Different set of points

[motorbikerx]

Found a couple of new sets of XS650 points that Ive had for years today.
Decided to fit them but halfway through the job I find theyre slightly different as in when theyre in place only half of the locating screws hole is visible!
Must be slightly different points in a 79 Special?
Last 650 I had was a TX650 and they may have been the spares for it.
Anyway gonna mark where metal needs removing to gain adjustability the die grind some clearance I guess.

 

[motorbikerx]

Got around the problem of the lower timing plate screw hole thread being stripped as the thread goes further before becoming blind so I cleaned up the threads and sourced slightly longer allen bolts to use the unused portion of thread...seems to work ok .
Just gotta make these points fit now.

 

[TwoManyXS1Bs]

I was looking at some XS650 points offerings a couple days ago, and also saw the unusually large screwhole on the aftermarket points. The points on the left in your pic have the Yamaha logo, OEM points. Good heads up. Those points on the right would cause problems.

On your other screw fixes, you'll want to ensure that the screws don't protrude beyond the backside surface. Otherwise, the points plate may not seat fully...

 

[motorbikerx]

Timing plate screws are 3mm off bottoming out so they work great
Points on left are genuine yes but they needed the location/adjustment slot die grinding out to the size of the set on the right so I could fit them.
All good now, static timed ok then went to timing light...too much advance at full though.
So Ive set idle timing right on the F mark and JB welded a couple of bits of thin metal plate to the inside of the stops to restrict full advance (as recomended here instead of risking breaking the stops by bending)
Will test full advance later when I get home and if it needs another bit JB'd then I will till full advance is on the mark.
Getting close to roadworthy now

 

[5twins]

It's a little known fact, but there were 2 different points sets and 2 different timing plates used on these bikes. There were the early versions, used up through 1973, then the later versions from 1974 on. The location of the points mounting screws was changed slightly and that required the hole in the points set to be changed as well. I don't know why Yamaha made these changes.

The points set on the left in your pic, the one with the smaller oval mounting hole, is an early set. It's part number was 256-81621-10. It will only fit on the early points plate. If it is left over from way back when you owned a TX650, that would make sense. The 1973 TX650 would have been the last year with the early points plate .....

The points set on the right in your pic, the one with the larger sort of diamond shaped mounting hole, is a later set. It's part number was changed slightly (last digit) to 256-81621-11. This set will retrofit and work on the early point plate. It is the only points set Yamaha lists now .....

The early points plate was part #256-81620-10. In 1974, the new replacement was part #447-81620-10. As with the points, this is all that is listed now. Apparently, if you needed a points plate for your '73 or older machine, you were supposed to retrofit the newer plate.

If you're shopping eBay for points, it's important to know the difference between the early and late sets. Many of the early ones still pop up there. That's how I discovered the difference. I scored some N.O.S. points dirt cheap only to discover they wouldn't fit, lol. They were the early version with the small oval mounting hole and part # ending in "10".

 

[motorbikerx]

They will fit with the Mbx mod
Send em over to me if ya like
A few mins carefull die grinding and they fit!
Go easy on the JBing metal to the advance stops but cos a midnight startup verified I went too far!
Now not getting full advance.
Ill get my mini cutoff wheel in there later today and grind em back to perfection

 

[TwoManyXS1Bs]

It's a little known fact, but there were 2 different points sets and 2 different timing plates used on these bikes. There were the early versions, used up through 1973, then the later versions from 1974 on...

Great info, 5twins! I never knew.
Picked up some points plates a few years ago, now gotta check them...

 

[5twins]

I thought this might interest you 2M, and I'm kinda surprised you weren't aware of it already. I've never compared an early and late plate to each other, but that's what probably needs to be done to discern the small changes made. I have been looking at pics of the backs of the plates on eBay though. The most readily apparent difference appears to be in the size of the clearance hole around the half plate's point set mounting screw. It's much larger on the early plate .....

If you look closely at the relationship between the points set pivot pin and it's mounting screw on the left side of the plate, you can see a slight difference there too. They appear to be a little farther apart on the later plate.

 

[motorbikerx]

Go easy on the JBing metal to the advance stops but cos a midnight startup verified I went too far!
Now not getting full advance.
Ill get my mini cutoff wheel in there later today and grind em back to perfection

Had to remove the C-clips ,weights and springs to get my mini cutoff wheel in there and carefully remove some of the .8mm thin plate I'd JB'd to the stops.
Still not enough though as I'm a little off full advance still , roughly 3mm,
I think if I bring the idle advance up to its max that it'll then give me full total advance.
Those C-clips are a bastard but, was worried about losing em to that strange place small parts go when they dissapear without a trace.
Careful holding while prying off did the trick though and theres tiny thin washers behind the weights too!
Grinded as much as I guessed I'd need off the stops then careful reasembly.
Tiny dab of moly grease on each pivot post.
C-clips lost tension but when pushed back on and wouldn't stay put so careful squeezing together with pliers restored them....I hope!
Put chrome cover back on to catch bits that could fly off just in case!.
Test run went ok though and nothing flew apart.....
Fine tuning of advance later today...

 

[FLEA]

thanks its good to know ,especially that the late model points will fit the earlier models , have got 73 tx and a 74 xs projects for the future and no doult could be doing a bit of cannibalising in the process

 

[weaselbeak]

"Must be slightly different points in a 79 Special?"

points still used in 79?

 

[motorbikerx]

"Must be slightly different points in a 79 Special?"

points still used in 79?

Yep...in Australia at least...good ol contact points.

 

[5twins]

Yes, 1979 was the last year for points, at least in the U.S. They may have hung around for another year or 2 in other markets.

 

[gggGary]

It was all kinda new to me but they are saying only TWO types early up to 73, and late; 74 til they went electronic in 80
Yet another 256 447 motor parts change for the list.

 

[motorbikerx]

Should I fit new C-clips or ya reckon theyll hold?....held for a few minutes so far

 

[5twins]

Yes, 2 versions, '70 to '73 then '74-on. I'm surprised Yamaha didn't issue a tech bulletin on this, it qualifies as a perfect candidate. Or maybe they did but it's been lost over the years.

 

[5twins]

I keep a big bag of the advance circlips on hand. Besides zinging off into never never land, they often break in half when you remove them. I've needed to dip into my "stash" bag several times already, lol .....

 

[motorbikerx]

Are they likely to fly off if reused?
Should they be a one use item or have you succesfully crimped em back up?

 

[gggGary]

I've recrimped and used, haven't lost one yet. Think I've crimped down a bigger one from "something else" in a pinch too.

 

[TwoManyXS1Bs]

I thought this might interest you 2M, and I'm kinda surprised you weren't aware of it already...

Lemme see here,
Old dog, ..........check
New tricks, ..........check

Sure 'nuff, this definitely got my attention.

...I've never compared an early and late plate to each other, but that's what probably needs to be done to discern the small changes made...

...The most readily apparent difference appears to be in the size of the clearance hole around the half plate's point set mounting screw...

...If you look closely at the relationship between the points set pivot pin and it's mounting screw on the left side of the plate, you can see a slight difference there too. They appear to be a little farther apart on the later plate.

Yes, I see that now. Good eye.
Checked my new, unwrapped points, genuine Hitachi, later model with the larger hole. My other points and plates stash is buried, will dig them out sometime and check. Yup, a future research project...