BASE GASKET BLOW OUT

[don46]

Maybe I'm crazy but anything that works better and makes my life easier, Im all about It. A gasket that doe's not need to be glued In place and never blows out and comes off cleen when your done with It. How could you not want that

What he said! cleaning and scraping leads to the potential of scratching the surface causing further possibilities of a leak. Cometic all the way. and if you need special gaskets they will oblidge you.

[Mhardee]

Maybe I'm crazy but anything that works better and makes my life easier, Im all about It. A gasket that doe's not need to be glued In place and never blows out and comes off cleen when your done with It. How could you not want that

What he said! cleaning and scraping leads to the potential of scratching the surface causing further possibilities of a leak. Cometic all the way. and if you need special gaskets they will oblidge you.

I will quote something my father beat into my head when he was "teaching me" mechanics...
"NO GASKET is better than a gasket and a half"..

Make sure the surfaces are clean and free of any old gasket material and a thin silicone rubber coat never hurts. Remember, there's only 4 bolts to tighten AND it's aluminum - careful, slowly and methodically tighten..

The voice of experience IS talking...

[BDI]

Maybe I'm crazy but anything that works better and makes my life easier, Im all about It. A gasket that doe's not need to be glued In place and never blows out and comes off cleen when your done with It. How could you not want that

What he said! cleaning and scraping leads to the potential of scratching the surface causing further possibilities of a leak. Cometic all the way. and if you need special gaskets they will oblidge you.

I will quote something my father beat into my head when he was "teaching me" mechanics...
"NO GASKET is better than a gasket and a half"..

Make sure the surfaces are clean and free of any old gasket material and a thin silicone rubber coat never hurts. Remember, there's only 4 bolts to tighten AND it's aluminum - careful, slowly and methodically tighten..

The voice of experience IS talking...

The gaskets that I'm referring to are rubber coated metal gaskets that do not require any goop to make them seal or stay put. The gasket surface is always clean because they don't stick. They are modern day gasket technoligy. I first used them In 98, It was the first time I ever used them. I was skeptical at first now I will use nothing else they are the next best thing to having every thing on your bike O-ringed. It makes working on my bike a pleasure and nothing on my bike leaks. you would probably have to use them for a few years on a bunch of different bikes like I have to truly appreciate them.

[monster malibu]

I still don't know if the Cometic gasket#c7045 will work on my bike or not. My bike is a 87 kx500 with the stock bore (86mm) and the gasket Cometic lists for it is a 88mm bore gasket. Will this gasket work?

[gowen]

The head gasket will not work, but the base gasket should.

[BDI]

I still don't know if the Cometic gasket#c7045 will work on my bike or not. My bike is a 87 kx500 with the stock bore (86mm) and the gasket Cometic lists for it is a 88mm bore gasket. Will this gasket work?

    Call cometic and talk to them I think they offer that gasket In stock and over bore. I have ran over bore gasket on a stock bore In a pinch with no problem but cometic should be able to get you the right one. If you choose to run the base gasket that I like you should call and specify It because They still make the old paper ones. they are aluminum with foam rubber coating If you dont word It right they will send you steel with rubber the same thing they make head gaskets out of and the same price as head gaskets.

 P.S. please make sure the bottom of your cylinder Is flat no matter how good a gasket  is  it will not fix a warped deck or base and It will leak again, blown gaskets usually have a root cause.

[don46]

Just for kicks I went and measured a stock kawasaki and Cometic headgaskets, yep you guessed it, they measure 88 mm. The base gasket will be different between 86, 87, 88 and the 89-04 the newer motors have the 3 KIPS shafts whereas the older motors only have the 2, the cases are a bit different on the older motors as well in the KIPS area. The headgaskets are much larger and thicker on the older motors.

And as far as using Silicone for gaskets in the motor, I would'nt reccommend it, gasoline will dissolve most silicone, if you must use some sealer use something on the order of a copper coat or whatever the permatex hi-tack. I haven't bought a stock KX base gasket in quite some time, I would think they would be using the same material as Cometic since they do on the 125 and 250 base gaskets.

[Mhardee]

And as far as using Silicone for gaskets in the motor, I would'nt reccommend it, gasoline will dissolve most silicone, if you must use some sealer use something on the order of a copper coat or whatever the permatex hi-tack. I haven't bought a stock KX base gasket in quite some time, I would think they would be using the same material as Cometic since they do on the 125 and 250 base gaskets.

Just to add more fuel to the fire

Silicone Rubber is used as a gasket aid in most if not all of the race motors built today - I've built and have helped build literally hundreds of 700 - 900 HP small/big block gasoline, alcohol, nitro fueled motors. Gasoline will attack Silicone Rubber - that's a fact.. If it gets to the Silicone placed on a paper head gasket, you "fo'  d**n  sure" have other issues, not limited to, but most likely, a crummy mating service (i.e. gouges or warpage).

Just hate to hear blanket statements like that - most gasket manufacturers recommend it. We could all get all of this behind us if one could lay his hands on a .040 solid copper gasket and keeping his butane torch handy..

I would also like to thank you for posting the reply about the heating of expansion chambers to remove dents and the added "benefits" of heating air... I was really thinking about it... but, Alan came through with a new pipe I just got yesterday...

Mark

[don46]

Cometic will make a copper gasket, definately for the head and probably for the base, they built me a couple of aluminum spacers to lift the cylinder and some .010 gaskets.

don't get me wrong, my statement about using silicone was that there are better sealers, at least in my opinion, Yamabond is one of the best but a real pain in the a$$ to clean up. I would agree with your statement about the crummy mating surface, which is what led to the discussion about the base gaskets BDI was talking about.

[stewart]

i think cometic  has great kx 500   gaskets i like the metal with the fiber type coating base gasket they make

[BDI]

At one time I had some head work done by RPM, they shaved my head flat on a lathe then I put the motor back together, I rode the bike for a couple of hours and it blew the head gasket.  I assumed It was due to the high compression so I tried again and again but It kept blowing the head gasket, so I had a copper head gasket made I even used hylomar but after I put the copper head gasket on I could not get It out of the driveway without It spiting water from the head. What had happened was, my cylinder and head had spent so many years together they had become warped but they were mated so they did not leak. Once I had the machine work done they were no longer mated and It leaked like hell.  It was not until I fixed the warped deck that my problem went away.  A copper head gasket does not compress on a kx500, there is to much surface area, the sealing work is done by the sealant and not the gasket itself that's why you can use the steel shim head gasket. The metal part of the gasket will never compress it is only a spacer, it is the coating that does the work. The moral of this story is if all the surfaces are not flat It will not seal and a copper head gasket will make It worse because it will not compress and fill the voids like a fiber head gasket will. If a gasket blows there is a root cause, first you must find that cause and fix it.

 P.S. silicone Is a good way to keep two part that do not fit together very well from leaking, for awhile.

[FactoryPhil]

The moral of this story is if all the surfaces are not flat It will not seal....... If a gasket blows there is a root cause, first you must find that cause and fix it.

 P.S. silicone Is a good way to keep two part that do not fit together very well from leaking, for awhile.

Bingo!! You have the patience of a saint BDI.  RTV silicone is for the backwoods, redneck, bandaid, demolition derby type applications. No offense anyone. 

[monster malibu]

Before I put the base gasket on I coated it in a thin layer of silicone to help seal it up and it still blew out. I'm going to call Cometic and get a new gasket on the way, and it won't be one of there paper ones again. When I replaced the topend I couldn't find my torque wrench so I did it by hand, this time it will be done right.

[Hillclimb#42]

Skip the silicone. Just get it super clean. Surgical Clean. Finger tight on nuts. Then go a half turn on each in a crossing pattern until torqued. That silicone will not help base gaskets.

[kaw rider]

when i install a cylinder, i install the cylinder with out the piston and base gasket. And torque to spec. and look for gaps around the surface. and use small feeler gauge for clearance. Kawasaki stud are known to be on the soft side. we had this problem on the jetski motors. the problem most of the time are high spots around the area of the stud. I just had the buttom of my cylinder cut and it was .004 off.