Head gasket.

[maybe73]

1st I would like say that this is not my video, but it shows my problem although mine is not so severe. So the engine comes out again, hopefully this weekend, ugh!... I have been looking ahead at the shop manual at re- assembly for head torque values and a variable of 13.7 - 15.2 ft-lbs seems like a lot (1.5 ft-lbs). So does anyone have a preference as to high or low end of torque value? Also using the correct tightening sequence, am I to go rite up to correct torque in one round of tightening or do it in two rounds and split the torque value in half for the first round, then go again up to full value? High school auto shop teacher made us do it in two rounds on cars. But that was 35 years ago. It was suppose to help seat head gasket more true. Thanks in advance.
     
    https://www.youtube.com/watch?v=IrxmcaY3O20 

[18Bravo]

There's even more variance reinstalling the cap nuts (26-29 ft. lb) so I wouldn't sweat the variance too much. If your torque wrench hasn't been recently calibrated you may be getting 1.5 +- without even knowing it.  As for tightening in one round, I never do that.  I'd at least split it by thirds in your case - finger tight, then 5, then 10 then your final - hell, split the difference and call it 14.5.  At 5 ft. lbs you may not even feel it, but certainly at 10.  When torquing my rotors, hubs, sprockets, etc, if memory serves I was torquing them to about 65 ft. lbs, based on the specs of the hardware since there was no manual for my bike, and I think I started at about 25 and worked my way up. And obviously there wasn't even a gasket to deform in those cases.

[TOOLS1]

Unless yours is pouring oil as fast as that bike, you do not have a head gasket leak. If it is just seeping a little oil, it is the rubber seals (nickles) under the cam towers that seal the holes for the head bolts. It is a very common problem on the SOHC engines. You only need to remove the cam, and cam towers to replace the nickles. However if you are going to remove the head, you might end up breaking the seal on the base gasket, so plan on replacing that as well. You might get away with just re-honing the cylinders, and using the old rings if the engine has good compression before tearing it down. As for torquing the bolts, I do it in 3 steps ending at 15lbs.
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[maybe73]

Thanks for the reply 18Bravo and I have to agree with your comments.

[maybe73]

My SOHC is not leaking near as bad as the video, but it is coming from the bottom of the head. It leaks bad enough that after riding for a while the oil that leaks travels backwards on the fins and fly's off on to both side covers and the insides of my jeans. I would love to not have to remove the head. Cylinder compression is good on all 4 cylinders, and bike is running pretty damn good, which makes my think that you are rite in suggesting that it might just be the rubber seals under the cam towers. If head gasket was even marginal would it show in compression test? If it is just the rubber seals where does the oil escape from engine and would oil be getting into cylinders thus getting burned with fuel? I have noticed an increase in smoke from exhaust.
Do the rubber seals show wear or splits or cracking to the naked eye? What to look for? Thanks again.

[TOOLS1]

When you remove the cam towers from the head, you will find 6 hard, dried out rubber seals that are the size of a nickle. They seal the holes that the head bolts are recessed in, and when they leak, the oil comes out from between the fins where the head, and cylinder meet. There are also 4 small O-rings under the cam towers that will need to be replaced. They seal the oil passages between the cam towers and head. A head gasket can leak in several ways. It can leak oil, compression, or even anti-freeze in a water cooled engine, or all three at once. Is your bike burning oil, or is it dripping oil onto the exhaust making it smoke like it is burning oil? The best way to really check the condition of the engine is with a compression test.
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[maybe73]

Thank you TOOLS. You are the knower of all things SOHC cb750. You have given great advice again. Time will tell what I find under that valve cover and cam. If I have to pull the head, I'm going to have to decide how far I want to take this. All this on a $300 bike that I had alot of grins on this last summer.

[TOOLS1]

$300.00 is cheap for a SOHC CB 750.
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[maybe73]

Yes it was cheap, that's my dilemma. How much $ do I want to spend? Could do complete valve job. Maybe send the head to Cycle X and have them do what it needs to put it back into factory specs. 40 k plus miles on the odometer. So while it is apart do cylinders, hone, rings? $$$$$. I get the eye roll from the wife. TOOLS are you able to do machining? Just a thought.  

[TOOLS1]

No, sorry I do not do machine work. I send mine to Larry James at Donnell's Honda here in Kansas City. http://www.donnellsmotorcycles.com/ 
Instead of thinking in terms of "how much you paid for the bike" think of what the bike is actually worth when repaired, and put back into working order.
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[maybe73]

Good point TOOLS. I do have alot of fun on this thing reliving my youth. Thanks again for the info.

[maybe73]

I removed engine, got the head off. Not good.

#1 cylinder.

#1 cylinder head before cleaning.

#1 cylinder head after bead blasting. A lot of corrosion.

[TOOLS1]

The carbon build up is not that uncommon, but the corrosion could have been. It is a good thing that bike did not sit any longer, or it would have been stuck. When you put it back together, take a die-grinder, or Dremel and clean off the sharp edges of the corroded area, so you do not have hot spots. I would also suggest since you have it apart replacing the cam chain.
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[maybe73]

Thanks TOOLS. I sent the same picture to cycle x for their opinion. I can send the head to them and they suggest milling off about 5 to 10 thousands or to what they feel is necessary to clean it up. Then they have head gaskets that are over thickness to make up the amount that has been machined off. So I feel this is a good option because I had another engine shop tell me the head is toast. Of coarse cycle x has to have the head to give a proper assessment, which i can understand. TOOLS, do you agree?

[TOOLS1]

I seriously doubt that that head is toast. However it would not be a bad idea to have it milled. and if anyone can do the work properly, it would be Cycle-X.
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[maybe73]

The head goes to Cycle-X. Thanks again TOOLS. I will keep you posted on the prognosis.

[18Bravo]

I'm sure Cycle X does great work. I have to wonder though, if you might want to try it yourself.
I own four Sportster motors (well, two are actually Buells) and plan to install 1250 kits on at least two of them. Several builders redo their own heads because of damage or warping. Apparently all you need is a large piece of marble (check) and lots of wet/dry sandpaper. (check again) Admittedly, I have not yet done it myself. but it doesn't look like rocket scientry.  Could save you a few bucks...

[maybe73]

I am always up for saving $ but I think there's way too much grinding to do it with the method you speak of. But as always thanks for your suggestions.

[TOOLS1]

I use the flat surface, and sand paper method on heads off one, and two cylinder engines, but there is just too much surface area on an inline four, for me to feel comfortable using it on them. However you can go on and check the surface with a straight edge, and a feeler gauge to see if it actually needs shaved.
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[maybe73]

Just to clarify, my above pictures are of cylinder #4 not cylinder #1. My bad.