Valve issue help (video)

Playing the guessing game

I can't believe the variety of guessing games being played here. The fact that there is a clanking noise tells me that you are going to have to take it apart sooner or later!
So an inquisitive diagnostic mind would say that with the valve cover off and the rocker arms removed, you might probably find a stuck valve.
But then again, even if that is what is wrong, you're going to end up pulling the whole top end anyway. So taking it all apart makes total sense. Be sure and remove the lifters as well. So then you have the whole picture and can figure it out from there.

Video

Forgot to mention that from the video it looks like a stuck valve, or a broken lifter but I wouldn't want to guess about anything.

Exactly why I wouldn't rush in and pull the head. Nobody here has a idea what is the issue.
Connect compressed air in the spark plug hole and see if it comes out the intake. Pull the intake and you should be able to see if the valve is open.

My point of contention is the guys that just want to start tearing it a part when there is no confirmation what the is problem.

Exactly right because the problem is obvious

I stand by my previous suggestion that you compare the valve train operation to each other by slowly rotating the motor by hand (battery disconnected, front cover off) and determine if you issue is a stuck valve or a problem with the push rod, rocker arm or lifter. Before you go start "tearing it apart" check and adjust your valves and give it a few more spins by hand, there's a lot of space in between the adjuster and the top of the valve stem so it might just be a practice run on valve adjustment. Regardless of where the problem is you will at least have to pull the left side cylinder head to ensure you find the route cause of the problem and fix it correctly.

There is no mention of the bike running rough or on one cylinder during the "clack clack" noise so I would have to assume the valve is at least closing down on its seat. That is why with the information provided I think it might be a dislodged valve seat. If it did run rough or on one cylinder it could be a broken push rod, lifter, rocker arm, pulled cylinder stud, bent or broken valve stem or maybe something is stuck in between the seat and valve holding it open. So if you do tear it apart take a close look at the throttle plate of the carburetor to see if both screws are present.

I had no idea that my suggestion to troubleshoot an issue would cause such a heated discussion. I am surprised. I spent my entire life repairing things, first aircraft (27 years, 16 military and 11 years civilian) and another 18 years durable medical equipment. I cannot imagine what a pilot, or a person relying on his respiratory equipment to breath, would think if I told him that I didn't know what the problem was, but I will rip it apart to try to find out what went wrong. I was taught to think, use the correct troubleshooting tools, and my education to analyze a problem before I tear it apart. It takes only a few minutes to pump some air into the cylinder to see if the valve is stuck. No damage would be done, and it could tell us a lot. So could ripping off the head, dropping the pan to look at the cam, remove the cylinders and pull the lifters to check them. However, that would require an rebuild, new parts, and a lot of work.

I go with "do not turn the engine over" period. Until you take that side apart. My uneducated guess, could be a collapsed lifter, busted.

When I got my trashed R90 many years back, rode it one time. Quite noisy I thought? Both exhaust lifters were cracked, running in place, ruined the lifter bores and the cam surface. No biggie. Pulled the head and started ordering parts. But that's just one scenario. Good luck. Two cents.

Snap

Let me clarify my comments.

First, if there was no SNAP then clanky clank, I would not be so adamant about not running a compression test or running the engine. Loss of power on one side is one thing. A loud snap and clank is not. I can understand turning things by hand to compare sides and such as to see how one side functions versus the other. IF doing the turning by hand, resistance is felt, it can be stopped before something worse happens.

If a leak down test or pressure test is done and the pressure holds or the test shows nothing, would I start the engine and run it? NO, not until I found out what went snap and clank.

A snap and a clank means something will have to come apart at some time or another regardless if it is a stuck valve, broken pushrod, valve, valve seat what ever. Something will have to come apart and be fixed.

I NEVER take things apart until I have to take them apart and sometimes, I have to take them apart to see what is wrong with them. I am not equipped with X ray vision. Nor do I have an X ray device handy. St.

Taking the Head and Cylinder off is pretty easy and quick; that's what I'd do. Then you could get to the lifters too.
You could do all the work above slowly in about 30 minutes.
I would not start it or even turn it over by hand but that's just me.

All the experts have done their somersaults so far! Let's hear what chris.poole has to say.

/Guenther

Note

I don't do summersaults.

I try to help someone who asked for help/advice/opinion.

I never claim to be an expert either, just someone with common sense and experience. St.

Not a pulled stud as your rocker rotates easily but has excess clearance - 1/8” or so. Adjusters look to be positioned ok by the number of exposed threads. The spring pocket and collet are still together. Do the pushrods rotate smoothly when you try to turn them by hand? If so. Probably not the lifters. Springs intact not broken. Valve spring appears to be compressed and held tight by stem seated in pocket. Seems to me that indicates the valve seat may have come loose and has jammed the valve open. If this is the case, the valve may have had contact with the piston and may be bent as well. You should pull the head. It’s not going to fix itself I’m afraid and no amount of guessing is going to substitute for taking a look inside.

toooldtocare said:

I had no idea that my suggestion to troubleshoot an issue would cause such a heated discussion. I am surprised. I spent my entire life repairing things, first aircraft (27 years, 16 military and 11 years civilian) and another 18 years durable medical equipment. I cannot imagine what a pilot, or a person relying on his respiratory equipment to breath, would think if I told him that I didn't know what the problem was, but I will rip it apart to try to find out what went wrong. I was taught to think, use the correct troubleshooting tools, and my education to analyze a problem before I tear it apart. It takes only a few minutes to pump some air into the cylinder to see if the valve is stuck. No damage would be done, and it could tell us a lot. So could ripping off the head, dropping the pan to look at the cam, remove the cylinders and pull the lifters to check them. However, that would require an rebuild, new parts, and a lot of work.

Click to expand...

So your saying in 27 years as an airplane Mechanic, every time you walked into the cockpit to talk to the pilot you automatically knew what was wrong?
You my friend are an amazing mechanic, and I can't believe you don't know the answer already.
Gator

No need for insults

gator said:

So your saying in 27 years as an airplane Mechanic, every time you walked into the cockpit to talk to the pilot you automatically knew what was wrong?
You my friend are an amazing mechanic, and I can't believe you don't know the answer already.
Gator

Click to expand...

Please, there is no need to be insulting here.

I know I am touchy about it having had a bad experience with the Airhead forum moderators. That is the Airhead forum, not the MOA forum.

So far, the BMWMOA forum has been a great asset. How about we keep it that way? St.

gator said:

So your saying in 27 years as an airplane Mechanic, every time you walked into the cockpit to talk to the pilot you automatically knew what was wrong?
You my friend are an amazing mechanic, and I can't believe you don't know the answer already.
Gator

Click to expand...

I should not go here, but I will. Been riding since I was 20, owned flock loads of bikes, mostly BMWs. Because of my job, I've been to ride all over the world. I am now 74 and still riding.

My military experience, USAF Avionics Tech (Vietnam vet). Graduate engineer/with master's degree. Worked as design-test/integration engineer for another 12 years, first McDonnell Douglas, then Electronics and Space Corporation. Assigned to Japan as an military advisor 4 times. Assigned to Korea as an advisor. Also assigned to Germany, Spain and Greece as an advisor. Assigned to Pakistan and Israel as an advisor. Also assigned to US military bases all across the US. My job was to help those countries (and the US military) repair complicated equipment. My specific experience includes, B52s and KC135 (flight control and navigation systems), F18 (flight control), Harpoon/Tomahawk missile (guidance and control), C130 (Combat Talon radar), and RC12 aircraft (Guardrail Common Sensor).

After that, I went into durable medical equipment, traveling the US and Canada training our customers on their equipment. Volunteered 12 years at Wings of Hope assisting in repair of aircraft used to fly medical supplies to remote villages in South America and Africa.

When training our customers I always spoke with knowledge that I had an idea what their issue was. Not, "I'll rip your system apart to look for the issue." If I had, I can guarantee that my assignments would have come to a rather rapid end. My employer would have my head. Imagine you taking your car into a shop and the tech tells you, I don't know what is wrong, but I'll take the engine apart to find out the issue.

I agree, it is probably a stuck valve, bad valve seat. But, spend a few minutes to verify that before you rip it apart. That is ALL i recommended. Know what you are looking for before you rip it apart. And, assume that others here have advice to offer too, instead of insulting them.

Take apart

When I talk to a customer, I have an idea as to what is wrong as well. I don't start pulling things apart with blinders on nor do I take chances to diagnose something by doing something which may cause more damage. In this case perhaps a compression check.

There is something wrong with the valve train not the carb, not the transmission. I know how the system works, and I know what can go wrong with the system. Hence, I make my diagnosis based on experience and common sense. I don't start tearing apart things at random. Oh yes, the customer has to sign off on the work.

I have said I would not run the engine at all due to the fact if the valve is stuck open or broken and so forth, it could impact the piston and cause more damage. I will cede to turning the engine slowly by hand to see how things move and if they move with freedom. If someone feels they must run the engine fine, their risk. Not mine.

IF the problem is visible, fine, you have found it right away. If it is not visible, I do not see how you are going to see what is broken or out of place without doing some kind of disassembly. Not willy nilly tearing things apart but methodical disassembly. Take apart one thing at a time and look at what is going on/what condition things are in. Oft times, I have taken apart heads looking for a simple problem needing repair only to find something else wrong. The part that broke may not be the cause of the break.

Regardless, things will have to come apart to fix anyway. Unless, the problem is fixed by magic or goes away. I don't believe in magic nor that it will go away.

I really hope for the owner's sake it is something very simple and he can fix it without a lot of trouble. It will be interesting to see how it turns out if, he shares with us. St.

STEVENRANKIN said:

Please, there is no need to be insulting here.

I know I am touchy about it having had a bad experience with the Airhead forum moderators. That is the Airhead forum, not the MOA forum.

So far, the BMWMOA forum has been a great asset. How about we keep it that way? St.

Click to expand...

This was not meant as an insult by any means. I do apologize for the comment. I just do not understand his comment on how in his 27 years he could walk into the cockpit and tell a pilot that he did not know what was wrong with his airplane. I will say this if he enters the cockpit and tells the pilot there is an issue with the engine in the manner he stated of his airhead, the FAA requires disassembly of said engine.
Gator

Do we have an answer yet?

Hello, did I mess things up on this post by being too big a jerk?

Has the person in need of help given up with us and moved on for help elsewhere?

I really am interested in what he found to be wrong. St.

Update!!!

Hey everyone,

First, I want to say thank you everyone who threw in some advise. I’ve been a member for a few years, but as you can see, I don’t make it onto the forum often. I really appreciate everyones thoughts.

Just to kind of recap how I got here….

I went out for about 60mi on my ’76 R90/6 through some local country roads and experienced no issues/no noises. When I got home, I had my bike idling in the garage for maybe 2 or 3 minutes while I was putting my gear away. I then heard a fairly loud snap and then tic tic tic tic. I ran over and shut my bike off as soon as I could. It ran for less than 10 seconds in this condition. I stood there for a second trying to process what could have just happened and decided to start the bike back up so I could try to better assess the situation. (I know this was risky and a bad idea, considering I could have absolutely caused more damage.) It started right back up, but with a fairly loud valve tapping coming from the left side of the engine. I tapped the throttle twice and it revved easily, with no real noticeable problems - just the tapping. After maybe 6 or 7 seconds of running, I shut the bike back off and pulled the left side valve cover. I then noticed that I now had 1/8” of slop on the left side intake valve. I didn’t have time to go any further, and this is when I posted on MOA for help.

Where I’m at…

I had to leave town for a few days and haven’t had time to get back to the thread or the bike, sorry about that! I finally was able to take things apart today. Frustratingly, I can’t seem to find any failures. The pushrods appear fine, the valve isn’t stuck and seems to be seated properly, and the cam lifter looks completely normal. Thankfully, it also doesn’t appear that the valve came into contact with the piston. I don’t have a ring compressor, so I didn’t pull the cylinder completely off, just back far enough to get the lifter out. This also kind of limits how much I can inspect the camshaft/lobe, but I shined a small fashlight in there and it seems fine.

So, anyway, thats where I’m currently at. At this point, I’m tempted to put it all back together, adjust the valves to take up that 1/8” and start it back up. Clearly, something happened that caused this sudden gap, so I’m really hesitant to go that route. I’ll post some pictures and a video. If anyone notices anything that I’m missing, please, let me know! This is my first time taking apart one of these engines and I’m really leaning on the community for help. If there are any more images/videos that anyone thinks might be helpful, let me know and I’ll post them. Thanks again!! - Chris

This is a video from when I started the bike back up to assess what had just happened after the initial snap. As you can hear, responsive and smooth - just loud tapping.

One other thing...

I did notice that the intake valve sits slightly lower into the cap than the exhaust valve does. I thought maybe this was my issue but I pulled the valve cover on the opposite cylinder and it appears to be the same, and without a gap. Can anyone confirm that this is correct? And again, the valve is seated inside of the cylinder head.