Engine, Rake and Trail

acebars

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I read on this forum somewhere (but can no longer find it) that the rake and trail of an XS-1 and XS-2 is steeper than that of the later models post '72?

Also read that the engine power of the XS-1, XS-2 and first TX650 are superior to that of the later models after '73 producing more bhp, due to internal changes?

I've searched the net high and low for specific year on year changes to the XS650 to no avail.

Could anyone tell me a little bit about the years above and if this is correct?
 
Acebars,
From the Clymer Manual page157. XS2,TX650 and TX650A
Trail 3.9in (101mm)
Caster 63degrees

From page161 1975- Early 1978
Trail 3.9in (101mm)
Caster 63degrees

From page 162 1978(Late) XS650E,SE
Caster 27 degrees
Trail 4.53in (115mm)

The upper rear shock mounts were moved at some stage in the model run. Specials have a smaller rear wheel, these changes probably account for the change in trail.

I have read that the earlier cams have a wider lobe centres giving a more desirable power delivery, but do some more research as the number of teeth on the drive sprocket differs on some models.

The Australian XS650 Club website has some good info on model numbers and variation.
 
Not a longer stroke. Early (256) engines had slightly longer rods, and a bit more aggressive cam grind.
 
So the caster of the early bikes is in fact the same until the 78 models?

I'm a bit wary of the Clymer data, as a lot of it was wrong for my CB500t and CB450 including caster angles.

My Honda workshop manual cleared a lot of that up.
 
The Specials used shorter rear shock absorbers which affect the trail. First Specials were 1978 model. I also believe the 16" rear tire on Specials is nominally close to the same overall diameter as an 18" rear, but the width definitely affects handling.
If you use longer rear shocks, you affect the rake & trail, reducing it I believe, the effect being a quickening in the steering. That is why trackers usually use longer rear shocks.
 
Okie, thats not really what I'm on about, I'm talking about actual caster angles on the frames, and specific engine changes year by year.
 
You can kinda clump the models into 2-year groupings (like 1st year changes, 2nd year tweaks).
70-71 72-73 74-75 76-77 78-79 80-on.
Pouring thru my books, none of which are completely accurate, I came across an XS650B road test, which reports the major frame change of new 63.5° steeper head angle and 1.5" longer swingarm. This came from: "Yamaha XS-650 Performance Portfolio 1969-1985, Brooklands books, Surrey, England" (still available).
 
Just though I might add I've just bought '73 TX650! :D Other than the electric start I understand the engine internals and cams etc. are the same as an XS-1 and XS-2?
 
Yeah, pretty much 256 except for 306 parts, like starter gears cut into the crank, nubs added to the rockers for the compression release, 6-bolt tensioner and different lower camchain guide. And something else posted on this forum recently, lead plugs fitted into the right flywheel, the one with the gear cuts, possibly part of a vibration reduction mod mentioned in old rider tests.

Also, I understand the head and camcovers were changed. Thicker fins, no noise isolation buttons between fins, slightly different ports.
 
Yeah, pretty much 256 except for 306 parts, like starter gears cut into the crank, nubs added to the rockers for the compression release, 6-bolt tensioner and different lower camchain guide. And something else posted on this forum recently, lead plugs fitted into the right flywheel, the one with the gear cuts, possibly part of a vibration reduction mod mentioned in old rider tests.

Also, I understand the head and camcovers were changed. Thicker fins, no noise isolation buttons between fins, slightly different ports.

I'm having difficulty finding info on the engine on this forum, forgive me if my searching skill are no good!

Does the TX650 produce the same bhp as the XS-1, XS-2? I understand the later cams are more relaxed and the later engines don't have as high a compression ratio etc. overall is it an improvement on the earlier engines?
 
There's several subtle differences that occurred over the years, nothing dramatic performance-wise. That book I mentioned earlier goes into much more detail than can be posted here. I believe the biggest difference, performance-wise, is in the gradual weight increases over the years, with the early XS's at just over 400 lbs, to nearly 490 lbs with the final models...
 
I did read somewhere that the compression was slightly reduced on the TX650 compared to the earlier models, just trying to ascertain what exactly is in the TX650 engine compared to an XS-1!
 
The original XS1 had a chamber volume of 42.2cc, giving a compression ratio of 8.7:1
In mid `71, starting with XS1B s/n 23130, the piston crown was lowered 1.2mm, increasing chamber volume to 47.2cc, reducing compression ratio to 8.1:1
Published power rating remained at 53 bhp for all models.

There is a 70-73 service manual reprint, which includes model supplements and bulletins, available from Bear Motorsports on eBay. The above info comes from that manual, bulletin #313. They also have the previously mentioned brit publication.
 
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