Building a 1981 Yamaha YZ465 Factory Replica...

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

  1. spdtrpl

    spdtrpl Red Coat MagnoliaTx

    Joined:
    Dec 12, 2004
    Oddometer:
    210
    yz465 1.jpg

    Great thread, trying to keep it going with a pic of my 465
    Norty01, Brewtus, Michael N. and 4 others like this.
  2. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    ^^^ Nice!

    how about some details on that rocketship!
  3. spdtrpl

    spdtrpl Red Coat MagnoliaTx

    Joined:
    Dec 12, 2004
    Oddometer:
    210

    Thank you, as you asked:

    Pro-Form Racing pipe and silencer
    Cylinder is ported
    Knurled crank
    490 Clutch
    Moto Tassinari reeds
    Airbox modded
    Decompression valve
    XYZ Triple clamps
    Fatbars
    Wide footpegs
    cr480 brake stay
    Buchanan Sun rims, rear is 18"
    Front fork internals from Racetech
    Racetech G3-S shock
    and probably some other changes that I've forgotten, or am unaware of.

    If you're wondering - The Racetech suspension is excellent

    yz465 2.jpg
    thirsty 1, FJ_Kevin, Brewtus and 2 others like this.
  4. Michael N.

    Michael N. Adventurer

    Joined:
    Oct 15, 2015
    Oddometer:
    34
    Location:
    Graz, Austria, Europe
    Whow, this is a nice one!

    Just the reeds fron MT or the complete intake?
    What changes did you do to the Airbox and why did you add a decompression valve?
    I can start mine while stay sitting on the "couch"...

    Cheers, Michael
  5. wfopete

    wfopete Suffer Fools; Gladly!

    Joined:
    Aug 19, 2004
    Oddometer:
    850
    Location:
    Somewhere North of Dover, AR
    I talked to the Moto Tassinari folks last year. I believe p/n V303-FM which is for a 89 YZ250 will fit the 465 motors. It's a complete reed block (not just the reeds). It does not include the intake boot that the carb clamps to. A lot of folks use a pop it type of decompression valve which requires you to "set it" each start up. Boysen has a dual stage reed set up but it only replaces the metal reeds with fiberglass reed pedals. Which is better? Who knows but the current thought is that the MT VFORCE3 reed block is superior to the 35 year old Yamaha design.
  6. Michael N.

    Michael N. Adventurer

    Joined:
    Oct 15, 2015
    Oddometer:
    34
    Location:
    Graz, Austria, Europe
    Thank you Pete!
    I ment the Reed block, not the whole Intake system....

    I run the boysen reeds already and wonder if there is a big difference ftom the V-Force Reed block to the Boysen
    reeds.

    Talking about the intake boot, do you maybe know where i can get a good one?
    The one on my 2nd 465 is in bad shape, has some cracks.

    Thank you, Michael
  7. wfopete

    wfopete Suffer Fools; Gladly!

    Joined:
    Aug 19, 2004
    Oddometer:
    850
    Location:
    Somewhere North of Dover, AR
    They are out there...for a price:

    http://www.thevintagespoke.com/shop...500-INTAKE-BOOT-CARBURETOR-29026-x4522294.htm

    These guys have them to:

    http://amsracing.com/product/1980-1981-yamaha-yz-465-intake-manifold#!prettyPhoto

    The current school of thought (Including Boysen) is that the CF reeds give better all around performance and response to the fiberglass or the OEM stainless steel reeds. Would CF reeds be a big differance to what you are using I can't say as I don't know what your definition of "big differance" is and even more important, I have not tried either of the reeds...yet. I suspect they would be a little better but not night and day better. FWIW; I plan to go with the VForce3 reed block this summer.
  8. Michael N.

    Michael N. Adventurer

    Joined:
    Oct 15, 2015
    Oddometer:
    34
    Location:
    Graz, Austria, Europe
    I see i have a problem saying what i want to.... i am in need of the boot that connects the carb and the airbox.....
    I will try the V Force Reed block later this year, the boysen reeds work currently good in the Racebike.

    Thank you, Michael
  9. wfopete

    wfopete Suffer Fools; Gladly!

    Joined:
    Aug 19, 2004
    Oddometer:
    850
    Location:
    Somewhere North of Dover, AR
    Michael, before you order the VForce 303FM, double check that it will work. I've been known to get bad info sometimes.
  10. wfopete

    wfopete Suffer Fools; Gladly!

    Joined:
    Aug 19, 2004
    Oddometer:
    850
    Location:
    Somewhere North of Dover, AR
    First, my apologies in advance to Kevin for derailing this thread away from his machine.

    Some of you are wondering about Moto Tassinari reeds, I ordered this Delta 3 Reed Valve System p/n V303-FM for a 1989 -1996 YZ250. I paid $130 (including shipping) for the kit on evilbay. The system was a drop in fit on both my ported and standard cylinders. The reeds in my 465 were the original stainless steel reeds that came with the bike. Reed pedals that old can give you fits with jetting and the jetting of these motors is all ready problematic. Plus, as the reeds fatigue they can chip or break off sending them right into the cylinder (not a good thing).

    Here is what you get:

    [​IMG]

    If this picture is any indication it should move a bit more product. There are several promising revelations in these next pictures.

    [​IMG]

    [​IMG]

    Oh, oh! But what about this side? No problem once you compare your intake boot you'll see there is plenty of room for the reed cage to work.

    [​IMG]


    Here are a few measurements comparing the VForce to OEM. The OEM block was a shade over 49mm. The flange itself on the Vforce cage is about twice as thick as the OEM Yamaha flange.

    [​IMG]

    Below the OEM block measured in at 44.22mm

    [​IMG]

    Square peg, round hole? Not really, these OEM "wings" get cut off as part of the installation. It's all in the instructions.

    [​IMG]

    I'll let you know how they work out on my bike in another forum thread. Really what I am hoping to gain is better low end response and smoother transition throughout the power delivery. Well a boost in torque would be nice too. So do you really need a new reed block as opposed to simply replacing the reed pedals? Well considering your OEM reed block has 30+ year old technology...

    And now back to our regular FJ Kevin programing.
    FJ_Kevin likes this.
  11. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    Hi Pete... Those reeds look pretty cool & glad you posted the details on them, will make a nice reference for the future. Will be looking for the ride report on these...
  12. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    OK boys, there has been lots of progress on the 83 YZ490 and finally time to provide some updates on all this work.

    And now even though it is almost done, I still plan to post all the gory details as I am finding these threads very helpful in keeping track of the work performed on the various bikes I am working on (ha, I have too many for sure!) as well as some of the literature I have collected.

    Anyway, the last updates (many months ago) mostly covered the frame prep, powder coating, assembly of the triple clamps and adaptation of the wide Honda CR foot pegs and KTM front fender brace taking us to right about to the photo below,


    [​IMG]


    Even before this point, there was considerable work done and the updates on that work will be made now.

    First up is the swing arm. Recall that this bike is being assembled from scratch using major components that were collected over a long period of time, and whenever they could be purchased cheaply :-).

    As it turned out I had collected two '83 swing arms at about $15 each. The 490 shares swing arms with the 250 and so they actually pop up fairly frequency at low prices. The real trick is to find one close enough to get low cost shipping. In any case, I got very lucky on these as the swing arm bearings where in great shape and only required cleaning and greasing. The bearing sleeves where like new also, however I did replace the side thrust needle bearing as they are the same as the YZ465 and I ready had new ones (~ $13 x 2) on hand.

    [​IMG]

    [​IMG]

    The plastic chain guide (~$28.50) and front chain protector (~$15) got replaced as well. You can see them (those nice bright white pieces) and the swing arm test fitted into the frame here,

    [​IMG]

    One of the reasons I bought the 2nd arm was because it came with shock linkage (arm relay & connecting rod) and linkage hardware I did not get with the first arm. The relay arm is used on the YZ250 and also on the '83/84 IT490.

    Here is the so called "connecting rod". One end connects to the frame (tabs shown in picture) and the other connects to the bottom of the "arm relay". One of the connecting rod bearing and sleeve assemblies showed some wear so I replaced it. Note the pivot bolt include grease fitting for ease of maintenance. In fact all the suspension pivots have grease fittings, a nice touch I think!

    [​IMG]

    That bearing pressed out pretty easily using a only few sockets and a vice,

    [​IMG]

    This photo shows the newly installed needle bearing, the bearing sleeve and the dust caps containing o-ring seals

    [​IMG]

    Here is another view showing the "arm relay" . The bottom shock eye is connects to the top of the arm relay. The two bottom pivot points of the arm relay are below the swing arm and can't be seen in this photo.

    [​IMG]

    This view from the right underside of the swing arm shows how the "arm relay" attaches to the underside of the swing arm as well as the "connecting rod".
    In summary, the "arm relay" has 3 pivots while the connecting rod has two. All this linkage works together to provide a progressive suspension characteristic not possible in the original monoshock design.

    [​IMG]


    Here is a nice mechanical view showing the system in more detail (83 YZ250)

    [​IMG]

    This one is cool too as it shows the evolution of the non linkage monoshock along with the first version using linkage (1982 J-model)

    [​IMG]

    More to come...
  13. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    And now this '83 Yamaha brochure (in European colors) touting this greatly improved rear suspension system. :pynd

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]


    More to come...

    [​IMG]

    [​IMG]

    [​IMG]
    RCmoto and 996DL like this.
  14. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    Rear Shock

    So it actually took awhile to figure out exactly which shocks would work in the '83 YZ490 frame. I thought for sure the IT490 shock would work but no, not only was it too short but the top of the shock is wider than the YZ version and would not fit into the YZ frame. I also found out that the '84 YZ shock is shorter than the '83. And the '85 version of the shock is even shorter than the '84!

    The only two shocks will work, the '83 YZ250 and of course the '83 YZ490. Because of this it took a little while to find a decent specimen at a reasonable price. I bought the 1st one ($50) just to have something to get started with. It is in reasonable shape, no leaks, no excessive wear but is missing the form/rubber bumper.

    Not too long after a 2nd one came up for sale ($80). This one still had the bumper plus what appeared to be a replacement racetech (blue) spring. It is in good shape and still seems to have plenty of nitrogen charge given the way it extends a compressed shock shaft (as tested with spring removed). I decided to build the bike with this shock... I'll send the other one out for a refresh sometime down the road.

    You can see the two shocks to the right in the initial pile of parts I had collected.

    [​IMG]

    Here is a summary of info I have on the shocks at the present time. I'll try to update this once I have the spec's on the '84.



    [​IMG]

    From the above table it is apparent that the trend was to go to a shorter shock in successive model years, probably for decreased weight and a more compact package.
    Not only is the shock body shorter on the '85 but so is the oil reservoir, by 3 inches meaning there is significantly less shock oil in the 85 vs the '83 shock (always a price to pay).

    And now for the photo lineup, left to right are the '83 YZ490, the '83IT490 & the '85 YZ490. You can see the BASS cable on the '85 shock. This was intended to connected to the brake pedal in order to reduce compression damping during braking.

    [​IMG]

    The top mount on the IT490 shock is wider (on right)

    [​IMG]

    83 YZ490 shock (on left) as compression damping adjuster not present on IT490 shock.

    [​IMG]

    '85 shock with easy access compression adjustment via slotted screwdriver.
    The '83 versions require seat removal to gain adjuster access.

    [​IMG]

    Blue racetech spring on left, stock yellow spring on right. The blue one appears to have a progressive spring rate judging by the coil spacing.

    [​IMG]

    More to come!

    [​IMG]

    [​IMG]

    [​IMG]
  15. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    Started this one yesterday... fired off 2nd kick! Hoping to ride it at the farm this weekend where I've added a new loop with off camber leading into a steeply graded uphill!

    [​IMG]
    Baja Perro likes this.
  16. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    I was just admiring the view in your photo... you are in a nice part of the world there. Bike looks good too!
  17. FJ_Kevin

    FJ_Kevin Been here awhile

    Joined:
    Dec 28, 2010
    Oddometer:
    731
    Location:
    Maryland ==> originally from Long Island
    Pete,
    I seemed to have missed your comment here. Are you running a decompression valve on your YZ? Can you give some details.
    What do you think? Should I add something like this to my IT490 so I can start it out in the woods after I've worn myself out? Dang, maybe I would have had a chance of push starting after my kick starter fell off! :lol3
  18. wfopete

    wfopete Suffer Fools; Gladly!

    Joined:
    Aug 19, 2004
    Oddometer:
    850
    Location:
    Somewhere North of Dover, AR
    Here you go Kevin: http://www.thumpertalk.com/topic/843225-cr500-decompression-valve-pics/

    The feller you want to contact is Larry at 815-623-8940 after 5 Central time weekdays, anytime weekends, or email him at wiechman@charter.net . I talked to him and he is leaving today for the week to go riding but he can supply you with a Comp. Release for around $20 or you might want to call Goodson Automotive Supply at 507-452-1830. They sell a good quality unit but they come 2 in a package. Thread size is M10x1 I think.

    If you visit some of the big bore 2 stroke forums this subject "pops" up from time to time.
    FJ_Kevin likes this.
  19. spdtrpl

    spdtrpl Red Coat MagnoliaTx

    Joined:
    Dec 12, 2004
    Oddometer:
    210
    I would highly recommend adding a decompression valve to any big bore YZ, it makes the bike much easier to kick, I dont think theres a downside to having one.
    Maybe tall, young, fit riders wouldn't need it.. But then I'm not tall, fit or young.
    spokester and FJ_Kevin like this.
  20. anotherguy

    anotherguy Long timer

    Joined:
    Jun 18, 2009
    Oddometer:
    15,491
    Location:
    the hills
    Yeah I'm considering modding the chamber for modern pump gas and installing a release on the 465. Mine starts relatively easy but I have to stand up on the footpeg while leaning on a tree or something to keep from falling over sometimes. Thinking a shorter kicker and release will render that procedure obsolete.
    FJ_Kevin likes this.