CBR 1000F "Hurricane" 1987-1996 CBR 1000F

Blown head gasket between cylinders

  #1  
Old 10-21-2018, 10:42 AM
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Cool Blown head gasket between cylinders


not what I wanted to run in to but this is my luck.
After taking each cylinder to bottom dead center and applying 60 psi of compressed air I listened for air leaks from the intake side, exhaust side, crank end and the spark plug hole of the neighboring cylinder coming up with the following results
no intake air leak on 2,3,4 cylinders just 1.
Exhaust air leaks on all cylinders some worst than others.
air leaks between 1 and 2 also between 3 and 4.
So I suspect an overheating condition,
I was contemplating just cracking the engine far enough just to replace the busted alternator chain and tensioner and leave the head alone, not now.
Now the head has to come off for sure and I will have to check for cracked head and or cylinders, darn it.

PS I came up with a home made gadget to pressurize the cylinders with a compressed air regulator a length of hose some clamps/fittings and a bolt the same size and tread as the spark plug with a hole down the middle, works great.
Not happy with the condition of the upper end of the engine, but better find out now than skip it and deal with it later.
Hit me with anything else that I can still check before I crack the head off.
 
  #2  
Old 10-22-2018, 10:15 AM
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That's an interesting test. Did you come up with it yourself? Some good info there, but I wouldn't mourn the engine just yet. The exhaust valves usually leak a bit, or at least they will until you go in and lap them back in. Ditto for the intake valves

If you had a cracked cylinder or bad gasket you would have had some combination of oil and/or coolant leaking or mixing. When you drained fluids did they look okay? Did the bike have any known leaks? I'd probably also want to see a compression test before stressing out too much about major failures

That said, you'll be taking it all apart to do the alternator chain, so you'll have a perfect opportunity to thoroughly inspect all the parts of the engine. I almost envy you, but I also remember how much work it was

If you start a build thread I''m sure a few of us would be interested to follow your progress. Good luck
 
  #3  
Old 10-22-2018, 12:59 PM
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Talking Haha I got "Mechanics Itch" so the compression


test is out of the question. I bought the bike with the "won't start" thing. I did research and knew of more or less worst case scenario (busted alternator drive chain).
Taking the engine out of the frame I found a suspicious patch repair on the right rear coolant pipe. Engine/radiator had no coolant/oil mix, they could have been drained/flushed in the past, who knows.
On removal of the head the head gasket came out stuck to the head and I mean stuck had to un stick it with a screwdriver. The cylinder air leak is between the cylinder, I noticed that the cylinder skirts (jugs) have a gap between 1,2 and 3,4 sort of odd arrangement. I can't find any tell tale sign of gasket failure between the cylinders, it looks good. I have a theory of what happen but this is just that - I believe that the engine got hot enough to melt the black coating of the head gasket causing a compression leak between cylinders only. I am going to do something stupid since time I got lots off. I am going to take all the black coating off the head gasket and re install it and run my backyard test and see if the leak is still there.

The leak test I copied from a leak down test procedure, that basically does the same thing, I just focus on where the leak is at instead of percentage of leak down.
Yea I figure like you that a good valve lapping will bring the head around, minimum swap valve stem seals with new ones.
 
  #4  
Old 10-22-2018, 01:50 PM
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How do the cylinders look? I'd also check for warped head. If it was concerned about damage caused by overheating, those would be top of my list

Does it smell like burned oil?
 
  #5  
Old 10-25-2018, 10:40 AM
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Post Yea it does smell like burnt oil but not that bad

Originally Posted by tentacleslap View Post
How do the cylinders look? I'd also check for warped head. If it was concerned about damage caused by overheating, those would be top of my list

Does it smell like burned oil?
Looks like the valve stem seals where not doing their job, probably they got cooked just enough.
Cylinders are decent most of the cross hatch is there, the pistons show very little wear on the skirts at the point they rub/slap the cylinder walls.
I need to get a straight edge metal rules to be able to check the head for warp condition.
Got the valves clean ready to lap, none of them are burnt, pistons had no carbon accumulation in the ring grooves, so cleaned the tops and check other than that I am going to slap m in.
Friging valve stem seals are expensive for as little as they are.
 
  #6  
Old 10-30-2018, 09:36 PM
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I used upgraded Viton seals for the job, Vesrah, seals were cheaper than OEM too, done 6-7 years ago so I have no link, I got off E-bay, still good!
 
  #7  
Old 10-31-2018, 10:22 PM
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Post Thanks but it's too late I alredy

Originally Posted by jarvid View Post
I used upgraded Viton seals for the job, Vesrah, seals were cheaper than OEM too, done 6-7 years ago so I have no link, I got off E-bay, still good!
Ordered them.
Plus all I want is to get the bike sort of running and decide what I am going to do once I ride it.
If I decide to keep it, I am most likely to tear her apart and take care of everything that needs TLC since she's a classic as it is at 30 years old.
Also I found out this bike had the alternator chain drive tensioner come loose originally and replaced, chances are the chain was not replaced.
 
  #8  
Old 11-11-2018, 01:06 PM
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Lightbulb Not a blown head gasket after all (Funny)

Turns out the head gasket had been good all along.
Due to operator error and ignorance of the ins and outs of the engine. I thought there was actual compressed air leaking between 1-2 and 3-4.
There is a connecting passage between 1-2 and 3-4 cylinders at the top of the head where the spark plug screws in to the cylinder head. This and the fact that my compressed air attachment does not seal very well and last but not least, I was using a thick piece of garden hose that of course will not fit in to the spark plug hole.
So after inserting a thinner hose in to the spark plug hole of the opposite cylinder being tested I could not hear any leak, just awesome .

At any rate since there where leaks on the intake and exhaust valves the head had to come off anyways. Now there are no leaks to speak off other than the crank and that was expected.
So the valve lapping was a success.





PS If any of your spark plugs wire head booths are bad and leak water in the spark plug hole rest assured that the spark plug next door will flood too.
 

Last edited by jaimenv; 11-11-2018 at 01:12 PM. Reason: picture
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