[/size] I really need advise bad. I am new to 4 strokers. Never owned one in my life. Would someone please tell me how to start the thing? What will I need to do the job. Also what is the difference between a 2 stroke and a fourI've been out of RC over 30yrs and am starting to get back into it.Please send me any info if you will to [email protected][sm=71_71.gif]

Use the same stuff you use for your 2 strokes with one addition - get a tachometer. It is extremely difficult (very close to impossible ) to set the idle and top end PROPERLY without a tach. I also suggest and highly recommend, using OS "F" type plugs in ANY 4 stroke.

The primary difference in the fuel is the oil content - MOST 4 stroke instructions say to use 18% oil. I use the same fuel (Byrons 10% ) for both my 2 strokes and 4 strokes with no problems. My Saito 72 has over 4 gallons through it without a problem.

The other major discussion with 4 strokes you will encounter is whether or not to use castor oil in the fuel. I add a couple of ounces to a gallon of fuel. While I do get varnish build up, I like the security of the castor if I get a lean run.

I do the same as campy when it comes to fuel. I run 2 stroke 18% synth/castor mix on os and saito. Seems to like it good enough. I have about 200 hours total on all four of my saito 120's. This winter I spent time cleaning them up and doing valve jobs on two of them. Wasnt that much carbon build up but I cleaned it out anyway since I was servicing them. Same fuel is run on 4 saito 120s, 2 os91fs surpass, saito 180. I have others but they havent been run yet.

The quick explaination between the two is - 4 strokes have valves, pushrods, and cam. 2 strokes dont.

(edit)
I should mention that I dont tune my engines for every little bit of rpm. I like to prop them between 8k and 9k rpm. You can run them faster, its just harder on the engine. Thats just my opinion.
Edwin

Most thanks to you Sir! Rev. Bill [sm=spinnyeyes.gif]

A big "THANK YOU", to you sir as well! Rev. Bill [sm=spinnyeyes.gif]

The other differences.
4 strokes need to be bigger than 2 strokes for the same application.
Example: That 61 you have would be about equal to a 40 size 2 stroke and should be used in a 40 size plane.
2 strokes run at higher RPMs and are great for speed.
4 strokes have higher torque and are good for aerobatics and climbing.
4 stroke require you to adjust the valve lash from time to time. It is not hard to do and not required often. I set mine during the winter downtime.

Four strokes are most easily started by first priming them until they are really wet, usually the carb intake is inacessable for choking with your finger so instead, plug the muffler outlet with your finger while turning the prop to pressurize the fuel tank and force fuel into the carb.

Now that you have the engine primed really wet, make sure the fuel line is full of fuel, no air bubble between the carb and the tank, close the throttle to idle, closing the throttle is very important, connect the glow battery, and then use a chicken stick and flip the engine backwards. This usually gets the engine started. You don't want to flip it through the compression stroke, you only want to bounce the engine against the compression stroke. I usually just grab the spinner and give it a flip backwards. They are extremely easy to start once you have the technique down.

If you use electric starters to start your engines, close the throttle to idle so that the starter isn't fighting so much compression.

if its a newer OS 4st engine then OS recomends using a electric starter,just make sure there is fuel in the line and apply the starter to the prop spinner after attaching the glowstarter and after a few revolutions it should fire right up.
don't over wet a newer OS engine or it will just flood it, just make sure there is fuel in the line the engine will draw the fuel when you spin it with the starter,as well read the manual and follow the instructions for starting and break in procedure,if its a older engine and you don't have the instructions you can get a copy from hobby services@ www.towerhobbies.com they will send it to you via e-mail just let them know exactly which model engine you have.
also get a tach a necessary tool for getting the proper rpms over reving a 4st is fatal to these engines when you get it running properly and in tune there great,I have 4 of the OS 4st motors they are solid engines.

OS recommends using an electric starter only on all of their engines now, two and four stroke. I don't know why, maybe a CYA thing. It didn't make me run to the hobby store and buy an electric starter for my .46 FX. Starts so easy that it makes you wonder why people even bother with electric starters. Joe Wagner reviewed the new .56 Alpha 4S in the latest Model Aviation and stated that he had no problems hand starting it, in spite of OS recommending an electric starter only.

the older engines have a choke to make it alot easyer to flip start the 4st, and OS deleted it when they came out with the newer models, so they do start alot easyer with the electric,but my 46AX starts with a quick flip as well sometimes when its a little cold it can be a bit harder to start it on the first run of the day.
I do like keeping the fingers out of harms way

I wont tell anybody how to start their engines, but I dont stick my fingers in the prop anymore. A lapse in judgement and eighteen stitches across three fingers with dead nerves stoped that. You dont know how much you need your finger dexterity until you loose it. Just my opinion. I have a riding mower starter that will be built into a big gasser starter when I need it. A friend of mine made one to start a three cylinder 93cc engine. Easily turned it over.
Edwin

yea, i didnt use and electric starter at first either on my .46 os on my nextstar until oneday it kicked back on me twice and i still have the scar. i probably could have gotten stitches but i used some CA to close it up. from then on im a wimp on started manually.

I never said that I start my engine using my fingers. I use a stick if I flip the engine through compression to start it, when back flipping, I grab the prop by the spinner. An electric starter doesn't guarrantee that you won't injure yourself, most of the really bad accidents happened with engines that were already running.