Compression problem

[Antonio]

I have a stock 1980 XS1100SG, and thanks to this website and the members who always are willing to help I was able to restore my XS1100 and have been riding it for the last year. Put 4000 miles on it. Now I have a new problem and need your help. Slowly my XS1100 started fouling. On several occasions while I was riding down an expressway I would loose power but after awhile it would start operating normally. I checked my plugs and I was not getting any spark on cylinder 2. I rewired the coils and fixed the spark problem. Started the XS1100 and it worked fine for about 5 min. Then it started knocking loudly. Now I have no compression on piston 2. The spark plug anode is shorted with the tip of the plug. I guess the piston hit the plug. The piston is still moving up and down. I am guessing maybe the piston has a hole because there is no compression.

Any ideas what might be the problem? I am not a mechanic but I am handy with tools and mechanically inclined. I think I could fix the problem with a little help of my friends on this forum.

[steelraider]

What plug are you using?

[Antonio]

i am using NGK-BP6E S

[crazy steve]

I would suspect that you may have broken a valve; there's no way the piston could hit the plug unless the rod broke, but if a chunk of valve (or the whole head) was loose in there, that would do it.

You'll need a service manual to tear the motor down, and it may prove to be cheaper to just replace the motor. Pulling the cylinder head off will tell the tale....

[BA80]

+1 on what Steve is saying. Pull the head and see what's going on in there and what kind of damage there is.

Then take it from there.

[Rasputin]

I would try a leak down test and that would verify which is the culprit. Valves, holed piston, rings bad, you name it. Does not sound good though.

[cywelchjr]

I would say that if you have zero compression that a leakdown test is a waste of time as the just as Steve and Greg (ba80) have said the head is going to have to come off anyways, and zero compression you either have a hole in a piston, a piston not moving or a valve broken/bent. The spark plug damage points to the valve head broken off or the piston not attached anymore, but I'd suspect the valve more likely, and there is probably a hole in the piston as well by now (or at least a crack or lots of dents )

[Antonio]

Thanks for all the input. I will remove the head and check to see how bad the damage is. I shut the engine down real quickly when it started knocking. If it is a broken valve and the piston is ok do you think the engine would be repairable? I love my xs1100 and will teardown and rebuild the engine myself. I am no mechanic but I sure will give it a shot with a little help from my friends. This will be my winter, spring, and summer project. I don’t know if I can find the parts I need to repair the engine. I do know I could probably find a gasket set for the engine online. I would appreciate everyone’s thought on this.

[XS1100_OEM4ME]

Very Sorry

1st, I am very sorry to hear of what happened to your bike. After reading everything you said happened with the knocking and also that the piston still goes up and down when you crank the motor, It is most likely a valve drop or breaking off. The fact that you shut down as soon as your heard the sound won't change the outcome. With the piston going up and down many times times in less then a secound, you can't avoid damage when it happens. As to the parts being out there, most are, but at many$$, The piston rings are a wild card, you would have to luck out on Ebay or somewhere to find those. Even if you could find all the parts you would still most likely need a doner motor for the cyl, head, piston and such. Open it up and if it is as some of us think, a good used motor would be your best / cheapest fix. Some fokes on here might be able to help you find on close to where you live or if you find a complet used bike cheap that runs, you will have a doner motor and many other usefull parts for other needs. Again, very sorry about your bike and best of luck on getting her back on the road

I have a stock 1980 XS1100SG, and thanks to this website and the members who always are willing to help I was able to restore my XS1100 and have been riding it for the last year. Put 4000 miles on it. Now I have a new problem and need your help. Slowly my XS1100 started fouling. On several occasions while I was riding down an expressway I would loose power but after awhile it would start operating normally. I checked my plugs and I was not getting any spark on cylinder 2. I rewired the coils and fixed the spark problem. Started the XS1100 and it worked fine for about 5 min. Then it started knocking loudly. Now I have no compression on piston 2. The spark plug anode is shorted with the tip of the plug. I guess the piston hit the plug. The piston is still moving up and down. I am guessing maybe the piston has a hole because there is no compression.

Any ideas what might be the problem? I am not a mechanic but I am handy with tools and mechanically inclined. I think I could fix the problem with a little help of my friends on this forum.

[GLoweVA]

I've changed out a piston on my 80G before, but it was a burnt hole and not any valve/head issues.
If you did drop a vavle and the jugs are still okay, then maybe you can get away with just a head and piston replacement.
Like those above had said, you won't know until the head comes off.
Pics would be nice.
He's my hole:

[DGXSER]

You have the correct plug so that is not to long causing the issue. You lost all compression. So there is a hole in the "Balloon" letting all the air out somewhere. If the cylinder is/was not blowing oil all over the place or into the header, then most likely your piston is still intact. You could start by removing the valve cover and checking valve clearances. If one of them is huge or zero that could tell you part fo the tale. But at the end of the day, you will need to pull the head too either repair the valve in question or see what is the problem.

[pcmcse1]

81 xs1100 h

I would suspect that you may have broken a valve; there's no way the piston could hit the plug unless the rod broke, but if a chunk of valve (or the whole head) was loose in there, that would do it.

You'll need a service manual to tear the motor down, and it may prove to be cheaper to just replace the motor. Pulling the cylinder head off will tell the tale....

Hello there crazy-steve! I'm in need of a complete head thats not been disassembled and has come off a good running bike.

The valves need to be in good condition and relatively low miles. No bent or burned valves. Additionally the bike should not have alot of chatter as this indicates out of clearance specs between the cam and the shims, as well as pontential excessive wear due to lack of lubrication.

Please let me know if you can help out.

Send reply to:

k.jordan61@comcast.net

Thanks to all!

[DGXSER]

Hello there crazy-steve! I'm in need of a complete head thats not been disassembled and has come off a good running bike.

The valves need to be in good condition and relatively low miles. No bent or burned valves. Additionally the bike should not have alot of chatter as this indicates out of clearance specs between the cam and the shims, as well as pontential excessive wear due to lack of lubrication.

Please let me know if you can help out.

Send reply to:

k.jordan61@comcast.net

Thanks to all!

Best way to find parts on this site is to post in the for sale section under Wanted to Buy.

[Barnfresh]

Another quick way to tell if there is serious valve / piston damage is to pull the carbs and exhaust.. the offending cyl will have metal in the port and then there will be tears on the floor.

[XS1100_OEM4ME]

Your bike?

Hi Antonio, just checking to what you found out about your bike? I am hoping for the best for you, I know it is tough when they give us grief, I do hope it goes well and cheap for you getting her back on the road.

I have a stock 1980 XS1100SG, and thanks to this website and the members who always are willing to help I was able to restore my XS1100 and have been riding it for the last year. Put 4000 miles on it. Now I have a new problem and need your help. Slowly my XS1100 started fouling. On several occasions while I was riding down an expressway I would loose power but after awhile it would start operating normally. I checked my plugs and I was not getting any spark on cylinder 2. I rewired the coils and fixed the spark problem. Started the XS1100 and it worked fine for about 5 min. Then it started knocking loudly. Now I have no compression on piston 2. The spark plug anode is shorted with the tip of the plug. I guess the piston hit the plug. The piston is still moving up and down. I am guessing maybe the piston has a hole because there is no compression.

Any ideas what might be the problem? I am not a mechanic but I am handy with tools and mechanically inclined. I think I could fix the problem with a little help of my friends on this forum.