Hay People, I rebuilt the engine in my mini bike about a year ago. I know, MINI BIKE, wrong forum, but I got it going and did a speed run with it and behold, the valve cover was puking oil. Since it's a mini bike, I'll try not to mention it again and just focus on the engine.
Anywho. When I rebuilt the engine to make sure everything was good inside, I ported the block, swirled the valves for better flow. If you used a flattie engine stock on anything, then port it out, you know you really wake up the engine. It's just a HD 3.5 hp engine with the ball bearing on the output shaft. Probably after porting about 4 hp, LOL. SO.... Finally got the bike, (sorry) done and been tuning it in. Fastest I got it up to was 34 mph on a short hop down the street. Later that week took it to a long parking lot to try to go faster but was too bumpy and too short, did it all on camera on my Channel. Now to do 34 mph, ofcourse I played with the governor. At factory, gov was set at 1/4 throttle, after playing with the spring and linkage, it's set at I think 1/2 throttle or around there.
Back to rebuilding the engine. I purposely didn't do this mod to the valve cover to make the engine puke oil because The first vid I did on this subject, it was on just the part and didn't put it on anything to show that it actually fixes the problem. I see every body putting catch cans on or just having the engine dump the oil onto the ground, not good, not good at all. You want to keep the oil in the engine where it belongs, anywhere else and it's not doing it's job. On the test ride on my vid, everything went great, no puking but didn't even come close to my speed run in the parking lot as compared to the one that I did on my neighborhood side street which lasted maybe 20 seconds and no puking. Just about to pack it up and told my kid I'll give it one more try on the main road off camera to see if I could go faster then 34 mph. I turned on the GPS and locked it which was dum because it turned it off and didn't find out till I got back, OH WELL. I left and got on the main road with the traffic and just opened it up all the way. Took a minute to get up to speed with the cars, LOL, everybody was watching me in between the cars in traffic. I kept up with no problem and held the speed for about 2 to 3 miles on it, turned around and did the same thing back to the van. Got back and looked at the bike (sorry) and behold, it puked, LOL. It's at the end of the ride vid.
OK, The problem.... These engines have a cover where the valves are and at sustained high revs, blows oil out of the valve cover or PCV or whatever you call it. I forgot what it's called, so I'll call it a valve cover, LOL. This valve cover has multiple purposes. It covers the valves (ofcourse), carries the fumes from the crankcase to the carb to be ingested by the motor for emissions, and is a oil/air separator. The last one is what makes it puke oil into the carb. It's very simple how it does this and can be modified to work better. I made a video of this fixing this problem and keeping the engine oil in the engine. This can be done on the flattie engines with this part and the OHV engines with this part on it. I think the oppey engines have 2, never worked on one yet but pretty sure they have 2, maybe a little help in a comment to verify. Tecumsa motors have them also. I'm sure Kohler has them also, little help here also. So this modification can be done to other name brand engines also. Plus does not matter if it's a vertical or horizontal shaft engine, My videos tell you what to look for. I did this mod on horizontal engine. For vertical shaft engines the holes you look for (mentioned in the videos) will be in a different side of the valve cover.
Sounds like it has too much oil in it.. most small single briggs donot take a full quart of oil.. when i use to race gokarts we would keep a oilchange in a 20oz mt dew bottle for a fast turn around.. lol
LAWN MOWER MUDDER Established Member
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Age : 23 Join date : 2013-04-08 Points : 5203 Posts : 913 Location : Central Pa
@Jarhead As I remember, the oil level was right in both engines. The valve cover filles up with oil when running the engine higher than what the governor was originally set from the factory. The holes in this part is made to handle the original governor rpm set by the factory. If you pass that rpm limit, then the engine is puking oil out the hose because it can't suck the oil back into the engine from the valve cover fast enough. Bigger holes means more rpm without the valve cover puking oil.
Subject: 
July 26th 2016, 9:56 pm
