crank only rotates 340 degrees

Old, neglected XS2 engine.
In one direction the crank stops rotating about 10 degrees before it hits TDC. In the other direction, the crank stops rotating about 10 degrees after TDC. The same difference away from TDC in each case. It's as if I had a piston stop in the spark plug hole, except I don't. I can see all four valves move, and they appear to close as far as I can tell.
I'm not much of an engine guy. Anyone know what this means?

Someone dropped a cam cover or points screw in a plug hole?
get a borescope in there.
spose something could be stuck in the primary gear?

Thanks. Both are interesting ideas.
Bike was bought in baskets, with intention of parting out. There's a couple of other little things with the engine. One spark plug almost threads all the way in, but the bottom-most threads need chasing. And there is a tiny hole drilled on each side in the fin close to each exhaust port. I think it's okay to part out this engine. The crank will fetch more than the complete engine, and will save someone else's project.

I'd be looking in the side with buggered plug threads.
If you tear it down, tell us what you find?

Will do.

The crank now has full rotation.
This was advertised as a stuck motor. I assume the seller determined that it was stuck by using the kick lever, which had no movement. Or, he might have determined that it was stuck using the e-start, but I think this is less likely.

Anyways, I think that I unstuck it by simply repeatedly rotating it the 340 degrees of movement that it had in either direction. Still don't know what the hang-up was, but I'm guessing I'll see something on the piston or cylinder.

I mentioned the spark plug hole threads that needed chasing. I had tried to give them a simple chasing using a spark plug and PB Blaster as a lubricant (I don't have a spark plug tap). Possibly the PB Blaster in that cylinder freed something overnight.

Was the engine uncovered before sale?..i have seen motors develop a slight rust ring in the bore if damp has got past open valves..maybe you've just took the crust off with the rings,enough to turn it over anyway.

Sometimes using stethoscope it's possible to listen for a "thud" or a rough portion of a cylinder as you roll an engine...but if you're tearing down...

Elsewhere (gary?) spoke of bore-scope.

Any compression?

The engine was loose. What I got was an almost complete bike in baskets, a frame, and an engine. I don't know how it was stored, but probably not very well.

I had a pair of wheels that had tires on them, and using them, I put everything together enough so that it looked pretty much like a complete bike -- PICS BELOW. This was so I could get a sheriff's inspection, which is the first step in getting a bonded title -- the sheriff will only sign off on "complete vehicles."

Without an engine stand, the engine-in-frame-on-wheels made a good, stable substitute, making engine disassembly, stuck-on case cover removal, clutch removal, rotor removal, removal of head bolts, etc. easier. It also made repeated rotations of the 340 degree crank easier, which is what really lead to the successful freeing-up of the engine in this case.

BTW: Here's how to get a bonded title for a vehicle that is "out of the Texas system" because it was last registered before computers:
Stop one: Sheriff's inspection, Auto Theft Unit -- free.
Stop two: So-called "Letter of Rejection" from the state DMV -- a letter that says they can't provide a new title because there is no old title -- $15.
Stop three: Title Bond from insurance agency -- $100
Stop four: county tax office to apply for bonded title -- payment of tax on my "claimed" purchase price, and various fees -- this is for a title ONLY, no registration fees, because I'm not paying for it to be road legal -- that can be done once a vehicle is running and inspected -- $45.50.

Four different locations I had to go to. It just so happens that all four locations are fairly close to me, otherwise I'd never bother to do this. The lines everywhere were short, so the whole thing took less than 4 hours. And a total cost of $160.50.
The first stop, getting the inspection, was done with bike in my El Camino. All the rest of the running around done on motorcycle on a beautiful day.

This was all so that I can sell the frame as being titled. Hardly worth the trouble, but I know the process, it was a 72 frame, and I know that if I didn't do it it would never get done, and the frame would end up being melted down. I'd never do this for a 74 and later frame.

gggGary said:

Any compression?

Click to expand...

Too late. I'd already committed to tearing it down by the time the engine freed up.

DogBunny said:

And there is a tiny hole drilled on each side in the fin close to each exhaust port.

Click to expand...

Could be the holes were used or intended for springs holding exhaust pipes into slip fit spigots/ flanges. Maybe more common for 2 stroke chambers, but also used on some 4 stroke exhausts. Or for lockwiring. Could this engine have been used in a race bike?

I thought exhaust springs too. You'd expect to see marks from the spring hooks, or whatever it was the holes were used for, but no. I may post a pic. Race bike? Anything's possible, but no other outward signs of modifications.
If only these bikes could talk. Only 19K miles on the clock, but has had a top end job at the least. Was it done at the 19K mark, but something got screwed up, and it never ran again? Seems you should get at least 19K out of an engine, so was it done earlier, and why? The started gear is absolutely pristine -- was it replaced at 19K, but the bike never ran again?

arcticXS said:

Could be the holes were used or intended for springs holding exhaust pipes into slip fit spigots/ flanges. Maybe more common for 2 stroke chambers, but also used on some 4 stroke exhausts. Or for lockwiring. Could this engine have been used in a race bike?

Click to expand...

Well, here's a closeup pic of KR on a Thuet prepared OW72 from '77 San Jose Mile. If you happen to have a Thuet head, well..........don't sell it (well, maybe to me)

The hole. One only, but same, mirror-image placed hole on the other side.

The XS2 crank ( and possibly XS1's, TX650) had weights that come loose and hit the rod which locks the crank. Common problem. Take a look. Could be your problem

DogBunny said:

View attachment 243975
The hole. One only, but same, mirror-image placed hole on the other side.

Click to expand...

Mebby the PO thought it was a Norton and needed to keep the the spigots from unthreading?

One friction plate was broken (and the rest were VERY stuck). Never seen this before. I don't have one handy, but I think the later years friction plates are on a metal backing?
(I still haven't reached the cylinder.)

Got sealant?
Excess sealant on interior head walls, tappet adjuster screw and nut, valve spring retainer, and exterior of cylinder head.

Oh ya never can have to much sealant


even on the fork seals