Dead cylinder

I've been plagued with one set back after another this year. I am hoping someone can help me.
My '74 850 was brought out of hibernation after 3 years. It had a cracked head.
I took the head off my '73, had new valves and guides put in.
Had the studs repaired and the head surfaced.
Got it running, took it on 3 long rides and then noticed that the head gasket was blowing out the right side. Turns out that head bolts were real loose.
I deceided to pull the head and replace the gasket thinking it got damaged when all it needed was a retorque because the gasket looked perfect.
It always started with 1 or 2 kicks.

So now I replaced the gasket and it won't start.
I did a compression test and the right side has 125 lbs but the left side has 0.
You can put your finger over the plug hole on the right and feel it pull and blow like it should but the left side is like nothing.
The valve opens and closes fine with the right amount of lash so I know it isn't an open valve.
When it was running before the left side exhaust felt warm while the right side felt hot.

So, I ask you all, why does the left side have 0 compression?
Rings? Frozen from sitting so long? It would smoke, right? It didn't.
I looked into the plug hole at the piston and it looks fine.
It's a new gasket, thats all I did and nothing else.
Any ideas?

Wonder if one of your valves is stuck open for some reason. Just a wild guess. Wouldn't know why. Might check both your in and exhaust valve tappet clearances. If it doesn't fire on one cylinder, you would know it, it's real hard to start and without compression it won't fire. It will feel like a large single without one side, I know, kind of like if the plug wire came off, not as if that has ever happened.

Dave
69S

It pretty much has to be one of the things you yourself mention:

-rings
-piston
-vavles
-gasket

The only think really left is if the rod is gone and the piston isn't moving.
I would be highly suspicious of the valves. I know you checked them, but...

Russ

Another possibility is something stuck between a valve and the seat, or maybe something stuck between the head and cylinder when you put it back together?

Sounds like a nightmare ,sure you didn't torque down the head with pushrods not seated properly ? Bent pushrod ? Stuck up valve yes is possible. Remove all 3 valve covers ,spark plugs, and get assistant to kickover whilst you observe valve actions . Good luck.

I did all the things mentioned. You can see each valve open and close. I measured the lift and closed height of each valve thinking something might be stuck between the valve and seat.
Used my bore scope to see into the barrels for a hole, crack or something.
The head sits flat, push rods all perfect.
The one thing which gets me is that when it was running a couple of weeks ago one side, the left side, exhaust was just warm while the right side was hot like it should be
leading me to believe that it had a compression problem in the first place eventhough it ran before so I have to believe there are some froze rings of cracked piston.
Any rate, I'll be tearing it back down for the 3rd time this year.
And summer is almost over but I'll be damned if I am gonna let this stupid bike beat me.
I figure maybe 2 more weekends of working on her and countless bucks before it's all over.

Guido, When you sort it out, the drill as far as the head goes is to go for a ride long enough to get the engine up to temp. Let it sit overnight and re-torque the head. Repeat. Use anti-seize on all the head nuts and bolts.

P.S. You mentioned that it had a cracked head. What was that about and how did they fix it? When you had the valves and guides done did you get it back assembled or did you get a chance to check the valves and the seats before you put it together? Who did the work? Don't know about Sacramento, but there area lot of experienced Brit bike machinists in the bay area if it comes to it.

If valve clearances measure ok I would look at doing leak down test first to find were air is going to either out intake or exhaust thru rings or head gasket best of luck

I feel for you, it's just coming into the real riding season, at least here in the Mid-Atlantic. I guess you need to get into the head or cylinder and find out what is going on. Good luck.

Dave
69S

rpatton said:

Guido, When you sort it out, the drill as far as the head goes is to go for a ride long enough to get the engine up to temp. Let it sit overnight and re-torque the head. Repeat. Use anti-seize on all the head nuts and bolts.

P.S. You mentioned that it had a cracked head. What was that about and how did they fix it? When you had the valves and guides done did you get it back assembled or did you get a chance to check the valves and the seats before you put it together? Who did the work? Don't know about Sacramento, but there area lot of experienced Brit bike machinists in the bay area if it comes to it.

Click to expand...

The cracked head was a different head I had removed from this bike. I had a good head from my other bike that I had all the work done on from Phil Radford of Fair Spairs and from Rabers in San Jose.
I did inspect the head as it was dissembled when I got it. It all checked out.
I'll be ripping it apart soon.
It's not my first rodeo working on Nortons.
Can't tell you how many times I almost sold these bikes only to give it another go at keeping them on the road.
It's always been problems with the heads. Now it looks like the middle end needs some attention now.
I'm running out of dough and patience for this year.

I'll do a leak down test tomorrow.
Been doing my 2010 taxes all day today.
Yeah I know, a little late but thats how small businesses do it.
Kinda reminds me of that Beatles song

Tax Man

Guido said:

I took the head off my '73, had new valves and guides put in.
Had the studs repaired and the head surfaced.
Any ideas?

Click to expand...

When new guides are pressed in particularly bronze guides, they can be quite tight to the point that the clearance can become too small.

With mine, after a few runs, I ended up tagging one of the valves with the piston and loosing a cylinder just like you. I pulled the head and got 2 adjustable reamers. when they are that small the range is too small to get to where I needed with just one. I gingerly reamed the bore of the guides to bringing back to spec. I replace the valve, put it back together and all was well.
I hope your issue is this easy.

pvisseriii said:

Guido said:

I took the head off my '73, had new valves and guides put in.
Had the studs repaired and the head surfaced.
Any ideas?

Click to expand...

When new guides are pressed in particularly bronze guides, they can be quite tight to the point that the clearance can become too small.

With mine, after a few runs, I ended up tagging one of the valves with the piston and loosing a cylinder just like you. I pulled the head and got 2 adjustable reamers. when they are that small the range is too small to get to where I needed with just one. I gingerly reamed the bore of the guides to bringing back to spec. I replace the valve, put it back together and all was well.
I hope your issue is this easy.

Click to expand...

If there was an award for Idiot of the Year I would have won first prize.

I just pulled the head today and found that the exhaust valve on the left side had tagged the piston.
How could this have happened since all I did was put a new head gasket on and tried to start it but it never fired.
Like and idiot, as I was installing the head and after I torqued it down, I tried to kick it over and it locked up.
I immediately realised that the pushrod hadn't seated in the tappets.
It never occurred to me it was the valve hitting the piston.
I loosened the head up, reset the pushrods in their tappets, torqued it down, put it all together and tried to start it and that is when I posted the post "Dead Cylinder".

So after all that I should be able to just get a new valve and lap it in, right?
Since it never started, can the head gasket be reused even though it had been torqued? It never stuck to the head.

I'm going to order a valve tomorrow. Will I need a new gasket?

I would get a new gasket if you are using the eyelet type, if copper simply anneal it and use it again.

dave M said:

I would get a new gasket if you are using the eyelet type, if copper simply anneal it and use it again.

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Phil at Fair Spares said it should be ok to be reused since it was never heated.
Just looking at it, it looks new. Still has the curl to it.
It the eyeleted type, flame ring.
My gut told me to get a new one.

I went with his advice. We'll see tomorrow when I put it all back together for the umteenth time.
I have had this freaking head off this bike 3 times this year cuz of leaks, pulled studs, a bend valve.
I need to ride it or I am going turn it into a boat anchor!!!!!!!!!!

I went with his advice. We'll see tomorrow when I put it all back together for the umteenth time.
I have had this freaking head off this bike 3 times this year cuz of leaks, pulled studs, a bend valve.
I need to ride it or I am going turn it into a boat anchor!!!!!!!!!!

Click to expand...

Its states like that that make me reflect on how much this C'do hobby is a manhood testing one. All the rest of us get em right and tight the first time every time : )

Gasket must be the copper or the real FlameRing kind with grey powderish sealing coating and rather firm though out, NOT the mere copper foil covered paper kind or the newish 'flamering' offering or might have another head let down and even a fire consumed cycle with it blowing loud jets out the oil hole at speed.

So far so goodie on Trixie using plain copper Orange/red annealed and Blue Hi Temp Racer Hylomar which is rated to 600' F - about 200 higher than Norton heads get at top speed WOT a long while.

Hope this time does it for ya.