Oil Leaking from Air Box

[Greg O.]

I have a 1979 GS 750L that leaks small amounts of oil out the left side of the air box. It isn't much, just enough to make a mess when it runs down around the left side of the engine. I used less than a quart of oil durring the summer, about 5,000 miles. The compression is about 135psi on all 4 cylinders, but there is some blow by. I asume some blow by is normal, but don't know how much. Has anyone else had this oil leak from the air box problem? There is a drain on the bottom of the box, but it seems too small for oil to flow through, and it is not plugged. Is it normal for some oil to be blown out through the crankcase breather tube?

Thanks,

Greg O.

[Dave8338]

Hey Greg: The reason that there is a drain hole in the airbox, is for that very reason, these bikes do have a tendency to "throw" some oil over the cam chain and out the crankcase vent that is located at the top of your valve cover. This is more likely to happen under higher stress/hotter operating temps and higher RPMs, but unless it is excessive, it is nothing to be concerned about. Your compression figures are well within normal and look great as it is! \\/ One thing that you might want to check, is to ensure that you have not over oiled your air filter, as some times, this may add to the oil drainage that your seeing. Just a thought. By the way, in my opinion, you have one of the best looking GS bikes on the planet.... :-D

[Greg O.]

Thanks Dave,

I have to agree with your opinion about the looks of the L series. I love the way they look and ride . My only complaint is the seat is a little hard. I am going to get mine rebuilt and maybe some better foam.

I have thought of welding a larger drain tube into the bottom of the air box, and run the hose so it drips on the chain. I just wanted to get someones opinion about the oil blowing out. The cams are really flooded with oil, which is a good thing. I guess it is expected some will be forced out. Like I said, I only used about 1 quart in 5000 miles.

Thanks,

Greg O.

[Dave8338]

Now there's a thought, never thought of that! :-D What weight oil are you running? I've had the best luck with 15W-40. As far as your consumption goes, 1 quart per 5000 is again, well within spec. I think you've got a solid runner there and just think, if you do the valve clearence check every 7-10K miles, oil filter and change every 2500, you'll be good for 100K miles or better. Sounds almost too good to be true! Welcome to the GS world! \\/

[chef1366]

Under your breather cover there is a screen like filter. This is supposed to "catch" the oil. Maybe it needs cleaned.

[Greg O.]

Dave,

I think I am running 15w-50 Mobile 1. I will have to look, but for sure moble 1. I found the synthetic hold up better when it is hot outside. When I bought the bike two years ago, I was practicing for the skills test to get my motorcycle liscense, and I noticed the clutch started to chatter when the oil got warm and thinned out. I then decided it was time to let it cool down, and also to change to synthetic. Have never had the clutch chatter since.

I need to check the valve clearance before spring, and I will check the screen at the same time as well.

Thanks guys,


Greg O.