[sm=confused.gif]It looks like I ruined my B&S 34cc engine. It was running nicely, but suddenly stopped after about 10 minutes of running (at various throttles), and was very hard to turn over. When I took it apart I found small metal chunks inside the crankcase, and a couple of gouges in the cylinder wall.[sm=omg_smile.gif]

Before running it I filled it with 10W40 oil and the temperature outside was over 50 degrees. I let the engine run for several minutes to warm up before throttling up. It ran much better since drilling out the jet but still went a little lean at wide open throttle. Max RPMs I got it to were 6000, which doesn't seem like over-revving to me. I guess it was the oil I used.[sm=confused.gif]

If I were to try one of these again I would use only the recommended B&S synthetic oil! The owners manual states that using 30 weight oil below 50 degrees can cause cylinder bore damage! The manual says that the synthetic oil is good for any temerature.

It's too bad because it was running beautifully before it seized up![sm=cry_smile.gif]

Jim

That's probably an excellent idea. I would try to avoid using a passanger car oil, because the manufacterers are reducing the level of zinc to help reduce more emissions. These engines don't require much oil anyway, so use the very best.
Jan

I suspect something else let go. I worked on lawn mowers for 35 yrs. and never saw a motor blow up in 10 mins because of the wrong kind of oil. Find out if you can where the broken pieces of metal came from. I've seen motors totally destroyed just because the butterfly screw fell out. The pieces in the crankcase are what destroyed the piston and cyl. Make like a detective and try to find out what let go and why. Such things as over reving can cause a motor to blow too, especially a 4 stroke.

I will bet it was not just a wrong oil problem. Clean things up a little and post some photos of it. We are all kinda like detectives!!! Capt,n

I took the head off and looked down inside, and I couldn't see any damage to the piston at all. When the piston is at it's lowest point you can see the start of two scrapes, and you can feel them from inside the crankcase. I'll take the head off again and take a picture to post.

Jim

That tells you all the mess happened in the crankcase. Check and see if the bearing cages are intact. Are the broken pieces aluminum or steel or both ? Do they have machined or cast edges? Are there any broken pieces from the skirt of the piston.

A couple times my 34cc sounded like it was starting to sieze and grind, and I was using synthetic oil. I stopped it and tilted the engine around so that oil could get all to all the bearings and it seems to be OK. My thinking is that the engine was designed to be bounced around and tilted as it is used for a weedeater and that the oil would get to all the critical areas. When it's flying, it shouldn't be problem either, but just stting upright on a bench the oil mostly sits at the bottom. Not sure about that tho. 3 oz. of oil seems like so little. As you see in the photo, I doubt that the oil comes up to that inner crankcase. I would like to put a plexiglass back on the case and watch it as it runs.

Rod S

It might be a good idea to add 2% oil to the fuel. Just may save the engine doing so....won,t hurt to try! Capt,n

For all B&S 4-Stroke conversion fans, a couple of new 34cc engines are currently listed on eBay starting at $50 plus shipping e.g. item 330050017613.

I purchase mine from this seller a few months ago and had it converted by Brillelli. It turned our real nice and not very expensive.

Maninder.

That's what I figured. I looked like mostly aluminum, but the pieces were tiny, so it was hard to tell. I'll take a closer look at the bearing...it did seem awefully noisy when the engine was idling, but I figured it was normal for this engine. I did look at the piston skirt, but I'll take a closer look.

Jim

Here's a picture with the head removed. It looks like a couple of pieces of metal were shoved up from below. If they were above the piston rings, they would have gone up higher, I think. The gouges go all the way down to the bottom of the cylinder.

Tomorrow I'm going to take the back plate off again and look closer at the piston skirt and the bearings.

Jim

WARNING: Have small children leave the room before viewing this picture! It is an ugly scene!

Check to see if the wrist pin locks are still in it.

Bet it's pieces of the ring. Gouges have that perfect square look.

That's sounds reasonable. I just have to figure out how to get the piston out to look.

Jim

The flywheel has those two studs with the starter pulley hooks on them. How are they removed? Are the pins pushed in? Threaded in? Etc....

Kmot,

They are pressed in, not threaded. I had all of my flywheels milled down for weight, cooling and to fit inside the fuselage(for the DVII),so the guys just drilled out the top of the pins before milling. Those pins are hardened, by the way. If I remember correctly,Propnut said he got his out by prying them off with a screwdriver. I tried this when I first got my engine to see if I could get them off, but gave up for fear of breaking something. Also, a couple of my flywheels were also VERY difficult to get off,even with a flywheel puller, so perhaps these things vary from engine to engine

I usually have to heat the flywheel with a propane torch and gently pry with a screwdriver to get it off. Also, you can put a nut on the end of the crank and tap with a hammer while prying.

You can drill through to the pins from the back side, then use a piece of hard wire and a hammer to tap them out.

Jim

Thanks fella's!!! [sm=thumbup.gif]

FWIW, I used a three jaw puller and my flywheel popped off easily enough.

So what are you going to use your engine for?

Probably a plane like Prop Nut built.

Nice! I got my engine about the same you did and probably from the same guy on ebay as well. I'm using mine in a Baby Bootlegger instead of the Ryobi that I have because the Ryobi is about an inch taller than the BnS.

Anyway, How do you guys cut the flange off the Briggs?

I used my mitre saw with a grinding wheel attached. Rather low-tech, but it worked well and was quick. I then finished up any rough edges with a Dremel.

J

I have not cut mine yet. I have been thinking about the best way. I might try a coping saw, and if it works well just finish up with the Dremel.

I believe I used a cut-off wheel on my dremel and made a couple dozen plunge cuts, then smoothed it up with several methods. Make sure you leave the mount for the magneto.[X(]


RS

I am using Castrol all-synthetic 5w-30 and have had good luck so far(knock on wood). Temps here lately have been around freezing or below and while my hands get icy cold in the propwash, there have been no problems with the oil.

J