Low compression. Worn rings?

[Munzo]

I had my bike running, but the 3rd cylinder wasn't firing. Carbs have been cleaned and dipped twice and, the valves have been adjusted. I tried swapping the spark plug leads and sure enough the 3rd cylinder warmed up. So I thought it had to be the spark plug cap. So I went ahead and replaced it. Now the bike won't fire, I have spark on all the cylinders. It turns and turn but just won't start.

I ran a compression test, with the engine cold obviously, since I cant get it started.
Here is what I am getting:

Cylinder 1 : 120
Cylinder 2 : 120
Cylinder 3 : 60
Cylinder 4 : 110

I put a little oil in cylinder 3 and the PSI shot up to 150.

So I guess the questions are. Does it sound like I'm dealing with multiple issues on this? Not starting is one and compression is the other? Or is the compression issue causing the bike not to start? With the results of the compression on cylinder 3 and the results I got from adding oil am I looking at worn rings on cylinder 3?

 

[tkent02]

The compression is not causing the non starting, something else is amiss.
What's the history of the bike? If it has sat a long time the compression may come up after running it a good bit. Rings sometimes get stuck in the pistons or whatever, they work themselves loose and work fine.

 

[Buffalo Bill]

Compression is plenty good?

Compression is plenty good?

The compression is plenty good, it's hard to get consistent compression readings, but I think you did good. Move on to the next possibility.

You got the right wires going to the right cylinders?
Are the plugs messed up with residue?
Is the gas good?
Has the gas line hose or the vacuum line to the petcock kinked?
Have you flooded the engine?
Have you tried a little shot of starter fluid into the airbox?
Are you using the OEM airbox, and it's all properly connected?
Did you have a look down each main and idle jet with a magnifier to see if it was clear?
More stuff to do.
Check this guy's site for tips as well: http://www.dansmc.com/indexindex.htm

 

[Munzo]

I don't have a whole lot of information on this bike. I bought it back in late April and it was running, just on 3 cylinders (which I found out later, this is my first bike so i didn't realize it at the time). I had sat over the winter in the PO garage, and before that I don't know. The PO had bought it from a finance company who gave him no information. It ran for a while but the carbs needed cleaned, which I did. I'm just trying to get all the kinks out of it to get it to run consistently.

Thanks for the info. I'm going to tinker with it some more and see if I can get it at least to fire up again, and then go from there.

 

[Munzo]

The compression is plenty good, it's hard to get consistent compression readings, but I think you did good. Move on to the next possibility.

You got the right wires going to the right cylinders?
Are the plugs messed up with residue?
Is the gas good?
Has the gas line hose or the vacuum line to the petcock kinked?
Have you flooded the engine?
Have you tried a little shot of starter fluid into the airbox?
Are you using the OEM airbox, and it's all properly connected?
Did you have a look down each main and idle jet with a magnifier to see if it was clear?
More stuff to do.
Check this guy's site for tips as well: http://www.dansmc.com/indexindex.htm

Thanks for the check list.I've checked some of these and not others. I will go through this list again tonight.

Regarding the spark plugs.They've been through a lot of running with lean or rich mixture while I tried to get the carbs tuned.The plugs did have some residue. They were still getting spark and I had cleaned them up. I was wondering if I should just replace them?

 

[Buffalo Bill]

Maybe so?

Maybe so?

On a recent project bike that kept flooding during startup with the choke on and caking the tips with carbon soot, I had cleaned them off so many times with a wire brush that it left a glaze impregnated on the ceramic cone. I finally put new plugs in and it started right up. That bike (Yamaha XJ750R Seca) had a way to rich choke, and it could not be fixed. I just learned to lay off it or use it judiciously. Didn't need the choke in warm weather anyway.

 

[Munzo]

Jeez

Jeez

So solved the starting problem. Had a friend who works on motorcycles over and was saying "Yea it ran, all i did since then was new plug caps, and put on intake boot rings", he reaches down on the engine and says "You mean rings like this one?" Apparently one ring managed to fall out as I installed them.

So we get it started. Cylinder 3 and 4 aren't firing now. And it is just pouring smoke. My friend friend recommends overhauling the top end, or swapping in a new engine. Not sure if I'm willing to put that much work into it yet. Any thoughts on what it'll take to do this and cost associated with it?

 

[tkent02]

There's really not much point in opening it up unless you have some idea what's wrong with it.

 

[blowerbike]

i/m local and semi-knowledgeable.

 

[Munzo]

There's really not much point in opening it up unless you have some idea what's wrong with it.

Would you suggest a leak down test as the next step?

 

[tkent02]

You said it was running, make it run again. The low compression is not the main problem.
Spark, fuel, air, all in proper proportions and at the right time and it will run, even if the engine is shot. It's not. This is all simple stuff. Have you even checkeded the valve clearances yet?
Find out why it smokes now when it didn't before, is it fuel smoke? Oil smoke? Something else?
A leakdown test would be useful, but so would a good long ride.
Blowerbike has offered to help, he knows this stuff. Take him up on it.

 

[Big T]

Your current problem of not running on 3 and 4 may be as simple as fouled spark plugs

Did you check to see if you have spark on all 4?

 

[Munzo]

Thanks for bearing with me guys. I'm not as dumb as I seem, I'm just new at this.And I've finally learned something important. Don't trust what the PO has done and double check. I had the spark plug leads connected to the cylinders the PO did. On a whim I double checked the wiring diagram today, sure enough wrong cylinders.

So sure enough go swap them all around. And magic I am firing on all cylinders. I pulled the 3rd cylinder plug and it is covered in oil. Took it for a spin to see if I could there was just maybe residual oil causing the smoke or if I can get the rings to loosen up.

After about a 30 min ride. It is still pouring smoke out of the exhaust. And I get off the bike to find oil all over under the gas tank. Its up on the carbs, on the air box and all over the crankcase.

I attached an image. All I had was my cellphone so the quality isn't great.

 

[blowerbike]

your oil level is/may be over full.
that or you have a hole in the #3 piston.
check the oil level with the bike held straight up and down..level should be in the middle..little lower or higher is ok.

 

[Guest]

Where is the crank case breather hole located on that bike?
Blowbye?

 

[Big T]

The oil on top of the motor is probably coming from your breather, or lack thereof

On the top of your cylinder head cover, at the back, is an outlet that should have a hose coming from it that runs to the airbox. I'm guessing that hose is missing

Your problem with #3 is probably causing excess blow by, that breather is where the blowby will come out and thus all over the back of the motor.

Some Gunk engine bright will take care of the mess.

Then, check your oil level as noted above

Then, pull the #3 plug and put something into the cylinder - Marvel Mystery Oil is the product of choice, Seafoam or penetrating oil will do. A couple of ounces is enough. Let it sit for a day or two,rotate the motor every few hours, then try running it again. This is know to unstick rings.

If you have access to a borescope, you can look down into the cylinder and see if you have a hole in the #3 piston