Okay,

A friend of mine has a 2001 Road Glide. During it's life and prior to my friends ownership, this bike has been bored out etc. to 117ci. It runs pretty well, but the actual parts list used on this build is pretty much unknown. He has a problem with this bike and I'm trying to help him with it.

As stated, the engine pulls and runs well, most of the time. That said, at about 75 mph on the freeway, this thing starts pumping oil out of the breather tubes and into the carb as well as all over the bike. It's fine until you hit 75 and then things get ugly.

Recently, we checked his oil when this happened and it barely registered on the dip stick. After letting the bike cool for a couple of hours, the oil level was closer to normal, having actually lost about a pint. This suggests to me that the oil is getting trapped up in the rocker boxes. I presume this rules out any kind of "sumping" problem.

One person has suggested opening up the drain holes in the top end, but I wanted to see what people here thought might be the issue before I did that to his bike.

All ideas and suggestions most welcome.

 

bumpety bump

 

I say that with the large pistons, your building up pressure in the crankcase and that's keeping the oil up top and blowing it out the breathers. I don't know if there's a way to vent the cases like the older evos used to do, but I'd bet having 2 ways for the motor to vent the pressure would solve the problem.,,

 

Drilling the drain holes on the breathers is very common on big inch motors. It helps a lot from what I have heard. Oil pump alignment could be a problem too. How much oil is he running? I run my bike a half qt low and now have zero problems. I had blown oil one time and it's a big mess when it happens.

 

He's been running the oil at the normal level. Are you saying that making the breather holes larger as opposed to opening up the drain holes might be a better way to go. If the larger pistons are creating to much crankcase pressure, where would I need to relieve that?

Thanks

 

Please dont take my advice without second opinions, but I know on my souped up xs650 I put brake check valves on the breather tubes to cause negative crankcase pressures. I was blowing seals left and right. Did this mod and problem solved. I dont really know how you could do that with TC88 or even it should be done. But its just a thought.

 

I'd start with the easiest possible solution first....try it with 1/2 quart less oil.

 

Im talking about the holes under the umbrella valves. It's common to drill those out to 1/8" and chamfer the holes. I think you should run it a half qt low first to see if it helps or cures it.

 

I'd would have a look in the oil pump for scoring, unless the 1/2 quart less oil fixes it.

 

I know what you're saying, but the problem seems to be that the oil is staying up in the rocker boxes too long, hence the return to more reasonable dipstick oil level after its been left to sit for a while. The bike makes good oil pressure and there seems no obvious reason to suspect a scavenge problem as it isn't the crankcase which is getting full.

I truly appreciate everyone's input.