I have been out of the hobby for the last 15 years and always flew 2 strokes in the past. I just acquired my first 4-stroke, a OS 48 Surpass. I need some help on plumbing the fuel lines. (I got this engine from a Widow and it had no instructions). It has 3 fuel line nipples. One at the carb., one on the bottom of the crankcase, and one on the muffler. My tank has 2 connections with an option for a third. I assume that I get tank pressure from the muffler, but I am not sure what the one on the crankcase is for. Also, I plan to run this engine inverted. Are there any other issues with 4 strokes that I need to be aware of such as after run oil, special fuel, needle setting etc. Please advise....Thanks.

TXDave,
4-strokes fool a lot of people, so don't worry about it. There are only 2 parts of the fuel system. The fuel intake at the carb goes to the pickup line on your tank, and the muffler pressure tap goes to the vent line for the tank. The third nipple that you mentioned is the crankcase drain. It allows excess oil to drain out of the crankcase. Hook up a small piece of tubing to this nipple and route that outside the engine cowl or fuselage so it can drain out of the engine without building up inside the fuselage.

As for other things to worry about there are a few to take into account. Oil content in your fuel needs to be 18% or higher. Other than that you can use just about any fuel you want to, you can even use the same fuel that you use in your two stroke engines. I use Cool Power 15% in everything that I fly (both 2 and 4-stroke) with no problems. The other thing that you'll need to worry about it the valve clearance, make sure that it's set properly. I looked on OS's website but couldn't find a manual for the 48, but here is a link to the 52 Surpass
4-stroke. [link]http://osengines.com/manuals/fs-52s-manual.pdf[/link]Setting the valves should be similar for both engines so you can use this as a guide.

Hope this helps

Ken

Thanks Ken...With the engine inverted, the crankcase drain will be on top. How will this affect the build up of residue inside the crankcase? Will internal pressure take care of it or does gravity normally do the job?

Dave,
Pressure and gravity will take care of it, even with the engine inverted.

Ken

Thanks for the help Ken.....What time zone is this website located in? The time indicated on the posts must be Singapore's time zone. Any idea if the webmaster has been notified of this problem? Thanks again for the assistance.

The times that it posts are set for the time zone you are located in. You set that in your personal settings screen on RCU. Once you set that time it will display all of the post times in your local time.

Ken

If you don't set your clock, I believe it defaults to GMT. Grenwich Mean Time or ZULU in aircraft parlance.

Grenwich, England

I am certainly not an expert on engines so consider this post worth the price I charged for it :-)
Once I got my first 4 stroke I quickly gave up the two stroke engines, never had issue with the two strokes, just like the 4 strokes better.
All of the engines I am currently running are OS and Magnum 4 strokes.
As a general rule of thumb when you select your prop you will need to choose one that will load your engine between 9000 to 10000 RPM sustained on the ground, a little more than 10k is ok but I would not load it below 9k.
You will need to set the needle valve / RPM with a tachometer (I am sure there are people out there that can do four strokes by ear but I would not recommend it to start off with). While the GloBee tach has has its share of criticism I have had one going on 3 years and it works great.
Don't adjust anything other than the needle valve unless there is a very good reason to do it.
My experience has been that the four strokes have required no more maintenance than the two strokes.
Don't mess with them and they will run fine for a prolonged period of time.
I recently switched from 10% nitro to 15% fuel (just because I got a good deal on it) and I got aa average of 500 RPM increase on my OS engines and 900 RPM increase on the Magnums. I did not expect this much difference but needless to say I would now recommend the 15% nitro.
There are props that say they are 4 stroke props, I have some of them and I like them fine, right now all of my planes have either APC or Master Airscrew Scimitar props on them (just because I like the way they look). Bottom line any prop for a glow fuel engine will work.
What size prop to run ?? Well I don't know what to recommend for the 48 Surpass but the RPMs listed below for the various engines were all measured in the last two weeks. I live near Dallas so the temp was 100+ and humidity was between 40 and 60%.
15% nitro, 20% oil, sustained RPM on the ground:
OS 91 APC 14x6 9600 rpm
Mag91 APC 14x6 10200 rpm
Mag 70 MAS 13x6 10000 rpm
OS 70 MAS 13x6 9700 rpm
Mag 61 MAS 12x6 10200 rpm

I would guess 11x6 would be a good starting point.

Oh a couple more things, I would run the engine right side up on the test stand before mounting it upside down in a plane, it will just be easier to fiddle with that way. Forget the choke and use an electric starter, again its just easier.

Hope you have fun with it.

Thanks Charlie....sounds like lots of good advice. I already bought a gallon of 5% cool power. I won't need much nitro. It will be in a J3 and I won't be doing any pattern maneuvers or racing. I guess I do need to invest in a tach. I appreciate your response.

One thing to watch for on 48's and 52's is exhaust valve clearance. If set to tight it will run ok on the ground but when airborn it will heat up more and become too tight and lose power, or quit altogether. I've had this happen to me with two 48's and also a 52. The book says to set them to .004 to .010 mm and this is fine for intake but the exhaust needs to be set more towards the .010 side to accomadate the heat when it starts to work a little. many people think that the smaller setting is optimum and strive for .004 and have trouble with stoppage and deadsticks when a few mm's more clearance will fix it.