XS Handling Comparison

[jetmechmarty]

Roy,

With your bike lowered like that, how do you get around a corner? Mine drags pegs easily with stock ride height. I can assure you that the Grizld1 has the short legs you'd expect of someone of his stature.

 

[gggGary]

I'm guessing the average racer went for the early bikes because...........
They were cheap, real cheap. And light no starter to remove. The early engines made a bit more power. and they were cheap.
I would guess Yamaha added the bracing, weight, and bigger diameter forks to make the bike more flexible. Sneaky bastards.

 

[grizld1]

Roy, my SV650 has taller seat height than the XS650 (~32") and doesn't cause problems for me. If you want to get closer to the ground without screwing up the handling, however, there's an easy way to do it. Strip the junk foam off your seat pan and cover it with 1/4" of isolastic gel under 1-1/2" of medium firmness memory foam. The result will get you closer to the ground and be kinder to your glutes as well.

Gary, those 256 motors weren't so cheap for guys who wanted to do more than rack up a streak of DNF's. Small end stretch is a real issue with stock 256 rods.

 

[TwoManyXS1Bs]

Royboy, with your bike vertical, not on a stand, under it's own weight, what is your seat height?

Have you ever ridden a stock XS1 or XS1B?

 

[GreasyC]

It would be interesting to see some pictures of a frame modified for racing. I'm no racer, I can only report my experience riding one old bike which is like I said, terrible forks and shocks but no sign of the mythical hinge in the frame. I've seen that old magazine review that basically claims the thing will go into a deadly tank slapper at anything resembling speed and can only imagine who paid them to say it but it doesn't match my experience. it does fine for a 42 year old bike.

 

[gggGary]

I did a full blown, front wheel hopping off the road side to side tank slapper at speed on a bone stock 71, damn near killed me. That was back in the day. There was a reason for the that big ole damper knob Yamaha put on those bikes.
Full disclosure it was a used bike, It was a spring trip to Florida from Wisconsin, I no longer remember how much crap I had strapped on the back but it was probably quite a bit. If I loosened that knob, the front end would start it's death dance at about 60MPH.
One day "soon" I will have an early bike back on the road, then I'll have a chance to compare a fully sorted early bike back to back with the later chassis.
I talked with an old "early bike" flat track racer, he said the frames were prone to cracking and breaking. Can't remember just where.

 

[Speedthriller]

I would guess Yamaha added the bracing, weight, and bigger diameter forks to make the bike more flexible. Sneaky bastards.

 

[patentgeek]

Resurrecting this thread which has been dormant for 10 years.

I'm putting together plans to build an XS650 equivalenty of a Triumph desert sled. For the chassis I'll probably go with a stock frame (trimming off unnecessary tabs), an early (center axle) XT500 fork with RaceTech internals, and quality rear shocks.

Relative to frame selection, I have a 1970 XS1 frame hanging in my garage, and a friend has offered me a free mid-70's XS650 frame. Numerous internet articles indicate the early 1970-73 frames had worse handling characteristics than the 1974-79 frames, but from what I can tell, there's not much difference in early vs. later frame geometry to explain that. I've also read here that the earlier frames were lighter than later frames, but have not seen any data quantifying that. I understand the triple clamp offset and fork tube diameter changed with the later frames, but I'm focused on frame differences since I'm planning to use an XT500 fork.

I would appreciate any comments as to which frame would be more suitable for my needs.

 

[gggGary]

Early frames were lighter and the neck to engine area was a bit ahem, willowy
Also the rear engine mount to swing arm area was prone to stress cracking if the bike's used hard.
For desert sled I'd vote for the later frame.
Not to mention cough cough XS1 frames, if in decent shape, have value going on for restoration projects.
I've recently put about 4,000 street miles on various XS1s.
They aren't bad just not as stiff as later model frames.

 

[patentgeek]

Early frames were lighter and the neck to engine area was a bit ahem, willowy
Also the rear engine mount to swing arm area was prone to stress cracking if the bike's used hard.
For desert sled I'd vote for the later frame.
Not to mention cough cough XS1 frames, if in decent shape, have value going on for restoration projects.
I've recently put about 4,000 street miles on various XS1s.
They aren't bad just not as stiff as later model frames.

Thanks! So frame geometry is essentially the same? I read something about the 1970-73 swingarms being shorter than the later swingarms?

The later stiffer/stronger frame seems like the way to go given I'm building this bike to bomb through rough roads.

 

[gggGary]

Some of the blame also lay with early forks, the triples had a deeper offset from neck to fork tubes. Narrower also.

the 70-73 neck is about 1/2" shorter top to bottom than the later frames.

 

[patentgeek]

Larger offset moves the tire contact patch forward, thereby reducing trail, resulting in faster steering. Which would exaccerbaate a flexy front end.

I'll have to check the XT500 triple clamp offset to see if it is somewhat close to the later XS650 triple clamps. I believe XT500 forks are 36mm, so could probably bore out a set of later 35mm XS650 triple clamps to fit.