GS 750 to 850 Conversion Issue

[Guest]

Hi,

I just did a 850 conversion on my 77' 750 with no real issues other than when it hits about 3,000 rpms it starts kicking oil out through the breather cap. Does anyone have any suggestions on how to solve this? Since i'm going to be running K&N pods that breather line is going to be just dangling, so I figure I can create a makeshift dry sump system by mounting an oil overflow tank below the breather cap / above the oil filler cap and tap and run the appropriate lines.

Thoughts?

[dorkburger]

How much oil? A bit of oil mist is not uncommon, but actual liquid oil could indicate a problem.
I think there should be some type of filter type material under the cover where the hose connects. Perhaps its missing?

Edit / add - parts fische for an 850 show four oil separators under the cover.

[KornGirl666]

it's actual oil not a mist. I have the mesh screens and the gasket under the breather..

[Steve]

How much oil did you put in the sump?

There shouldn't be any real pressure in the crankcase, so if you DO have pressure, the only source is blow-by coming past the rings.

.

[KornGirl666]

3.5 liters as per the manual with a filter change. I'm planning on doing a compression test. I should be hoping for 130 PSI warmed up, right?

[dorkburger]

Not sure if the numbers, but the test should be done with the throttle wide open to get proper numbers.

[gsrick]

3.5 liters as per the manual with a filter change. I'm planning on doing a compression test. I should be hoping for 130 PSI warmed up, right?

That's about right. The main thing is even numbers between the cylinders, with about 10-15% difference allowed. Like Glen said make sure you open the throttle all the way and a fully charged battery.

[KornGirl666]

Got a chance to do a compression test over the weekend.

Here are the "dry" readings.

Cyl 1: 100
Cyl 2: 105
Cyl 3: 108
Cyl 4: 120

"Wet" readings with 1 ounce of oil in each.

Cyl 1: 130
Cyl 2: 125
Cyl 3: 135
Cyl 4: 137

So i'm obviously loosing compression through the bottom end. My question now is: How can I tell if it's the jugs or the rings? The rings are brand new and I did a hone on the cylinders before assembling. Any suggestions for tests / what to look for?

[Steve]

If you have new rings and a fresh hone job, how many miles on the engine since that work was done?

Unless you have several hundred miles on it, breaking it in PROPERLY, and those are cold numbers, they look pretty decent.

.

[gsrick]

Yeah, it may take care of itself once the rings and cylinders get reacquainted with each other.

[KornGirl666]

15 minutes of idle runtime on it only. I guess i'll have to create a temporary wet sump system to break it in.

[gsrick]

15 minutes of idle runtime on it only. I guess i'll have to create a temporary wet sump system to break it in.

There is a break in technique that needs to be followed. Some say take it easy and alternate speeds while never staying at one rpm for any length of time for multiple 15 minute intervals with a cool down time in between and others will say run it like you stole it. I've also hear people say to use oil with a high zinc content and to never use full synthetic. It's too slick to let the rings get the friction needed to form to the cylinder walls.

[limeex2]

Correct on the synthetic.

[KornGirl666]

Finally got a chance to ride the bike around the block for a few hours and oil is still spewing out of the breather box hose on top of the valve cover. Any information on what is happening, and how to solve this would be great. As mentioned above the compression numbers seem decent.

[cowboyup3371]

That is about normal and from what I have read, most people with pods (I don't have them) will attach a separate filter to the breather hose