I have a .25 and .35 os fp engine and was wondering what the steps to tuning them are. I had to clean up the .35 as it was pretty gunked up. I removed both the screws and the main needle. I counted how many turns it took to get them out and put them in that many although im sure they're slightly off. I didnt count the main needle turns however. someone said to turn it 2 turns out and lean it out from there. Any help is appreciated!

Since you have already taken the idle screw and the needle out, you need to start from the basics. Refer to the OS site for the manual on both engines.

Usually on my other engines, for the low speed screw, you turn it in all the way with the carb fully closed and then turn it out by 1.5 turns. BUT MAKE SURE that this is what the manual asks you to do for your engines before you do this.

For the high speed needle, again check with the manual. Since you have cleaned out the engine, I think you should start a little on the rich side to what the manual says and two turns sounds like what the manual says. Use an electric starter if the engine is suitable for that (I think it is) it it doesnt start by hand. Run it a little rich initially at idle (about a minute or so) so that everything gets sufficient lubrication and then lean it by sound. Once you determine the peak rpm, open the neede half a turn to richen the mixture so that the engine does not quit when you take off (engines gain rpm when in the air). I am assuming the engines have been run in. If not follow the running-in procedure in the manual after initial rich start.

Hope I have not written anything wrong. Others, please correct me if so

Ameyam

Most any engine in good shape will tolerate running too rich and there will be a nice smoke trail to prove it. If the engine is running OK like that, then the final high speed setting can be arrived at from what you see and hear in the air. The last 500 rpm doesn't have much value if it is going to fry the engine, so there is a price to pay for greed.

Tuning an engine is an art form. It's kind of like tuning a guitar. You have to listen for the changes and react accordingly. Generally on small OS engines, like you have, turn the needle all the way in until it seats carfull not to put any undo torque on it that would mar the needle seat or needle. Then turn the needle out 2 turns. The "fp" engines have "air bleed" carburetors so you will see the idle adjustment screw going horizontal accross the front of the carb body and a pin sized hole in the center of the carb body. That screw restricts airflow through that hole. The starting point for this is to have the end of the screw obstruct half of that hole so adjust that screw to that point. Select a prop apropriate for your engine otherwise tuning will be more difficult or even impossible. You are now ready to start the engine!

Allow the engine to run to temperature at these settings vary the throttle to keep it running. You may have to leave the glow ignighter on to keep it running. After the engine is warmed up (about one minute running) open up the throttle to full and listen to the engine. It should sound kind of "four strokey" with an occasional pop and burble of unburnt fuel as well as a smokey sloppy mess exiting the exaust. Turn the high speed needle (HSN) in to lean the mixture just a few clicks at a time giving 5-10 seconds for the engine to react to the changes untill you get to a "two strokey" sound. You know, like a dirt bike You should still have a good smoke trail but not so much oily goo exiting the exhaust. This is now a safe setting. You can fine tune this by ear or tachometer. Slowly a click or maybey two at a time lean it listening to the engine speed. when you get to the point it wont go any faster or has even slowed a little go back to the richest setting that gave the highest speed. Then turn it open 2-3 clicks more. The speed will drop some but you will get that back in the air. If you take it all now it will burn up you engine in the air.

For the low speed you may be fine right where it is at. Allow the engine to idle and listen for the "pops and burbles" of being too rich or that smooth "two strokey" sound. Do not try to make this adjustment while the engine is running. stop the engine prior to any changes to this idle screw. If you have that "four strokey pop and burble" then you unscrew that screw just a touch to allow more air into the idle mixture. If it's already smooth and two strokey, then it's probably just fine but you can close that screw a little untill you get the rich setting then back it back off so it just goes into the propper two stroke setting.

This is how I tune my engines. It has worked for every engine I have ever used and I have never burnt up an engine by going too lean. With engines I am unfamiliar with I look up the factory needle settings as a reference and then use my own technique here to tune it in. As a note, remember the idle screw on these airbleed engines lean when you unscrew them and richen when you screw them in. This is OPOSITE of how a dual needle carburetor works. Good luck.

This is blasphemy from a self proclaimed speed freek!

Key point to remember with 'Bleeder Carbs' as described by Mr67stang, is that the adjustment screw works opposite of all the conventional double needle types.

To Make the midrange mixture leaner you back that screw out. To make the midrange richer you screw it in.

An easy starting point that works well with all the FP series Bleeders as well as the LA series carbs is to insert a heavy pin or large safety pin opened up into that hole in the front with that horizontal screw backed out. Now screw in that horizontal screw untill it starts to pinch the pin but you can still pull the pin out. Thats a good starting point for the midrange.

John

ok so the long needle on the left side (cockpit view) is the hsn, the horizontal screw on the right is the idle speed screw, so what is the 3rd screw for? believe it sits on top of the carb going down

That is a throttle stop screw. Completely useless on airplanes. Open that up to the point the caburetor barrel will close all the way. Then set your control servo so at the lowest throttle setting with the trim up all the way will leave about 1mm open throttle. Then you can pull the throttle trim down to close it the rest of the way and shut the engine down by choking off the air supply.

I know my post was a bit long winded so just check the last half of the last paragraph

Yes,

Yes and

The vertical screw on some versions is a idle stop screw that limits how far the barrel can be closed. This should be adjusted for RC so that the barrel is fully closed when the throttle arm is in the closed position.

John

Sorry Stang I missed that last part, Now where did I leave that bottle of Geritol[8D]

That's all right. We are both trying to help trainer25 out. I just didn't want you to think I missed something

Nope I would not have thought that, These things are at their best in a team effort and you have contributed much in your posting.

John

Aw heck that Geritol has to be round here someplace?

trainer25,

Once you have done that, proceed to a finer adjustment.

Read this useful thread regarding low end adjustment:

http://www.rcuniverse.com/forum/m_88...tm.htm#8844410

Some additional information:

http://www.gettingairborne.com/engines.html

http://www.masportaviator.com/ah.asp?CatID=8&ID=46

http://www.masportaviator.com/ah.asp?CatID=8&ID=47