Revtech 110 blowing oil out front exhaust and breather

Hi Mbcchops, you need to do a compression test on both cylinders. Good luck and have nice day.

Oil coming out of the breather is normal on these engines by the way of design, with basically no way to stop it. There is about 1/2 qt of oil in the bottom end of an engine, as the pistons travel downwards, the air that is under them is being pressurized and is vented out of the engine by a rotary breather valve in the case. The air picks up a small amount of oil from the bottom end as it leaves, then the air/oil mist is vented either into the air cleaner (EPA Regulations) or best if vented to the atmosphere. When it's vented into the air cleaner, some if it recirculates into the engine and out the exhaust, the rest saturates the air filter and then eventually gets blown all over the side of the bike. The best way to vent it, is to route a hose from the breather system down to the frame between the engine and trans, run it under the bike on the right side, point the hose down to the ground and zip tie it in place...Be sure to point the end of the hose down & away from the tire.
If your breather bolts start to leak oil...remove them, and use brake cleaner to completely remove all oil from them, the washers, brackets and threads in the head. Use liquid teflon thread sealant on the bolt threads, and a light film of black rtv on the faces of all the washers and brackets, install everything, let sit for 24 hours, then ride.......if done properly and rtv is CURED, it won't leak...
Also note that most HD's with the oil tank mounted under the seat and are left sitting for a couple months will PUKE oil from the breather, this is due to the gravity....the oil will slowly seep through the oil pump and collect in the bottom of the crankcase and get blown out the breather when the bike is started ...

Good luck...i hope this helps

How many miles do you have? You probably need to have your oil pump alligned. They get out of wack and cause over oiling. I believe it caused by not being able to return oil efficiently. An evo tappet block alignment tool is now used to align the TC internal oil pump.

Your RevTech engine is a copy of an H-D Evolution engine. Just as with the Harley engine, it vents it's crankcase pressure through ports in the heads. There are "umbrella valves" made of rubber in the center section of the rocker box covers. These valves are made of a rubber like material and they will harden with repeated heating and cooling. If they get hard enough, they may not work as well as they should. This system does a fair job of removing the oil mist from the exhausted air but there is still some oil left in it. This oil will accumulate in the breather and drip out. You must clean the inside of the air breather occasionally to prevent this. However, if too much oil is coming out, you may have too much blow by on the rings or your breather gear in the cam chest may not be doing as it should. Harley uses a plastic breather gear and I've seen them break a tooth and stop turning. I don't know if RevTech uses a plastic gear or a metal gear. It depends on how much oil is coming out of the breather as to whether or not you have a problem. There are kits available aftermarket to reroute this vented air pressure outside of the air cleaner.

Good Luck


too much oil; bad umbrella valves in rocker covers;

An overfull oil tank will do it. Even if not overfull just about all harley's will blow oil out the air filter. Unless there is a bunch of oil coming out, it's not a problem

What I've found is that the air filter eventually gets saturated and then starts to leak through. The level in the oil tank doesn't seem to matter. If you change the air filter the problem goes away, until the new one gets saturated and then it starts all over again. My plan is to get a K&N air filter, which you can clean yourself and save having to buy a new air filter every 4,000 miles or so.

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