Building a 1981 Yamaha YZ465 Factory Replica...

*** Thread now expanded to include vintage Husqvarna's (around pg 23), vintage motocross (Unadilla) and cross country racing! ****

Hello Gents,

My interest in vintage motocross and enduro bike has really taken off the last couple of years. Right now I am rebuilding a Yamaha YZ465 with the ideal of participating in some VMX events this spring. My goal is to build a OW replica bike.

This is what I started with...



That plus some other junkers got me to this point...



Plus a lot more work to get to here...


I hope to have a completed motor installed next weekend.

Finally, here's Bob Hannah at Southwick riding a factory OW

Sweet! Did they come with gold rims in 81'?

Nice! Looking forward to seeing the end result. Big motor in that one.

D.T., you are correct. The 1980 model came with silver rims and the '81 with gold. You have a sharp eye there!

In fact, the 1st bike I bought was a 1980 model. It was in such terrible shape that it has more or less morphed into a 1981 model as I have replaced so much of it.

In reworking the wheels I chose to stay with the silver as I am going with the earlier look overall.

One thing I have found it that 30+ years is a long time for these old motocrossers. The insides of most of the motors I have are screwed up in one way or another. Some are just plain worn out, others have been assembled incorrectly or hacked up in some way by previous owners.

Thanks too Euromad... it's been a lot of work but I have been enjoying it.

As I have a pretty complete photographic record of my work to this point, I thought I would share a little more of the details for those who might be interested.

It turned out that the 1980 bike I started with was in far rougher shape than 1st thought. I found a considerable amount of frame corrosion under the tank and the seat rails were bent up pretty good from loop outs. One of the frame rails had cracked and someone did a pretty crappy job of welding it up.

I began to think it would be best to find a cleaner frame rather than repair the 1980 frame. Frames turn up fairly regularly on auction sites. After a little searching, I wound up with a nice straight 1981 465 frame for $100.

There are a few minor differences between the 1980 and '81 frame. The airbox mounts are different and the steering head is 1/2 degree steeper. The '81 model uses a longer shock reservoir and the reservoir mounts on the frame accomodate this diffference. It is also believed that the '81 frame is slightly lighter due to wall thinkness in some frame tubes however I did not weigh them.

Here is another view of this wreck.



Rust in the frame tubes inder the tank...


The '81 frame was stripped, epoxy primered, and painted with top quality Glasurit black paint. The Glasurit was left over from my BMW R100 repaint. Normally I would say this product is too expensive to use on a dirt bike but since I already had it on the shelf...







Hannah again...

Looking forward to seeing this come along. Nice work so far. Have you had any problems finding replacement parts for this?

Yer' gonna' buy some of those sweet Scott boots and JT "Hurricane" gloves to wear when you ride it, right?
(I think I've still got those gloves around here somewhere)

Jason,

Parts availabilty is pretty good overall. The yz465 seems to be very popular in vintage racing so there is pretty good aftermarket support. It helps too that the IT enduro bikes are very similar and share most parts. And it turns out that a lot of parts are the same for the 250, even some motor parts like the clutch basket.

Then there is the yz490, basically an evolution of the 465. I am finding that a lot of the 490 parts can be made to work on the 465. Sometimes the parts are directly interchangable sometime some effort is needed to make them work. The 490 has had a production run of ~10 years and so lots of stuff gets listed on ebay. There is still a considerable number of parts available from yamaha as well.

Greg,

Yeah I like those Scott boots too! However I do have a couple of pairs of High Points I still use. And I picked up a new pair of JT gloves... gives me all the protection I need when driving the mouse.

Reassembly:

With the frame fleshly painted, the next step was to move it onto the lift where I could start reassembly.

It turns out the airbox from 1980 is not a direct bolt in as some changes were made in the mounting brackets. Instead of changing the brackets I sourced an '81 box off the vmx site vintagemx.us. While the new box was in good shape overall, the rear bracket was missing (seems to be a common problem) so I milled a simple replacement out of aluminum plate.

By this time I had also ordered replacement All Balls brand stearing head, swing arm, wheel and crank bearing kits. I found these kits to be of acceptable quality with the exception of the swing arm bearing kit. I thought that one fell well short of the OEM in terms of fit and quality... more about that later.

Here is a few more photos of the build up...


Fitting airbox and inner rear fender...


Here the steering head bearings and triple clamps are installed. New Yamaha OEM fenders are also bolted up.

I removed the old bearing races out of the frame before painting. This was a bit of a pain as I was unable to catch the edge of the races in order to knock them out with a drift.

I wound up welding a strap across each race and then hammered against that. I am happy to say the ALL BALLs replacement steering bearings fit well and seemed to be of good quality.




Here are the various bearing kits from All Balls



Making the missing airbox bracket.

I used a studded rubber mount together with the new bracket made from 1/4 aluminum. The one stud goes into the box where it is held in place by a large flat washer and nut.

The other stud goes into the bracket which is in turn mounted to the frame. The mounting is sturdy and I like the idea of having the old plastic airbox isolated against vibration and shock.






The next step was to install the swing arm. Before doing that I had some decisions to make regarding rear wheel options...

But first lets take a with Bob Hannah at Unadilla...

Excel rims and Buchanons stainless spokes. I oughta take a new photo of the damn thing. This one's getting old.

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Very nice

I'm currently rebuilding a G model 465. The previous owner did some good things but left plenty of work for me. I'll need to replace the swingarm bearings, what were the issues with the All Balls bearing kit for the swingarm?

Anotherguy..."Excel rims and Buchanons stainless spokes"

I agree that this is the way to go... since I started this project I have bought another 465 (another story!) that came with this setup. The quality looks really great. However, I am trying to control my spending on this project as I have a other projects going on at the same time.

So instead I found some used parts here and was able cobble together a decent wheelset for reasonable money. I'll give some more details on that in a future post...


WFO Pete,

On the swing arm bearings... I guess I was expecting the replacement kit to replicate the OEM parts. In fact, they differ in quite a few areas. First, the OEM design uses needle type side/thrust bearing whereas the All Balls kit came with thrust washers (no needle type bearing). I already had some new needle type bearing I had picked up earlier so this did not upset me too much.

The second issue is the pivot pins. The OEM has a hard chrome plating, like a wrist pin. The internal needle bearings ride on these pins so I think it is important to have a hard surface. The All Balls pins did not have a chrome plate finish. Perhaps they are still hard enough, I don't really know for sure.

The 3rd issue is the rubber seals that go into the end caps. They seem to be too large and I was unable to fit the end caps on using these seals. Fortunately, I had a pair of used seals in good enough shape and put it back together using those.

There is something I liked about the kit also. The needle bearings that insert into the arm are wider than OEM. I think this is an improvement as it spreads the load over a wider surface.

I have seen cases where the pivot hole is ovalled a bit from poor maintainence or loose swing arm bolt, especially on the drive side. I think the wider needle bearing in the All Balls kit helps to overcome this problem if not too severe.

Here are some photos comparing All Balls with OEM parts to help clarify some of my description.

In this photo you can see the kit came with pivot pins, cartridge type needle bearing, plast bushings, inner seals, outer seals flat side thrust washers and dimpled side thrust washers.





The yellow side thush washers from the ALL Balls kit are dimpled to hold grease. Compare this to the OEM needle type bearing to the right.

The large seals (upper left) seemed oversized and I could not make them work. The smaller inner seals fit fine, as did the replacement black plastic bushings. You can see the replacement pins do not have the hard chrome finish as with the OEM.



The needle bearings and plastic bushings press into the arm here. The hole in this arm is slightly worn at the edge. However, a tight fit was attained using the wider needle bearing in the All Balls kit. I dont think the narrow OEM bearing would have worked as well.




So again, overall I am pleased with the All Balls kits even though there are a few short coming in the swing arm kit. And I did not mean to sound too harsh with regard to these kits as I do appreciate the vendors that still make parts available for bikes like ours.

Kevin

Here's Hekki and Bob in 1978?

There was more than that. IIRC, they changed at least the rear axle diameter in '81 and very possibly the front as well. Rear axles were known to bend and get stuck in the wheel on the G..

Nah the front axle is the same. I'm using the '80 axle in my '82 490 forks on my 465.

Something else changed on the front end. I had an '80. Was it the forks? 38mm to 43mm?

That's it.

1980 forks.

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1981-later forks.

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Haha... they're coming out of the woodwork now!

More about my rear wheel saga...

My original 1980 rear wheel was pretty much done for. Not only were the spokes rusty but I discovered a small crack in the rim. Apparently, it is not uncommon for these old rims to crack as I found out when searching for a replacement on ebay. Lots of “good” wheels were listed with cracked rims, jeeze.
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It is also important to check the rim width when looking for a replacement. Keep in mind that the big bore bikes use a 2.50 x 18 rear rim. You would come up short with a YZ250 wheel as that one is only 2.15 x 18.
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Eventually I found what was said to be an IT 490 wheel. Although the rim is silver, it is not the same as the one on my IT490. The IT490 has squarer edges and is supposed to be stronger and heavier than the YZ rim. This one has a silver 18 in rim of the type a YZ would have.
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Perhaps it is a later, post gold rim, YZ490 model, I'm not sure. One thing in clear, it uses a “standard” type hub, not the z-spoke design.
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In any case, it uses the larger diameter axle (like the 1981 465 and 490's as others have mentioned). Another difference is the number of wheel bearings used. The 1980 hub has a single cartridge wheel bearing in each side. The 1981 YZ465 and 490 hubs use two bearings on each side, very beefy!
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The good news is that the wheel was in decent condition with good spokes. It also came with a brake plate and the axle assembly, including all the chain puller do dads.
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Of course, using the later model hub with large axle in my 1980 swing arm took some doing. Several steps were required,
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1) Mill open the axle slot in the swing arm. This was an awkward process as my mill is too small for this job. In the end, I simply bolted the arm to the table the best I could and took very light cuts until I was within 5 thou of the needed dimension. I then used a file to get the finished dimension. I only cut the bottom side of the axle slot. I used the “flats” of YZ490 chain adjuster spacers as a gauge to check my fit. The fit was kept tight across the slot to ensure the bottom side would remain parallel to the factory machined top side.
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2) It turns out the 490 swing arm is thicker than the yz465 at the axle mounts. This can be seen in the different in the chain adjust spacers and the internal width of the adjusters themselves. The fix was to mill the width of the 490 spacers to match the 465 spacers. As for the adjusters, I simply squeezed them down in a vice to the necessary size. I left the end portion of the adjuster outside the vice jaws. This allowed the adjuster side plates to follow the threaded end tab to give a neater appearance.
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3) Finally, I cut a new axle spacer for the left side. The right side needs no spacer. The 490 brake plate is different than the 465 plate (’80 or ’81) and the "spacer" is cast as part of the plate. In cutting the left side spacer I took care to keep the sprocket spaced off the arm exactly the same as on the 465 hub. I was willing to re-center the rim through spoke adjustment if needed. Fortunately, the wheel was well centered without having to do this.
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With all of this said and done, plus some new bearings, I had the 490 wheel mounted and ready to go.
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Here are the photos to go with the description.

First the ugly 1980 wheel. Note the studs in the hub to mount the sprocket. The '81 and 490 hubs use bolts that thread into the hub.


Next is a ugly 1981 wheel. These have the big axle and double bearings. I will re-lace with new spokes and rim in future.



And a nice clean YZ490 wheel test mounted in the 1980 arm



Milling the swingarm with very light cuts, final dimensioning by hand...


New All Balls rear wheel bearings. Note, bearing have seals on both sides, I like that!


Here are the axle adjuster spacers, left side is the 490 (too long), right is the 465.



Milling the 490 spacer...


Now they match!



Squeezed down 490 chain adjuster



More to come... but first,

Marty Moates at the Carlsbad USGP

Lovin' this thread! I just started a '78 YZ400 project so as you might image, this is very interesting and helpful to me. Also diggin' the, never before seen (by me) race photos. Subscribed.

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