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exhaust bridges in cylinders

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I saw someone on a CR 500 mill off the exhaust bridge on their cylinder. Is that a common thing to do with our CRs?

 

I have a cylinder where the bridge has a small crack. Repair doesn´t make much sense since a new cylinder is only 370$ from partzilla.

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Hey. It's quite common to remove the bridge on engines that has short running periods and where you change piston and rings more often, like on hill climb bikes and drag bikes. The support of the piston and ring is not as good of course and as the ring expands slightly more into the exhaust port it wears faster. it is very important to chamfer the ports carefully and try to not have a to flat roof on the port that the rings can hook up on. it doesn't have to be a problem with the crack in your bridge. just make sure that you smooth it out and relieve it enough.

Johnny

Edited by Johnnymannen

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width on a stock port in 79%. unless you put a generous arc on the roof and some fairly good size radius on the top corners i bet it eats rings fast.

 

do you have a photo of the crack ?  you should be able to bevel (chamfer) both sides of the crack and be ok. honestly thats what i would do

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thats not a cr500.  but anyways you have 2 options. either remove the plating, weld the crack and replate or buy a new cylinder. i have no idea which is cheaper, youll have to research that yourself.  i would not cut out that bridge

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The cr 500 has no power valve. That is the only reason its "possible" on that engine.

I would say its impossible on what looks like a cr125- 250 jug unless you were building a go cart engine and planned on not running a power valve.

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