First Motorcycle

[JCruze]

Hello, I recently purchased this '78 xs 1100E. When I first got the bike I went through and cleaned the engine/carbs and changed the oil and oil filter. Also replaced the old spark plugs and bled the rear brakes in order to get pressure again. The guy I bought it from told me the bike was is in good running condition and that he took it in to get the carbs cleaned, valves adjusted and replaced 2 fuses 3 years ago. Then, from what I gather, the bike sat for about a year in a storage shed. After running the bike we noticed that there was a miss and after doing a compression test found the first cylinder to be 30lbs low. I'm really trying to do this myself, using my manuals, this forum and my dads mechanical expertise. As of now I'm trying to work backwards to find the root of the miss and low compression. I'll keep you guys updated.

[DGXSER]

A good test is to add a teaspoon of oil to the cylinder that is low and see if it goes up. If ti does that indicates the rings a loosing compression. This can happen just form the engine sitting so long, you can run it for a while and see if the rings loosen up and regain compression.

[natemoen]

You say it is 30 low, but was are the numbers of them all. I agree that the rings do get stuck when they sit for awhile and usually running them frees them up and the compression will eventually come back up to normal.

Also, if that is a current pic of the bike, get some air filters on those carbs before you suck some crap in and wreck the engine!

Oh yeah, Welcome to the wonderful world of XS, it will drive you crazy but you will love it! And if you are new to motorcycles, take the MSF basic rider course!

[GLoweVA]

I had 30psi in #4 and 135-150 in the other 3. You might have a hole in your piston if the compression is that low. see pic:
http://s1197.photobucket.com/albums/aa422/gloweva/
One quick way to find out: with the plug out, pour about a cup of oil into the hole, have a dipstick (I used an allen wrench) handy to measure the oil sitting on top of piston, if the level drops pretty quickly, like all gone in less than 3 mins, then either you've got no rings, or there's a hole in your piston.
Pulling the head off isn't that difficult. In my carport, I did mine in about an hour. Just do some reading and research first.
ps. Don't be afraid to ask questions. We're all here to help and learn from what you find.

[JCruze]

Thanks for the replies everybody, I'm glad to be here, very good information. The thing is, it holds an even 90psi, by the way the others run at about 120psi. So that leads me to believe there is no hole or leak. I'll look into it some more and report back.

[CaptonZap]

Thanks for the replies everybody, I'm glad to be here, very good information. The thing is, it holds an even 90psi, by the way the others run at about 120psi. So that leads me to believe there is no hole or leak. I'll look into it some more and report back.

Check the valve clearance. CZ

[planedick]

Checking

Put compressed air from a hand held nozzle into the crankcase vent and see if it comes out the spark plug hole. If it does there is a hole in the piston. Put compressd air in the spark plug hole and if it come out of the intake port it has a leaking valve, same for exhaust. I suspect it probably is rings need seating as others have said because leaking valves or holed piston usually means no compression.

[JCruze]

Ok so I put compressed air into the first spark plug hole and it DID come out of the intake. What steps should I take to further solve the problem? From everything I've read here, its the valves and/or rings? There was also some fuel that came out with the first blast of air, as if it had been pooling or was still there from the last start, which was yesterday.

[cywelchjr]

Ok, first you gotta make sure the cylinder is in the compression stroke where both valves are supposed to be closed, otherwise the test means nothing as you were given only partial information for doing the test. You really need to pull the plugs from all the cylinders and turn the bike over either by hand or short bursts of the starter till it tries to push you thumb off the spark plug hole (that's when the piston is coming up on the compression stroke, and both valves are closed). Now you can do the test on THAT cylinder. Then repeat the process for each of the other cylinders if needed (IIRC it's just the one that has low compression) but the test requires that the valves be closed for the test. If you get air coming out of the carb or the exhaust when pushing it into the the spark plug hole after doing this, then you either have a burned valve or if you lucky just a valve that needs adjusted right away before it burns.

[JCruze]

Ok thanks, I'll get on that asap and let you guys know what happened.

[planedick]

Next

Rotate the engine a little just to be sure the valve isn't open because it's supposed to be and repeat. If the air still comes out of the same intake port it means the valve is probably bent and not seating properly. It seems I recall you had done a compression test and posted the results as higher on the other three cylinders, but I don't recall the results after putting oil in the cylinders and doing the test again. If after the oil the compression comes up considerably it means the rings aren't seating good and just running it will probably make improvements as well. I usually add a little MMO to the gas on a regular basis to lubricate the valve stems and loosen the rings.

[JCruze]

Thanks all, got the misfire taken care of. Added some oil down the spark plug hole and that seemed to help the rings out, giving me equal psi across all cylinders.

[cywelchjr]

That points to leaking rings. I'd suggest running it for a while before getting too worried and see what happens, it may just even out fine.

[cowboy1157]

I had a ring that was stuck (engine smoking) ended up having to put new rings on all the pistons to get the compression back up to 130. when I took the head off the pistons were covered in carbon. A friend showed me a trick to clean the pistons. He used antifreeze on the pistons to clean them and they looked like new. He said that he just soaked them over night and then just rinsed them off.

[GLoweVA]

Anitfreeze ?!? WOW, I've never heard of that. I'm pulling my pistons out (Probably this weekend) for a ring job and I've got carbon all over the tops of them. I might have to give this a try too.
Thanks, It never ceases to amaze me how much info I've gotten from this site and all you guys out there that have 'been there, done that'.
This forum is the one thing that will keep these bike on the road for ever!
(plus our neverending desire to ride them!)