650 Rear Drum Brake Plates


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Over the past few years, I've acquired several of these from different years and after examining them, noticed quite a few differences. Most are minor or cosmetic, but some are major. It's pretty common knowledge that the brake shoes are the same for all years and that any plate will swap into any wheel, but that's about the extent of the published data. I'm going to "fill in the blanks", so to speak. If someone acquires a separate brake plate without a wheel, this should help them I.D. it, and if it's missing some parts, you'll know which ones can be used.

So, I'll start with a picture history of the plates, mainly showing the fronts and the cosmetic changes that occurred. The first version was used from '70-'73. It is the most "plain jane" of the lot, with no added extras for checking brake shoe wear. It is the only plate that has it's full part number cast into it .....



The next version came along in '74 and was used up through '77. This one's easy to identify because of the electric brake shoe wear switch it had. The beginning of the part number was changed to "447", which is to be expected. This was the year the "447" bikes started. The full part number was no longer cast in the plate, only part of it .....



Mid to late '77 saw the same "447" plate being used but with a few mods. The electric shoe wear switch was eliminated. The casting was still there but the hole was not drilled and tapped. The bracket for the switch wire was cut off as well. A shoe wear inspection hole with a rubber plug was added to the top of the plate. From the machining marks found on the inside, it appears it was drilled. It was labeled with a foil sticker .....



In '78, a new cleaned up casting was introduced. The electric switch related parts of the casting were eliminated and the shoe inspection hole, along with it's label, were now cast in. The part number changed to 1T3-25026-00-00. Again, it was only partially cast into the plate. This plate was used from '78-'80 .....



Continuing with the pictorial plate history, we get to the last version used, from '81 to the end of production. Again, the casting was changed along with the part number. The first 3 digits of the part number changed to "4M4" but for some reason, Yamaha didn't change that on the casting. It still has the "1T3" cast into it. In 1981, the plates were black, later plates were polished alloy. A small change at the end of the part number reflects that. Other than the color difference, the plates were the same.


On this plate, the shoe wear inspection hole and rubber plug, along with it's label, were eliminated. But, the area they were located in was still cast into the hub. To take their place, Yamaha added a shoe wear pointer on the camshaft and a scale cast into the hub for it to work against .....



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Now I'll discuss the component parts. This mainly consists of the camshaft and it's spacer or spacers. The main goal here is to mount the brake shoes spaced out equally on both ends so they sit parallel to the plate .....


On the '70-'73 plate, this was accomplished mainly with the casting but in '74 that changed. The casting height on the inside of the plate on the camshaft end was reduced by about 6mm, most likely to provide room for that electric switch. Along with that, it was extended outward by the same amount on the outside. Basically, the length or depth of the pivot hole through the plate remained the same, it was just shifted farther out .....




But, to keep the shoes mounted square to the plate, the camshaft had to be spaced back in to make up for the 6mm of missing casting. So, a new longer camshaft was needed. The spacer used on it also needed to be rather special. It had to lock onto the camshaft so it would rotate with it and also needed a beveled or ramped area on it's bottom to progressively work and activate that electric switch.

So, here's the 3 styles of camshaft Yamaha used. The short one on the left will only work in the early "256" plate. The two newer longer ones will only work in the '74 and later plates .....


Now obviously, that funky spacer Yamaha needed for the electric switch models was difficult and expensive to make. Once they eliminated the switch, they didn't need that anymore. They switched to 2 thick flat washers. Again, this required a camshaft re-design, but Yamaha got their money out of this one. They continued to use it on a multitude of models pretty much right up to the present day. The early camshaft used just one thin shim washer (1/2mm thick) as it's spacing was achieved with the casting .....


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The "foot" on the end of the brake shoe that rides on the "flats" of the camshaft is about 22mm wide. That means those camshaft "flats" need to be at least that long. Yamaha gave us 23 to 24mm on them, a little extra. But wait, you're thinking what about that one with 27mm long flats? Well, the cut-out in that funky spacer that locks onto the "flats" is 3mm deep. Once fitted, it leaves 24mm of "flats" exposed .....


Now let's talk some more about the last camshaft used, the long "short flats" version. I was unable to pin down exactly when this came into use. My '78 has the previous "long flats" version with the funky spacer. My buddy's '80 Special II has the "short flats" version and 2 flat washers as spacers. The parts drawings are confusing on this. The '79 Standard drawing shows the older "long flats" camshaft but the '79 Special II drawing lists the newer "short flats" version. I don't have a '79 plate to examine and I think that's the only way we'll nail this down. So, anyone with a '79, please chime in.
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Now a little bit more on that last camshaft. There were 2 versions. In 1980 (and possibly 1979), the part number was 1T3-25351-00-00. In 1981 the first 3 digits changed to "4H7". Yes, it is a slightly different camshaft and was required for the brake shoe wear pointer. Yamaha needed a way to lock the pointer onto the camshaft so it turned with it. They also needed a way to "clock" it so it pointed correctly to the cast-in scale. They accomplished this by putting 3 little "tits" around the I.D. of the pointer plate that would fit into the splines .....


The 2 lower ones are sharp points and would fit between any of the splines. The top one, however, is larger, a "double-wide" you could say. To accommodate this, Yamaha left one spline off this "4H7" camshaft. The pointer will only fit on in one position and that "clocks" it .....



So, the "1T3" and "4H7" camshafts are the same except for that one missing spline on the "4H7" version. I've inspected the "1T3" version on my buddy's '80 Special II and it is indeed fully splined.
One little thing I forgot to mention - all these plates use a little felt seal ring around where the camshaft exits the outside of the plate. Knead it full of grease and it will keep dirt and water out of the pivot hole .....


If yours is missing or trashed, you can still buy them from Yamaha for less than $2 .....

A while back, someone asked about a wave washer shim on the camshaft shown on some of the parts diagrams. Personally, I had never run across one installed on any of the plates I'd seen. During my research, I solved the mystery. Turns out, this was an "as needed" addition for electric switch plates, as outlined in this tech bulletin .....


To confuse matters, the washer is also shown on the '77-'79 diagram. But, once the switch was discontinued, there's absolutely no reason for the wave washer. And to confuse matters even more, the drawings show the washer in the wrong place, on the inside of the hub under the normal main spacer. Here's a picture of the washer and as you can see, it has a pretty big O.D. There's no way it could be fitted on the inside. It would block the function of the switch, blocking access to the ramp in the spacer that activates it.


And speaking of the parts diagrams, here's a few more I "corrected". I included the brake stay in the '74-'77 drawing because it is unique. It has little tabs to hold the switch wire .....


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That is all very interesting! Thank you 5Twins!
Daniel Black and I both have '77 models and we have noted before when we get our bikes together that his bike has the rear drum with the wiring for the lining sensor,
While mine is like this
I now understand that hIs bike was an early 1977 production while mine came in the latter part of the year. Very interesting. By the way, I don't know if your excellent photo tutorial for rebuilding and servicing the rear brake is still around but I know I used it when I rebuilt my rear drum and found it invaluable. So many good tips were in it.
It kills me that so much of your fine work was lost in that S.O.B. Photobucket purge.
Thanks 5Twins.
It's not lost. I still have all the pics on my computer and have uploaded them to another hosting site. I just haven't replaced all the deleted ones in all the posts here. That would be too daunting a task I think. If any of my old posts do come back up with missing pics, I am replacing them. I'm just not about to go through my 14K plus back posts to correct all the missing pics, lol.
Just a few more items, I promise, lol. The special oval headed shoulder bolt that attaches the brake stay to the plate - there were 2 of them. The '70-'73 plate uses a 168-25378-00 (or 90109-08184). The '74 and later plates use a 341-25378-00 (or 90109-08338). The difference between the two is in the length, specifically the length of the shouldered portion. The later "341" bolt is 38mm long, about 18mm of that being the shoulder. The earlier "168" bolt is 2mm shorter @ 36mm, about 16mm of that being the shoulder. The reason for the difference is because of the brake stays used. The '70-'73 brake stay was a stamped flat bar. The '74 and later stay was a tube with the ends squashed flat. Apparently those ends were thicker so a slightly longer bolt was required.

The oval head and the diameter of the shoulder was the same on both bolts, so they will swap into any plate. The one you need will depend on the type of brake stay you're attaching it to.
And finally, the last item - the brake arms. There were 2 of these used as well. The '70-'73 plate lists a 214-25355-00-00 lever. The '74-on plate lists a 341-25355-00-00 lever. This "341" lever is N.L.A. and will probably be difficult to scrounge as it wasn't used on much else, and nothing any newer than our 650s. The earlier "214" lever, on the other hand, was another one of those parts Yamaha continued using pretty much right up to the present day. In fact, you can still buy it new from Yamaha if you don't mind paying near $34. But, since it has been used so much and for so long, scrounging one cheap is pretty easy. My early plate didn't have one so I snagged a later plate from a different model that used it, the XVS650 V-Star, off eBay. Now, sometimes parts change but the part numbers do not. Well, I've got 2M checking my V-Star lever dimensions against his original so we'll know soon enough.

Anyway, until then, here's what I've got. The V-Star (and hopefully '70-'73) lever is a little shorter and has less of a bend or offset than the '74-on lever .....





I've fitted the V-Star lever up to both my early '70-'73 plate and a later '74-on plate, and it looks like it will work just fine. It's offset enough for the brake rod to clear the plate.

If you're looking to scrounge parts for a 650 plate then the V-Star plate is a very good choice. They are dirt cheap on eBay and it's easy to find a complete one for $20 or less. I paid about $12.50 for mine (and free shipping!!). But you get lots more than just the brake arm. The camshaft is the same "missing spline" unit used on the last 650 plates. This is also still available from Yamaha for about $19. In addition, you'll get one of the camshaft spacer washers ($2.51), 2 brake shoe springs ($3.68 each), and the shoe wear pointer ($4.09). And in my case, there was one more "goodie" to be had - the brake shoes. They fit the TX750 wheel I have, so that's another $30 or so. Do the math and you can get near $100 worth of parts out of this thing. The only item I can't use is the brake plate itself, lol.
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Wow, this was a lot of work and an amazing amount of research and documentation 5twins. What a great resource for the forum.
Thank you for doing this.
We got over 2 feet of snow here last week so I was more than happy to just stay inside where it was warm and fool around with bike stuff, lol. I love finding cheap substitutions for the parts our 650s need. I've managed to source cheap used brake shoes for some of the other wheels I've fooled with (TX750, XS500) but haven't had much luck with the 650. The few models that do use the same shoes are as old as it is so good used shoes are hard to come by.

But, one of those models happens to be the RD350. I discovered recently that this bike was built under license in India for about 10 years, from the mid '80s to the mid '90s. It was very popular and still has a large following there today, and there are several active aftermarket parts suppliers catering to these folks. I ran across these brake shoes and have ordered a set. I'll let you know how they are once I get them. You can't beat the price, that's for sure .....

OK, got a couple little updates. 2M has verified that the measurements I sent him for the XVS650 V-Star brake arm match the original arm on his XS1B. That's good news as it gives us a large pool of cheap, good used ones to scrounge from. And being from such a recent model, ones in good condition are pretty easy to find.

I also received those brake shoes from India. I'm going to have to give them a "thumbs down". They're quite crudely made and are missing an important feature - the locating rib on the front pivots .....


Honestly, I don't know what would hold them from "walking" off the pivots while in use.
...Honestly, I don't know what would hold them from "walking" off the pivots while in use.

Yes, the shoe positioning on the pivot "anchor pin" is very important.
Some brake systems use a retaining washer atop that pin. I suppose something like that could be *engineered* on an XS650 brake plate.

Before:Drum Clean2.jpg

After:Drum Clean2a.jpg
Great stuff 5twins. Very helpful. Especially working on a super high mile bike that has probably been apart many times.
Adding some rear drum info.

Methods to clean up the rear drum, and remove the ridge on the outside edge where the shoes don't rub.


Once the outside ridge is removed, the drum inside diameter can be measured.


The center raised boss of the wheel bearing interferes with getting the ID jaws of a caliper in there, so here's a workable method.

Use a pair of drill bits that are in good shape, no burrs on their shafts. Tape them to the drum inner surface, vertically, directly across from each other.

The tape just holds them in position while they're clamped tightly to the drum walls.

Ensure that the drill bits are directly across from each other, perfectly vertical, and that a straight shank or flute section, not a groove, faces outward.

Now, take a caliper measurement across those two drill bits.

That was my old XS1B hub, showing 180.14mm.
Factory spec is for 180mm.
I'll run it anyway.

A good tutorial on rear drum brake servicing:

Rear backing plate geometries.

The center-to-center spacings of the anchor post, axle, and cam are 72mm.

The brake cam is 12mm thick, on a 14mm shaft.

The anchor post is 15mm diameter, its retaining notch is 12mm diameter.

Since the cam is 12mm thick, and the anchor post's retaining notch is 12mm diameter, any refacing of a brake shoe's expansion pad must be in alignment with the shoe's protruding anchor notch.