Fork Swapping

[Its been a long time]

Frame neck
View attachment 257139

stems with a tape measure
View attachment 257140View attachment 257141
All I had in the files.

Thanks for that. Appreciated.

I can at least size the inner and outer bearing sizes off the stem I have. Then it's a question of stem length. And that will have to wait until I drop the Yamaha yokes out.

The depth in the frame neck where the outer cups go is very narrow width. 5 and 7.5mm. Not a lot of support for the outer bearing race cups.

 

[Its been a long time]

Just measured the Bonneville bottom yoke and it's 185mm from the top surface of the bottom yoke to the underside of the first adjustment nut. Seems to me if the Yamaha head tube is ~189mm tall, then I'm a few mm short of a drop in item on the Bonneville stem. Bonneville taper head bearings sizes 26x47x15mm 30x55x18mm.

It looks like the All Balls fork swap database is correct for conversion bearings. The lack of depth in the Yamaha bearing outside diameter locations though is going to leave the outside bearing race unsupported for about half it's depth, the top bearing specified by All Balls has a 14mm wide outer race and the bottom one a 12mm wide. Close but no cigar on this occasion, I think.

 

[gggGary]

Yes the all balls races end up quite a bit proud of the bearing retainer bores but it hasn't been an issue on hundreds, or thousands of XS650's converted to tapered rollers.
I'll see if I can get a stem measurement done today.
@jetmechmarty ??

 

[Its been a long time]

Yes the all balls races end up quite a bit proud of the bearing retainer bores but it hasn't been an issue on hundreds, or thousands of XS650's converted to tapered rollers.
I'll see if I can get a stem measurement done today.
@jetmechmarty ??

Point taken. I'll not over think that one. Thanks for your assistance, it's appreciated.

 

[jetmechmarty]

I'll see if I can get a stem measurement done today.
@jetmechmarty ??

I would, but I’m not at home today.

 

[Its been a long time]

I would, but I’m not at home today.

Thanks anyway. There's nothing spoiling on this. I need to sort out the stock front end then I'm in a position to buy a set of conversion bearings and offer up the Triumph yokes. It'll be an interesting exercise. And if it works it without too much trouble, it's a modern front end option with a 70's vibe.

 

[jetmechmarty]

Thanks anyway. There's nothing spoiling on this. I need to sort out the stock front end then I'm in a position to buy a set of conversion bearings and offer up the Triumph yokes. It'll be an interesting exercise. And if it works it without too much trouble, it's a modern front end option with a 70's vibe.

Sportster has been done. I understand that offers a lot of brake options.

 

[Its been a long time]

Sportster has been done. I understand that offers a lot of brake options.

Thanks. I already have the complete 38mm fork, twin disc front end ready to bolt in. It was going to be fitted to a Bonneville but that's going to be sold. Hence wondering about the XS650. I think I'll be able to work it out. Worst case is pressing the Triumph stem out and making a copy of the XS650 stem adapted to the Triumph top yoke. Bolting the Yamaha clocks on to the top yoke etc is small beer. The Yamaha handle bar risers will bolt into the Triumph rubber mount bushes with minimal attention.

It'll be a while before I do it. But it'll get done.

 

[gggGary]

Measurements; this should be consistent within production tolerances from 1974 to end of production.

I'll clean this image up and repost it when I've got that done. (don't hold your breath....)

It appears the stem is drawn to reduce diameter at about 217mm and a threaded bung is inserted and welded in place at the top for the top fixing bolt.
When removing bottom race; prize out and save the rubber seal first, it is quite pliable and will stretch to remove over the race.
Reinstall this seal not the all balls seal, after the new race is in.


Once that is done the bearing race can easily be tapped off.

 

[Its been a long time]

Measurements; this should be consistent within production tolerances from 1974 to end of production.
View attachment 257193
I'll clean this image up and repost it when I've got that done. (don't hold your breath....)
View attachment 257187
It appears the stem is drawn to reduce diameter at about 217mm and a threaded bung is inserted and welded in place at the top for the top fixing bolt.
When removing bottom race; prize out and save the rubber seal first, it is quite pliable and will stretch to remove over the race.
Reinstall this seal not the all balls seal, after the new race is in.

View attachment 257189
Once that is done the bearing race can easily be tapped off.
View attachment 257190

Thanks, that's really helpful.

 

[Wingedwheel]

Yes the all balls races end up quite a bit proud of the bearing retainer bores

About the only issue I encountered was it makes the headlight bucket ears loose. Easily fixed with a large o-ring.

 

[Wingedwheel]

Looking through all the parts manuals they vary from site to site. All I’m trying to find out is will a set of inner fork tubes from a ‘73 TX650 work with the internals on a ‘75?

 

[nj1639]

Regarding a stem swap.
Some years ago I swapped the stem on my '83 to take a set of '77 xs750 forks. The base of the stem on the XS650 arises from a 3mm machined platform in the lower triple. That platform had to be built onto the xs750 lower triple, which had none, to work with the xs650 bearings.
FWIW