Oil leaking from air filter?

http://motorbicycling.com/showthread.php?t=55201

I'm Replying, but note my bike is a DIY not a Kit.

From my thread where I have the same problem but to a greater degree where the airfilter eventually after enough hrs run time clogs the filter with wet oil mist.

My next time I run it I'll check my own adaption to my Briggs 4 stroke on a 17 degree back slant will see a oil seperater and additional larger breather. The larger breather automotive type is not the screw type you can take apart to clean or replace the foam, but I'll modify it to do that anyway later if necessary.

MT

PS:

It may be a while as it is an off road only bike and I not ready to go so soon. I do climb some very steep hills so that could be my additional problem and hope this fixes it. Emptying a small amount of oil from the bottom of the tube at the oil seperater will also be something done once an a while.

tOO MUCH OIL...............

This I posted on Smokestack, it is what I know to be the probable answer to wet air filter, which I know now not to be oil, but gasoline mist.

Re: Briggs 80202 oil on paper air filter problem
A lot of information maybe not necessary to tell, but it is the intake valve opening too soon which when the piston is still going up it should only be the exhaust valve opened which is the problem, I think. Read on at your own risk, or feel free to skip down to the bottom.

Tilt of these engines allows to 15 degrees I saw on the Briggs site. Maybe newer engines are just the same as the older and 17 degrees won't matter much anyway.

What I am onto now is that it was oil on the paper air filter at one time, but that was fixed by replacing the oil breather that had a stuck spring and was always open.

I for a short while did disconnect the hose from the breather and plugged the hole on the air filter box where it was going to for a short test. The air filter still got wet. This is meaning that it had to be from the intake port going the wrong way, that is out flow at the air filter.

Now that I really have no intention of cutting the bike frame and widening the space to mount engine flat across, I was still looking to find what is still wetting the paper air filter.

Turns out as before I thought it was oil and it was and I figured that with the original air filter being and oil bath type so extra oil mist would not matter as I never knew there was a problem anyway back when using it with the Vacu-jet carburetor that it was meant to run with. No paper air filter to get sopping wet and restrict air flow was my idea.

An oil bath type of filter would be hard to get mounted on my carburetor and I am also set with the gravity feed system on my bike as it is better suited to my design.

So I cut the paper element out of a paper air filter that is used on the air filter box for my carburetor and kept just the side neoprene gasket and a large opening screen that gives it structure.

I bought foam high filtration air filter foam (blue). I bought the special type of oil and cleaner in spray form for the foam filter material. I fitted and high temperature Permatex RTV'ed the foam cut material in place.

I ran the bike and it seemed to run even better than with the paper air filter. I checked to see if oil was still getting on the filter and how much. I felt since even though it was the wrong type of oil to have on the foam air filter material it would not matter much anyway. When it so bad that it needed cleaning I have a whole can of cleaner and no need to keep buying paper filters to throw out.

This was my intended work around. I knew that something like oil was wetting the filter not much at all by the breather hose back to the carburetor box, but the opposite way of flow through the carburetor throat.
Long time waiting to know what it really was. I left the fuel valve on and the ignition switch off. I had the air filter off the throat of the carburetor. I wanted to put my hand over the throat so I could feel if it was not just pulling a vacuum, but also pressure coming out the opposite way.

I could not get a seal on my palm to check. I decided just to pull the recoil starter and look. I saw a spray of gasoline mist shoot out the throat intermittently. This verified that it was no longer oil as before, but gasoline in a mist form.

The venturi effect is just the same inflow or outflow. But why would there be out flow and I thought of the valves.

I had lapped the valves in their seats. When I still did not have the engine running right an low compression a friend had mentioned that the angle of the valve and seat is damaged after too much lapping and re-cutting valve and seat to proper angle would help. Since idling was a problem and I had not much power I had a shop do this.

I would have done all the work myself, but although a valve cutter for $25 was cheap, The seat cutter would be over $500 and I instead had a machine shop do the work. Two engines I had worked on. $10 per valve and $40 later I have engines that should be reassembled.

I did not work on an older 5S, but the 80202 0430 the one in question I did. I also remember the machinist say that he would grind off the same amount of material that in combination is removed from valve and seat to keep the timing the same.

When I pulled the recoil way back then I noticed a puff of air coming out the intake port. My friend that told me about valve cutting and angles that could be lost due to age or over lapping, mentioned something else. In relation to air coming out of the intake he mentioned scavenging that increases power. These engine I don't believe are meant to operate this way. He did say that early opening of the intake and the mass of flow in would over ride exhaust going out. It could not be seen as it is only at operational rpm of the engine.

Now I know that scavenging is not right in this engine, and the bottom of the valve stem is still too long. I think the machinist did not remove enough from the bottom of the valve stem since my prior lapping also removed material and that was not included.

Now I down loaded a pdf file on Briggs Engines and I found the specification for Intake and Exhaust gap between the tappet and the bottom of the valve stem. I'm going the measure it and if it is too small or non-existent, I will remove from the bottom of the valve stem enough to get the valve timing right.

Here is the think for the pdf:
http://www.oldengine.org/members/mur...20Handbook.pdf
Note that it is a picture scan so it is not useful for searching, but looking at the table of contents I found my information in compression; chapter 4, page 41, table 6 (Valve Tappet Clearance).
My engine is a 5 digit B model so 0.007 inch max to 0.005 inch min for intake clearance. Exhaust is 0.009 inch max to 0.007 inch min.

I have not had the time to see what I measure, but I bet I find this is where it all went wrong.

Maybe as when the engine is operating the way it is now the fuel soaks the foam air filter for a micro second and then the fuel is grabbed back with addition fuel added during the piston going downward and I get greater amount of fuel that was intended in the engine. If there is enough air flow then I am getting a better charge and horse power is up?

I think better compression and less fuel, or the right amount is probably the right way to go anyway. No messy wet air filter.

Some good information on valves and maybe some bad information from a friend on them also is what I have experienced.

Well now I think I know to refer back to this pdf file with a wealth of info. Thanks to oldengine.org

Smokestak was down when I was looking, but I know they link one another anyway.

I think I have it licked now, will let you know!

https://vimeo.com/103665228?utm_sou...4NWYyMmU4NTc4fDQ3NzgyODJ8MTQwODMxNzg2M3w3NzAx

Link to Vimeo video of carb with ignition off and looking at throat of carb. Airfilter is off temp so can see. It is fuel and not oil that is being shot out the intake due to venturi effect as timing is off or hopefully not leaking intake valve.

Bottom of valve stem to tappet measurement gap not yet had time to do.

MT

I verified that the valve clearance on the exhaust OK for the range for valve/tappet clearance at 0.007 where allowed 0.007 to 0.009 inches.

The intake has no clearance and so the video of gas shooting out toward the air filter the wrong way through the carburetor throat makes sense now.

I'll take it slow, just using a flat surface of metal and using a flat file trying to be square as possible with the grind.

Any idea for a jig to make and use, I don't have a bench grinder handy, so hand tools will have to do. I'll go slow and keep measuring a lot of times to be safe I don't take too much.

It have seen it noted that many engines are junked like this one I bought at the San Jose Flea Market ages ago, that wearing into the seat the valve/tappet clearance changes. This is in addition to my lapping, and then finding I thought cutting angles again at machine shop. Angles are all lost from lapping at a point. Checking clearance is a must and so I learned this a little late, but know how to fix it now!

http://www.oldengine.org/members/mur...20Handbook.pdf

---------- Post added at 09:41 PM ---------- Previous post was at 09:38 PM ----------

On page 40 5 digit B serial number has intake 0.007 to 0.009 inches. I'll shoot for 007 like James Bond, if I get Crazy 8's that's OK too!

---------- Post added at 09:45 PM ---------- Previous post was at 09:41 PM ----------

It is gasoline on filter not oil.

MT

All valve work done and will eventually see it run to check out how it does.

I found the sealing surface on the intake valve head and the seat perfectly clean. Th upper portion of the valve I cleaned but kept away from the sealing surface. The gold coloration lower down on the stem that seals I did not want to scratch, so cleaned as best as could the carbon.

The exhaust I could have ground a bit off, but will do that if necessary later. It had a lot of carbon, but similarly the sealing surfaces were perfect.

It was touch and go putting the cup back on the valve bottom with the spring only working with a flat blade screwdriver and a needle nose pliers.

I also checked the PCV breather and it works and is not stuck. I replaced that about a year ago when it was stuck open. It was probably the original from the 70's era.

Later to test it, but I verified looking at the piston movement for bottom and top dead centers and how the valves opened and closed for timing to be correct.

MT

OK Im guilty of scanning the thread so I may have missed this explanation. Its common to have oil exit the breather in an Indy engine when revved pretty high. That's why racing karts have catch cans. The situation can be eased by adding/opening the drain back holes found in the breather well. The other fix(do both) is to add a pad of Scotch Brite cut to fit the breather well(Chore Boy works well also) These act as an oil /vapor separator keeping the oil in the breather.

I can't change the name of the thread, but note the oil breather is fine, it was gasoline that was the final problem that was needed to be fixed. It went the wrong way out the throat of the carb since the intake valve timing opened too soon with the piston still going up. Ground the bottom of the intake valve so the clearance between it an the tappet were in the range. It actually was no gap when I started.

http://vimeo.com/103665228?email_id...e_complete-finished-20120100&utm_source=email

The above link show it spit fuel wrong way.

Gotcha. That is a common problem with leaking intakes. The seat/valve eventually wears settling into zero clearance. Saw many a mower come in with out the air filter because it would saturate and the user removed it. Finally the leakage was so bad the mower wouldn't start. By then the rings has suffered.
The breather mod is still useful on ungoverned faster turning engines.

Glad you got it fixed.

So now I tested it and the air filter does not wet with gasoline. Valve timing back to normal. I now have an issue with idling. It was before that I needed a paper air filter, and switched to that. That allowed it to idle OK.

Before that I had a very restrictive foam air filter which did not idle. Now that I have more recently made my own foam air filter with the proper oil sprayed onto it, it was working OK idling. This was before it was stored away for a while and before I fixed the intake valve timing.

I got the thought to switch back to the paper air filter and put a new one in. It idled a few moments and the cut out. This happened a few times more. There are no replaceable jets or any mixture or idle screws for the cheap 27 dollar Briggs carb. Only the throat butterfly valve (throttle).

I thought for a while and was going to see about the spark timing at the point gap. Then I realized it probably did not matter.

The fact that it idled a bit on and off, I correlated it with maybe the fact that the tank was emptied and also the carb bowl too, which may have left a gummy residue. I had to get the tank valve for the first time a bit of force to turn it which made me think somethings up.

With the fuel filled in the tank it loosened up and works fine. No leaks as I can see, but maybe it is time to get a new tank valve to keep handy just in case it is wearing some part not replaceable.

The tank valve maybe had some gas that varnished it up and made it gunky. If that got past the fairly wide mesh screen of the inline fuel filter I have, then it could be causing havoc in the carb too. I intend on getting carb cleaner and breaking down the carb and seeing after that what happens.

MT

You re on the right track cleaning the carb. If its a later Briggs style carb(sounds like it by the price you mentioned), it does have a main jet near the bottom of the float bowl on the carb body. The idle circuit is fed there also. Mower carbs many times don't have idle mixture screws as they operate above the idle circuit. If your carb has a mixture screw remove it and spray carb cleaner into it while looking onto the engine side of the carb, you should see spray coming from several tiny holes. Spray into the tube on the bottom of the carb that the bowl nut screwed into. Try to seal the bottom of the hole with you fingers to force the cleaner into the idle circuit. You should see the same thing in the carb bore.
If you have done this right and you don't see spray the idle circuit is plugged. Soak the carb in in a good solvent(remove the bowl gasket) and try again. Also clean the main jet with spray and a WIRE(torch cleaners are great for this). These are cheap carbs but they run well when in proper order.

Yours may have been plugged a while and idled from the fuel soaked into the air filter.