Fixing the 1980 yz465

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

  1. anotherguy

    anotherguy Long timer

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    My YZ still has the stock cutaway. I went with a leaner needle jet and needle. It pulls cleanly from idle to shaking like a mofo with a big boost @ 5K or so. Have any of you done the head right,i.e. squish clearance?
    #61
  2. mudmantra

    mudmantra Been here awhile

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    Sounds good. That's why I left one slide stock. I have a good selection of jets and needles for the YZ. At what clip do you have the needle set at? The motor in the YZ465 has been bored to 482 cc's, the head and ports have been modified by Eric Gorr to run on pump gas. Ports were set up for trail riding, But the motor still thinks it's a dragster. :evil
    #62
  3. anotherguy

    anotherguy Long timer

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    Mikuni 6F8 needle in #3,sometimes #4 when running a heavy load of oxygenated fuel on a cool day. Cannot remember my needle jet and the log at work,but it's one step leaner than what was in it stock. No air jet.
    #63
  4. slideways

    slideways España

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    Eric Gorr is the man when it comes to two strokes.

    He also wrote a great book about running and maintaining offroad bikes.

    [​IMG][/IMG]
    #64
  5. mudmantra

    mudmantra Been here awhile

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    :thumbYes Thanks. I checked your post on page 1. Q-0 needle jet and that seems right, stock needle jet is a Q-2, according to my notes. I need to keep better notes. I have to pull the carburetor again to check what I have in it. I'm going to be a pro at removing the carburetor. Good thing I have a new intake. :1drink
    #65
  6. anotherguy

    anotherguy Long timer

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    Keep it new with silicone spray every washing.
    #66
  7. mudmantra

    mudmantra Been here awhile

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    Thanks, that looks like some good reading. I wonder how they deal with a motor that has had some port change's already? With an old motor, who knows what's been done with it.
    #67
  8. slideways

    slideways España

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    I had an 2001 CR 250 that I sent the cylinder and head to Eric Gore for porting. He used epoxy to fill in and reshape the intake tract. It made a huge improvement it the performance of the bike. The bike ran so well that I was accused of running a cheater motor.
    #68
  9. mudmantra

    mudmantra Been here awhile

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    :thumb Yeah, I believe it. I'm real impressed on how well the YZ465 motor runs. After I start and test out the YZ490, I'll at the very least have the cylinder head mod done by Eric Gore. I have a 2nd 1981 YZ465 cylinder, and I plan on sending that to him too. :beer
    #69
  10. brucifer

    brucifer Long timer

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    How tall is 1st gear in your 465? I took my '84 CR500 down in the woods behind my house for the first time Saturday and man, it's definitely no good for tight single track (which I have a lot of). 1st feels like it's good for 40 mph. :lol3 I didn't kill it but it's too much work.
    That, coupled with the crappy design of the kick starter makes it a no-go for a woods bike for me.
    #70
  11. mudmantra

    mudmantra Been here awhile

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    With the 14/46 sprockets, on the YZ465, 1st gear is very usable in the tight stuff. I would compare it to stock sprockets(15/44) 1st gear an XT500. Riding a MX bike in the woods is more work for sure. You really have to be thinking ahead of the machine, or it well launch you at trees and bush very fast. :eek1 I can't wait to get the YZ back up into the woods. :D
    #71
  12. anotherguy

    anotherguy Long timer

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    I run 14/48 and have never found a hill it won't climb. I ran 14/50 for a little while. 1st was useless. But 5th was capable of some amazing stuff on some gnarly uphills with major obstacles.
    #72
  13. mudmantra

    mudmantra Been here awhile

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    I forgot that I put a 48 rear sprocket on the YZ465. I know I added 2 over stock with my new sprocket. I just found the old sprocket, it's a 46. When I changed to 14/48, I thought I was gearing it down a little. But I forgot to check the front sprocket, it was a 13. So 13/46= 3.538, at little lower than the 14/48 = 3.429 ratio I have now. Still plenty low for tight trail riding. Yeah 14/50 would be low. I might try that with the YZ490. With the 490 4 speed, 1st gear is the same ratio as 2nd gear on the YZ465.
    #73
  14. wfopete

    wfopete Suffer Fools; Gladly!

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    I bought a 3.5 slide for my 465, spent some thoughtful moments jetting/timing the motor and changed the final gearing. Rode it in several AHRMA Cross Country events last year. The 465 was a blast and I often found that riding the bike in 3rd gear was the most usable in the woods. Third gear was soft & smooth enough at low RPM in the woods but gave you all the boost you wanted when things "opened up". I credit the jetting for the majority of my smiles.
    #74
  15. mudmantra

    mudmantra Been here awhile

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    Sounds Good. I think getting the jetting right is the most important step also. What did you finally end up with for jetting and final gearing?
    #75
  16. wfopete

    wfopete Suffer Fools; Gladly!

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    Hmmm. Good question. I need to take apart the carb and drian the fuel anyway.
    #76
  17. mudmantra

    mudmantra Been here awhile

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    That would be cool.:thumb I'm still collecting jetting info. Are you running pump gas? I keeps notes when I change the jets, But I just realized I didn't date the notes, so I have to guess on the last set. I'm going to pull the carburetor again and check. I'm going to try the 3.0 slide and jetting for that first . Then I'll try the 3.5 slide and jet for that second. What ever I can get to work the best well stay in.
    #77
  18. mudmantra

    mudmantra Been here awhile

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    Still fixing things and getting it closer to trail ready. I welded up the rear frame to fix the fender support. I bought a new DG exhaust, and now that I know where all the brackets go, Ill fix the old one too. I'm sure I'll dent them up, and now I'll have a spare when I'm fixing the other. I think I've got the jetting pretty close. Slide 3.5, main jet 390, pilot jet 45, Needle jet R-0, Needle 6DH4 clip #3, float 27mm, mix 40:1. When it gets hot it was hunting a little at idle. I thought it might not like the V-Force reeds. Today, I used better non alcohol gas, and it ran better, with no hunting after it got hot. I also installed a new seat cover, and today I welded an extension on the kick stand. The 79 YZ250 kick stand was just to short. I install new rear brake shoes, and have new front shoes on order. I ordered a new mounting bracket for the exhaust side panel. I need to fix the mounts in the air filter box to install the right side cover. The last step, new levers, new rear tire and fix the skid plate. Getting closer. :beer
    [​IMG]
    #78
  19. anotherguy

    anotherguy Long timer

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    Have you tuned the idle circuit with the screw? If so how many turns off the seat?
    #79
  20. mudmantra

    mudmantra Been here awhile

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    I kept fooling with it, with the poor quality gas at first. Now I think it's just less than the 1 and 7/8 turns out that the service manual calls for. I think I've had it out as far as 2.5 turns. I'll check it again, and give you an exact number.
    #80