I recently posted about my cam chain tensioner cap (this is what it is called. It’s the small cover on the other side of the cylinder from the cam chain tensioner). The gasket on this cap seemingly failed and oil began coming out of the bolt hole. I’ve got 3,000 miles on my bike, it’s a 2019 with intake, exhaust, Ivan’s flash.

The only thing I did differently before it leaked was rerouting the crankcase breather hose as shown on the threads here. After this the gasket blew, and it seems the cam chain tensioner gasket seeped a little bit. I checked everything and the hose wasn’t kinked or bent wrong in any way, I simply rerouted it to the left side of the bike and faced it forward, using a hose end filter and zip tied it into place.

I’ve done some research and the only thing that could cause gaskets to fail like that with my engine being so clean and new is a pressure change, which most correlate to the crankcase breather being clogged or something similar. Was the reroute enough to bring up the pressure in my engine and cause the gaskets to fail? Maybe the end filter was not very high flow. I’ve seen some say that in its stock position the crankcase is under a slight “vacuum” from the intake sucking in so pressure stays constant so I don’t know if this plays a role.

Well since then I replaced the gasket on the cap and put the hose back to stock location. The new gasket has held up good and the cam chain tensioner does not show any sign of wear or weeping. The original reason I did this mod was for engine preservation and I didn’t like that oil would build up in my air filter and sometimes even come out when riding hard. I’d like to preserve my engine and not have any oil leaks or inconveniences. However I am now nervous to put the breather to its alternate location. I preferred this and had no oil leaks or anything before this, but now I’m worried that if the pressure change was enough that the increased pressure will find its way to another gasket like the cam tensioner or god forbid a head gasket. Any thoughts on this? Anyone have the reroute and seeing a similar or no issues? Or someone who has it stock and a lot of miles. Very curious. 

Was the reroute enough to bring up the pressure in my engine and cause the gaskets to fail? Maybe the end filter was not very high flow.

The aftermarket breather filter doesn't flow much at all. Crankcase pressure is created from the small amount of blow-by of a healthy engine and isn't a problem as long as there are no "detectable" leaks. Blow-by creates very little pressure but anything above atmospheric will slowly force oil out to the lower pressure side wherever it can. An almost undetectable vacuum is all it takes to lower crankcase pressure enough to make the outside pressure higher than what the blow-by can possibly make inside so the pressure outside pushes back on anything that would otherwise escape thru a marginal leak. Only small leaks can go undetected and never cause a problem. You can run a motor with no crankcase vacuum until a seal wears and starts leaking then add vacuum and the leak will stop until the seal wears sufficiently enough to need replacing.