Head gasket

[Dunn111987]

Just wondering what the signs of a bad head gasket are? And is it simple as just changing it out to fix? On a B+ engine. Notice I have some oily gas type residue around the top fin on the cylinder between where the head and cylinder meet. Is this a sign of a failed gasket? The head has been torqued to specs.

Thank you,
Ryan

[Hydraulic Jack]

Post a photo if you can. It helps to see what you are looking at.

But, there shouldn't be any dark oily stuff on the top fins of the cylinder. I am assuming you mean the topmost fin of the barrel, under the head. Probably a leak. Has it failed? If it is leaking, arguably it has failed. It may not yet be a fatal leak, but it won't get better on its own.

Replacement is needed if the original has failed. To minimize down time, purchase a new gasket or two. Then carefully remove the head and inspect the gasket and both sealing surfaces. Pay attention to the area where the oily leak was and look for scratches or cracks on the head and cylinder top. The head and the barrel can be carefully sanded if there are scratches or burrs, but it has to be done using clean W/D sandpaper on a very flat surface, such as a glass table top, a drill press table, or some other true surface. If there is a very small defect, sanding will improve the situation. If the defect is too large to effectively sand out, other steps may be needed, but I would have to see the defect to know which way to go. If you have never flat sanded an engine part, proceed very slowly with this, and ask questions when needed.

If the only problem was that the gasket itself failed, a good cleaning and a new gasket will do. While it isn't supposed to be necessary, I like to spray head gaskets with copper sealant. Torque head nuts in stages, and in a sequence. Never simply tighten one, then the next and don't go around the circle. Use a criss-cross pattern. Torqueing too much at one time will warp the head or will at least defeat your attempt to seal the head. So work up to final torque in steps using a torque wrench calibrated in inch pounds. Don't creep up on the torque spec in tiny increments, but do use perhaps four or five equal steps so that everything stays uniformly snug.

While you have the head off, take a look at the cylinder bore and clean the combustion chamber if needed.

You might also want to consider buying a shop manual because of the detailed steps to repair and maintenance found there.

[Dunn111987]

Took a couple of pictures. There almost seems to be a stamp on the surface of the actual cylinder itself. And I found there was 2 head gaskets under the head.

[Hydraulic Jack]

The stamp is normal. Clean mating surfaces and use one head gasket on reassembly. Aluminum head gaskets can be reused but require annealing first. There has been discussion on the forum on how to anneal head gaskets. All else fails buy a new one. Can't imagine why someone would use two unless the rod bearing is worn to the point of letting the piston hit the head, in which case two gaskets would not fix the real problem. Or, someone thought it might help in using 87 octane pump gas, but I wouldn't use two gaskets.

Head and cylinder look clean. I wouldn't worry about sanding anything. Wipe down with solvent and proceed.

[Dunn111987]

Think I may have found another problem! A loose stud with the bottom threads gone! I tried threading the other end down in the hole and it took hold. So I ordered new nuts, washers, a new stud, and new gasket.

Ryan

[Hydraulic Jack]

Stripped threads would be a problem. Is it the stud that is stripped, or the aluminum engine block?

[Dunn111987]

Seemed to be the stud itself. There were no threads left on one end. But I started another one down in the hole and it was threading in and tightened up, so hopefully I will luck out there. Is there a way to fix it if it won't tighten?

[thrownchain]

Helicoil, or weld and re-tap.

[taber hodaka]

The studs were threaded longer where they screw into the engine, screw them in all the way. -------ClaRENCE

[Hydraulic Jack]

Is there a way to repair stripped aluminum threads? Yes, but what needs doing depends entirely on how damaged the threads are. I would not force a stud into a suspect hole without first looking closely at the threads. Screw threads on studs or bolts are not designed to cut or repair damaged threads in soft metal. For this you would use a thread chaser or tap. However, since you have already screwed the stud into the hole, as long as you didn't have to use vise grips to drive the stud, you may be okay. Whatever you do from here, do it carefully.

The question would be how the stud got stripped, but the engine block didn't. I would check all four studs. Remove them gently as you can without using lots of force, and see if all four are good. If they are, someone probably stripped a head nut, knew it, and reversed the stud thinking it would work or no one would notice it. It may have been done just before you bought the bike, and may be one reason it was sold. Whatever. If you can not remove any of the other studs without using vise grips, stop. I would tend to leave them be rather than risk damage from unsticking a stuck stud.

If the aluminum threads are a bit smeared but mostly intact, you can chase the threads and see if a clean stud will engage and hold. If so, you are good. If not, I would consider using a heli-coil. Any repairs here will require you to be careful not to lose metal chips into the crankcase. Having already screwed a stud into this hole, you may be okay, but I would be curious about what damage a stripped stud would do to aluminum threads.

Anyway, inspect all four studs and report. We can go from there. If you are lucky, all you need is a new cylinder stud and no further repair needed to the stud hole.

[Bill2001]

"No threads on the stud itself" sounds like the stud pulled the threads out of the aluminum case. I don't see alloy case stripping a steel stud.
Either Helicoil it or take it to a shop and have them do it.

[matt glascock]

Are you sure that was a legit cylinder stud or some home grown replacement fabricated out of rod stock ran through a die. Threads "gone" sounds sketch.

[Dunn111987]

Well it very well could've been some temporary fix.... since there was 2 head gaskets also. Was just a motor I bought off eBay. It seems to be clean inside. Makes me wonder if the top end was rebuilt not long before I got ahold of it. One other thing I did notice that someone mentioned on here was one of the nuts was stripped and wouldn't come off the stud and took the whole stud with the nut still attached. I'm sorry guys. i wasn't trying to be stupid and mess anything up. This is pretty much my first time messing with a motor, so I'm being honest about what happened. I'm in a learning process. Just trying to get on the right path. Would love to ride the old bike this fall when the fire danger goes down again.

[Dunn111987]

One other thing I noticed about the stud that is stripped. It has a shorter end and a longer end of threads? Is that correct? And which end goes into the engine half? The shorter thread end is stripped... and the other 3 studs seem to have the longer threaded end at the top instead of in the engine half. Is that sounding like someone maybe rebuilt this engine and put the studs in upside down?

[ossa95d]

Yes it does sound like someone put the studs in upside down. The longer threaded end goes into the case to give more contact (and tensile strength) with the soft aluminum cases. Clarence mentioned this in a reply above. Jack's theory sounds plausible that someone stripped the top of the stud with the steel nut and then inverted it to hide the problem. follow the rest of Jack's advice and hopefully you won't have to repair the case. Good luck!

[Dunn111987]

Thank you! Now to figure out the best way to remove the studs without damaging anything. I will go ahead and try to replace them all. Is there a certain way to extract them? And is it easier with the cylinder off? I'm full of questions. And appreciate the advice you all are giving.

[Hydraulic Jack]

I usually use a double nut arrangement to extract studs. What most folks call a jam nut arrangement. You may not want to use the actual head retaining nuts for this, but instead, use two common metric nuts if you have them, or buy a few from the hardware to use. Install two nuts half way down the threads on top of the stud and tighten one nut against the other using opposing wrenches. Use the bottom nut to try to loosen and remove the stud. I think this is better than using vise grips on the stud shaft because of the potential for stress damage to the stud using grips. If two nuts locked together won't remove the stud, leave it in place.

Cylinder off.

[Dunn111987]

Ok thank you! I will have to try this soon! Would a little bit of oil help around the threads before I extract?

[taber hodaka]

A stud remover would work also. I like a little more bite than a nut, I cut a head nut in half and use that half along with a normal head nut, it gives me a little more surface area for extraction, I think a single nut could strip easy. I do not thread chase these as I like them tight, as long as they are not stripped. -------Clarence If it was a rider for myself, I really would not remove them unless there was a problem. Depends on the level of rebuild

[matt glascock]

Kano Kroil is the best penetrating oil I've found but here a lot of folks use PB Blaster for loosening stuck hardware. Also a 50:50 mixture of automatic transmission fluid and acetone is a great penetrating oil - just don't get any on paint.

[MTrat]

A regular 'stud remover' is pretty inexpensive and will last forever.

[Hydraulic Jack]

A stud remover would work also. I like a little more bite than a nut, I cut a head nut in half and use that half along with a normal head nut, it gives me a little more surface area for extraction, I think a single nut could strip easy. I do not thread chase these as I like them tight, as long as they are not stripped. -------Clarence If it was a rider for myself, I really would not remove them unless there was a problem. Depends on the level of rebuild

That's why I suggested using two ordinary nuts. I have never had threads strip using jam nuts because they don't exert enough force to do that. Which is also why, if jam nuts won't extract the stud, I suggested leaving them be. Two nuts jammed together are like a slip clutch. The nuts will slip on the stud before the aluminum threads in the engine case are pulled out, and the slipping nuts won't damage the upper threads. Using full thread contact, as in two head nuts, can overpower the aluminum, and can distort or strip the upper threads. Since there is no compelling reason to actually extract the other three studs if they are firmly inserted, using two standard nuts will pull them if they want to come easily, but won't force the issue to the point of damaging the engine case.

[Dunn111987]

The studs seemed to come out pretty easily. I tried to be extra careful taking them out. Is there a certain torque for them when installing the new ones? Or just snug them up?

[Hydraulic Jack]

I don't think there is a torque value needed here. Make them snug. Once the head is installed, the head nuts are torqued and the whole stud assembly is in tension.

[Dunn111987]

Ok! Thank you for all of the advice! Really appreciate it! Will let everyone know how it goes after I get the studs in the mail and am able to install everything again.