Restifying My '72 XS2

Huszarail

Huszarail

XS650 Enthusiast
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Droitwich Worcssestershire U.K.
During the restoration of my XS2 I would like to encorporate some later Yamaha conponents and make some mods to assist with the rideability and reliability of the bike.

So, would there be any mileage in replacing the '72 electric starter with one for a later model? As the later bikes deleted the decompression lever, is the starter more powerful?

Clutch. Any opinions in fitting a later clutch assembly? Pre'79 or '80 on? How about clutch pushrod? retain the one piece (if that's the one I've got, the bike's not been stripped) or use the companion later push rod and engine lever?

I plan to fit progressive springs to the forks and I notice 34mm valve emulators are available from race tech, worth the investment?

Taper roller head bearings and broze swing arm bushings naturally.

How about frame and front fork bracing? I'd like to make a fork brace that fits under the fender. Perhaps a thick, hardened sheet metal affair rather than the bar style over the top. A brace between the down tubes to fill in between the motor mount brackets. A bit like the later style motor mount but less obvious.
Any thoughts how to brace the swing arm mount 'invisibly'?

I'd like to build the bike as if Yamaha had the benefit of 20-20 hindsight and a few more years of R & D.

Thanks in advance for all your comments.

Mark.
 
Highly suggest spliting the cases then and putting in the 5th gear od. Thats probably the biggest one on yamahas part imho. Close ratio trans on a big 4 stroke.....great idea.....
 
This caught my eye awhile back. Another member added cross-bracing between the downtube and swingarm pivot zones. In addition to other 'stiffening' mods and bronze swingarm bushings, supposed to reduce that 'hinging' feeling.
 

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CDNTX650 said:
Highly suggest spliting the cases then and putting in the 5th gear od. Thats probably the biggest one on yamahas part imho. Close ratio trans on a big 4 stroke.....great idea.....
Click to expand...
I do not think the 5th gear will work for the early trans. Check the details.
 
Easy fix, buy the whole gearctluster. You dont need to change both sets, only the one with the gear you need to replace. Just did it in my new engine. One set is a 78, one a 74. You just cant put new style gears on old style shafts and vice versa. But sets themselves whether old or new mesh fine.
 
Mikes650 has a OD 5th for 256 engine now.
 
So the strip down went well but had to strip down the motor to free off the cylinders. The ring pack was stuck fast on one cylinder and a build up of compacted blacky carbon rain from the head prevented any of the freeing fluids reaching their intended victim.
All done now though and the bores cleaned up nicely with a hone.
Considering now refurbing the starter motor.
I have two, the original '72 XS2 one and one from a spare 447 motor.
My question to the forum oracles which is a beter candidate for re-build? Any difference in power between the two as one used the decompressor and the later did not have decompressor assistance?
Your advice, as ever is priceless.

Mark.
 
The XS2 306 motor is complete, now free with NOS pistons, rings and pins. The 447 motor is a parts lump needing pistons and is an unknown quantity regards condition.
So I thinnk I'll pull both starters down and overhaul and fit the best one.
The fantasy is to build a 447 re-phase from the ground up, but that's just fantasy as I said.
 
On the starter I think the big improvement was a stronger battery. If you have a choise between the 256 or 447 starter use the 447 it may be stronger.
On the fender. On my 75 the built in bracing is very heavy. If you have your stock fender get a 74/75 fender to compare the bracing.
In 74 the did many things to help improve the handling, adding stronger and more bracing was most of it. If you can find pics or a diagram of an early and a 74 up frame you can see the changes.
The early frames had very little bracing across the frame at the upper shock mounts. The later have much more.
On the forks springs I like a straight rate spring. Start out with the Minton Mods on the stock dampers, this help a lot. If that improves things your not out much money. You can always add emulators later.
Using the 6 inches down method of oil filling works well. Trying different oils and weights might help.
Leo
 
Thanks XSLeo. I'll follow up your leads.
I've completed the swing arm mount brace as in TWOMANYXS's post above.
I'll look into beefing up the upper shock mounts too.
Can you educate me on the straight rate/progressive rate spring arguement?
Mark.
 
A straight rate spring compresses at the same rate weather going over big bumps or small bumps. This makes the bike ride about the same over most any size bump.
Progressive springs increase the rate as bumps get larger. Small bumps easy ride bigger bumps the springs get stiffer, ride gets harsher. Sounds kinda backwards too me.
Wouldn't it be better if on bigger bumps the spring rate could decrease not increase? That way the front end could compress more easily over big bumps. Wouldn't that improve the ride?
Alas, springs can't be made that way. Straight rate is the closest we can get.
Damper rod action has a more pronounced effect on the ride than the springs.
I did some experimenting with the forks on the 75. Several weights of oil for starters. The stock springs are a bit progressing, hence the tighter wound coils on the one end.
I got straight rate springs and Minton mods. I have a couple sets of forks to mix and match parts. So far the best ride and handling comes from the straight rate springs, Minton Mods, And ATF.
The ride is firm, some may say sporty. I feel much more confident in the bikes abilities.
Leo
 
Thanks for the explation Leo.
Would the Minton damper rod mods reduce the fork dive under braking?
I've heard folks put reduction in diving down to progressive springs but from your explanation that would only be due to the increasing spring rate and if the road surface had lumps and bumps any shock loading of the front end would be amplified by the increased spring rate. Not good for assured even braking or handling eh?
Have I just answered my own question?
A thought on ATF that crosses my mind.
ATF contains friction modifiers to help automatic transmission clutches grip does it not? I can't see this being a good thing when ATF is used in forks.
Ever considered using a power steering fluid? Not the do all trans/steering stuff but dedicated fluid for power steering. That would not have the friction modifiers of trans fluid? It's not keeping me awake at night but I'd be interested in someone elses take on it.
 

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