Building a 1981 Yamaha YZ465 Factory Replica...

[wfopete]

Gee Kevin, why didn't you just fire 'em up and ride them out!

[anotherguy]

Good news.

[FJ_Kevin]

Alright, things have finally settled down after recovering my two YZ465 so I am now ready to refocus and continue on documenting the rebuild process started many months ago.

Recall from earlier posts that the transmission has been reassembled and I had decided to assemble the rest of the motor using,

- 5-speed yz465 gear set
- 1985 YZ490 engine cases with offset clutch actuating arm bore
- The YZ465 clutch basket with helical cut gear
- The corresponding helical primary gear for the crank
- YZ465 crank and cylinder

Remember that using the late model engine cases requires I use the YZ490 clutch pressure plate too. This plate has a longer adjuster bolt that helpd make up for the offset in the clutch arm bore. Unfortunately you cannot simply swap the adjuster bolt into the yz465 pleasure plate as there is a difference in the casting that prevents this.

I would have used the improved YZ490 straight cut basket as discussed previously but I did not have an extra straight cut primary gear at the time of assembly (although I do have one now).

Here is one last photo of case comparisons that I did not post yet.

I think the point of this one was to further show the difference in case venting between the early yz465 cases and later 490 cases. It also shows compares the casting numbers I found across various serial numbers.

One final point is the difference in the early and later style clutch (pinion) shaft bearing. The early bearing is unsealed. For some reason they switched over the an internally lubricated sealed bearing. Perhaps this was to keep gear teeth shavings out of the bearing? I noticed Yamaha also moved to a sealed bearing behind the counter shaft sprocket as well.

[FJ_Kevin]

I was fortunate to have several good crankshafts around from which to choose in my rebuild. Of course I had some bad ones too!

One thing I was curious about at this point where the differences, if any, between the YZ465, IT465, IT490 and YZ490 crankshaft assemblies.

This is what I found from the parts books.

First, the exploded view of the YZ465 crankshaft assembly,




Cross referencing the part numbers shows the crank to be interchangeable across all YZ465's and YZ490's.
The rod assembly is interchangeable for all of the YZ's and IT's.


There is a difference, however, in the crank flywheels between the YZ's and IT's. The YZ cranks have lightening hole in the flywheels that allow them to spin up more quickly. The IT cranks are solid making the IT465/490 more tractable and less likely to stall in a slow corner.

Here some photos of the IT490 crank.





Compare these with the YZ465 crank shown below.



For this build, I have stayed with the YZ465 crank.

Now, even with what appears to be a good crank, there are several potential issues to watch for. For instance it is not uncommon for a crank seal lip to cut a grove into the crank over the course of time. Here is an example where a grove has worn into the ignition side of the crank bearing surface. This crank was fine otherwise.



It is not necessary to repair this. The solution is to assemble the motor without the crank seal. Then, after careful measurement, you insert the crank seal into the case at a depth that avoids placing the seal lip into the groove.

Other issues to watch for are keyway condition and galling on the crank taper. Galling can occur when a flywheel key shears allowing the flywheel to move on the taper.

The taper should also be checked on the flywheel,especially when mixing and matching parts for motors you do not know the history of. One of my flywheels was severly damage on the internal taper in addition to having an extra key picked up by one of the magnets!




With a good crank selected, it is important to install it into the case without disturbing its alignment. From one of the previous pictures you can see that I chose to assemble the transmission and crank into the left hand side case first ( I think either side is OK though). When installing the crank I used a stack up of large sockets, washers and nuts to pull the crank through the (new) crank bearing.

The idea is to pull against the crank bearing inner race as you do not want to put a side load on the crank bearing. And make sure your sockets or spacer do not impinge on the crank taper as you tighten so as not to damage it.



more to come...

[anotherguy]

I have a parts fiche in PDF for the YZ if ya want one PM me an e-mail address.

[wfopete]

Kevin,

Good stuff.

Another option for the damaged seal area on the crankshaft is to go to your auto or bearing supply store and obtain a stainless steel sleeve for the diameter of said crankshaft. This as been done for years on trucks and autos where the damper area has been damaged. The sleeves relatively are cheap and EZ to install.

http://www.vsm.skf.com/en-US/HeavyDu...ediSleeve.aspx

[FJ_Kevin]

Originally Posted by anotherguy

I have a parts fiche in PDF for the YZ if ya want one PM me an e-mail address.

Thanks much for the offer. Over time I have been able to collect all the 465/490 pdf parts manuals so am in good shape now. I have most of the printed owners manuals also. I would like to scan them when I get some time.

Thanks Again!
Kevin

[FJ_Kevin]

Originally Posted by wfopete

Kevin,

Good stuff.

Another option for the damaged seal area on the crankshaft is to go to your auto or bearing supply store and obtain a stainless steel sleeve for the diameter of said crankshaft. This as been done for years on trucks and autos where the damper area has been damaged. The sleeves relatively are cheap and EZ to install.

http://www.vsm.skf.com/en-US/HeavyDu...ediSleeve.aspx

Hi Pete,

This is a cool idea. I will hang on to the link for future reference.

Thanks!
Kevin

[FJ_Kevin]

Originally Posted by nachtflug

never get tired of good 70's mx shots. got anymore in a larger size? thats really sweet. so is your YZ 465, I think if I had moved from a KDX 400 to a YZ 465 I could have had one more brush with greatness in 82....

Nachtflug... thanks for the note. I do have some more photos and will keep posting. Speaking of photos, I have been admiring your photos on avdrdr for quite some time. You are seriously talented in this area!

Perhaps you can let us in on some of your techniques and/or advise on the setup you use?

Here is the 125 experts leaving the line at Bridgehampton in 1978. I am behind the guy on the suzuki... with yamaha down the sleeve of my jersey.



How about one of you on that kdx400?

Thanks Again,
Kevin

[FJ_Kevin]

Originally Posted by Twin-shocker

You can generally weld mag with commonly available rods no problem. However if this proves to be impossible, then get a scrap case and cut this up to make filler material. Repairing with epoxy makes welding much more difficult, as its very hard to get rid of the epoxy completely before welding.

Sorry for my slow reply on this.

As mentioned above, I used a so called "general purpose" magnesium rod I got from the welding supply shop several years ago. I have only welded magnesium a few times but have generally found it to be more challenging to weld than aluminum and even more sensitive to contaminants such as oil.

Although I did try to clean my clutch cover thoroughly, there may still have been some oil residue deep within the pores of the crack I was repairing. I believe this to be the case as I was experiencing some outgassing in the puddle while welding and the outgassing left behind some pitting in the weld.

I was also getting a fair amount of soot while welding even though I turned up the flow meter a good bit more than what I use for aluminum.

Later I found this helpful youtube video on welding magnesium. They seem to recommend keeping the tungstun electrode very close to the puddle as you weld. Perhaps this gives better shielding. I dont think I was as close as shown in the video.

I used straight argon. I think this is perferred over a lower cost nitrogen/argon mix often used when welding steel.

Here is the youtube link.

http://www.youtube.com/watch?v=weqTWwaaL0g

Below is a photo of my repaired cover. I put extra filler into the area of the kick shaft bore for added support. It is not too pretty (note the pitting) but it did not leak either. The photo was taken after the bike was laying in the rainy ditch for a couple of days after being recovered from being stolen. It looks especially bad as my polished mag cover was already reacting with the moisture.



Compare above with an original cover for an idea of the extra filler added,


Twinshocker suggests that pieces from another cover be used as filler rod. This is something I would like to try as the pitting could also be due to a mismatch with the rod that I used.


Hope this helps!

[mxbundy]

Originally Posted by FJ_Kevin

OK, next up is side panels and seat. Like everything else, these items were beat to hell on my bike. Just as well as I was planning to replace the yellow number plates with a style closer to that of the factory bikes.

To see what I mean, here's a photo of Bob Hannah's 1979 250cc OW40. You can see the side number plates are of a lightweight translucent type material.



It turns out there have been a few different suppliers that made factory look replacement number plates for the 465.

Somehow or another I wound up with four different sets that are all a little bit different from each other. The photo below shows them all lined up. I will try to point out some differences.

First up is the Maier. These are solid gloss white. I bought these directly off the maier web site. As you can see, they come undrilled. They are solid white, not translucent as on the OW40. The quality appears good however they do not have the molding for the airbox vent (see left side plate) as the yamaha OEM or the other plates do.

The next up is DC plastics. These plates are a matte like opague finish. They look durable and fit pretty well. Mine came drilled. I would prefer to get them undrilled so I can optimize the fit to a particular bike.

I got the 3rd set of plates off ebay. I have no idea who made them but they are also of very good quality and fit. They are a little bit thicker than the DC plates. These seem to be the closest to OEM in form and finish (except for color). These came undrilled.

The 4th set of plates came with another bike I bought. These are the only plates that are translucent like the OW. They are pretty thin and are not formed as well as the others. Being as crude as they are, my first thought was to toss these in the trash. But looking back at the OW photo, those plates are crude too! My plan is to use a heat gun to get a proper fit on the bike. In the end, I will probably use these for display and the DC plates for racing. The other plates (1 & 3) will be saved for the other bikes I now have.


Seat.

I knew I was going to replace the seat cover but as the rest of the bike was really starting to shape up I decided to replace the seat foam as well.

In selecting the cover be sure to check for the lettering on the back side. Some covers have YAMAHA in the sides but not on the back like the OEM cover does. I am happy to report the fit and finish of cover and foam I received were great! I'll try to dig up the supplier info for the benefit of others.

The installation itself is simple. Remove the staples, cover and foam. Assemble in reverse order .

In my case, I aligned and stapled the front and back first. I then worked from front to back, pulling down and stapling the cover so as conform to the contour of the foam.





Here is a progress photo with the cover just laying on the seat. I have removed the tank decals before sanding and polishing the tank. The panels are the number 3 version (photo above). The green ovals and front number plate are from Vintage Iron and are high quality.



To brighten the tank up I first sanded it using 400 wet/dry working up to 1000 grit. I then used a buffer with polishing compound followed by new tank decals. Not perfect but much better than what I started with. How about those KYB decals on the forks? Just like the OW
.



Heikki Mikkola - check out that KOHO Fin fighter mouth guard

Thanks for the props on the seat foam. Its one of mine for sure, to my knowledge I own the only mold for the 465 seat foam!

bundy

[mxbundy]

Here is a few pic of one I built for my buddy!

[anotherguy]

How much better than the DG is that ProForm pipe?

[mxbundy]

Originally Posted by anotherguy

How much better than the DG is that ProForm pipe?

Night and day!!! The Pro-Form really cleans up the bottom end. The stock pipe and the DG seem to over schvange the incoming fresh fuel charge and really contribute to the jetting problems for the 465.

Bundy

[wfopete]

mxbundy:

I understand the 465 Pro Form pipes are tuff to get as the builder has more pressing deals with his pipes. Also, that earlier this year the builder was re-designing the 465 pipes due to fatigue and cracking issues.

Any insight on this?