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HEAD GASKETS Blowing!?!?!

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In the last 6 months, my bike has blown 3 head gaskets. After the first one, I had the head checked and ended up getting it milled. The bike is blowing the gaskets in the water jackets, getting too hot possibly??? It has a Boyesen Hy-Flo water pump on it, stock radiators.

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Here is a question for you.... How are you torquing the head down? Are you doing it in a couple of different passes or are you just torquing it down to the specified torque in one shot? I had an issue with a bike that someone put together that did the same thing as yours and I dug and found out that they were tightening it down at once and it ended up leaking from the water jacket to the outside. Just a thought...

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Here is a question for you.... How are you torquing the head down? Are you doing it in a couple of different passes or are you just torquing it down to the specified torque in one shot? I had an issue with a bike that someone put together that did the same thing as yours and I dug and found out that they were tightening it down at once and it ended up leaking from the water jacket to the outside. Just a thought...

What he said. It's very important that the head bolts be tightened in a criss-cross pattern and incrementally torqued to spec.

I probably make about 5-7 passes on each bolt before they are torqued to spec.

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Does it have a high compression piston in it? If you milled the head and have a high compression piston also, it may have too much compression. Do you run race gas? You may have to if you milled much or have the high comp piston.

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what year bike?

I saw a lot of 2010's with this problem..

Always had to surface head and cylinder very, very lightly.

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Sorry, it is a 2008 model, and it has a 13.5:1 Wiseco in it, and Pro Circuit PC3 cams in it if that makes a different. I run 93 in it. I torque the head, loosen it, torque it again, and run over the bolts another time or two. I drag raced for years and this is how we always did it to mash the gasketf, so I just figured it was a standard procedure. Gonna get my local machine shop to check the cylinder for trueness Monday.

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Yep, both cylinder and head have to be flat. How much was removed from the head when you had it milled? If it wasn't too bad, I used to use a piece of glass with sandpaper laid on it. I would do a figure 8 motion and check for high spots.

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Yep, both cylinder and head have to be flat. How much was removed from the head when you had it milled? If it wasn't too bad, I used to use a piece of glass with sandpaper laid on it. I would do a figure 8 motion and check for high spots.

The head wasn't too bad, it just had a slight scar from where the first gasket blew and left a shallow run in the base. It probably would have been fine, but I was TRYING to avoid what I am doing right now. I really don't feel like the surface mating is the problem, I may be totally wrong, but the gasket never blows in the same place, and theoretically, wouldn't it blow in the same spot, or close to it if it were a mating problem? I am just fishing for answers here, I will investigate every suggestion I get because I am ready to put this bike back together for the LAST time.

I ride in the woods alot, so I have ordered oversized radiators, I figured they can't hurt. Another theory that is running through my head is with this hy-flo water pump, if I don't keep this bike in the wind like a racer would, could the water possibly be flowing through the radiators too fast to get cooled down? I know this was also a problem when I was drag racing, so it is just a thought. I really feel like it is steam blowing these gaskets, but I am no top mechanic, so I am taking everyone's advice and checking what you all suggest. Thanks for all your help!!!

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Another thing is that the washers need to be lubed with engine oil, not installed dry.

And I don´t know about loosening the bolts what that would help? Just torque them down incrementally criss-cross until full torque is acchieved.

Sometimes these things can be confusing, I know this guy who reused an RM-Z 450 head gasket 3 times. It was probably 2-300 hours old, and still worked perfectly.

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I really feel like it is steam blowing these gaskets, but I am no top mechanic, so I am taking everyone's advice and checking what you all suggest. Thanks for all your help!!!

If the engine is overheating you SHOULD notice coolant spewing from the overflow long before it would affect the head gasket, unless the coolant has left the engine un-noticed while riding.

That being said, I wouldn't rule out detonation with 13.5:1 and 93 octane.

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If the engine is overheating you SHOULD notice coolant spewing from the overflow long before it would affect the head gasket, unless the coolant has left the engine un-noticed while riding.

That being said, I wouldn't rule out detonation with 13.5:1 and 93 octane.

Holy crapola! I overlooked this detail. You need to be running race gas with that kind of compression ratio! I bet that thing is detonating. At least run a 50/50 blend of 110 and 93.

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That's why I asked what piston he was running and how much the head was milled. Race gas would be needed on this one.

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Alright, I will try it with race gas. This is the piston that was in the bike when I got it, and it ran fine until it blew the first gasket. I just wonder what has changed, but I am going to try everyone's suggestions and see if I make any head way. I think while it's down I am going to put a new timing chain in it, mine looks to be a little stretched. Any suggestions on head gaskets? I have been running OEMs thus far.

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Alright, I will try it with race gas. This is the piston that was in the bike when I got it, and it ran fine until it blew the first gasket. I just wonder what has changed, but I am going to try everyone's suggestions and see if I make any head way. I think while it's down I am going to put a new timing chain in it, mine looks to be a little stretched. Any suggestions on head gaskets? I have been running OEMs thus far.

Perhaps the previous owner ran race gas? Usually when someone moves to a high comp piston, they'll run race gas. I personally think the OEM gaskets are just fine.

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I too had that (very frustrating) problem. I sprayed the head gasket with a very light coat of Permatex Copper Coat on each side. Installed, with no further issues.

Do a search, many swear by this stuff. I do now, I'll put it on every head gasket I do from now on.

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I too had that (very frustrating) problem. I sprayed the head gasket with a very light coat of Permatex Copper Coat on each side. Installed, with no further issues.

Do a search, many swear by this stuff. I do now, I'll put it on every head gasket I do from now on.

Funny you should say that. I talked to a friend of mine who is a local ATV/Bike mechanic here and he handed me a can and said try this. This has frustrated me to no end. Bike ran fine for over a year and then BAM, started blowing head gaskets. I am going to try it with the copper seal and race gas and see if that helps. I also ordered the oversized radiators because the older I get, the more I putt around...lol. And lord knows these 450s don't like to putt!! I hope I can get to the bottom of this. I have worked on my own bikes since I was a kid, but this one has me second guessing all of my ability!!! Thanks again for all of you guy's input, this forum is great!!!

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Thats really high compression, and honestly for a woods bike its not doing you any favors. That extra compression builds up a lot of extra heat. Absolutely run race gas mix and the extra compacity radiators. I put the bigger dual core rads on my 12:1 compression kx450 woods bike and it likes them A LOT. Starts up MUCH better, literally its a one kick wonder every time dont even need the hot-start even if i have been riding in some slow sloppy crap and really heating up the bike.

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oh and I we used to take the 3 layer head gaskets apart on Honda b-series vtec motors and just use the middle layer of the gasket. (more compression)

Take the motors, put a bigger crank, 12:1 compression, ported head, and the thin headgasket and coat it with the copper permatex stuff and throw it all together and spin em up to 9,600 RPMS and it always worked great. lasted forever

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