| Author | Message | ||
     Barrick09 |
This is a continuation of the perpetual head gasket blowout thread I posted a couple months ago. As per many requested, the engine is apart and I have pics! Looking to get everyone's opinion on the looks of everything. As well as what all should be replaced moving forward (bolts, gaskets etc) and part numbers. here come the pics!     | ||
| Essmjay |
Since it is a continuing problem, I would replace the cylinder and the head. There is something wrong with the mating surfaces and if you re-deck them your squish will be off. just my opinion | ||
| Sportyeric |
Disagree, Shane. The stock engine is built with a lot of slop in terms of squish area. You can probably take 20 thou off the head, thereby cleaning the blemish in the mating surface,and still be a ways away from a good tight squish measurement. I haven't looked at the previous thread, but, Anthony, if you want a quick explanation of the squish area, send me a PM. | ||
| Barrick09 |
When this happened the first time the gasket was just replaced. The second time a year later. The cylinders, all gaskets and bolts were replaced as well as I had it re-bored and resurfaced. This lasted 1 whole season and most of last years season. | ||
| Fahren |
Essm, you may be right, but you can get different gasket thicknesses from Cometic if you need to change squish. | ||
| Rocket_in_uk |
Clearly visible on the underside of the head there is some sort of damage where the problem has occurred. From the pic it looks like the sealing ring on the gasket has been breached by this damage, allowing combustion gas to eat away at the gasket leading to failure. Solution, skim both heads. Rebuild with Cometic gasket of suitable thickness. Rocket in England. | ||
| Pash |
Why are you using O rings on the spigots? The gaskets come with instructions telling you not to. I bet this is not helping... | ||
| Barrick09 |
Rocket, I see the damage you are talking about. I will most likely have to have that resurfaced hopefully and not replaced. How might one compensate for the gasket thickness or the difference between front and rear? Pash, I did not do the previous rebuild so I cannot answer that. | ||
| Pash |
My money is on the O-rings... | ||
| Rocket_in_uk |
Assuming you know what gaskets you have now you can determine their thickness. So, if you skim the head by 10 thou then use a 10 thou thicker head gasket than you have now. Skim both heads regardless. You might also want to pull both cylinders for inspection and cleaning, and replace both base gaskets too. Again you should be able to determine what base gaskets you have and their thickness too. The assumption here is that the last time it was rebuilt both base and cylinder head gaskets were of correct thickness. This said, if you have a few quid, sorry bucks, to spare, you would benefit from having your heads worked and squish tightened. Even going to as far as a porting job. Or find some heads tuned and ready to fit - perhaps in an exchange deal with one of the BadWeB sponsors? This way you'll get the advice on gaskets, and future upgrades should you decide to go for a hotter cam or bigger carb etc. As I said though, if you're just wanting back up and running quick with little cost, then a head skim is in order and new gaskets, will suffice. As I can't see the damage in detail I can't determine from the pic if you could dress the damage with files and smooth paper. It's a delicate area where the slightest of marks to the surface area will result in a repeat of what's happened before. Rocket in England | ||
| Barrick09 |
So I've been calling around locally and WOW talk about variation. Some say it would be cheaper to just replace the head. Plus if I just resurface the front then I have a compression issue. How serious? no one seems to know. If I choose to replace the head that doesn't solve my issue either because I would still have to replace both at the same time because the rear has been machined before as well. I really do not want to take the rear apart in fear, since this has happened before, that the heads aren't even my problem. I'm at a lose at this point.  | ||
| Essmjay |
Right, I forgot you can get different gasket thickness. I see now that the cylinder was replaced, but not the head. Pash is right, no o-rings with the cometic gaskets, and I think not with the new HD ones either. What I hear here is that if you mill the head and cylinder and set up the squish correctly, using the right thickness gaskets, you should still be able to match compression with the other cylinder. If you have to pay someone to do that, but you could just replace the head and cylinder on your own, then it might be cheaper to replace parts. That way the only special tool you would need is the valve spring compressor. I bought one when I needed it, but I think one could be improvised. Regardless, just replacing the gasket again looks like you would have the same problem again. | ||
| Barrick09 |
ok so. replace the head, no o-rings and replace the gasket with a gasket thickness to get me as close as i can to match the rear. What would be acceptable as far as compression difference? | ||
| Yo_barry |
I'd replace that head gasket, It's toast! OK, I picked up a used head on ebay for $100. It was the front one with good threads in the mounting holes. That was the problem I was trying to solve. There are parts out there. Barry Hollister, CA | ||
| Ratbuell |
It almost looks to me like its time for a new torque wrench. You can get issues like this if you overtorque the bolts, and "bend" the head down at the bolts, allowing it to come up at the spot where you blew out the gasket. Doesn't help that there are o-rings at that end, too... | ||
| Rocket_in_uk |
Take your damaged head to a machine shop and have them lightly skim it until the damage is removed. Or do it yourself with a sheet of plate glass, valve grinding paste and plenty of elbow grease. You'll be surprised how soft and how quick you'll skim it by hand and eye! If shop, they should be able to tell you how much they've removed. If it's close enough to a relative gasket thickness to get you back to where the head was before you skimmed it, you're good to go with the thicker gasket. If not don't worry about it too much. A few thou removed from the head won't make your bike run noticeably different. It's not like you're going racing - are you? All it should cost is the price of a skim and a gasket. Fresh oil and filter. New plugs. Rocket in England | ||
| Barrick09 |
Ok, so after about 20-30 phone calls i finally got somewhere. A shop is going to machine the head, they said under $50 for the cost. I will not be using o-rings when I re-assemble this time. I assume the rear has them as well, will this be a problem? (once cylinder having them and the other not) I do not plan on tearing the rear apart. If it ain't broke don't fix it. Now I just need Part numbers for gaskets and bolts that should be replaced upon rebuild. Thanks for the help everyone has provided. To Do List: Machine Head Order Parts Upgrade/re do Catch-can system (any suggestion are welcome, I know there are 100 different ways to do this). New muffler (to replace my non existent one) Should be on the road by the end of the month!!!! | ||
| Pash |
I would say if o rings are on the rear it will go the same way as the front eventually... Part numbers are here: http://www.twinmotorcycles.nl/webshop/parts.asp?ja ar=2001&model=AC73B93A-C6A7-4D2C-98C5-8B8AE19372FF &sid=A2218026-1E75-4EEE-8E82-64EE82D0120E http://www.twinmotorcycles.nl/webshop/parts.asp?ja ar=2001&model=AC73B93A-C6A7-4D2C-98C5-8B8AE19372FF &sid=427CC82E-7655-46AF-A0D3-C628F83CBAB0 | ||
| Oldog |
after looing at this I am inclined to agree with RatBuell and say you might want to look at the wrench. IIRC you torque them in steps and then turn them 90 deg for final tighten that you are doing this on oiled washers. The top of the jug and the head are damaged so as the parts are cleaned up pay close attention to the clearances.... | ||
| Arizona_buell |
My money is on the O-rings. WHATEVER you do I would not take it back to whoever put that together..my 2cents. I would lay the head on the jug after cleaning it all up with no gaskets and check with feeler gauge the thickness and check that against the new gaskets . It has to smash the gaskets if that helps you at all.. Mark | ||
| Rocket_in_uk |
There is what looks to be a clear explanation as to why this engine is failing repeatedly. It is the visible damage to the cylinder head surface as seen in the pic above. If the other cylinder is functioning correctly there is no problem with a quick fix to the damaged cylinder only, then my advice is for you to go ahead and do as you want to do. There is no point and no reason to get into the other cylinder if you don't want to right now. If it fails at all in the future then that is a matter for you to consider if or when that happens. Right now though I do not see a problem caused by o rings or incorrect torque procedures. What I will say is if you can lay your hands on a leakdown tester and have access to a compressor, you could very quickly test the percentage of cylinder seal you have in your good cylinder. Rocket in England | ||
| Barrick09 |
Pash seem to be correct after further looking at the head the mark just wiped off with my finger and there seems to be no damage. | ||
| Rocket_in_uk |
You've only just found this out after wiping the head with your finger? Leave it to professionals. Rocket in England | ||
| Barrick09 |
Rocket, when I took the head off it was late at night. I didn't even notice the "damage" until someone mentioned it. My bike is not at my place where I can simply go outside and check every 5 min. when I finally got around to checking it I found it was actually just soot on the head. As for "leaving it to the professional" I did that the first time, and the second time, and this is where it has gotten me. This time I'm doing it myself so it's done right. Am I a "Professional"? by no means but at least I'm willing to learn and get my hands dirty which is more than I can say about most people. | ||
| Rocket_in_uk |
You've an ongoing issue which relates to head gasket failure. You had time to take pics but not to rub your finger over what looks like an obvious area of concern until now does not tell me you want to be doing this on your own. There are too many simple things to check before you can even begin to know what direction to go now. If two professionals have failed you need to know why. You can forget the o ring theory. The failure is in the middle of the stud spacings which is as far away from the o rings as possible. That is not your problem. You either have a mechanical issue with the components. Be it damage or warping to head or cylinder or both. Or you have a clamping issue. Be it incorrect fitting or a mechanical issue preventing the correct clamping. Or inferior parts. I'm not seeing anything else which could be the cause of these failures. Someone that knows what they're doing should sort this out well within a working day. It's not that difficult! Thus, save the cost of parts this should not be an expensive fix, even if left to a professional (a good one). In fact a good one should be the least expensive as they'll know immediately where to go and what to do without fussing and costing you more. That would be my opinion. Rocket in England | ||
| Davefl |
I would at least put the head on a flat surface(plate of glass) and check it with a feeler gauge . If it is not dead flat it needs to be milled. | ||
| Reepicheep |
The best flat surface I found when chasing a similar problem on a KLR-250 was the machined aluminum surface of my table saw. Much flatter than any piece of glass I found in the house. The feeler gauge test Dave mentioned will tell you right away if there is a problem. Surfaces must be surgically clean on reassembly. Figure 8's with wet 2000 grit paper on the table saw surface will also show you the high spots as they will be the last to polish. Rocket's point is valid, even if it came off a little rudely. Patience and preparation are everything when you have a chronic head gasket issue. If you go slow the job goes pretty quickly. If you rush it, you will just keep doing it over. If you are a personality that struggles to be methodical, it's a good job to farm out. | ||
| Firemanjim |
Older Harley gaskets required o-rings, newer did away and Cometic best bet anyway. | ||
| Bluzm2 |
Like Jim said, the gasket inthe above picture appears to be the old style HD units that DID require the O rings. The new ones do not. The Cometic and James do not either. I'd just go with Cometic and be done with it. Plus you can tweak the squish if needed after cleaning cut up the heads. | ||
| Rocket_in_uk |
Rocket's point is valid, even if it came off a little rudely. In my defense, I was upset after being outdone by the simple rub of a finger  Rocket in England |
