The backer / spacer on the brake shaft can be installed backwards, it will make the wheel bind because will push the shoes against the side of the drum
If you come up with a chain tensioner, pls post up what you have come up with. Wouldn’t you put the tensioner on the bottom which is where the slack would be? I have a problem of the chain rubbing on my reinforced swing arm and a tensioner would help eliminate this. Haven’t looked into it in any depth yet.
Might wanna consider taking the existing tensioner off and see what happens. Could be the tension from that along with the new pivot position is setting up a resonate vibration in the chain. Couldn't hurt to try it...I already have one on the bottom, it’s not cutting it though. I’ve heard of people using two. Might try that.
Might wanna consider taking the existing tensioner off and see what happens. Could be the tension from that along with the new pivot position is setting up a resonate vibration in the chain. Couldn't hurt to try it...
The backer / spacer on the brake shaft can be installed backwards, it will make the wheel bind because will push the shoes against the side of the drum
Speaking of which, I measured that built-in spacer in three I have, a '77, '78, and an '80-'83 one. They all measure pretty much the same and seem to match what you found on yours. The spacer sticks out on the inside about 6.5 to just over 7mm, and the overall length of the spacer from the inside edge to the outer face is about 32mm.
I think the main problem with the suspension design is having the pivot point below the bottom run of the chain rather than between top and bottom like normal, that and the distance of the swing arm pivot from the front sprocket
do you find you get a lot of squat/compression of suspension under acceleration?
I'm sure if I could find my compasses and could remember all that stuff about radians and arctans and cosines I could work it out but here goes.
From the picture above you seem to have moved the pivot point of the new "swinging arm" considerably rearward of the pivot point of the old swinging arm. This means that the radius of the circles it describes is much smaller, and the arc of the circle it describes is tighter.
View attachment 172781
This means that as the suspension compresses the arc of the new arrangement departs from the path of the old arrangement and moves inboard.
View attachment 172782
Your chain slack may be coming from the bit I've marked in yellow.
To not have any additional slack introduced as the suspension moves the pivot point would have be the same as the centre of the front sprocket. Obviously, this is difficult to engineer so normally the swing arm pivot point is just kept as close to the sprocket as possible.
Of course, I could be wrong.
I understand why it's doing what it's doing, I'm looking for ways to limit its affect.
I'm not an engineer, and I'm not implying any criticism.The work is outstanding. Far beyond my abilities. Hope you get it sorted.
Dave
Just had a look at the dimple on the splined shaft and mine is pointing the wrong way. Will flip it around once I get the center stand installed. Can I expect a noticeable improvement in the rear braking? Thx for the tip!I don't have a wheel hub apart at the moment to check the internal spacer lengths, but I managed to find that info (or links to it) on the site here. For you, it's sorta good news, bad news. Good news - your internal spacers appear to be correct and OK. Bad news then is they aren't the source of your binding or rubbing .....
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So, it may come down to, as Machine mentioned, the assembly and installation of the brake camshaft and it's funky shaped spacer washer into the brake plate. '74-'79 brake plate castings had a boss below the camshaft hole for an electric brake wear switch. Even though the switch was discontinued about mid '77, the casting remained .....
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On the funky spacer washer used, the top side was cut out for the camshaft to fit down into and the bottom side was dished out on one side to clear the plate casting .....
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That dished out section must face down towards the bottom of the brake plate. One more little thing on the install. This doesn't have anything to do with rubbing but rather best braking operation. The camshaft is not symmetrical, one side of the cam portion extends off center slightly more than the other. This moves one shoe slightly more than the other to compensate for the difference in distance between the shoe pivot point and the contact point of the cam to the shoe. The difference is so small, you can't see it with the naked eye so Yamaha marked the outside end of the shaft with a dot. This dot should be faced in, towards the axle .....
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You've not created a problem. Its a "development opportunity". You think the guy who thought up the points ignition was disappointed by burning points and gave up? Nope, he added a condensor to solve the problem. Bikes don't start easily with static timing. So a doo-dad was added to retard it for start up. Heck, the XS1 has a decompressor. I'd like to have been a fly on the wall at that first test start before the "fix". (BTW - The first time I ever saw the starting cable pull and heard one start on one cylinder I thought it was the coolest thing I'd ever heard. I was hooked.)
You'll sort the problem and you'll be able to say , "The design of the suspension keeps the back end clean but of course I've had to add a chain tensioner top and bottom to take up the slack at full compression."
How cool is that?
sorry! my mistake, I take back what I said about the pivot point, I thought the bolt below it was the pivot, was viewing on my phone while at work, like Dave I’m also not being critical, I”d be to scared to undertake a project like that myself, just trying to put ideas out there that might help, the only thing I can think of is to use a shock with adjustable compression damping, if your current one doesn’t have it that is.
I don't have a wheel hub apart at the moment to check the internal spacer lengths, but I managed to find that info (or links to it) on the site here. For you, it's sorta good news, bad news. Good news - your internal spacers appear to be correct and OK. Bad news then is they aren't the source of your binding or rubbing .....
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So, it may come down to, as Machine mentioned, the assembly and installation of the brake camshaft and it's funky shaped spacer washer into the brake plate. '74-'79 brake plate castings had a boss below the camshaft hole for an electric brake wear switch. Even though the switch was discontinued about mid '77, the casting remained .....
![]()
On the funky spacer washer used, the top side was cut out for the camshaft to fit down into and the bottom side was dished out on one side to clear the plate casting .....
![]()
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That dished out section must face down towards the bottom of the brake plate. One more little thing on the install. This doesn't have anything to do with rubbing but rather best braking operation. The camshaft is not symmetrical, one side of the cam portion extends off center slightly more than the other. This moves one shoe slightly more than the other to compensate for the difference in distance between the shoe pivot point and the contact point of the cam to the shoe. The difference is so small, you can't see it with the naked eye so Yamaha marked the outside end of the shaft with a dot. This dot should be faced in, towards the axle .....
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