What happens to 2 strokes during break in?

[Jeepster_nut]

So we know that 4 stroke's oil catch any metal particles during break in and can be drained out (for the most part) during an oil change.

What about 2 strokes? There isn't crankcase oil to catch the metal particles. Do they get mixed in with the gas/oil mix and burned off during combustion?

 

[Cujet]

I think the wear metals go right out the exhaust.

My experience with 2 stroke engines is that they are Broken in right away. A few piston heat cycles may be critical in tight clearance engines. But other than that, I spend no time breaking in a 2 stroke.

By the way, I have some of the longest lasting 2 strokes around!

Chris

 

[Brett Miller]

Some stays in the bottom of the crankcase forever.

 

[Blue99]

Normal break-in should only produce fine dust like particles that will be carried in the oil film on the cylinder walls.

As Cuejet & Brett are indicating, some of it probably gets exhausted out, some will eventually migrate down into the crankcase.

I just recently re-built a small Stihl chainsaw that had been run on straight gas.

Pulled the cylinder off and the crankcase surfaces immediately below the cylinder were covered with a thin layer of dark grey dust, which is what's left of the material that came off the badly scored & burned piston.

So material from the piston/cylinder will fall down into the crankcase, but my example of dust/debris from a bad piston has to be 1000 times greater than any amount of normal break-in material.

 

[gj]

when my boat engines were new,a yamaha 5hp,and a 1998 force 40 hp they recomended a higher mix ratio for the first 2 or three tanks.then go to the 50:1 .i always mix a little on the rich side,engines have never been any trouble.

 

[cousincletus]

I've been told to mix the oil rich for the first couple of tanks too. I can't see how any wear metal could remain in the crankcase since a 2 stroke engine breathes through the crankcase. The fuel comes across the bearings before it's sucked up into the cylinder.

 

[wileyE]

Extra oil in the mix is precautionary and may prevent a seizure or light scoring of a new motor. Has little to do with wear metal or trying to suspend it. Wear metal in a two stroke goes where it want to go, nothing we can do about it.

 

[Cujet]

I am a true two stroke fanatic. I own 4 2 stroke motorcycles and a number of other 2 stroke powered things.

While I have never seen any wear metals in a two stroke crankcase, I think it could happen, airflow and all. I have taken apart golf cart 2 strokes that had a little carbon in the crankcase. This was due to short circuiting of the exhaust gasses (poor port height design). Maybe some of that carbon had wear metals?

But mostly, two stroke crankcases are perfectly clean when operated properly.

Chris

 

[Master ACiD]

as said they usually remain clean. i have seen blown up 2 strokes with chunks of metal in the crankcase, but thats because the engine was self destructing.

 

[rphart]

Keep in mind that mixing the oil richer than the manufacturer suggests (more oil per gal of gas) causes the engine to run lean, all other tuning parameters remaining equal. Yes, you are getting more oil on the critical parts, but with the engine running lean you may overheat or detonate and cause engine damage. Always stick with engine and/or oil manufacturer instructions.

 

[Steve128]

Off topic: This oil richer debate can be confusing to the amateur's (ME

) on this board. Many manufactures have you run richer during the first tank or say you can run 25:1 unless in California then run 50:1. So if richer is damaging, then why would they have you use it for engine run in or every place but California?

 

[Master ACiD]

going from 50:1 to 25:1 is such a small ammount of extra oil that the air/fuel ratio would hardly change at all. yes it does change, but it aint gonna hurt anything to run it a couple precent leaner. espically when you consider that the gasoline isnt the only fuel. the oil also acts as a fuel.

 

[GT Mike]

I just run Mobil 1 Racing MX2T in everything at 32:1. Probably gross overkill, but this way I don't have to have three different cans with 32:1, 40:1, and 50:1 for all my various 2-stroke engines.

Never once had a failure.

Talking about rich fuel/oil ratios...I had some old Power Products (Tecumseh) 2-stroke engines on 1950s vintage lawn mowers, and they recommended MS grade 30wt. oil mixed at 3/4 pint to one gallon of gas (that's 12:1!) for the first 5 hours, then 1/2 pint to a gallon (16:1) thereafter.
Yes, they smoked profusely.

 

[mtgrs737]

I have never seen any wear metal inside of a two strokes crankcase. I don't believe that the constant fuel/oil/air vapor traveling thru the engine would not wash out the micro fine particals. I wouldn't Worry about adding extra oil for break in perposes leading to leaning an engine out. I don't think that it would be any worse than the normal air density fluctuations that are already incountered day to day and from season to season. I run Mobil One 2T at 32 to 1 in EVERYTHING I own, even the engines that recomend 50 to 1 without plug fouling, carbon build up, or any overheating problems. It's a fact that too little oil will damage/destroy a two-cycle engine and that a little too much oil won't hurt. IMHO

 

[gj]

using 3 oz per gallon i usually add about 12 0z then fill the boats tank up with 3.5 gal of gas.don't think that's overly rich.had it since 1998 40 hp force/mercury.also change plugs at the begining of each season.runs like new.

 

[bob_ninja]

Heat is the enemy #1 for any air cooled engine. There are many factors besides oil/fuel ratio that affect engine temperature. One of them that you could control (depending on the tool type/usage) is run time. I always prefer richer oil mixture as bit of extra oil causes less problems than not enough. I simply limit run time. For my chainsaw I'll run it for 5-10 min, take a break to let it cool off some but not back to ambient temp, then another 5-10 min run, etc. That way engine remains warm at all times, but doesn't overheat.