2-stroke copper base gaskets--ke100?

[RayAlazzurra]

A copper base gasket is probably a terrible idea for a 2 stroke. It would transfer more heat to the crankcase costing power, and it may not seal very well.

Even so I am considering having a custom copper base gasket made for my KE100. Base gaskets on this little bike only last a thousand miles or so before they are squished all to hell and fail to seal. The ring seal is still good at this point, so I am forced to renew the top end more often than otherwise due to gasket failure. My local Kawasaki shop mechanic is also a KE 100 rider, and he has replaced his base gasket about 5 times. The problem seems to be thermal cycles. Every time the little engine gets hot the cylinder expands and crushes the base gasket. The gasket deforms plastically, and the head nuts start to get loose. Re-torque the head, and the problem slowly gets worse with each thermal cycle.

We have tried making sure that the mating surfaces are perfectly flat. The shop guy has even removed the studs and lapped the cylinder to the case to assure a perfect fit. 1000 miles later the base gasket is starting to squish out from under the cylinder.

The KE100 uses an annealed copper head gasket and it seals pretty well. The head gasket also has a lot more surface to seal between the combustion pressure and the outside. The base gasket is only a few millimeters wide in places. The copper head gasket is used without any type of sealant. I wonder if pre-coating a copper base gasket might make it seal for a while? Btw. I checked with Cometic and they do not make an improved KE100 base gasket.

If anyone has any experience with this issue on any 2 stroke bike--not just the KE--please advise.

Thanks

[stainlesscycle]

i have had a base gasket blow out on a it200 (twice). i now use some hylomar on the base gasket (even though it's probably not spec'd for it) i also use some disc-lock washers (best invention ever. i use them on motor mounts too - no more retorquing every 8 hours.).. i've found no need to re-torque and haven't had a base gasket blow out since (knock on wood).

i don't think copper is the best solution for a base gasket...

[Shocktower]

I wonder if you can get an O-ring base gasket, just like the O-Ring head gaskets , sounds like a great ide IMHO


Have someone turn the cyclinder with a groove for the O-Ring and use a silicone O-Ring

[stainlesscycle]

Originally Posted by Shocktower

Have someone turn the cyclinder with a groove for the O-Ring and use a silicone O-Ring

huh? i assume you're being sarcastic. there are transfer ports in the base....

[PSchrauber]

I would use sheet of heat resistant multi layer seal material that is as thick as the copper gasket. I would cut it out like the copper gasket ans that's it?

If you have difficulties getting the right thickness you can mount a couple of them to the base joint, (2 to 3).

[vtwin]

Try applying Copper Kote to the gasket and see if that helps. In the many times I've installed metal gaskets in cars, never had a failure except the one time I didn't use it.

[RayAlazzurra]

I should have been clear. The original gasket is paper. I was thinking of using copper? Don't know what other options might be. When I consider the cost of fresh nicasil, new piston and rings, plus gasket set, and my time the additional cost of a custom gasket is not that great.

[PSchrauber]

Originally Posted by RayAlazzurra

I should have been clear. The original gasket is paper. I was thinking of using copper? Don't know what other options might be. When I consider the cost of fresh nicasil, new piston and rings, plus gasket set, and my time the additional cost of a custom gasket is not that great.

There are heat resistant paper gasket sheets available with permanent 250 °C (around 500 °F) durability and works too up to 400 °C (around 750 F), for a shorter time, never had a problem with them:

here in 0,5mm thickness: http://www.ebay.de/itm/Dichtungspapi...item35c015aa86

and in 2,00mm thickness: http://www.ebay.de/itm/Dichtungspapi...item4d057e0d14

also in 0,40, 0,60, 0,80, 1,00 ... mm avaiable.

If not where mentioned you might look up dealers that are specialized in tuning parts in the US.

Surly you can try to make a copper gasket, but watch out you don't have any grates / ridges left when cutting out the gasket. Getting the right thickness wil be a task.

[stainlesscycle]

Originally Posted by RayAlazzurra

When I consider the cost of fresh nicasil, new piston and rings, plus gasket set, .

are you out of bores? is that why you are nikasiling? don't get me wrong, i like nikasil, but if you're just riding normally, just go to the next size and bore - saves about $150.00....and if you maintain rings/piston occasionally you should not need another bore for a long time..


also - your gasket is blowing out because either surface is not flat or you've hogged out your transfers too big. a k100 doesn't vibe that much to loosen the head bolts i would think - maybe your motor mounts are loose and it's the problem?


i forgot to mention my base gaskets were blowing out because i have the transfers at just about as big as they will go, and have very little flat surface for the gasket left. copperkote will probably solve the problem.

[RayAlazzurra]

Originally Posted by stainlesscycle

are you out of bores? is that why you are nikasiling? don't get me wrong, i like nikasil, but if you're just riding normally, just go to the next size and bore - saves about $150.00....and if you maintain rings/piston occasionally you should not need another bore for a long time..

Bike had original electrofusion lined bore in AL alloy. No iron liner so no overboring w/o fresh nicasil. The old scotchbrite trick works for a few times, and then she won't seal well w/o a nice crosshatch hone job.

also - your gasket is blowing out because either surface is not flat or you've hogged out your transfers too big. a k100 doesn't vibe that much to loosen the head bolts i would think - maybe your motor mounts are loose and it's the problem?

Motor mounts are tight, ports are stock, and the head bolts are not loosening. I guess you could say Kawaskai hogged out the transfers a bit too much since there is not much surface between the transfer port and the outside world. The reason the head needs to be retorqued is that the base gasket compresses. Upon installation and after the first ride and cool down it is still thick. After 600 miles or so the gasket has been squished to around 1/5 or the original installation thickness. Since the cylinder/gasket combination is shorter the head nuts are no longer at the same torque as when installed, and the pre-load on the studs is less even though the nuts never moved.

I forgot to mention my base gaskets were blowing out because i have the transfers at just about as big as they will go, and have very little flat surface for the gasket left. copperkote will probably solve the problem.

I may try the coppercoat on a custom copper gasket. Or I may try some other material.