Advance bob weights and springs question?

OK, I've got some spring info for you. The total length appears to be just under 22mm. Length of just the spring coils is about 10mm, they have a diameter of about 5.6mm, and there are 10 of them. The wire diameter or thickness is .75 to .80mm and the hooks on the ends are bent out at 90° to one another. Turns out I also had some from MikesXS. The only difference appears to be the silver color, all the other measurements look to be the same, and they have the same number of coils ......

AdvanceSprings.jpg


AdvanceSprings2.jpg


AdvanceSprings3.jpg


AdvanceSprings4.jpg


AdvanceSprings5.jpg


And the part number shown on the package in the first pic is the correct one for the spring. It wasn't easy to find that. Of all the manuals I've downloaded, only one showed it. Most just shown the advance unit, or "Governor" as they call it, as an "assembly".
 
5twins said:
OK, I've got some spring info for you. The total length appears to be just under 22mm. Length of just the spring coils is about 10mm, they have a diameter of about 5.6mm, and there are 10 of them. The wire diameter or thickness is .75 to .80mm and the hooks on the ends are bent out at 90° to one another. Turns out I also had some from MikesXS. The only difference appears to be the silver color, all the other measurements look to be the same, and they have the same number of coils ......

View attachment 264301

View attachment 264302

View attachment 264303

View attachment 264304

View attachment 264305

And the part number shown on the package in the first pic is the correct one for the spring. It wasn't easy to find that. Of all the manuals I've downloaded, only one showed it. Most just shown the advance unit, or "Governor" as they call it, as an "assembly".
Click to expand...
Thank you so much. I have a spring manufacturer fairly close by. I wonder if they have anything on the shelf?

Looking at the picture, I suspect everyone who sells XS parts is selling the same spring.

Thanks again.
 
Watching your video, it appears your advance unit is assembled incorrectly, not timed right. The way you have it will throw the timing off 180°. The slash mark on the little center disc should point to and align with the slash mark on the backing plate just to the left of the "circle in circle" emblem (yellow arrows below) .....

Correct Advance Install.jpg


On yours, it's pointing in the opposite direction, towards the area of the backing plate with the direction arrow on it. This will throw the timing off 180°, unless the wires coming from the points have been swapped between coils. You'll need to check that. Correctly wired up, the gray wire should run to the top set of points (for the right cylinder) and connect to the right coil. The orange wire should run to the bottom set of points (for the left cylinder) and connect to the left coil .....

650Points3.jpg
 
5twins said:
Watching your video, it appears your advance unit is assembled incorrectly, not timed right. The way you have it will throw the timing off 180°. The slash mark on the little center disc should point to and align with the slash mark on the backing plate just to the left of the "circle in circle" emblem (yellow arrows below) .....

View attachment 264306

On yours, it's pointing in the opposite direction, towards the area of the backing plate with the direction arrow on it. This will throw the timing off 180°, unless the wires coming from the points have been swapped between coils. You'll need to check that. Correctly wired up, the gray wire should run to the top set of points (for the right cylinder) and connect to the right coil. The orange wire should run to the bottom set of points (for the left cylinder) and connect to the left coil .....

View attachment 264307
Click to expand...
Fantastic information. Thank you so much for taking the trouble to do that. What's becoming very apparent now is this motor hasn't run since it has had the at least the top end off. So I'm finding all kinds of things not right. I will give this some careful looking at on Thursday, the next day I have time available.

Oh the fun of bringing a bike without history back from the dead!
 
I did try different springs .Stretching and Cutting .. From a Multi purpose box and tried solder on more metal in the worn slots for the part where the weights connect.
It is doable .measuring and calculating a bit doing the math. Mr 5T has Kindly supplied the dimensions
I gave up ..To risky To much work and in my case it was the service on the rod that was the fault. Boyer solved much
I had poor charging also back then and got Simpler Starting

Looking at your video It looks as new .. A little oil or grease that can take the heat on the pivot posts and the vibrations +heat will make it work
I do believe
Provided the advance rod is actually working as it should Not sure about that . It gets hot up there

But if so I would be surprised if not working perfect after ca 100 -200 km
Jokingly ..No one has accused a twin not vibrating things loose . Be it the fillings in the teeth Ot getting white fingers or a advance unit.
 
Jan_P said:
I did try different springs .Stretching and Cutting .. From a Multi purpose box and tried solder on more metal in the worn slots for the part where the weights connect.
It is doable .measuring and calculating a bit doing the math. Mr 5T has Kindly supplied the dimensions
I gave up ..To risky To much work and in my case it was the service on the rod that was the fault. Boyer solved much
I had poor charging also back then and got Simpler Starting

Looking at your video It looks as new .. A little oil or grease that can take the heat on the pivot posts and the vibrations +heat will make it work
I do believe
Provided the advance rod is actually working as it should Not sure about that . It gets hot up there

But if so I would be surprised if not working perfect after ca 100 -200 km
Jokingly ..No one has accused a twin not vibrating things loose . Be it the fillings in the teeth Ot getting white fingers or a advance unit.
Click to expand...
Thanks, I see nothing wrong with the assembly except one E clip is missing and the springs are too long.

I got a quotation today to manufacture two springs to the details kindly supplied above. 96 GBP plus tax :yikes:
 
While we are on the subject, when I pulled my copper colored weights off, there was a thin little washer between the weight and the post.
I had discovered this when I put one weight down and the washer was on the back of it. I could not find the other washer until 2 days later when it was sitting in the well about 1/4 inch from the spark plug hole. Got lucky on that one and promptly plugged the hole with spare junk plugs.
I put it back that way but never did find an assembly drawing mentioning those washers.
 
Yes, it's a shim and probably also a thrust washer between the weight and the base. They are often lost because folks aren't aware that they're there.
 
And drum roll........... Close enough? I would have to twist the hook ends 45 degree at each end to get the right orientation. But spring is a standard item and can be had ex stock. I think.

Close enough to the above NOS spring?

1000001562.jpg
 
I guess all you can do is try them. It looks like you may have one good original spring but the other is too long, maybe bigger in diameter as well. You might try one of these new springs with the good original. Then maybe try both new springs. The spring rate is the important thing. Too stiff and it won't advance. Too soft and it will advance too early and easily. Only test running will tell you this.
 
5twins said:
I guess all you can do is try them. It looks like you may have one good original spring but the other is too long, maybe bigger in diameter as well. You might try one of these new springs with the good original. Then maybe try both new springs. The spring rate is the important thing. Too stiff and it won't advance. Too soft and it will advance too early and easily. Only test running will tell you this.
Click to expand...
Absolutely. I'll get myself a few of these and see how it goes with a timing light, see if it goes full advance too early or too late. A very mildly tuned engine like this shouldn't be too fussy give or take a few hundred rpm to full advance. Biggest concern for me is to get the bob weights properly retarded at start up. At the moment without pushing them home, they don't fully retard. That's bad news for either kick or electric starting.

Next thing on the list though is take another look at the auto advance assembly and sort out correct installation. The points and coils are wired correctly as per the manual for left and right side.
 
OK, if the points are wired as Yamaha intended then the timing will be 180° off the way you have the advance assembled. Fixing it is pretty simple. Remove the little disc from the advance rod on the advance side, rotate the rod 180°, then re-install the disc. The advance rod has a locating pin sticking out the side of it for the little disc, also one on the points end for the points cam. The problem arises because the hole in the advance rod on the advance side at least, goes all the way through. That means you can install the locating pin sticking out either side. One is correct, the other is 180° off. The trick is to have both pins facing in the same direction .....

Advance Rod.jpg


Yamaha was also kind enough to include those slash marks on the advance side to aid in getting the proper assembly and timing.
 
5twins said:
OK, if the points are wired as Yamaha intended then the timing will be 180° off the way you have the advance assembled. Fixing it is pretty simple. Remove the little disc from the advance rod on the advance side, rotate the rod 180°, then re-install the disc. The advance rod has a locating pin sticking out the side of it for the little disc, also one on the points end for the points cam. The problem arises because the hole in the advance rod on the advance side at least, goes all the way through. That means you can install the locating pin sticking out either side. One is correct, the other is 180° off. The trick is to have both pins facing in the same direction .....

View attachment 264334

Yamaha was also kind enough to include those slash marks on the advance side to aid in getting the proper assembly and timing.
Click to expand...
Thanks again for taking the time to explain this. I really do have to check every nut and bolt on this bike.
 
There's one more locating pin involved in the set-up and that one is for locking the advance unit to the cam in the right spot to get proper timing. You should probably check that one too while you're at it. There's a hole in the side of the cam for the pin .....

AdvancePinHole2.jpg


Then, on the back of the advance unit, there's a slot to lock onto the pin .....

Advance Pin Notch.jpg


This locks the advance unit to the cam in the right position for proper timing. If the pin is missing, the timing could be anywhere. Also, sometimes the slot gets damaged if the advance unit loosens up on the cam. The slot can get all wallered out and not fit exactly like it should, or in exactly the right spot to get the timing right.
 
5twins said:
Watching your video, it appears your advance unit is assembled incorrectly, not timed right. The way you have it will throw the timing off 180°. The slash mark on the little center disc should point to and align with the slash mark on the backing plate just to the left of the "circle in circle" emblem (yellow arrows below) .....

View attachment 264306

On yours, it's pointing in the opposite direction, towards the area of the backing plate with the direction arrow on it. This will throw the timing off 180°, unless the wires coming from the points have been swapped between coils. You'll need to check that. Correctly wired up, the gray wire should run to the top set of points (for the right cylinder) and connect to the right coil. The orange wire should run to the bottom set of points (for the left cylinder) and connect to the left coil .....

View attachment 264307
Click to expand...
OK. Had a few minutes to look at the auto advance unit on my bike. I have a couple of questions please.

Indeed the marks are not in the correct position on my advance unit.

Question #1 - If I remove the bob weights, can I turn to advance rod 180 degrees and refit the bob weights?

If yes, then happy days.

If no then Question #2 - If I have to remove the centre nut to pull this disc, then it just pulls off? Is the centre nut left hand thread? (If I were designing it I'd make it left hand thread because the camshaft rotation is tending to loosen a right hand thread nut.)

Finally, it appears the Yamaha manual has the auto advance unit it images flipped. The rotation arrows are going the wrong way? See below screenshot.

Thanks.

1000001582.jpg
 
Well, that depends on whether or not both locating pins (for the points cam and the little advance disc) are pointing in the same direction. You'll need to determine that. If yes, then yes, just removing the weights and spinning the advance rod 180° will work. If not then the disc will need to come off, then the rod spun 180°, then the disc put back on. If you look at my first pic in post #23, of the advance unit, you can see the pin slot peeking out from under the nut and lock washer (green arrow). Then if you look at the second pic, of the points plate, you can see the slot peeking out from under the nut and washer on the points cam. But, this doesn't always happen, lol. Sometimes the lock washer covers the pin slot and the only way to locate it is by removing the nut and washer (or at least loosening them up). This seems to happen more so on the points cam side so I mark the top of the cam with a Sharpie so I know where the locating pin is .....

PinSlot.jpg


The threads on both ends of the advance rod are just normal, not reverse (left to loosen, right to tighten). And yes, it looks like Yamaha had the images flipped in that early manual, lol. But at least it seems they got the drawing right.
 
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Good to go I would say. Both keyways are aligned at six o'clock. Just waiting for the new E clips and springs to arrive. Then I'll spin the advance rod 180 degrees, reassemble and use the new clips and springs. Going to degrease and put a spot of low strength Loctite on the advance rod nuts.

For good measure, just ordered new Daiichi points sets. No point going this far and not replacing the points. Already fitted new condensers.

1000001584.jpg


1000001583.jpg
 
Before buttoning things back up, you should probably insure that the bushings in the end of the cam are well greased to keep the advance rod lubed. You can leave the points cam on, just remove the advance disc, and then pull the advance rod out of the cam from the points side (as shown in the last factory pic in post #35). Then you'll see the outer bushing in each end of the cam has grooves cut into it's I.D. These are to retain grease and keep the advance rod lubed .....

GreaseGrooves.jpg


Clean out any old grease and pack them full of fresh stuff. The factory recommends a moly grease of some sort .....

GreaseGroovesFilled.jpg


Greasing the advance rod is a maintenance item but none of the manuals mention it. Granted, it needn't be done often, like maybe every 5 to 6 years, but it does need doing from time to time. The problem is most of these bikes haven't had it done since the bike left the factory. Now that the bike is over 40 years old, it's long overdue.
 
5twins said:
Before buttoning things back up, you should probably insure that the bushings in the end of the cam are well greased to keep the advance rod lubed. You can leave the points cam on, just remove the advance disc, and then pull the advance rod out of the cam from the points side (as shown in the last factory pic in post #35). Then you'll see the outer bushing in each end of the cam has grooves cut into it's I.D. These are to retain grease and keep the advance rod lubed .....

View attachment 264476

Clean out any old grease and pack them full of fresh stuff. The factory recommends a moly grease of some sort .....

View attachment 264477

Greasing the advance rod is a maintenance item but none of the manuals mention it. Granted, it needn't be done often, like maybe every 5 to 6 years, but it does need doing from time to time. The problem is most of these bikes haven't had it done since the bike left the factory. Now that the bike is over 40 years old, it's long overdue.
Click to expand...
I agree. It would be daft to go this far and not do that. I was completely unaware of that re-lubricating job.

This thread has been absolutely invaluable. Thank you to those who have contributed and a special thanks to @5twins .

Without this thread, I'd have been posting about why everything seemed good but the engine wouldn't fire! I think I've now got half a chance of it starting.
 
Advance rod removed and inspected for lubricant. Very clean but bone dry so I'm very grateful for the suggestion to remove and grease it. Reassembled with plenty of grease where it matters, turned so it's timed properly and the nuts fitted with a spot of low strength Loctite as insurance against them falling off. All is well now until the new E clips and springs arrive.

:)

1000001596.jpg
 

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