75 vs 79

[yamageek]

I recently bought a 75 XS and this a.m. I picked up a 79 parts bike. I am considering swapping out the 75 spoke wheels for the disc front and rear mags off the 79. Question is will the needle bearing swingarm kit for the 75 work for the 79. I'm assuming there are difference between the disc swingarm and the drum but am pretty much ignorant about these things. Same question for front wheel. Can I just swap mag wheel into existing 75 forks . I'm changing neck bearings to tapered so not a big deal but as they say a little knowledge is a dangerous thing. Thanks in advance for any advice.
George

 

[Jim]

Question is will the needle bearing swingarm kit for the 75 work for the 79 (?).

I'm not the expert here... but yeah, pretty sure both yrs are the same. You'll need to swap the swingarms 'cause the brake stay mount is different 'tween the disk and drum setup.

Can I just swap mag wheel into existing 75 forks (?).

Don't think so. 75 had 34mm fork tubes and 79 had 35mm. Also... the caliper mounting is different on those yrs. You'd prolly have to swap the whole front end.

 

[gggGary]

It's generally felt that swing arm pivot is not a good place for needle bearings. That being said one of my bikes has an allballs needle bearing kit in it and is fine so far. and yes one kit fits all 74 up XS650.

Front wheel; just the rotor needs to be from the 75, the rest of the wheel is plug and play.

 

[yamageek]

Thanks for the input guys.
gggGary Do you know what the perceived shortcoming of swingarm needles are?

 

[gggGary]

needles in short movement applications tend to dent the race and flatten the needles, a lot like ball bearing neck bearings.

 

[yamageek]

OK Makes sense. Sounds like bronze bushings are the way to go.
Thanks

 

[fredintoon]

I recently bought a 75 XS and this a.m. I picked up a 79 parts bike. I am considering swapping out the 75 spoke wheels for the disc front and rear mags off the 79. Question is will the needle bearing swingarm kit for the 75 work for the 79. I'm assuming there are difference between the disc swingarm and the drum but am pretty much ignorant about these things. Same question for front wheel. Can I just swap mag wheel into existing 75 forks . I'm changing neck bearings to tapered so not a big deal but as they say a little knowledge is a dangerous thing. Thanks in advance for any advice.
George

Hi George and welcome,
both wheels will swap.
Front artillery wheel needs the wire wheel disk.
(Or swap the entire front end to get the '79's 35mm fork tubes & use the "search" box to find post '76 brake upgrades)
Rear artillery wheel needs an extra tab welded onto the swingarm (easy to do) and master cylinder hardpoints welded onto the frame (not so easy)
(note that the artillery wheel is a 130/90-16 vs the wire wheel's 110/90-18 and will stodgy up the handling just a bit)
Like they said, don't put needle rollers in the swingarm bearing. Bronze bushes are better.
OK then! Put the '75 engine into the '79 frame. It'll be easier.

 

[yamageek]

Fredintoon
Thanks for the input. Can't do the engine swap as there is no title for the 79.
Just to be clear. Could I use the 79 forks with the 75 spoke wheel without mods? I did see somewhere on here that stem were different on different years. Is that an issue here? Sorry to be so dense but these bikes are all new to me.
Edit I found the thread in the tech section about head bearing swap. According to that thread 75 and 79 necks are same length. Guess that just leaves question of width of spoke wheel vs mag.

 

[fredintoon]

Fredintoon
Thanks for the input. Can't do the engine swap as there is no title for the 79.
Just to be clear. Could I use the 79 forks with the 75 spoke wheel without mods? I did see somewhere on here that stem were different on different years. Is that an issue here? Sorry to be so dense but these bikes are all new to me.
Edit I found the thread in the tech section about head bearing swap. According to that thread 75 and 79 necks are same length. Guess that just leaves question of width of spoke wheel vs mag.

Hi George,
tried to title the '79 frame?
Yes, a '75 wire-spoked wheel will fit into '79 forks. BTDT.
I put '75 wire wheels on my '84 but found them a bitch to keep clean so swapped back to stock.
You will need to remove the '75 wheel's 2-piece brake disk and replace it with the cast wheel's one-piece
brake disk because the disks are dished differently so that the '75 disk will not line up with the '79's brake caliper.

 

[XSLeo]

I would stick to the Spoke wheels. Much lighter.
As for adding a disc rear brake, it's more work than it's worth. If the 79 has the disc rear, keep it there.
I put a disc rear brake on my 75. It was a lot of work getting the master cylinder mounted in the right place. As far as the pedal goes they are the same. Everything the pedal hooks to back you need to change.
Rearranging the pedal stop takes some work too. The drum stop is vertical , the disc is more horizontal.
I also swapped my 75 forks over to the 35 mm forks. Easy swap. Use the complete 79 front end on the 75. It's a straight up bolt on. Use the 75 front wheel with the 79 brake rotor.
A bit of work on the forks. Try a bit more oil in the forks. 7.5 ozs. Or the 6 inches down method. The more oil helps decrease brake dive.
If you have good paper on the 79, get it road worthy then compare the way both bikes perform.
Always nice to have more than one to ride. Have one set up for around town 2 lane back road romping. One for more laid back cruising.
Leo

 

[5twins]

If you want to do a mag swap, easiest solution for the rear would be to find an '81 drum rear mag.

 

[yamageek]

5twins
Yes I see one on Epay but its over 200.00 without the guts. I only paid 250 for the complete parts bike
I would like to have some beer money left when I'm done. I will keep my eyes open though.

 

[5twins]

Yes, it's sort of a rare wheel because it only came on the '81 models in the U.S. Canada got it for several years though. All your current "guts" will swap into it (spacers, brake plate).

 

[yamageek]

XSLeo
I don't have any paper on the 79 and I have no idea how difficult it would be to get a new one in NYS. Pre 72 was only a registration and that's usually not much of an issue.
I have a 2001 Kawasaki w650 on the road which I like a lot so the 75 will be an alternate when done. I'm probablty going to do as you suggest re the brakes and front end.
I do wonder how much difference 1 mm can actually make. Seems like thickness of tube wall would be controlling factor. But then I know nuttin about Japanese 2 wheelers.

 

[XSLeo]

The main reason I did the swap was to use the later style brake calipers. Easier to find. Wanted to do the dual disc up front. Used 5 mm thick slotted rotors, about 20% lighter than 7 mm rotors. A bit more with the slots.
The later calipers were single piston alloy. Lighter than the older twin piston calipers.
They do handle better. The tubes are larger. Even with the same sidewall thickness a larger tube is stiffer.
Might have to do some weights on the parts next time I have the wheels off. Rotors, calipers and such. Just to see the difference for unsprung weights.
Leo

 

[5twins]

The '75 is a very classic looking version of this bike. You'll loose some of that (front fender w/stays, instrument cluster) with a newer front end swap. For the type of riding you will most likely do, you probably wouldn't notice much difference between the 34 and 35mm forks. Thoroughly renovate the 34mm forks (slightly more fresh oil, maybe new springs) and I'm betting they'd be fine.

 

[member28833]

Wanted to do the dual disc up front. Used 5 mm thick slotted rotors, about 20% lighter than 7 mm rotors. A bit more with the slots.
The later calipers were single piston alloy.

Curious as to which caliper hanger brackets you used ? XS ?
Thanks -RT

 

[XSLeo]

Yes. Easy to find the right side. The left is a bit tougher.
Like our Xs650's used the right side only, other models used a left side only.
Some used dual sets ups with our calipers.
With a bit of shopping around you can find them. I found most of what I used on Ebay.
Just look very closely. Some dual's used different calipers and rotors than ours.
I used what I did to do it with all Yamaha parts.
The XS1100 standards used our calipers and rotors, specials didn't. They even used different style of forks. I think the same applies to the XS750 and 850's.
Try searching for Yamaha front brake, That's what I did. I made a few mistake purchases. that's how I learned these differences.
On rotors be sure you get the measurement on the diameter. Some used a smaller rotor. Ours are 11 3/4 inches, others can be 10 1/2 inches. this size was used on the rear of the XS650's that had rear disc brakes.
Leo

 

[member28833]

Thanks, Leo!
I too am sampling components and caliper hanger brackets from a few models.
Models which came with 5mm thick discs seem to have hanger brackets with a narrower cast gap for rotor clearance.
Late XS1100 ? XJ650RJ?
Perhaps there is better centering of the caliper with some model hanger brackets vs other model hangers like the XS650 for example which has a wide cast gap to accomodate a 7mm wide disc.
Maybe there are benefits of brake piston positioning in the bore (deeper) if the optimum bracket hangers are identified ?
-R

 

[yamageek]

I gotta say of all the brand specific sites I've seen this has got to be at or near the top. So many choices. I may end up just using the exhaust from the 79 as that's the main reason I bought it in the first place. I have all the parts to refurbish the 75 front end and as as 5 twins said I will likely be satisfied with the smaller forks. I am certainly no canyon carver maybe a valley rambler would be more like it.
Thanks everyone for all the terrific feedback. I'll buy you all a virtual beer.
And in case you don't visit the "Let's see the XS" thread here's my 75. Just the way I bought it.