Number 3 from left wont fire

[dashingEMT]

Ok, my first post here and my first XS1100. Although not my first old bike. I have an 81 special that I bought from a guy who did an 85 percent restore. It is nearly a cafe style, but its hard to call it that being so damn big. Anyhow, I was riding today and lost a lot of power all of a sudden. Was still able to drive it home on the freeway but I noticed a lot of oil coming out of the right side exhaust. I hadnt done a plug/wire swap so I stopped at the shop and got plugs.

Long story short, after touching the headers, number 3 was "cold". Ok, yanked the plugs and sure enough they were snotted up something fierce. Yanked the wires and while I was dirty changed the oil. Started her up and everything was awesome! Fired right up, all 4 cylinders were pumping and a ton of white smoke started pluming out of the right side exhaust. "great" I thought, the oil is burning out and the 3rd is turning. Had that nice, in tune sound, great pick up when I twisted the throttle. Everything is swell. The white smoke was getting thick so I figured Id shut her off for a while. Came back an hour later, started her up and 3 wont fire again.

What I have done:
Changed plugs
Changed oil
Checked to see if carb is flowing
started bike a few times
verified 3 is getting spark

What I havnt done:
Compression test (dont have the tool)
Changed coil or wires (cant take wires off coil, dont have access to new coils)


So any thoughts? I am deeply concerned about the oil coming out of exhaust. Burnt ring maybe? I am puzzled by it working right after plug swap, running great, then nada. I am 90% sure its not a carb issue, but I have learned you can NEVER be SURE. But everything I am seeing is pointing to it not being carb. I have had a few late 70/early 80 bikes and have never had this issue.

Thanks for the help!!!

[James England]

It looks like number 3 is allowing large quantities of oil into the cylinder. It's not the carbs. It looks like you have a serious mechanical problem with #3. Cracked piston ring. Valve oil seal damaged. It looks like a lot of engine oil is getting into the cylinder, burning as much as possible before the plug fouls up and stops sparking.

You need to do a compression test and, if I were you, I'd take the camcover off and also the cylinder head, in order to see what's going on....

Throwing out large quantities of white smoke and oil coming out of the exhaust pipe is a indicative of a serious problem. I would stop tyring to start the bike and I'd get the head off asap....

[natemoen]

I would agree that you are probably fooling out the #3 plug and that is why it goes cold. Pull the plug and clean it or pit a new one in and then switch plug wires with the # 2 cylinder and try again and see what pipe goes cold. If it stays at 3 then you have an issue somewhere in that cylinder (carb,ring,valve,etc) if it moves to #2 then it is an issue with the wires or coil.

Compression check would also be good. Some auto parts stores will loan a tester out for a ridiculous bit refundable deposit.

[dashingEMT]

Ok, so it is as bad as I feared. I'm not scared of doing a ring job but I'm wondering can it be done with the motor on the bike or do I need to pull the motor?

[natemoen]

It may not be rings, switch the plug and swap the wires like I said and do a compression test. If it shows low compression I would suggest doing a leakdown test before stripping the engine down because that will tell you where the issue is for sure. Also if the compression is low it could be that a valve is burnt or being held open. Just don't jump on without knowing for sure.

If it does come down to rings it can be done in the frame.

[dashingEMT]

Headed to store now to buy compression tester. Leak down test is something I've never done...looks like I got some reading to do. I hate when it is "finishing touches" time then something like this pops up.

[crazy steve]

The top end of the motor can be removed while the motor's in the bike; that's the good news. The bad news is rings, and particularly pistons, are very hard to find; you'll almost surely end up using used pistons if you need some.

You might want to look around for a decent used motor...

[dashingEMT]

If it comes to needing to motor swap, I'm selling. I did see some piston rings online, for around 40 bucks. Are these not right?

[crazy steve]

No, those $40 rings will probably be ok, although you may have to file a set down to fit. Those are NORS rings; rings/pistons have been discontinued for years from most vendors, although you can supposedly still get new ring sets from Yamaha (for $50 per hole!).

Don't let a engine swap scare you off; that may prove cheaper as used motors can be had pretty reasonably if you hunt around a bit.

[dashingEMT]

Well....

Did my compression test. I do everything 3 times so here are my results.

1st
1-120
2-125
3-115
4-125

2nd
1-125
2-125
3-115
4-120

3rd
1-120
2-125
3-110
4-120

So 3 is weaker, but not nearly as low as I was expecting. is 10-15psi death? I know its not ideal, but Im not so sure...

[bikerphil]

Those readings look all pretty close to each other. Did you hold the throttle wide open while testing? They all are a little on the low side. If the bike has been sitting for a long time, one or more rings may just be stuck and hopefully will free up after a few hundred miles.

[dashingEMT]

I did hold the throttle open.

Stuck ring...I dont see it freeing itself, but lets just say it can, how would I get it to do this?

[crazy steve]

As far as the relationship to the others, you're fine; as long as all cylinders are within 10% of each other, that's considered acceptable. But all the numbers are somewhat low (you should be seeing about 140+). You did hold the throttle wide open while you ran the tests, right? If not, that will give you low numbers. Recheck with the throttle opened. It doesn't appear that you have a holed piston, which would have been my concern.

Still low? Try squirting some oil in each cylinder, then re-perform the test; if the numbers come up significantly, the rings are worn. Little or no change, the valves are worn. If it's worn rings, you might want to go up one heat range on the plugs to slow down the fouling. If it's stuck rings, time/mileage will sometimes free those up.

With that said, the motor should still run ok with these numbers, you'll just be down on power. You may have a sticking float valve on #3 carb and that hole is being flooded, which could account for the smoke. Or it could be ignition issues, although you'll usually drop two cylinders at once. Remove the end off the plug wire (it unscrews), trim 1/4" off, then reinstall. Also check it for resistance; it should be 5K ohms (4.8-5.4K range will work) if it's good. You should be seeing about 25K ohms between #2 & 3 plug wires with the ends on the wires. More resistance or open, you want to get a new end. Most metric bike dealers should stock these, about $3-5.

[natemoen]

Were you holding the throttle wide open when you did the test? You should be.

Either way those #'s are all close enough and I would say rings and valves are ok. When you refilled the oil how was the bike sitting and how much pop did you put in? Should be sitting on the center stand and it should only be around 3.5-4 quarts of oil with a filter swap. There is a small sight glass on the clutch cover with 2 lines on it, oil level should be between those lines when on center stand.

[natemoen]

After running the engine for awhile and just the heating and cooling cycles the ring almost always free up.