XS11 back from the brink.

[Orange4]

Aaaannnd... With the magic of the intertubes I found one with the original metal flake orange paint:


Metalflake Wixom Fairing- $40 by bellboy1721, on Flickr

[MaximPhil]

Orange MetalFlake screams 70's
Nice looking fairing.
Phil

[Orange4]

Replacement head apart...

Interesting residue pattern on the intake ports. Looks like line of sight flow to me...



This pattern was the same on all intake ports. Flow seems to have traveled straight from the carbs to the valve and seems to have created turbulence beside the guide boss. I think the soot is from reversion due to the greater timing overlap on these later heads. This may be another clue as to why there are such pronounced lips by the seats. Apparently this helps reduce inversion at low lift.



Looks like the flow went most strongly through the piston wall side of the curtain.



Correct me if I'm wrong. Just learning new stuff.

[CaptonZap]

Probably the reason for the "clean" wall of the seat area is that the flow coming in from the carb has to make a "corner" at the shoulder. That creates turbulence, which imparts a scouring action on the wall just after the shoulder. Think eddy in a stream flow that goes around a rock. The eddy scours the silt from behind the rock, and the eddy in the port does the same for any carbon buildup on the wall in that area.
Some sources say that is a good thing, as it breaks up any condensed fuel drops that have accumulated on the wall, and other say that the energy spent on creating the motion of the mixture in the eddy is not used in charging the cylinder. Pick yer poison.
All of this is my own interpretation of what is going on, so feel free to argue or ignore.
And just to tweak a few noses, peruse this site
http://www.mototuneusa.com/power_news_--_homework.htm

CZ

[Orange4]

Yeah, That all makes sense. Just like a rear window in a car that collects dirt. I have done a bunch of studying on aerodynamics which helps to a point, but Air moving through an object is very different from an object moving through still air. The Reynolds numbers are different too. In thinking about ports and valves there is the charge sequence to deal with and the momentum of the air which is so important. Super interesting stuff though.

Best article I have found so far: http://www.popularhotrodding.com/tec...g/viewall.html

It actually supports some of "Mototune's" Ideas (without all the retina scarring) but I think he's ignoring other aspects of the art like the part about the short side radius. It looks like his port filling increases that radius which may have a lot to do with keeping velocity up as a larger radius encourages attached flow. He also makes it all about smaller ports rather than about overall shape, including size. He sounds like a one trick pony, that's probably why some people scoff. Also: retina scarring.

[CaptonZap]

Interesting article.
Makes a fella wish he had the facilities and backing to experiment with this stuff, ala Sir Harry Ricardo.
In one of my more weird mind scenarios, I tried to figure out how to make a rotating plate valve for a flow bench, so that it would more closely resemble the actual flow behavior through the test object. Variable speed, velocity, etc.
Oh well, next incarnation maybe.

CZ

[Orange4]

Some progress

Hi all,

So I managed to get something done on my project over the last few weeks. I have cleaned up and polished some bits and pieces and flushed the brakes.

I found the matching pistons to the cylinders I bought and they are in great shape. I got the old cylinders off and cleaned the mating surfaces and I took the glaze off the "new" set of cylinders.

I am now making a copper head gasket partly because I'm cheap and partly because It's fun.

Results of some cleanup:



The jugs off. Luckily they came off without too much protest. Those pistons are pretty bagged but the small ends are still tight.



No sign of original surfaces on those skirts. The rings are new though, just as the seller said. Go figure. Ring grooves are pretty loose.



The "new" pistons from an '80 with minimal wear. Old '79's in the background. Now I can keep the compression decent.



Patient awaiting transplant...

[jjz28]

That's a good looking bike man. Seems like you know your stuff so it should be a good one for many years to come.

[Orange4]

Thanks.

It's indecent shape other than the engine and missing a few parts here and there. The seller didn't want to see it parted out and I wanted a project so there it is.

I know enough to get into a lot of trouble... hopefully the guys here can steer me through the rough patches.

[MaximPhil]

Thanks.

It's indecent shape other than the engine and missing a few parts here and there. The seller didn't want to see it parted out and I wanted a project so there it is.

I know enough to get into a lot of trouble... hopefully the guys here can steer me through the rough patches.

Hi orange4
Ask before doing anything you are not sure of. Lots of TechTips for your reading pleasure
Phil

[Orange4]

Just finished re-greasing the steering head bearings and cleaning up the front rim.

I had a good idea for keeping the black paint on the rims looking nice is black shoe polish. Water repellant and makes them black again without refinishing.

Also: New toy...



Damn! Should not have tumble dried the XS.

[sparkfly88]

Is that the Prius version of the XS???

[Orange4]

Sure. You could say that. It's the XS1: Extra Small, 1 horsepower.

It's actually a 1974 Auranthetic. Converted to electric by a company in California from a Gemini SST minicycle frame. They made several thousand. This one is #000012. Not the right batteries but they work better and I didn't have the heart to cut the frame to make them fit.

[Orange4]

I'm all set to start the rebuild except for the valve stem seals. Any hints on the best deal for those?

I have the early cams, later head with the bigger valves, later pistons and the copper head gasket ready to go.

It will be interesting to see how these cams work with the bigger valves. Anyone care to chime in on valve intereference issues? I'm hoping that it will not be an issue because they inset the valves on the later heads to keep them farther apart.

[TopCatGr58]

Wish I had known about this site in 2000, I paid ~$8.00 EACH from Yamaha!

Valve Stem Seal

#01-0136 | Yamaha XS1100 (1978-1981)

Valve Stem Seal OEM Ref#1L9-12119-01 , 1J7-12119-01
US$ 3.00



Fits: XS1100 (78-81)

If you didn't already have your copper head gasket, then I would suggest getting the whole gasket kit they sell, has head gasket which alone goes for ~$75.00, plus the valve seals, and others for a little under ~$100.00 .

T.C.