Anyone's advice appreciated.

21R cylinder plating has cracked across the exhaust port bridge.

Q1. Will replating be succesful? Has anyone had this fault succesfully repaired without any later problems?

Q2. Who in the UK delivers the best results regarding plating e.g. finish, accurate bore dims, bridge relieving, durability etc?

Ta!

Best bet is try to find a second hand good cylinder. They do now and again come up on ebay and often sell for less than the cost of a replate.

Yes the crack can be welded up but they do often re-crack which can be more than alittle annoying.
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If I have to take the carbs off once more...

Hi,

Are you aware of any particular reason why the exhaust port bridge plating should crack. Last thing I want to do is locate another cylinder for that one to fail in a similar way.

My 21R is standard apart from the splice. All carb settings are standard. Plugs suggest it's running fine and I know each nsr reacts differently to jetting.

If the crack has develoved as a result of the rear cylinder running too hot, would you think it's wise to go up a size on the main jet?

Mark.

The crack is caused by the heat the exhaust gases and/or rapid temp changes. I personaly think they are prone to cracking though not warming the engine up enough causing the bridge to exspand faster than the area around it.

They do seem to crack quite often though once repaired.

On a stock NSR where the bridge is quite wide I can only see poor warm up being the cause where as on tuned barrels/RS barrels where the bridge is very narrow I'm sure the pure heat build up in the bridge is enough to crack it if youre unlucky enough.

Only my thoughts though.
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If I have to take the carbs off once more...