Building a 1981 Yamaha YZ465 Factory Replica...

Discussion in '2 smokers' started by FJ_Kevin, Mar 11, 2012.

  1. mxbundy

    mxbundy Long timer

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    YES to all of the above.
    YES Eric is hard to deal with!
    YES he redesigned the pipe with a different head pipe!
    And YES you will wait on getting one. But I have used the DG (when I first got into the vintage mx racing/restoring) and have them crack the pipe mount off the first time the bike was ridden!
    I will be by there tomorrow (PRO-FORM / MAICO ONLY) and I can ask on the availability of the pipes.

    Bundy
  2. mxbundy

    mxbundy Long timer

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    The best thing a builder can do on the engines is to get the crank Dynamically balanced, it will drastically reduce the shaking!!!! :deal

    Bundy
  3. anotherguy

    anotherguy unsympathetic

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    My YZ 465 pulls cleanly from just off idle 'til the pipe signs off with the DG. It took about a year but persistence paid off.
  4. FJ_Kevin

    FJ_Kevin Been here awhile

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    Bundy,

    Thanks for joining us! Yes, I was very very pleased with the seat foam. Shape was perfect as is the density. It is good you chimed in as I was unable to find the order information from my ebay purchase.

    So no one misses it, you can get the seat foam here,

    http://seatconcepts.com/

    This is a very high quallity product!
    Kevin
  5. FJ_Kevin

    FJ_Kevin Been here awhile

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    Great job on this, I like those triple clamps!
    Kevin
  6. FJ_Kevin

    FJ_Kevin Been here awhile

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    So far I too have had good luck with the DG pipes on the both the 465 ad my IT490. No cracks and like "anotherguy" both bikes are running clean from bottom to top after careful jetting (details to follow). I have to say those cone pipes sure look cool though.:evil

    Kevin
  7. FJ_Kevin

    FJ_Kevin Been here awhile

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    With the transmission and crank assembled into the left hand case, I was now ready to close things up.

    I applied a very thin coating of blue permatex sealer to ensure no leaks.

    You can also see here that I am using the shift drum with the factory welded "star". The shift drum must be rotated to a position such that does not interfer with castings in the right hand case as the cases are assembled.

    [​IMG]


    As the before, large sockets, spacers and washers were used to draw the crankshaft through the right hand crankshaft bearing (sorry, no photo). You want to keep the cases parallel as you draw the crank through. It all goes pretty smoothly if you take your time. Watch for binding on the transmission shafts as the case drops into position. I used a rubber mallet to gently tap the case as I pulled the crank though. Other than the crank, it is really only the clutch shaft offering any resistance as it slides through its corresponding bearing.

    Turning the transmission shafts periodically is also helpful to ensuring the case goes down square and minimizes binding.

    In the next photo the cases are together. I have inserted the crank seal to a position such that the seal lip rides on a smooth area of the crank journal. Case screws are inserted from the left hand case and tightend in several intemediate steps to their final torque setting.

    The seal retainer is screwed into place and the primary gear O-ring is positioned into place.
    [​IMG]

    Examination of motors and parts books show that this O-ring is used on all the 465's as well as the 1982 YZ490.
    It's purpose seems to be to keep transmission oil and or air from leaking pass the primary gear where it slides onto the crank shaft. Interestingly, one of my 465 motors was missing the o-ring.

    Another interesting point is that the 1983 and later 490's do not use the O-ring. I also noticed the primary gear part number changes from 1982 to 1983. Is this related to the elimination of the O-ring?

    With the cases together and o-ring in position, the primary gear and shift drum stopper are assembled into place.

    [​IMG]

    Now the clutch spacer, kick start idle gear and shift shaft are added.

    [​IMG]

    The kick starter shaft, spring and gear are next.

    [​IMG]

    The 465 and 490 clutch hubs appear to be the same. Ridging from clutch plates didn't seem to be as much as a problem as on the baskets. However, you can see the hub on the left has a broken stub and is unusable.

    [​IMG]

    With the basket and hub in place (dont forget the two thrust washers), the next step is to tighten the clutch hub nut. I did not have a tool to hold the hub in place while the nut was tightened. To keep moving I whipped up a very crude tool by welding some old steel clutch plates and shop scrap together.

    [​IMG]

    And here it is with the clutch plates and pressure plate installed. Again, this is the 465 clutch basket, clutch plates and primary gear in combination with the 490 pressure plate.

    [​IMG]


    More to come...
    [​IMG]
  8. anotherguy

    anotherguy unsympathetic

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    I'm real curious to see where you ended up w/jetting. We live in the same state so it'll be interesting. When I got it mine was so fat on the bottom it blubbered 'til 5 grand or so then it cleaned up exploded into the upper powerband where it's kinda brutal. Made it interesting in the tight stuff. The original owner broke his leg and parked it for a decade or so. My ex bought it for me for XMas. I kinda miss her around the holidays.

    My YZ was missing that o-ring too.
  9. mxbundy

    mxbundy Long timer

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    I guess the real benefit to the Pro-form pipe is that it does most of the jetting work for you. Much, much easier to jet in.
    And since I was the test rider when we were developing it, I LOVE THE POWER BAND!!!:D
    Has smooth roll on power.

    My bike ran the same as yours did with the DG pipe, and I just got to frustrated to with it after countless jetting attempts.

    Bundy
  10. FJ_Kevin

    FJ_Kevin Been here awhile

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    The next step in the assembly of the engine was to decide on the cylinder/piston combination.

    With more than a few 465/490 cylinders to sort through I was hoping to find one in reasonably good shape.
    And that is exactly what happened as one cylinder appeared little used after a recent rebore :wink:.

    It measured at 1mm oversize (4th over) and was in great shape with no score marks. Although it had been run previously, careful measurement with a bore gauge showed it to be well within spec (~0.0025). The piston was missing but I was able to source a new Yamaha piston off ebay.

    Rather than having the cylinder bead blasted, the paint was simply removed using paint stripper and left bare aluminum.

    Here are a few photos of the measuring process and tools used,

    First, the inexpensive bore gauge used for measuring,

    [​IMG]

    Before setting up the guage I do a quick check of the 3 inch mic (an old Brown and Sharpe) using a 4 inch standard.
    I havent used it for a long while but the standard showed the old MIC was just fine.

    [​IMG]

    Brown and Sharpe factory in Providence, RI

    [​IMG]

    The MIC is then set to the english equivalent of 85mm+1mm=86mm (the target size) and the bore gauge is set within the MIC so the dial can zeroed out.

    Here is the bore gauge assembled and in the MIC. This is just for the photo, usually I will hold the MIC in a vice while zeroing the dial.

    [​IMG]

    And now the bore gauge in the cylinder. Several measurements are taken to check for taper and wear.


    [​IMG]

    more to come...

    [​IMG]
  11. FJ_Kevin

    FJ_Kevin Been here awhile

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    After stripping off the many layers of the paint the next step was to hone the cylinder to restore the cross hatch that holds the lubricant and helps seat the new rings.

    In the old days we used Ammco 3800 hones with good results. Surprisingly, I found these are still available new (~$180) but I went the used route with a couple found on ebay for about $30 each.

    What I like about the Ammco is the twin arms holding each stone. These do a good job of keeping the stones parallel to the cylinder wall and helps prevent stagging of the large ports in a 465 cylinder.

    As far as a honing lubricant, kerosene or WD40 both work fine.

    Ammco 3800 hone

    [​IMG]

    Porting

    For a short while I was considering some porting modifications. But the reality is that these bikes are more than fast enough for me these days.

    Never the less, I have been collecting porting information (when I can find it) specifically for the 465/490 that I will post at a later time. Of course if anyone has information to offer, please feel free to share :evil.

    Now, having said all this, I did take a quick look at case matching the transfer ports. For those who are unfamiliar, case matching involves matching the opening of the tranfer ports at the botttom of the cylinder to the corresponding seating surfaces in the engine cases. The idea is that a protruding step or mismatch due to manufacturing tolerances will perturb transfer flow and degrade performance. The time to examine and take care of this issue is when the cases are apart.

    In looking at this, I found that Yamaha had already done an excellent job here. It appears any gains in this area would be small.

    Photos:

    First is a wide view photo of a typlical 465 cylinder inserted into a typical 465 side case. Again, the area to focus on is around the transfer port at the cyliner/engine case interface (where the base gasket goes).

    [​IMG]

    Zooming in, this next photo shows no real mismatch in this area... pretty darn good!

    [​IMG]



    This one is a YZ 490 barrel in the same engine case... also very good.
    BTW, these two photos show some real differences in the 465 and 490 transfer port design.

    [​IMG]

    Danny Laporte on a center port 500

    [​IMG]

    More to come!
  12. FJ_Kevin

    FJ_Kevin Been here awhile

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    Comparing the 465 and side port IT490 (I do not have a YZ490 to compare) cylinders reveals several differences in intake port sizing and transfer port design. Although I am still measuring, generally, it can be said that the 490 ports are all larger than those of the 465.

    The 490 cylinder also has a bridge in the intake boost port that is not present in the 465.

    Now have a look at this photo of the 465 cylinder. I have laid a straight edge across the cylinder base to highlight differences in depth of the transfer port dividing web vs the 490 in the next photo.

    [​IMG]

    And the IT490, It can be seen that the cylinder liner is cut further away (deeper) than the 465. Notice too the
    angle left in the liner towards the intake port (right side of photo).
    [​IMG]

    If the width of the transfer ports look larger in the 490, thats because they are! At some point I will post all the measurements I come up with.

    Now lets have some fun with the following very interesting photos...

    Starting first with with a standard 465,

    [​IMG]




    Compare above with next set of photos of a 1980 vintage LOP YZ465 cylinder that appeared on ebay awhile back.

    Recall that Marty Moates holeshot (and won) the 1980 USGP on his LOP YZ465:wink:!

    Check out the LOP stamp.
    [​IMG]

    Lots of grinding in the transfer port area. The cylinder liner appears to be cut back like the 1983 IT490 cylinder shown above. The liner also has a similar angle towards the intake port (like the 490).

    [​IMG]

    Here LOP has added two additional ports from the intake port to the transfer ports. This is similar to case induction ports.

    [​IMG]


    And below is a view of the new ports as seen from the intake port.


    [​IMG]


    Now it gets even more interesting!

    Next up are photos of a factory Yamaha OW cylinder!

    This one has the two extra ports from intake to the bottom of the transfer ports like the LOP cylinder.

    But wait, theres more!

    Notice the rectagular port at the bottom. This port from the intake track to the engine case is not unlike the case induction used on some Suzuki RM motocrossers. If you look closely, you can also see that the cylinder liner is cut away in the vicinity of the case induction port (also seen in the 3rd picture below).

    [​IMG]


    [​IMG]



    [​IMG]

    So again, while this is all very interesting my motor went together basically stock. But perhaps I will try some of this in my next rebuild over the winter:evil.

    [​IMG]

    [​IMG]
  13. dtysdalx2

    dtysdalx2 PITA but useful

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    :bow


    Whooly sh#t MXBUNDY, what a beeeuuutiful white 465!
  14. mxscot

    mxscot n00b

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    Thank you Kevin, this thread is pure gold! :clap

    I have just acquired a 1981 YZ465 and have just started the strip down prior to rebuild for racing in twinshock events and have been soaking up all the info in these pages.

    You have a photo displaying several springs, the stiff one has a blue dab of paint on it. I am wondering if you or anyone reading this thread is able to identify and put a weight to the springs used?
    The one on my machine has a green dab on it.
  15. FJ_Kevin

    FJ_Kevin Been here awhile

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    Hello MXSCOTT,

    Glad you are enjoying the thread and great to have you join us.

    I looked through some manuals I have on hand and found spring rates for the YZ465 and the 82 YZ490 that may be helpful to you.

    Recall that the YZ465 uses a spring made of a tapered wire to get a progressive spring rate whereas the YZ490 uses a constant diameter wire for constant spring rate.

    It is the link on the 490 that changes the mechanical advantage to give an effective rising rate. This acts on both the spring and the damping. Of course this comes at the expense of additional pivots and weight.

    Anyway here are the tables. The 490 page is on left and 465 page is on right. It looks like the green dab on your spring means it has a lower string rate than stock.

    [​IMG]

    Perhaps you can fill us in on these twin shock events. Do they run a class for your monoshock?
  16. FJ_Kevin

    FJ_Kevin Been here awhile

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    So how many remember these?

    The JT chest protector made by Sinisalo were really the business, dont you think?
    These cleaned up pretty well after soaking them in a bucket of hot water Tide solution.


    [​IMG]

    [​IMG]


    [​IMG]
    Here is the Oneal version also made by Sinisalo

    [​IMG]

    Back in the 70's my racing buddy wore Jofa pads just like this. I had Jofa pads too but not as nice as these. Mine did not have the white plastic in the chest and back area.

    [​IMG]
  17. mxscot

    mxscot n00b

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    Thanks Kevin,

    That shock info was just exactly what I was looking for! Not good news mind, I'm not getting any thinner in my old age. I'll need to get searching for a heavy spring.

    Most of the racing I do these days is with the Twinshock Scrambles Club in Scotland.
    http://www.scottishtwinshock.com/

    They organise various national championships for older bikes & riders. I ride in the over 50s which allows me to ride a pre 1990 "evo" model and for that I restored a Maico 500 1986
    [​IMG]

    However I've been trying to get an entry to the annual Vets MX des Nations event at Farleigh Castle (Chuck Sun, Mike Bell, Ryan Hughes, Doug Dubach, Jeff Ward and Ron Lechien all made the trip across this year) and also want to do selected National Twinshock Championship events, especially at Hawkstone Park. This is an English based championship and their rules mean I need to ride a twinshock machine.
    TWINSHOCK. ANY BIKE MANUFACTURED WITH TWO REAR SHOCK ABSORBERS AND WITH DRUM BRAKES AND AIR COOLED INCLUDING UPTO 1984 HUSQVARNAS, PRE 82 MONOSHOCK YAMAHAS AND WATER COOLED ORIGINALS THAT WERE MANUFACTURED PRE 1982. FORKS MUST NOT BE OF GREATER DIAMETER THAN 46MM.

    http://nationaltwinshock.co.uk/


    So a couple of weeks ago I bought a Yamaha YZ465 imported from California with a view to restoring and racing it in these twinshock events. I have it all stripped down and it is in pretty good shape. The exhaust and the suspension need some work, but not too bad and the rest is just tidying up.


    Cheers!
  18. wfopete

    wfopete Suffer Fools; Gladly!

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    Kevin, Not to hijack your thread but I picked this little number up from E-bay this week. I wasn't interested so much in the arm but the clutch extender that came with it. Not as sexy looking as the CNC versions out today but the price was right.

    [​IMG]

    These became real popular in the 80's to reduce clutch pull effort and there were several designs out (such as EZ-Pull) which fit most bikes but had so much slop that it was a pain to keep adjusted. That was a problem with these, yes it made the clutch pull lighter but the clutch adjustment range became very sensitive. This clutch arm was for an IT465 and was in slightly better shape than my YZ clutch arm.

    Here is a picture of the differance in arm length:

    [​IMG]

    Plus I think the IT arm is a little beefier.

    [​IMG]

    Five minute deal to drop in place.

    [​IMG]

    Turned my four finger clutch pull into a two finger pull. These extenders go for as much as $40 but the arm with attached extender was around $25 shipped. Nice.
  19. FJ_Kevin

    FJ_Kevin Been here awhile

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    Hi Pete,

    Well this is quite funny because I just bought this one (photo from the ebay listing),

    [​IMG]

    I am just using the extension, will save the late model clutch arm for another project.

    [​IMG]

    You got a better deal though, I paid $31 delivered.

    This one is for the IT490. After 30 minutes in the tight woods I need some help, glad to know this does the trick!

    And nice that it installs so easy.

    Kevin

    [​IMG]
  20. anotherguy

    anotherguy unsympathetic

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    The YZ trans was designed to shift under power w/o the clutch and will do so for a long time.