Head gasket?

[Joe Nardy]

Well, my Saturday plan of doing a bunch of simple maintenance tasks sure went south in a hurry! First things on the list were chain clean and lube and oil and filter change. So I wanted to go for a quick spin to warm up the chain and oil. I put the key in, turned the key, and thumbed the starter button. The bike turned over as usual for a few seconds, sputtering a couple times like it was going to fire. It is a little cold blooded and I don't like to heat the starter up by cranking it constantly so I let off for a few seconds then thumbed the starter button again. It turned over as usual for a second or two then the sound changed suddenly. Now it doesn't fire. There weren't any nasty sounding noises or anything else that I noticed when the sound changed. It sounded similar to when it is turned over with the plugs out (Uh-oh!)

So, I started checking things out:

Fuel in float bowls - yes
Getting spark - yes
Pistons rising and falling - yes

At this point I felt I needed further info, i.e. what's my compression like? I ran up to the auto parts store and bought a compression tester. Here are the (sad) findings: Cylinder 1-160 psi, cylinder 2-55 psi, cylinder 3-95 psi, cylinder 4-110 psi. Putting a bit of oil in the cylinders raises the compression a bit but not dramatically.

So now I need to try to find where the compression loss is. I pulled the valve cover and checked the cam positons to see if the chain might have jumped a tooth. Everything is correct there. I checked valve clearances. There are no tight or excessively loose valves. Not that it has anything to do with compression, but I verified that the ignition timing was correct and that the correct cylinders are firing at the correct times, all good.

What I'm trying to figure out is what could have gone bad so suddenly during startup. The last time I rode the bike was a two-day, 1400+ mile trip home from Florida. It ran flawlessly on the trip. I started it up a couple weekends ago and it started and ran normally. Since I didn't hear any major noises I'm thinking head gasket. It's the only thing that I can think of that could have let go withoout making any ugly noises

I don't think I have any choice but to pull the head but I figured I'd ask the collective GSR braintrust if there is anything else I should do first. Is there any way I can verify whether the head gasket is the problem before I pull the head? Are there further troubleshooting steps I should take before pulling the head?

*****EDIT****** Also checked head bolt torque.

Thanks in advance for your help,
Joe

[chiphead]

Joe, I might be sucking wind here but step back for a minute and take a look at things. I strongly believe your motor should definitely run with the compression settings you posted. Even if # 2 doesn't fire, it will still run on three cylinders. If it was me, I wouldn't take the top end off. It should at least fire and start.
Now what's wrong? I don't know. Is the spark being blown out under compression? Take a plug and snap the side electrode off and put it in the cap. If you have a nice strong ignition system, it should jump from the center electrode to the outside edge of the plug. All four plugs. That motor should even fire and run with just 1 + 4 or 2 + 3 firing.
Just some ideas. I wouldn't pull the top end apart. My 2 cents.
Good luck.

[chiphead]

If you have an inductive timing light, hook it up to each coil wire while watching the timing marks and spinning the motor. Might show something.
Or it might not even be electrical related.
Again, I could be sucking wind here but I would look a little harder.
You should at least get a bang out of that puppy.

[Joe Nardy]

Joe, I might be sucking wind here but step back for a minute and take a look at things. I strongly believe your motor should definitely run with the compression settings you posted. Even if # 2 doesn't fire, it will still run on three cylinders. If it was me, I wouldn't take the top end off. It should at least fire and start.
Now what's wrong? I don't know. Is the spark being blown out under compression? Take a plug and snap the side electrode off and put it in the cap. If you have a nice strong ignition system, it should jump from the center electrode to the outside edge of the plug. All four plugs. That motor should even fire and run with just 1 + 4 or 2 + 3 firing.
Just some ideas. I wouldn't pull the top end apart. My 2 cents.
Good luck.

Thanks for the input.

Yes, I agree that I should get some pop from the engine but the fact remains that I have some very bad compression readings. I can't see why anything electrical would have any effect on compression. Rings, valves, head and base gaskets are the only things I can see that would cause low compression.

I'm going to try the plug without the electrode thing and see what happens.

************** EDIT *************
********************************

I cut the electrode off a plug and tired it on all four wires. On each wire the spark jumps all over the place to the outside of the plug............

Thanks again,
Joe

[Joe Nardy]

If you have an inductive timing light, hook it up to each coil wire while watching the timing marks and spinning the motor. Might show something.
Or it might not even be electrical related.

Chip,

I haven't hooked up a timing light but I have tried spinning the motor manually and watching the spark. It occurs at the correct times according to the timing marks.

Thanks,
Joe

[chiphead]

I still think it should run, maybe not great, but it should run with those compression settings. I've been out of the business for 15 years. Maybe I'm senile.
Anyone else want to weigh in with an opinion?

[Joe Nardy]

I still think it should run, maybe not great, but it should run with those compression settings. I've been out of the business for 15 years. Maybe I'm senile.
Anyone else want to weigh in with an opinion?

Chip,

I'm sure you're not senile....not any more than me anyway!

You may be onto something. I checked the voltage to the coils and it is only about 8.5v despite having close to 12v at the battery (I've run it down a bit turning it over so much today.) I'm in the process of trying to figure out where my voltage drop is. Stay tuned......

Joe

[chiphead]

It's late and I'm on my way to the sheets but maybe....just maybe...low voltage is causing an extremly retartded spark so the mix is lighting up while the exhaust valves are still somewhat open....???
Nah, pretty far fetched. I'd like someone else to post recent compression readings on a similar motor. Something in the back of my head says 90-100# compression will run, but maybe I'm thinking about the 2 strokes I cut my teeth on. Hope I'm on not leading you down the wrong path.
IMHO you should definitely have 12 VDC to the hot side of the coils.
Good luck and I'll follow the story tomorrow.

[Joe Nardy]

Chip,

Thanks a lot for your help. I agree that the bike should fire, at least on cylinder 1. When I say I have less than 8.5 volts to the coils that's without the starter motor cranking. That will definitely drop the voltage even more and if there's a bad connection somewhere it may heat up with the additional draw of the starter and drop the voltage even more. Regardless of whether this fixes this problem or not, it certainly isn't right and needs to be addressed. Have a good night's sleep!

Joe

[Boondocks]

...Here are the (sad) findings: Cylinder 1-160 psi, cylinder 2-55 psi, cylinder 3-95 psi, cylinder 4-110 psi. Putting a bit of oil in the cylinders raises the compression a bit but not dramatically.

So now I need to try to find where the compression loss is. I pulled the valve cover and checked the cam positons to see if the chain might have jumped a tooth. Everything is correct there. I checked valve clearances. There are no tight or excessively loose valves. Not that it has anything to do with compression, but I verified that the ignition timing was correct and that the correct cylinders are firing at the correct times, all good....

Well, Joe it sounds like you have done all you can to determine the problem except pulling the head. Cylinder 1 is the only one with a normal reading. You seem to have eliminated a cam timing issue. Excessive cylinder/piston/ring wear or stuck rings will cause compression loss, but not the sudden catastrophic loss you have experienced. Burned valves can cause compression loss, but again this is not something that happens suddenly when starting.

That leaves the head gasket. I agree that this is the most likely cause of the compression loss, but it would have to be an atypical gasket failure. Most head gasket failures seem to be a "slow leak" which is noticed by an oil leak, and which doesn't greatly impact starting or performance. In your case, if it is the head gasket, it would have suffered a major rupture affecting 3 of the 4 cylinders. Why something like this would happen (much less when starting) is a matter of speculation. If it's the head gasket, it must have been severely damaged and weakened, waiting for an opportunity to blow. In that case, if that's what it is, you're lucky that it happened in your garage.

In any event, I hopefully think that pulling the head will allow you to determine the cause of the problem. Good luck.

[Joe Nardy]

Well, Joe it sounds like you have done all you can to determine the problem except pulling the head. Cylinder 1 is the only one with a normal reading. You seem to have eliminated a cam timing issue. Excessive cylinder/piston/ring wear or stuck rings will cause compression loss, but not the sudden catastrophic loss you have experienced. Burned valves can cause compression loss, but again this is not something that happens suddenly when starting.

That leaves the head gasket. I agree that this is the most likely cause of the compression loss, but it would have to be an atypical gasket failure. Most head gasket failures seem to be a "slow leak" which is noticed by an oil leak, and which doesn't greatly impact starting or performance. In your case, if it is the head gasket, it would have suffered a major rupture affecting 3 of the 4 cylinders. Why something like this would happen (much less when starting) is a matter of speculation. If it's the head gasket, it must have been severely damaged and weakened, waiting for an opportunity to blow. In that case, if that's what it is, you're lucky that it happened in your garage.

In any event, I hopefully think that pulling the head will allow you to determine the cause of the problem. Good luck.

Yeah, none of this makes any sense. There is no indication whatsoever of a blown head gasket. It is bone dry all the way around the head. The bike was running perfect the last time I rode it.

I spent the evening going through some electrical stuff since I haven't convinced myself I haven't missed something. On Chip's advice, I went through the entire circuit from the battery to the coil and found several voltage drops. There was a .5 volt drop going through the fuse panel. I disassembled it, cleaned all the male contacts, crimped the female contacts, and applied dielectric grease to all the contacts. This got the drop down to .1 volt. There was a .8 volt drop across a connector inside the headlight shell. I sprayed some contact cleaner/conditioner (Caig Deoxit 5) and got that drop down to almost nothing. There is a .5 volt drop across the kill switch. I cleaned it and applied dielectric grease but the voltage drop is about the same. The contacts are very small so I guess there's nothing else I can do about that. Through it all there's now about 1.5 volts more going to the coils than when I started. The battery is pretty low now from all the testing I did so it's on the charger overnight. An electrical problem such as a corroded connection would make some sense since I hit a significant amount of rain on the 3500 mile trip I took (that was the last time I rode it).

Tomorrow I'm going to look at the starter motor and it's wiring. The only thing that seemed to change when the problem started was the sound when the motor turns over. Listening closer, it could be the starter making a noise. Also, I did a couple more compression tests and the results varied significantly. I'm wondering if the starter motor is varying in speed. I think this could change compression readings. I would think the motor needs to spin at a decent speed to get meaningful compression readings. I'd think you would get lower compression readings if the motor were truning over more slowly.


Thanks,
Joe

[Planecrazy]

Bummer, Joe! Wish I had something meaningful to add, but it sounds like all the bases have been covered, including the possibility that the slow starting is causing your compression readings to fluctuate. It'll be interesting to see whether that stabilizes after a good night on the charger. Let me know if I can be of any help, should you need to dig deeper into the motor.

Regards,

[Boondocks]

...Tomorrow I'm going to look at the starter motor and it's wiring. The only thing that seemed to change when the problem started was the sound when the motor turns over. Listening closer, it could be the starter making a noise. Also, I did a couple more compression tests and the results varied significantly. I'm wondering if the starter motor is varying in speed. I think this could change compression readings. I would think the motor needs to spin at a decent speed to get meaningful compression readings. I'd think you would get lower compression readings if the motor were truning over more slowly.


Thanks,
Joe

Yes, a weak battery or erratic starter turning the engine over slowly will give lower compression readings. Remember when running the compression test to open the throttle all the way. Not that you have any way at present to do it, but the test should be performed on a warm engine to get accurate results. Also the engine should be turned at least 4 revolutions or more while the compression gauge jumps to a stable reading. Maybe the first compression results that you noted are not accurate. If the main symptom is a funny sound when the starter is applied, I agree it's a good idea to check out the starter itself before tearing into the engine. If the engine was running perfectly before this happened, it seems very unlikely to have suddenly developed a problem like a catastrophic head gasket failure. Some type of starter malfunction now seems more likely, since it all began when punching the starter.

The Caig Deoxit is really good stuff. Radio Shack had it on closeout recently at very low prices and I bought three applicators (2 regular and 1 Deoxit Gold) for about 1/3 of the regular price.

[KEITH KRAUSE]

Are you positive the vacuum line is good? Eyeball it carefully if any doubt.

[Joe Nardy]

Are you positive the vacuum line is good? Eyeball it carefully if any doubt.

Keith,

Are you referring to the vacuum line from the carbs to the petcock? I'll take another look to be sure but it must have been okay since all the carbs had fuel in the floats.

Thanks,
Joe