GS 750 to 850 Conversion Issue

[KornGirl666]

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? :-k

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.

 

[Guest]

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? :-k

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

.

 

[Guest]

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.

 

[Guest]

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

 

[Guest]

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.

How much riding have you been doing since you posted last? If less than 100 miles, then I don't think it has had enough yet. My FJ1100 came with a Tupperware container hiding under the tank, with the breather hose stuck in it to catch excess oil blow by, but it you run a long enough hose and put a small filter at the end you will at least keep it from getting all over the valve cover.

 

[Steve]

I've also hear people say to use oil with a high zinc content and to never use full synthetic.

Correct on the synthetic.

I am going to have to disagree on this point. :-k

We replaced the rings on my son's bike ('80 1000G) this summer. Have run nothing but Rotella T6 since the rebuild. I think he has gone about 6000 miles since the rebuild. Just before the last trip (about 750 miles), he made sure the oil level was proper before leaving home. Checked it a couple of times on the ride, but did not add anything. When he got home, the oil was just below the FULL mark, where it started. At that rate, it would probably take about 10,000 miles to get the level to the FILL mark.

My bike also had the rings replaced this summer. My oil consumption has decreased considerably since the rebuild, but things went awry on our "Little Ride v2" when the base gasket sprung a leak. That is something I will blame on an aftermarket gasket, rather than synthetic oil, but there have been no problems using full synthetic oil (Rotella T6) in OUR bikes. :encouragement:

.

 

[Nessism]

How much oil are we talking about here? I suggest a 10 mile ride with the breather hose dumping into a catch bottle of some sort and then measure the exact quantity that gets expelled. If it's more than a couple cc's or so there is something wrong with the engine. But before assuming that, did you verify the oil level is somewhere in the middle of the sight glass when the bike is on the center stand? What kind of oil are you using? What kind of hone did you use, grit and type? OEM Suzuki rings? How many miles were on the cylinder and did you measure out of round and taper in the bores?

To assure a good service life for the engine the bores should have no more than .001" out of round and taper. Use a 240 grit bottle brush hone and OEM Suzuki rings. The valves need to seal well so at minimum a good lapping job is needed. Personally, I recommend having the valves faced with a centerless grinder before lapping. It's cheap enough and assures you are starting out with a perfect surface. Too late for this stuff I suppose, just shooting some stuff off the top of my mind which may help you determine what's wrong.

Oh, and what oil to use isn't overly critical assuming it's not thin auto oil and the like. Synthetic or mineral oil shouldn't matter much.

 

[KornGirl666]

We're talking 500 ml of oil overflow. It's a lot of oil. The glass is foggy, so i'm measuring using ml and the manual. I put in about 3.5 quarts of mineral. I used a light hone from Canadian tire and went very light when using it. There was no grit rating on it, but it wasn't super rough. I didn't measure taper.

Sounds like I need to tear her down again.