Today while sanding the alloy out of my cylinder (for those of you who don't know, please don't ask ) I noticed that the rear part of my powervalve (the part where the shaft is) has a crack down through the center. Is that a major issue or something that won't affect anything?

Also, I noticed a very small crack going from one of the intake ports into the angled part of an exhaust port. Same question on that.
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Craig
MC21 SP Rothmans
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Andy.
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What I'm seeing on the powervalve:



The port crack, from inside the cylinder:



And the same crack from inside the exhaust port:

It looks to me like someone has been porting those barrels, there is a load more metal than that between the exhausts and transfers, and that exhsut bridge looks too thin to be stock.

But none of those cracks will be why it seized and they might or might not affect it in the future, however no one is going to recommend running a barrel like that.
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fontyyy wrote:however no one is going to recommend running a barrel like that.

Thanks fontyyy, these are the first cylinders I've seen so I had no idea they were messed with. What do you mean in the last part of your statement - is it because of the damage from my seizure or the porting? I am still in the process of removing the alloy to see if it is salvageable.

Craig

By the way, the RC valve is not cracked. It's in two pieces. You'd never get it in or out otherwise!

Matt@TYGA wrote:By the way, the RC valve is not cracked. It's in two pieces. You'd never get it in or out otherwise!

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Wait, the power valves come out? Next your going to tell me they should be cleaned periodically
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Charles Gallant

Of course not Charles. Everyone knows that you just bung a bit of Eeezy Off into the fuel tank and it cleans everything out on the way through

Sheesh, if I wanted that kind of abuse I'd listen to the guys at work! I guess the two piece valve makes sense. Now that I have my manual (thanks Charles, forgot to write to you before) I'll get them cleaned before putting everything back together.

I'm going to have 2 other used cylinders soon. Would you guys recommend running my "ported" ones or the stockers with similar seizure damage?

Craig

Craig,

I have found that using a small flat head screw driver, or dental tool to scrape the carbon off the valves (after you have them out), then using a scotch brite pad to really polish them up will bring them back to as good as new.

You will also want to make sure the landings within the cylinders are clean or carbon so the power valves land cleanly and produce a nice smooth transition from cylinder/exhaust port to power valves.

as for the cylinder you have pics of, I wouldn't use those. The port walls look like too much material has been removed and the heat build up is causing the metal to weaken and crack. This can lead to further failure and damage.

You could have them welded up, cleaned up and replated, but you will most likely end up with the same issue in the end.
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Charles Gallant