Speaking of old engine life, i'v aquired a o.s. max 35 from 1975 and it STILL runs[sm=biggrin.gif][sm=biggrin.gif]! Foams at the head and carb leaks but still manages to take my .46 trainer up! Go o.s.!!

Yeah I ran an air filter. But the needles were the biggest problem. They wouldn't stay adjusted and kept leaning out. It got to a point that the engine wouldn't smoke with the High speed all the way out. Probably had some air leaks somewhere.I think the dirt would get in every time I had to mess with it to get the needles set again. At the end They would just not get enough fuel. I am sure there could have been ways to get them running but the cars were just so boring I got tired of working on them.-BW

When I had the issue swith the 75AX, I wasnt as into technicalities as I am now. Will check it next time I use the 75AX. Right now I have 91FS on the same plane and it does about 70-80 deg (during the rich & lean run-in). As I pointed out in another post, the inverted engine has its carb about 1-1.5" below the C/L of the tank. Wanted to know if that is very critical since I cant lower the tank as the throttle rod runs below it

Ameyam

Well, as a general rule, the carb spraybar should be at about centerline with the tank...give or take a 1/4 or 1/2 inch below or whatever.

So if you can get it as close the correct as possible...it'd help your problem. Are you using a fuel filter? Who built this airplane and installed the tank, etc?

This is part of my problem....getting bored with just driving it around so now I need to "see what it can take." Then I break something and have to fix it..but it's all in good fun. And I have to admit I am impressed that little .15 can take all the beatin' I'm constatly throwing at it

HI have engines running for many years and still going strong some 400-500 10 minute flights and STILL strong all mine are two cycle glo i run only MORGAN OMEGA PINK FUEL now flying 20 years-ran MORGAN COOL POWER the first two years -shortened my bearing and cyclinder life FAR TO MUCHTHE ENGINE DESTROYER ( CRULE POWER )with omega i do not remember the last time i needed bearings or a liner (18 YEARS ) they need castor oil !-MY OWN OPINION IS THAT THE BREAK IN PROCEEDURE IS WHAT DETERMINES ENGINE LIFE-getting those internal engine parts -POLISHED FROM THE GET GO IS THE KEYthen running the engine correctly regarding the needle valve settingsset the top by ear to max RPM and back off a 1/4 turnset the bottom by running the engine about 1000 rpms above idleturn out the low end until the engine gets a little bit roughturn it in until it gets as smooth as is possible-do that twice- top and bottom now i pinch the fuel line both top and bottom to listen for some RPM increasethat is telling you those settings are a bit on the rich sideAS YOU WANT THEM- IF FOR ANY REASON THE RPMS START TO INCREASE AT THE USUAL NV SETTING ( AND SEEMS ODD ) YOU MOST PROBABLY HAVE AIR GETTING INTO THE ENGINE SOMEHOWFIND IT OR IT WILL OVER HEAT THE ENGINE BY MAKING THE ENGINE RUN LEAN ( EXTRA AIR ENTRY IS THINNING THE FUEL MIXTURE ) HEAT AND SOFT ALUMINUM DO NOT WORK WELL TOGETHER if the engine surges or cuts out during your flight (and you are at full throttle )your top end is to leanrichen 2-3 clicks - just my .02 cents and some basic glo stuff ENJOY REGARDS TONY

HI FOR break in i add 1oz of castor oil to my OMEGA fuel in the first tank only ( not in the gallon saves fuel )run the engine just below max rpms -on a 1 inch smaller prop than you will use to fly the engine (jet engines has very good break in info on his web site ) run the engine for a minute or two then let it cool downi like to keep the piston at the top of its travel so the liner and piston cool together (contract together just me ) what is happening hear is the metals are being polished and hardened at the same time from the heating and cooling temps ( the cooling is as important as the running now )do not for any reason overheat the engine at this timetouch the head with caustion (tap it ) to feel it -s/b very warm but not sizzling hot everi run a 16 oz tank for break inor until the engine will hold its nv settings (varies with engine mfg's )
i only use after run oil ( a mixture of 1/2 trans fluid and mystery oil ) when i am putting an engine to rest for a whilei use to use it every day i flew only to find the engine needed to clear it out before it would start to perform as it should for a days flying (worked against me the next day to get the engine performing well when flying a few days in a row) so now i only use it for storage-not required for daily use if using MORGAN OMEGA FUEL per the instructions again my .02 cents ENJOY REGARDS TONY

On a typical OS engine, 1/4 turn rich of peak on the high speed is too much. That probably put you over 1000rpm down and has it running very rich. Conditions vary but often 3-4 clicks back from peak is enough to get the recommended 300rpm rich sweet spot.

As others said you MUST learn to tune your low end also. The throttle response will improve drastically, fuel consumption will decrease drastically, and it will make your plane easier to land as you can hold a much lower reliable idle. Most engines Ive owned - OS included - are typically off a full turn (or more) too rich on the idle from the factory.


Well cared for most RC engines will outlast us. Ive got a 10 year old 46FX that has been on at least 5 different planes and probably had 30+ gallons through it. Right now its screaming at 16k rpm on a 120mph Q-500 ship I have a number of Saitos that have similar usage, some on their second or third set of bearings but otherwise they run like new.

HI 3-4 clicks -is a 1/4 turn on most needle valves i have worked withwe are saying the same thing here TONY

sounds lean on the high speed needle to me, set the high speed a bit rich first then set the low speed for throttle response second in that order
with the throttle wide open rotate the high speed rich till it hogs up then rotate lean till it crackles and wants to stall next set it on the high side of half way between the two, next on the low speed richen or lean the low speed to get good throttle response next blip the throttle form zero to half throttle back to zero if upon returning to zero throttle it wants to hog up and fall below idle you're too rich if upon returning to zero throttle the idle hangs up and takes a lil time to return to normal idle you're too lean correct accordingly on the LOW SPEED NEEDLE ONLY leave the high speed needle alone this has to be done in this order only to achieve proper tuning, the high speed needle is solely responsible for for proper fuel flow at WOT only.
I've tuned motors for so many guys that were ready to scrap them because they couldn't get them to run right but they were aimlessly fiddling with the needles with no idea what they were doing or what sequence to do it in if your carb is tuned right you should see a lil puff of smoke when you go from low throttle to mid or high with a blue smoke trail becoming a bit more and more noticeable as you move the throttle more towards full throttle.
hope this helps