Fixing the 1980 yz465

Discussion in '2 smokers' started by mudmantra, Jun 19, 2012.

  1. mudmantra

    mudmantra Been here awhile

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    I just picked up a YZ465 and intend to set it up for trail riding. Yes I know the IT465/490, it better for trail use. But I like the way the YZ465 looks and it's what I have. Step 1 is to just get the YZ465 running. I kicked it over a few times and the compression ratio, seems to be real high. I wonder if the IT465 compression ratio is lower? I found the compression ratio for the IT465 at 7.1:1. But I don't know the YZ465 compression ratio. Any idea's on how to set this machine up better for woods riding?
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  2. wfopete

    wfopete Suffer Fools; Gladly!

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    Why don't you get it running first and then see if you want to live with a 30+ year old big bore MX bike. If the bike isn't "mint" you can figure on dropping some big $ to get it to the point ridable as a trail bike. My 465G model runs well in the woods but it's a bit of work to enjoy the ride.
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  3. mudmantra

    mudmantra Been here awhile

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    Thanks. I figured out how to start it and got it running. The compression is pretty high, and kicking it over is a bit tricky. At first the carburetor was flooding, but it's not now. I still need to fix a lot more. I took a ride up in the woods. It was a blast, I can't wait to fix a few things and ride it again. I'm still looking for idea's to make it even more trail ready. :bmwrider
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  4. mudmantra

    mudmantra Been here awhile

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    A few idea's I've been thinking about. #1 is the crankshaft heavier in the IT465 motor? The crankshaft in the IT490 looks a lot heavier, but I can't tell with the IT465. #2 has anyone here installed a crankshaft from an IT465/490, and did it work? If I could just slow the power band hit a little, I think it would help a lot. Right now when it hits, it's instant wheel spinning, fun, but not very useful. :D Any other idea's on how to smooth out the power band would be good too.
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  5. baloneyskin daddy

    baloneyskin daddy bikaholic

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    Re cc the head or add a couple gaskets to lower the comp , a flywheel weight, go up a tooth on fr sprocket and or go down a bunch on the back is going to be the cheapest route to tame the horsepower. If theres a porting speciallist in your area you could have them take a shot at getting a smoother powercurve out of it but it ain't cheap. In any case the bike is to old to start throwing money at so just ride it and if you want a real woodsbike save up and get the real thing. There are people looking for vintage bikes to race in special classes and you may be able to make some money on it if its in any kind of original condition yet.
    #5
  6. mudmantra

    mudmantra Been here awhile

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    Thanks for the advice.:thumb I really like the bike, so I'll ride it even if it just stays the way it is. If I can improve the low end power and smooth out the hit a mid-range, that would be even better. I've checked a few tips on improving the head design, that appears to also slightly lower the compression ratio. Plus this mod should make jetting the bike easier. I'll check into the flywheel weights also.
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  7. mudmantra

    mudmantra Been here awhile

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    I checked into flywheels and the magneto flywheel on the IT465 has the exact same part number. And by that I guess it has the exact same weight. The crankshaft is another story. The IT465 crankshaft looks a lot heavier, and the IT490 crankshaft looks even heavier yet. The YZ465 crankshaft looks to be the same size, But it has more and larger hole machined out of it, to reduce weight. The motor runs now, so I'm not going to pull it apart just to change the crankshaft. Might be something to try on my spare YZ490 motor though. :D
    #7
  8. Kevin K

    Kevin K Adventurer

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    Have Eric Gorr port the cylinder for your style of riding. He can also fix the head to keep the motor from detonating.
    His prices are very reasonable.His porting will cost less than a IT crank.
    You may want to try the ignition coil from Black Ops Moto .It really cranks out a big blue arc to help the motor pull right off the bottom. With it and one or 2 more teeth on the counter shaft I can't see you needing more than that
    #8
  9. mudmantra

    mudmantra Been here awhile

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    Thanks I'll check into the porting work and cylinder head mods by Eric Gorr. I know the YZ490 really responds well to the cylinder head mod. Dose it also help the YZ465? I'm forced to run pump gas, so I'm thinking about the Cylinder head mod also. Just unclear if it's the thing to do on the YZ465. Gearing, I was thinking on gearing it down a little to reduce 1st gear speed a bit. I know gearing it up would reduce the tire spin, but I'd like to reduce my contact speed with the trees. :D
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  10. mudmantra

    mudmantra Been here awhile

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    I took the bike up in the woods for some more riding. It now seems to me, that a real improvement would be to get the low speed jetting and mid range jetting spot on. It seems that the stock jetting might be on the rich side. Sounds like it may be a good idea to look at the reeds too. I could get a set of Boyesen reeds for a low enough cost. I wonder if they would be an improvement. VFORCE reeds would be more, but still not to expensive. Yes, it's not a woods bike, but I had a lot of fun anyway. :D
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  11. anotherguy

    anotherguy unsympathetic

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    Getting the jetting spot on was the best thing I did for my '80 465. It now pulls clean from idle to where it signs off.
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  12. mudmantra

    mudmantra Been here awhile

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    Cool. :thumb Any details on the jetting that worked for you? I've been collecting info on jetting the YZ465. So far most install a slightly smaller pilot jet, main jet and modify the slide cutaway to 3.5. Each one, I've checked use's a different needle jet, at different clip positions. I also I think slightly different carburetors are in use. One is the Stock 38mm round slide and the other is a replacement Mikuni 38mm round slide. I don't know how different they are?
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  13. anotherguy

    anotherguy unsympathetic

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    45 pilot/40 if really hot out,1 to 2 turns on mixture screw(yeah it's that finicky,or is it me?),stock slide,Q-0 needle jet,6F8 needle,400 main. I run a DG National pipe and a Uni filter in the stock airbox. I ride from 500 to 2000 feet above sea level.

    That's for premium E10 pump gas,I fatten the needle up a click or two and raise the main for VP U 4.4 race fuel. It isn't cheap but the bike runs so much better and consistent with it the money is of little concern.
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  14. mudmantra

    mudmantra Been here awhile

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    Thanks. :thumb That gives me another look at the jetting for these machines. I ordered a float valve and gasket for the carburetor. I'll clean it and check all the jets. Who know's whats in it now. The first time I ran the motor, the carburetor was over flowing. I shut the gas off and started the motor. I then rode it almost 1/4 mile before it ran out of gas in the carburetor. I turned the gas on, and it hasn't overflowed since. I'm thinking it might be a good idea to pull it apart and take a look soon. :D
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  15. mudmantra

    mudmantra Been here awhile

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    Also, I forgot to ask. Are you using the stock YZ465 carburetor? I'm thinking it might be a good idea for me to replace the needle jet and needle on my 1980 YZ465 carburetor.
    #15
  16. FJ_Kevin

    FJ_Kevin Been here awhile

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    Hi,

    To me it sounds like your bike could use some rejetting. I think they generally came jetted too rich on the bottom. So the hit you get is rather sudden as you move into an rpm range where your jetting is better.

    I recently completed my 465 and purposely jetted rich to start off with. It ran poor and no grunt off the bottom. Fortunately, there are some well established recipes that often work well so long as the rest of your bike is in good shape (so make sure no air leaks!).


    Here is a setup that worked extremely well on my YZ465 and my IT490. These are for the stock 38mm carb.

    MJ=380 (a 370 made my IT490 ping when hot)
    PJ=40 (IT490), 45 (YZ465)
    Slide cut away is modified from 3.0 to 3.5 setting
    Needle Jet RO (247 series) for IT490 and Q8 for YZ465 (I think the RO would work fine in the 465 also)
    Needle 6DH4 (both IT and YZ)
    A 6DH3 is similar to 6DH4 and would also be OK I think. I tried a 6F8 needle and it did not run as clean.

    Both my bikes have DG pipes but are otherwise stock.

    The slide modification and replacing the needle made a big different in low end through mid-range. I cannot say this enough!

    In both cases, I modified my existing slide by hand using a file. I first marked out the arc I wanted to follow using a felt tip pen. The dimensions are from this drawing...
    [​IMG]

    You know you have filed enough of the arc away when you can pass a 7/32" drill through the cut away when the slide is held against a flat surface (bottom down).

    Others have fly cut their slides in a milling machine.

    [​IMG]

    The slide modification photos came from the yahoo yz490 group (a good bunch).

    A gearing change may also hep. My IT490 came with a 44 tooth sprocket. I dropped this to a 50 tooth for tighter trails. You may have a 48 tooth sprocket on your 465 as I think that is the stock gearing.

    With the carb modifications you should have no trouble woods riding your 465:freaky.

    BTW, these guys have great prices on Mikuni jets!

    http://www.psep.biz/store/mikuni_carburetor_part.htm

    Good Luck,
    Kevin
    #16
  17. mudmantra

    mudmantra Been here awhile

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    Awesome! Thanks for the details Kevin. :thumb I have some parts on order and well start working on it as soon as they come in. I just got the new chain and new sprockets. Stock this bike was 14/46. I'm going to try 14/48 and see how that works out. If I get the jetting sorted out, I think it well be good. Lots of things to do to get this bike the way I want it, but so far it's been a blast. :D
    #17
  18. mudmantra

    mudmantra Been here awhile

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    As far as gearing. Well the IT465 or IT490 gears work in the YZ's. From what I understand the IT gear set has a lower first and a higher 5th. I don't really need the higher 5th, but a lower 1st might be good thing. I also have a 1982 YZ490 motor in pretty bad shape. I wonder if an IT465/490 5 speed would work in it?
    #18
  19. mudmantra

    mudmantra Been here awhile

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    Are the 247 series needle jets used on both the IT490 and the YZ465 stock carburetors? My list has the 247-Q-8 and 247-R-0, next to each other, so I'm guessing they are pretty close to the same size. Maybe the 247-Q-8 is slightly smaller/leaner? Maybe I'll get a jetting chart, so I can understand a little more of what I'm doing. :huh:D
    #19
  20. brucifer

    brucifer Long timer

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    Cool thread. I have an '84 CR500 that I'll be setting up for the woods when I get a couple other projects out of the way.
    Do you have any pics of your bike you could post up? I always thought the YZ/IT 465 and 490s were good looking bikes.
    #20