Oil Dump from the Breather

[Guest]

Hey guys,
I've been scouring the forums lately looking for a large oil dump from the breather line on to p of the engine and haven't found anything yet. About a year ago I jetted my 1981 gs1000 and put pods and pipes on it as well. When I removed the air-box, I put a filter on the end of the breather hose coming off the top of the engine, and have ran it like that for a year. It ran pretty well the whole time, was a wee bit rich so I recently just put an extra little washed on top of the needles. It stopped falling on its face in the mid range, and ran great. About two days after I did that work, I went for a night ride and barely made it to end of my block and back, because my bike spewed out most of my oil through the breather. I my rings went bad or something, but the next morning I checked all my spark plugs to see if they were covered in oil and none were. I checked all the compression on the cylinders as well, and they are where they have been since I've had the bike: 90, 120, 90, 90. Cylinder #2 has always been higher compression. My next step I'm going to remove the cover on top of the engine and check the baffling where the breather connects to. If that all checks out, do you guys have any idea what could be the problem, because I'm pretty stumped?

[Steve]

My guess is that there is just barely enough air flow to get the oil vapor to the top of the engine, but it then condenses, leaving the oil droplets in the mesh screens. As they collect more oil, they might block the air flow until enough pressure builds up, forcing the oil down the line.

Since you have removed the device that used to ensure air flow through the line, you will have to take steps to get some air flow back, or just install a larger catch can. One of the ways to ensure air flow is rather against the grain for environmentalists everywhere, but it basically goes back to the way that engines were ventilated before the invention of the PCV device. Just use a LONG section of hose, connect it to the top of the engine, run the other end along the frame to a point just below the swingarm pivot. Cut the end at an angle so the open part faces the back. Now, when you go down the road, the air rushing past the end of the hose will draw any air out of the top of the engine. Be sure to have the end of the hose offset from the tire though. If it does puke a bit of oil, you don't want to be leaning into a turn when it comes out of the hose.

.

[Carter Turk]

Years ago 250 miles from home, my 1980 GS750 pistons #2-3 broke the ringland area between the top and second ring.
I had an airbox, so the breather hose was filling the front portion of the airbox all the way up to carbs.
Heading west on I-90, looked in the rearview mirror, the entire 2 lanes were covered in a huge cloud of black smoke.
The oil filled beyond the bottom of the carbs.
I found a gas station bought a quart of oil with a measuring window, duct taped to frame, routed breather hose into empty oil container and made it home.
I had to stop every 20 miles to recycle oil and retape container to the frame, around 13 times to get home.
My sparkplugs apparently weren't fouled as I restarted all those times.

[GregT]

It ran better - so you did what we all would do and ran it harder....

I'd go with Carter's experience and vote for piston damage.

[Chuck78]

Your compression test numbers are all below minimum. 90 psi means time for a top end rebuild. 120 is the minimum I look for... if they were all 110, you might be able to ride it for another few seasons. Try adjusting your valves 1st then ride it a bit and re-test compression?? That is a longshot but worth a try perhaps (more like a last ditch effort for someone afraid to tear into the top end of an engine), BUT I think your pistons and rings and bores are worn out or damaged at this point if you rode it with that low of compression for so long without thorough carb re-jetting/tuning and regular valve adjustments.


Your air fuel ratios are off due to low compression, and that can burn up a piston...

also, could have burnt valves if they've never been adjusted, which can also throw off the air fuel ratios and throw off the jetting and cause further damage.

Time for an overbore, head & cylinder deck resurfacing, and a valve job.
THEN a thorough carb tuning and re-jetting...

riding the bike harder with breather hose no longer connected to the airbox will definitely cause oil vapor to exit the hose, but if you're losing excessive oil this way, you are having some SERIOUS blow-by due to worn out rings & cylinder bores...

[Chuck78]

If you were closer I could coach you through a top end job or sell you a good 1100G engine we have, but I'll likely be parting it our to keep the top end for myself for 1000 chain drive builds.

time to learn how do do a top end rebuild...

$500+++ in machine shop fees plus $200 for cruizin_image_co ebay Japan pistons plus a top end gasket kit from Athena ($80) or full oem gaskets (triple that price).
BUT... you will have a brand new top end then and the bike will make WAY more power!

[swanny]

I'd agree that your rings are probably gone if you have low compression and lots of blowby. As a final check, squirt some oil in the spark plug hole and then rerun the compression test. If the compression increases you've confirmed it's the rings.

[bwringer]

Is there gas in the oil from a bad petcock?

[520eek]

Hi to all. Years ago I had a Yamaha XS750, 3 cylinder beast. I went on an epic ride...and on the second to last day, I dumped the bike. It was on a back road, dirt , out in the middle of no where. When i got it back up and re started it...it was just pumping out oil ( through airbox if memory serves me right) any way, my buddy and i dis connected host to air box and routed it to a soda can that we opened up and had attached to bike by means of the famous bungee cord. Bike ran great! we hooked up hose and it went back to puking oil. So we un hooked it and drove another day and got home. From what I can remember we cleaned the air filter and housing, put it back together and all was well again! So the long hose out the back of the bike seems to make sense as well!