Cylinder coating WESC on KX250A4 1978???

[oldyzman]

Hello,

I am interested in the above, The coating is Wire explosion Spray Coating. Done with molybdemnum and high carbon steel. Just wonering:
Is this a durable coating?
Can the cylinders be replated in nikasil or similar?
Is there a CI sleve available?
What is a dykes Piston ring?
Any help appreciated

[Stevo17]

Are we talking about the electrofusion process used on early 80's KX's but with a different name?  I have had several redone by Electrosil with no problems.

[oldyzman]

Thanks steve,

I have noted that Wiseco do a CI sleve. Pistons seem to be available as the same piston covers many years.

[TM BILL]

Dont sleeve it , get it replated  its not much more expensive and the benefits are worth it 

[vmx42]

A dykes piston ring is 'L' shaped in profile.

The shape of the ring allows the pressure of combustion to increase the ring pressure on the cylinder wall minimising the blowby, thereby increasing power.

Of course the difference would be very small and I doubt you would notice any difference, but improvements are made incrementally.

[mx250]

"Actually Dykes Rings have a lot of advantages and few disadvantages in the right application.  The Karts are single gear so raising the Ex port isn't a good idea since low-mid range will be lost.  So, the exhaust port wants to be as wide as possible to attain enough port time / area.    Dykes rings make this possible because they need very little outward spring force.  since they use compression to force them out against the cylinder wall.  So the rings have less tendency to "pop" out into a very large port.

The advantage is: The exhaust port can be run as wide as 80+% of bore without snagging a ring.  And the ring isn't dragging against the cylinder wall with a lot of force unless it's under compression.  By comparison a standard ring may be able to survive an exhaust port that is 72% of bore but that's pushing it...

They also provide much more precise port timing since the edge is so sharp, unlike the edge of the piston which has a small radius and doesn't touch the cylinder wall.

The disadvantage is that it's heavier and will flutter sooner than a conventional ring at high RPM, like above 10,000."

http://www.yamahait.com.au/forum/index.php/topic,10574.0.html 

Having said that I ran fresh DT250 rings and pistons (1/3 the price of MX 'competion' GYT  stuff 'back in the day') in my MX250 MX, DT, Road Racing and Enduro, and I never picked the difference. But i did have standard MX porting. Maybe I needed to hog out that exh port to get the difference .

"What is a dykes Piston ring?". Here's a close up of Dyke's Ring (there is probably a visual joke there but I'll avoid it not wanting to run a risk of been banned ).

[Lozza]

I think those advantages are imagined, a conventional ring still uses compression for it's tension not radial tension, nearly all kart classes are controlled so no porting allowed, fixed gear karts get wide powerbands from the perforated rear cone pipe well the ones that rev to 22,000 rpm do, 72% is no dramas at all with correct radius on the top of the exhaust port do that everyday. Dykes ring will break long before a conventional ring especialy with a bit of deto.

As Bill said replate the cylinder it will ping it head off hot. Replating is cheaper than sleeving.