XS400 parts on an XS650: Will it work?

[Wharfcreek]

I've had a '79 XS650 sitting out in my driveway for the past few years; a 'project' bike that someone has done some significant frame modifications to. As the bike sits, it's basically just an engine in a frame cradle, with the swing arm still intact, but the upper rear section has been hacked off and the rear upper shock mounts have been re-welded to the down-tube area of the frame. I'm sure pics would help, and I'll try to get some, but in the meantime, hopefully my questions here can get addressed.

So while surfing my local facebook marketplace ads, I came across an ad for a rolling XS frame, complete with a front end, mag wheels, and what appeared to be a rear disc brake swing arm. For $100, I jumped on it thinking that if nothing else, the front end would go on my '79 frame and I could go from there. Unfortunately, I wasn't able to make the trip up to go gather this up and bring it home due to having come down 'positive' for Covid. So, I enlisted the help of my girlfriend's son, who for another $100 made the trip a State away to drag the thing home for me. When it got here he parked my truck and headed home so he'd avoid any contact with me or Covid. So, I dragged the frame out of my truck and immeadiately noted some 'differences'. The short story is: It's an XS400, not a 650.

Now faced with this reality, the question is: How much (if any) of this will work on my 650 frame? I know that in swapping swing arms to get the rear disc set-up that my brake lever would have to be modified and a master cylinder installed. But, will those 400 wheels work, or are they actually 'smaller' than the 650 wheels? And, what about the front end? Assuming that nothing else will work, does anyone know if the front end off the 400 is basically the same as the 650, and if it will 'interchange' without any major problems?

Any help with this would be greatly appreciated, and many thanks!!

Tom D.

 

[jetmechmarty]

If that's a 19" front wheel, it swaps. Sell the whole mess. An XS650 frame will come up.

 

[Wharfcreek]

It's an 18" ft wheel! I figured it would work, but it was more the rear swing arm w/ the disc set-up that I was wondering about. But, maybe you're right! Just sell the whole lot of it and be done with it!

 

[Jim]

I've owned several XS400's. I think you'll find that very little swaps to a 650.

 

[jetmechmarty]

It's an 18" ft wheel!

If the XS650 brake rotor fits, an 18 inch wheel will turn in faster than the 19 inch. I say that not knowing what you ultimately want the bike to be.

 

[Wharfcreek]

Well, I've got $225 plus a tank of gas ($80) in it. So, $300 give or take. It was probably a bad decision, but at this point I've got little left to lose if I at least give a shot at swapping the front end on to the 650 frame. If that doesn't work, then I guess I'll just put it back on the 400 frame and let it all go for what ever I can get out of it. Too bad........ it was a good plan, just badly implemented. I guess being down with Covid affected my judgement and I just got 'hasty'! My bad, and my loss. At this point I still have the '79 frame (w/ title) and engine. Just a shame that someone 'chopped' the back part off. They also chopped off the original tank mounts, coil mounts, and modded the rear shock mounts. BUT.... they at least did 'hard-tail' it!! So, 'salvageable' at some level. I'm not much of the 'bobber' craze, but I can dig a good 'rat' bike...... so I think that will be this bike's destiny. That being the case, if the front end from the 400 'does' fit, then 18" wheel, 19" wheel..... I don't think that will really matter. I was hoping for the rear disc set-up. That was the objective. I may still try the 400 swing arm in the 650 frame just to see how far off it is. But, even if I can figure out a way to install it, I still have the issue of no 'master cylinder' set-up on the brake pedal. So.... maybe best to just find some stock 650 drum brake wheels and be done with it!!

 

[MarkL]

Well, I've got $225 plus a tank of gas ($80) in it. So, $300 give or take. It was probably a bad decision, but at this point I've got little left to lose if I at least give a shot at swapping the front end on to the 650 frame. If that doesn't work, then I guess I'll just put it back on the 400 frame and let it all go for what ever I can get out of it. Too bad........ it was a good plan, just badly implemented. I guess being down with Covid affected my judgement and I just got 'hasty'! My bad, and my loss. At this point I still have the '79 frame (w/ title) and engine. Just a shame that someone 'chopped' the back part off. They also chopped off the original tank mounts, coil mounts, and modded the rear shock mounts. BUT.... they at least did 'hard-tail' it!! So, 'salvageable' at some level. I'm not much of the 'bobber' craze, but I can dig a good 'rat' bike...... so I think that will be this bike's destiny. That being the case, if the front end from the 400 'does' fit, then 18" wheel, 19" wheel..... I don't think that will really matter. I was hoping for the rear disc set-up. That was the objective. I may still try the 400 swing arm in the 650 frame just to see how far off it is. But, even if I can figure out a way to install it, I still have the issue of no 'master cylinder' set-up on the brake pedal. So.... maybe best to just find some stock 650 drum brake wheels and be done with it!!

What are the dimensions written on the wheels? And are the cast wheels tubeless?
Mark