Frozen exhaust valve and busted up piston... what are my options???

[xHolepunchx]

...Ok, here's the skinny. This is my second xs, it's an 82 Heritage special I bought off Craigslist. Bike looks great, everything's in good physical/cosmetic shape. Seller told me it ran, but that the carbs were dirty so it wouldn't run for more than about 5-10 seconds at a time. I rebuilt the carbs and cleaned everything out and put it back on the bike and she fired right up. However as it was running I heard a mad dinging like someone hammering metal at the speed of the engine.

I cut the power and took the valve covers off. I noticed that the exhaust valve on the left side of the bike was frozen open and the sound was the rocker hammering the top of the valve. All three other valves were fine. The spring on the frozen valve still looks good, but it stuck compressed by the busted valve. I pulled the exhaust pipe off and inspected the piston top and there are metal fragments all over the inside of the cylinder, the end of the valve is gone, and it looks like the top of the piston is jacked...

So, heres what I know. Bike runs fine on the right side. Left side has a wide open exhaust valve. I assume I'll have to pull the busted valve, replace it and the guide. Replace the piston and more than likely have to re-hone the cylinder... My question is...

What else should I expect/prepare to find trashed?
Would It be more worthwhile to seek out a used engine that runs and just swap?
How much of a real mess do I have on my hands here???

Im new to the board, so hey, nice to meet you all! I've seen lots of great advice come through here. Now I need some advice my self. Thanks in advance! Cant wait to get back on the road!

 

[azman857]

Instead of guessing what could be wrong, get the motor out and take the head off and see whats going on. Sounds like you need a new piston and head assembly.I've seen pics of broken valve damage and it's just more sensible to get new piston and head assembly. Head and cover are machined togeather and should be replaced with each other. Never split them(as in one part on one engine and the other part on another engine). They are stamped with matching numbers so you know when your getting a matched pair.
Get them wrenches spinning and take some breaks now and then to shoot some progress pics to post. We'll help ya with moral support and advice. Check the tech and search tabs up near the top to help you along too.
Wecome to the club. It's a great ride. Trust me.

 

[irristeve]

if it has not run to long should be ok but id be splitting the cases & give whole thing a good clean out just 1 of bits of piston & valve get the crank etc it will be exspencive

 

[xHolepunchx]

ok, I think I follow. Ive seen entire top ends on ebay for about $70 (valves and springs, and then the top and rockers as well). I don't wanna start gutting my motor till I have a plan if I don't have to. Im more worried about the jugs, honing seems simple enough, but if I hone out one side and need an over sized piston will I have to hone out the other side to match? Ive never pulled one of these engines apart, so I wanna try to have most of what I need on hand and get the project done right. I may pull the engine this week and start taking pix if I need to. If it were more economical to just get another engine I figured Id take that route over ordering a bunch of parts that may or may not solve the issue. Thanks so far everyone!

 

[gggGary]

Throw a engine wanted ad out in your local craigslist or tell us where you live There are quite few engines around but no guarantees they will be any better than what you have......
Here's one that got rode a little farther. That engine is my mock up shell now.

Rod was destroyed on this one. Just a heads up that smashing into a valve a bunch of times is hard work for the piston rod etc etc.

 

[angus67]

i had to split the cases, new 6 over kit(680?) clean all passages, get the head seats ground, new valves, younger crank assembly(8K as opposed to the 14k it had.)
whent together easy. just follow the manual, and assemble the cases upside-down so the tranny stays where its supoosed to go.
Ive never rebiult an engine, and this engine is easy. if you are mechanically inclined, you can do it. justtake your time, make sure timing marks for the crank and cam are correct, and tap the cam bearings all the way in, so the points housing go on all the way so they dont leak.

 

[angus67]

btw. gggary, Idont know wich ide rather have to fix. that looks awefull. i think you win.

 

[retiredgentleman]

I'm always amazed when guys post asking for advice on what parts they should order or have on hand for an engine re-build.

The fact of the matter is that no one can tell you what components need replacing. There's only one way...................its called the discovery method. As azman857 said, take the engine out and start dis-mantling.

Looks like the PO told a big wopper, when he said it ran, or he just failed to mention a few things.

 

[azman857]

Yes,xHolepunchx, if you need to oversize one piston you do them as a set. If you don't, you get one side making more power than the other. Talk about a vibrating motor that will NEVER smooth out. It is possible you might have to replace everything from the top of the case, up.

 

[gggGary]

The term "beyond economic repair" comes to mind. But that isn't always the deciding factor for XS650 owners. This seems to be a "not unusual" failure mode and not just for our engines. Any engine that has set for a long time. A couple of the valves are sitting open, allowing rust to form on the valve stem where it is exposed to outside air in the intake tract. Guess this serves as a heads up if you are bringing a bike back from deep hibernation that lube and free movement of the valve stems is important. PB in the intake and cylinder? extended engine cranking oil or thinner lube for the top end before firing? Extreme caution on any bike that has been sitting in weather or damp areas especially with no or rotted aircleaners?

 

[XSLeo]

I agree with the take it out and tear it down. Vavles and guides are not hard to replace.
I would go first over with new pistons. Boring the cylinders can be had for under $100. JUst need the pistons first. The machine shop needs to bore for correct clearance.
While in there a new cam chain and front chain guide. Doing the Porsche elephant foot valve adjusters is a good mod while apart.
Clean up of the intake and exhaust ports, 750 kit, lots of upgrades possible.
How much you wanna spend?
Leo

 

[ReycleBill]

Yes,xHolepunchx, if you need to oversize one piston you do them as a set. If you don't, you get one side making more power than the other. Talk about a vibrating motor that will NEVER smooth out. It is possible you might have to replace everything from the top of the case, up.

Years ago my cousin bought a 283 chevy that no matter what we tried, never seemed quite right and it always seemed to have odd vibrations we couldn't explain. When we finally opened it up we found 5 different sizes of pistons in it.

 

[smolikj]

i have a complete motor good compression but is a points style motor i could sell you the top end ? i just want the right cover and tranny

 

[52Chevy]

Sounds like exactly what I have wrong with my bike. When I pulled it all apart one of my valves was sitting on top of the piston rod underneath the piston. As previously stated you never know what may have ended up in the crank case.

I decided on looking for a new motor for the time being. I plan on maybe rebuilding this one with a 750 big bore slowly for my next bike.

Man I am already hooked and don't even have a running bike yet :/