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Old 11-01-2008, 09:22 AM   #61
dawid OP
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The wiring diagrams in the IT 490/250 workshop manual from Yamaha are swapped and the coil in my bike is not the correct one.

There should be 2 windings the one is for lighting and the other is for charging.
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Old 11-01-2008, 09:42 AM   #62
Foot dragger
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I trailride regularly with one guy who has a YZ465 engine stuffed in a 03 YZ250F frame and another who has a 490IT engine scrapped into a 125 Yamaha frame.They appear to enjoy the pinging and jetting rituals that go along with this sort of tom foolery.I just ride along on my 04 KTM250,some times I will put a new plug in it out of boredom but it generally needs nothing done. These old leaking smoking rattling Yamahas are a laugh a minute but usually make it back to the truck.
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Old 11-03-2008, 11:26 PM   #63
JR Greenhorn
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Quote:
Originally Posted by Foot dragger
They appear to enjoy the pinging and jetting rituals that go along with this sort of tom foolery.....
With all due respect and no offense meant, the difference, as observed by myself when my primary mount was a '79 YZ125 and my YZ490-mounted friend, is those of you that have a bike to ride it, versus those of us that enjoy having a relationship with our bikes.

Different strokes for different folks and all that.

For various reasons, I bought a "gas-and-go" dirt bike this year (well, gas-and-go by my skewed standards), and while I'm enjoying it immensely, I also have this empty spot that misses fiddling with my air-cooled YZ every time I rode it, the ringing of the fins, the unique handling and feel of the classic Monocross chassis, having a better "sense" of what the engine's doing based on how it responds to temperature and such, and so on.

I just feel like I can instantly recognize the same qualities in your friends, Foot dragger, because those of us so-afflicted know who we are and know one of our own. Odd ducks, to be sure.


Quote:
Originally Posted by Helmet_Hair
The IT's were much easier to live with than the YZ's. Yes they had heavier flywheels for more inertia and chug in the woods. Better spaced gearing for woods riding, and tuned for more low-end. That being said, they are NOT wimpy by any stretch of the imagination. The big bore IT's are absolute animals, they'll climb a tree if there's enough traction. They don't turn real well (long wheel base, heavy) but very ridable bikes...love 'em!
My problem is I've got a fair amount of seat time on a few different DTs (a '75 250, '78 400, and '74 125), a great deal of seat time on a couple different YZs ('79 125 and '83 490), and a significant interest in the ITs, but no seat time. I just don't have a reading on where the ITs slot in, as far as state of engine tune. No doubt the DTs, especially the 400s, are absolute tractors, but are the IT engines closer to the DT or YZ end of the spectrum? Do the IT490s still rip WFO, or are they a bit short of breath up there, like a DT? How badly would a same year, similar displacement YZ spank an IT in a drag race?

I'd bet that the steering geometry between same year YZs and ITs is the same, and I know plenty well what you mean my slow-turning. I like the stability the lazy geometry provides, and enjoy deliberately muscling the bikes around to make them turn (feeling fast while going slow!). There's nothing like railing the berms on a smooth, fast trail with the good old [non-linkage] Monocross rear suspension. Man, I wish I could swing getting into another old Yamaha, but I just can't justify it right now!



The YZ465s kind of stand out in some ways as the zenith of the YZ400-to-490 progression. Do the same '80-81 IT425/465 similarly stand out among ITs? Or, in other words, those of you who have had the opportunity to sample several ITs, which are your favourites?
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Old 11-04-2008, 08:46 AM   #64
Helmet_Hair
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The IT 465 is, IMHO the best IT ever. It'll grunt down low without a problem, and there's plenty on top to zip you 90+ mph in a straight line and feel stable doing it. As far as the differences between a DT and an IT, I really don't know, but I'm positive there's more oomph on top with the IT than the DT. I don't believe there was ever a DT made that big (465 or 490) to compare it to anyway.
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Old 01-04-2009, 11:19 PM   #65
Dirtsampler
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IT465 questions

I'm finishing a refurb ( mechanically sound, but not really beautiful ) on
a 1982 that I plan to race in Evo class and general play ride. I'd appreciate
any tips on kick start mechanism health and assembly. The motor has new
piston / rings and healthy lower end and seals. The hope is that with a
good tune and proper start drill I can avoid broken cases and start gears.

Several of the tracks here are short and often muddy. This being a rather
large critter, any hints on fork position in the clamps for different conditions
would also help.

Thanks
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Old 01-05-2009, 06:49 PM   #66
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If the big ITs are anything like the 250 I had with the gearing you need they will rev and romp til ya overrevem. Beware.
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Old 01-05-2009, 11:47 PM   #67
JR Greenhorn
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Quote:
Originally Posted by Dirtsampler
I'm finishing a refurb ( mechanically sound, but not really beautiful ) on
a 1982 that I plan to race in Evo class and general play ride. I'd appreciate
any tips on kick start mechanism health and assembly. The motor has new
piston / rings and healthy lower end and seals. The hope is that with a
good tune and proper start drill I can avoid broken cases and start gears.
Yamaha did an update to an internal part of the kickstarter in starting in '84 or '85 on the YZ490. The tab that hits the stops to define the lever's stroke was manufactured differently, stronger. I don't remember all the details, but I remember holding both the new and the old parts in my hand once, when my buddy bought the new part for his '83 YZ490. I would expect that same part would drop into your '82 IT as well. Spend some time on Yamama's online parts catalog, looking at the kickstarter parts for the YZ490s from '83 to '85, and you'll spot the P/N change.


My buddy ran an iridium BR9EIX spark plug in his YZ490 for a couple of years (that one plug lasted for quite a while!). He's running cheaper plugs now (replaced more often), and he denies any difference, but I swear his bike was easier to start with the fine wire iridium plug.


The biggest starting problem the 490s (all the 465-490 engines, actually) have is twofold. First, a stroke of the kickstart lever doesn't get you much stroke of the piston. It takes the right kind of kick to get enough momentum built up to carry that crankshaft enough to get it to fire. Second, the lever is ridiculously long and positioned way too high, making it tough to give it the right kind of kick. By comparison, the '94 KTM 440 I ride is a peice of cake to start. The lever pivot is lower, and the lever stroke moves the piston more.

For cold starts, my buddy usually leans his 490 up against a tree or something (with the bar end), stands up on the pegs, hops up, and drops his 175-ish pounds on the lever. He doesn't use much muscle at all to actually "kick", like you would on a little bike. I think the trick really is to catch yourself with the other foot just before you hit the stop, to avoid breaking stuff. Also, beginninging with two halfhearted kicks seems to help "prime" the cases, saving your energy for a good third kick that will (hopefully) start it right up.
Luckily, I would expect the IT state of tune would lend itself to easier starting than the YZs.
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Old 01-06-2009, 12:32 AM   #68
JR Greenhorn
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Quote:
Originally Posted by Dirtsampler
Several of the tracks here are short and often muddy. This being a rather
large critter, any hints on fork position in the clamps for different conditions
would also help.
I don't expect you'll have as much trouble as you think. The '83 YZ chassis hugely favored stability, and I'd expect the IT chassis to be at least equal in that regard. When I first started riding my buddy's 490, I hadn't a lot of dirt-bike experience, but at some point I realized that on the 490 I almost never had the urge to put my foot down. You know, the classic rookie move to "catch" the bike if it slips out on a turn. Eventually, I realized it was likely that stable geometry giving me a sense of security and plantedness. Obvioulsy that comes at the expense of quick steering, but that's what it is.


These big engines are very versatile and have a lot of inertia. You won't struggle with stalling in the mud as much as you might on a smaller bike. Especially with the IT state of tune. It should be an absolute tractor.

I was surprised at how the YZ490 didn't feel that held back by its 4-speed transmission. My KTM has a 5-speed, but 1st feels pretty pointless a lot of the time and I rarely get a chance to wind out 5th. My bike would probably be fine with a 4-speed too, except when 1st gear is needed in the tough stuff to prop up the lacking low-end power the "little" 440 makes.

Compared to the YZ transmission, the IT adds a lower 1st gear, then 2nd-4th are about the same as 1st-3rd on the YZ, and finally the IT has a slightly taller top gear than the YZ. Bottom line, the bike has a wide spread of gears, and should be able to pull that tall gearing without issue.



If you're new to open classers, experiment with setting your idle speed lower than you might be used to, and learn to use the clutch to uncouple that engine inertia to keep it from driving you ahead even when you're off the power. Pulling in the clutch on a big bike will also help you make tighter turns.
On a little bike, you use the clutch to prevent keep the engine from being overpowered by the bike (bogging or stalling). On a big bike, you use the clutch to keep the engine inertia from overpowering the chassis.



For tires for the mud, pair a Michelin S12 front with an IRC M5B rear. The M5B comes in wide sizes for open class bikes. The M5B is really amazing in the mud, but rocks and hard terrain will chew it up fast. This is the combo I'm running on my KTM, and I love it. However, my next rear will be a Michelin S12. It also comes in wide sizes (although I've heard their wide sizes run a bit narrower), and I've heard they hold up a bit better on varied terrain, considering the S12 is a soft terrain tire. Basically, I've been told the S12 is a "general use" soft terrain tire, while the M5B is a mud/sand specialist.



If you're not used to drum brakes, you'll want to run grooved shoes, especially in the mud. Vesrah makes them:



You can also just cut similar grooves in the shoes you have with die grinder cutoff wheel or similar. Wet braking will be dramatically improved with grooved brake shoes.


Does your IT have the dual-leading-shoe front brake? The YZs got them in '81 (but I don't know with the ITs). If yours is a single-leading-shoe, the DLS setup will really help you get the most that drum brakes have to offer, while staying period-correct.




In case you're interested, here are the power differences between the '83 IT and YZ 490s, from period magazine tests:
(sorry, I don't have the '82 numbers)

..............IT........YZ..
RPM......RWHP....RWHP
3000.....15.24...........
3500.....18.09.....11.5
4000.....20.21.....16.0
4500.....24.31.....17.7
5000.....26.70.....18.9
5500.....32.09.....22.8
6000.....34.65.....27.3
6500.....34.65.....31.6
7000.....33.80.....36.8
7500..................40.7
8000..................43.9
8500..................44.7
9000..................41.5
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Old 01-06-2009, 08:40 AM   #69
Dirtsampler
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Wow! Thanks for all the info. My last bike was a 76 360 Husky, and that
was 30 years ago. I do have the DLS front brake, in fact I have the YZ
43mm forks too. I used to groove my brakes back in the day, riding in
Oregon requires some wet weather accommodation.

My Husky was the picture of plush with 6" of travel, so working with 10+
will be interesting. It seems that I remember reading that moving the fork
legs up or down in the clamps would give quicker or slower response. I'll do
some experimenting and see. At my age ( 61 ) we're not talking about big
speed numbers, just a little extra quick in the corners will be fine.
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Old 01-11-2009, 07:47 PM   #70
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I have just about completed renewing all the bearings, brakes, and cables on one of my IT465s (the white '81 model). Next is two sets of new tires mounted on wheels with new brake shoes, one for the trails, and one with ice screws for some ice riding this winter.

I am 51 and very tall so I am curious about how this bike will compare to my more modern bikes. I am fully prepared to be impressed, based on all I have read and heard.

Thanks for all the info y'all are sharing in this thread.
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Old 01-12-2009, 10:43 AM   #71
nachtflug
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Quote:
Originally Posted by Foot dragger

These old leaking smoking rattling Yamahas are a laugh a minute but usually make it back to the truck.
just remember at one time they were new and tight and you can guarantee they ripped just as well as your KTM and some day your KTM will be leaking and smoking too.
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Old 01-12-2009, 02:17 PM   #72
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New...



Raceday....



TC
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Old 01-12-2009, 11:08 PM   #73
Dirtsampler
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Race report?
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Old 06-03-2009, 08:48 AM   #74
sonic reducer
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who rides their IT465 on the street much? is it hard to find rebuild parts for them and are they super finicky with the jetting like the 490's? I'd like to do a 2t single cafe bike, and the IT465 was on my short list of big bore aircooled 2t with a wide range trans and lighting coil.
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Old 06-03-2009, 10:06 PM   #75
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My 82 IT 465, it has a TT 500 front end , can't remember the year, I think 85. She sure does haul the mail!!!

Harry
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