Hope someone here can give me a little advice on an Evo I've been working on for a while.

I rebuilt this whole bike last winter. While it was apart, I noticed oil in the exhaust ports. The bike's odometer showed 11k miles on it, its a 1997. I figured it had bad valve guide seals. I pulled the heads and had them ported and milled. He also checked the guides for wear, and put new guide seals in them. I used a three stone hone and honed the cylinders (very lightly) and put new rings in it.

I was getting slight smoke out of the exhaust, and very black oil drips coming off the exhaust/head studs. I took the exhaust off and found the exhaust ports wet with oil. I took the heads off and took them to the guy who ported the heads and he checked them out and said they were ok. He also recommended boring the jugs .010" over and installing new pistons. He bored them out, and also put em on the lathe and made sure the base gasket surfaces were true.

I put the engine back together and did a couple heat cycles then took it for a short ride....no problems really, just a very slight amount of smoke. I thought it was just burning off some assembly lube. After taking it for a longer ride a couple days later, it started doing the same thing. Oil in the exhaust ports, drips coming from the exhaust flange nuts.

I pulled it apart and found the middle rings upside down While it was apart, I found a nice scratch in the cylinder wall that I could feel with my finger nail. After talking to the guy who does my machine work, he said I could have gone with a higher compression piston anyway, since evo pistons are pretty cheap, I ordered up the right ones in .020" over. Had him bore them out and threw it back together.

While putting it back together, I noticed the umbrella's were on the wrong side of the rocker boxes I also pulled off the cam cover to make sure the breather was timed correctly with the cam....The lines line up.

After 25 miles, it leaks and slightly smokes again!!

The rings are in correctly and gapped according to mfg specs
The breather is timed correctly with the cam.....Lines line up
Umbrella's are in the right spot
Heads are breathing....I can feel it in the hose when the bike is running (S&S carb setup)


Pictures of the problem

Piston after 25 miles...wet with oil


Exhaust port

 

Im having the same problem. Front cylinder is smoking (heavy) after warm up.

 

Make sure nothing is blocking the oil drain holes...check the heads ,cylinders, and cases...any crud that just makes drainback slow will make it smoke like a freight train.

 

Were the Valves cut? What lifters you running? For laughs, what's the compression? You try leakdown?

 

Did he use torque plates when he bored the cylinders?

 

when you say the rings are in properly,Tell us how you set them in. For instance, you have 2 valves per cylinder. if the gap in the top ring is close to the position of the exhaust valve, you run the risk of hot gasses getting by the ring & going down into the cases causing excess case pressure. A gap too close to the intake is also not good.
the oil ring assy is similar. you dont want the gaps near each other because you can get oil bypass.
Did you install your rings into the cylinders without the pistons & mike the clearances? You might find that the center of the barrel is larger than the top. You might want to go with over sized rings & file them to spec!

what is your breather condition? If it has a lot of scoring, put in a new one, Their cheap like candy!
Have you honed or miked your lifter blocks? Proper clearance is important.
Magnoflux your heads to see if there are any cracks in them.
looking at your pic, your barrel bolts are stock. Pull them out & replace them with ones that are not flared at the bottom. Your torque values will never be consistent with the old ones!
You can modify your engine so the case breaths better, It might be over pressurizing for some reason forcing oil through your valve seals!
finally, pull your oil pump apart & make sure everything is in the proper order.
Keep us posted.
Hatch.

 

Just to be on the safe side, you might want to pressure test the port.

 

I cann't help but think, With that much oil running down the valve stem that you surely have a valve guide or seal issue. Just seems like there has to be an issue in that area. Does it give a decent puff of smoke when you first start the bike and then clear up a little after? Usually valve guide seals do that because of the leaking in the cylinder while parked. When its running thers not as much oil burning.

 

Seems like pressure testing the port with the valve installed might show where the leak is, whether it is coming from around the valve, or the guide, or possibly somewhere where the port was ground too thin...

Edited to add that it is also possible that the guide to head fit is too loose, and the guide may be moving a bit when the head heats up.

 

I did gap the rings according to the specs that came with the pistons. The gaps are all staggered. I always put the top and middle ring 180 from each other. Usually the top ring is in the 2 o'clock and middle in the 7 o'clock position.

The cylindes were bored using torque plates. Larry doesnt cut any corners. IMO he is one of the best in the industry, just not as well known as others.

The guides and seals were checked after the first build. I pulled the heads off and took them to him.

I am really leaning towards a bottom end breathing issue. I have not had the oil pump apart. That may be on my list of things to do this winter. I also just ordered the S&S reed style breather just to elminate a possibility of the breather being off. I never took the original one out of the engine to check for scoring. I'm not sure if the S&S is a solution, but I am starting to run out of ideas.

This winter the engine will come apart. Going to check over everything.

I will also pressure test the heads this winter.