and snickering and good advice of all here to help me.

Thank you for keeping this exact 2 stroke thread alive. The IT is the only 2 stroke I have ever owned so you guys have the wisdom I lack.

anotherguy 01-21-2012 05:29 PM

Lemme dig up my YZ manual. Maybe I can scan it for ya. It's no less or more difficult than any other transmission. I'll get back tomorrow.

Cordless 01-22-2012 08:53 AM


Originally Posted by anotherguy (Post 17801542)
Lemme dig up my YZ manual. Maybe I can scan it for ya. It's no less or more difficult than any other transmission. I'll get back tomorrow.

Thank you. I will appreciate it greatly.

anotherguy 01-22-2012 07:54 PM

I didn't forget you my scanner is a POS. Lemme work on it some more tomorrow.

anotherguy 01-25-2012 08:58 AM

Well it's still a POS. I could copy the needed pages and send 'em off to ya via snail mail. lemme know...............

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