KX Riders
Maintenance & Technical => KX500 Original => Topic started by: monster malibu on September 23, 2007, 10:36:20 AM
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Hey guys, I just replaced my bikes topend and the base gasket blew out. The cylinder was tightened and checked after the breakin period. I was wondering if anyone has had this problem with Cometic gaskets. The base gasket looked real thin, but I used it anyway. I'm going to buy a Winderosa topend gasket set in the morning.
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was the gasket all paper or metal with paper on both sides,,,,, how thick does it mike
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The gasket was all paper. I can't believe the new gasket blew out already, the bike has an hour total run time on it after getting a new topend.
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i just replaced my base gasket and head gasket with factory ones. no problem, other than the head gasket was 42.00 dollars and the base was 8.00. base was just hard paper.
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gasket meterial is key to no having problems. i know the buttom of cylinder is not flat. I only run oem gaskets.
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Are the oem gaskets metal/paper combo, or are they just made of paper? Anybody using Moose gaskets, or Vesrah gaskets with any luck?
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The OEM gaskets are paper only. In my experience they are less flimsy or flexible than most aftermarket ones. Honestly, I have used Cometic gaskets with great success in the past. You might want to check your cylinder and crankcase mating surfaces very carefully next time you replace the gasket. It is possible there could be some old gasket left or maybe a gouge from scraping that caused the failure.
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oem are paper base gasket.
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Cometic makes base gaskets that are aluminum with foam rubber on each side. These gaskets will not blow out sideways because of the metal in them. The foam rubber makes them seal much like O-rings would, plus when you have to take your engine apart they come right off with zero clean up, no gasket scraping means no scratches and no future sealing problems. If your base gasket leaks around the transfer area it is very likely that the base of you cylinder is not flat. This is usually caused by over torquing of the base nuts. You should check the bottom of the cylinder for flatness and have it machined accordingly then torque the base nuts using a crows foot to 25 foot pounds. You should first torqe them to ten then twenty then twenty five In a criss cross patern. Cometic makes the best gaskets I have ever used and this Is not my first rodeo. If you order your gaskets from a after market supplier you will get what they have on the shelve. If you order from www.cometic.com you will get what you specify. They even have stainless steal gaskets the are rubber coated but they are expensive. If a gasket blowes It Is generally not the gaskets fault. You must figure out why It blew and fix the problem.
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If a gasket blowes It Is generally not the gaskets fault. You must figure out why It blew and fix the problem.
Bingo!
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I checked out cometic.com and they list a topend gasket set for my 87 kx500. My bike has the stock bore 86mm, cometic lists a 88mm for my bike, will it work?
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Cometic makes base gaskets that are aluminum with foam rubber on each side. These gaskets will not blow out sideways because of the metal in them. The foam rubber makes them seal much like O-rings would, plus when you have to take your engine apart they come right off with zero clean up, no gasket scraping means no scratches and no future sealing problems. If your base gasket leaks around the transfer area it is very likely that the base of you cylinder is not flat. This is usually caused by over torquing of the base nuts. You should check the bottom of the cylinder for flatness and have it machined accordingly then torque the base nuts using a crows foot to 25 foot pounds. You should first torqe them to ten then twenty then twenty five In a criss cross patern. Cometic makes the best gaskets I have ever used and this Is not my first rodeo. If you order your gaskets from a after market supplier you will get what they have on the shelve. If you order from www.cometic.com you will get what you specify. They even have stainless steal gaskets the are rubber coated but they are expensive. If a gasket blowes It Is generally not the gaskets fault. You must figure out why It blew and fix the problem.
Correct. I have run Cometic for years and years without issue on every single bike I've owned.. I have also used Moose with success on my KX (Eric Gorr had a thick one designed for my KX or something like that).. Everything else had Cometic. I'd guess it was warped too.
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Regardless of the gasket brand, I like to glue my base gaskets with some type of form-a-gasket. Once rebuilt, the 500 tends to stay together for quite a while so I don't mind the extra effort to scrape/clean off the glued gasket during the next rebuild. However, I have had to do at least one rebuild because an unglued base gasket blew out (un noticed) and sucked dirt into the engine, ruining a out of town riding adventure. My K5 one (OEM) is nicely cemented in place with the last of my Kawibond. Cam.
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I agree. I use yamabond 4.
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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 :? I rate scraping gaskets right there with spooning tires,cleaning air filters and smashing my finger with a hammer. All things I'm capable of but probably would never do again If I did not have to.
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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.
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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... :-)
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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. :-D
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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?
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The head gasket will not work, but the base gasket should.
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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.
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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.
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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
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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.
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i think cometic has great kx 500 gaskets i like the metal with the fiber type coating base gasket they make
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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.
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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. :-D
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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.
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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.
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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.
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Copper head gaskets can work, what most people don't do is anneal them prior to installation, this is what Mark was referring to with the Butane torch, If you just install them without annealing them I can almost guarantee they will leak. If given the choice I would use a stock or Cometic headgasket over the copper, but, in some cases that's the only alternative for special applications. One of my motors uses a copper head gasket, I use a hopcolite sealer and have annealed the gasket, it doesn't leak, of course I'm afraid to take it apart because I know it will next time.
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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.
That is what was wrong with my cylinder deck it was like the stress from tightning the head nuts pulled the aluminum up around the studs making a high spot around every stud. That is why the fiber head gasket would last a couple hours and the copper head gasket would not seal at all even though It had been properly annealed and sprayed with the most expensive sealant on earth a.k.a. Hylomar.
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Hey guys, I called Cometic and they recommended their Nitro Coated Aluminum base gasket for my bike. These gaskets are for the stock bore 86mm, the part # is B0035018AFM if anyones interested. They don't have the gaskets in stock, but will make them in three days.
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What ever happened Is your bike running yet?
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I got the bike back together and my base gasket problem is gone. My bike runs fine again but it's bow season, so my riding is pretty limited.
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Ride on :wink: glad to hear It. What did you think of the gaskets?
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I thought the gaskets were kind of thin and flimbsy, but they work, that's what counts. I got my gaskets in three days just like Cometic said,that was cool.
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The first time I used them I was skeptical. They seem weird at first but they work great and wait until take your bike apart then you will like them a lot.
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I bought an extra base gasket just in case of another blowout. The head gasket was around $22, and the shipping on the three gaskets was $10.45 WHAT A RIP OFF!!! All the gaskets couldv'e been sent in a envelope and shipped for probably a few bucks.
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yes I'm going threw the same thing with them right now I wanted my gaskets by the week end but they wanted an arm and a leg to ship them when they could send them priority mail for less then ten bucks and I would easily have them for the weekend. :x
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Old topic I know but I just had my base gasket blow out. Never even heard of that happening on a 2-stroke before. My first thought was I'd wished I'd used Cometic last fall when I put it together. Met the founder in a bar one night, heck of a nice guy. Regardless, my point in posting in an old topic is that this thread is the first hit in google when I searched on the topic. I can confirm, yes the KX500 base gasket will blow and Cometic makes a nice gasket and I wish I had used one last time.