I recently bought a new OS max-25LA engine for my planeand it just wont start. I am turning it over by hand as i dont have a starter. When i turn it over it runs for about a second or two and then either locks on the compression stroke or just dies. As far as i can tell the engine should run. The glow plug is fine, the fuel is good and compression is good. I had a 20 year old engine before this and i could never figure out why it ran for a minute the cut out. I thought this new engine would be easy to start.

Any help would be appreciated

Thanks.

Sounds like it is getting too much fuel, or possibly not enough. Try getting a feel for the engine by running it of a prime with the needle closed. It should then fire and rev up before it dies. Then draw fuel to the carb and set the needle around 2 turns, prime as before and see what the engine does. If it just sputters and dies it is too rich, if it revs up before it dies it is too lean. Adjust the needle accordingly and try again etc.

Also, if you are using a handheld glowdriver it has to be absolutely fully charged or the power will be too low for reliable starts.

Thanks will try that. I will keep you posted

<div>Thank you for your reply to my message. I did as you said and finally got the engine running. It was great to hear. But now i have another problem. The engine will not run smoothly no matter what adjustments i make. I cant get it to sound right. Any time i open it to full throttle it bogs down and cuts out unless i bring it to idle. </div><div>This sounds like the mixture is too rich but adjusting the mixture doesn't do anything to aid the problem. I noticed that the engine was throwing oil out the exhaust and the side of the plane was covered in oil. Is this normal? </div><div>
</div><div>Any help greatly appreciated</div><div>
</div><div>Thanks.</div>

Yes it is to rich at midrange and you can only lean via the midrange screw which is that horizontal screw sticking out the right side of the carb. To lean the mixture mid range you unscrew that screw slightly which opens that bleed hole on the front of the carb and leans the mixture a bit. All engines with bleeder carbs to lean you unscrew or turn counter clockwise. This is backwards from the now more common double needle type mid ranges.

Yes oil and combustion products do get all over the engine and the airplane, clean it after a run.

You really need to get some experianced help either thru your local club or a mentor. Going it alone is no doubt why you never were ever able to get that first engine to operate.

Get live Help Depending entirely on a forum such as this will always result in frustration and failure to reach your goal.

John

There should always be plenty of oil coming out of the exhaust, don't worry about that.

For the tuning, set it around half throttle or as high as it will run and then tune on the main needle. There should/will of coarse be reaction, it is just a matter of finding out in which direction to go, and how much to change. From your description it could be either too lean or too rich.

I agree with the earlier post. To save both time and money, talk to an RC club and they'll help you out. If your engine is new it needs extra care in beginning, in needs to be run-in well in order to perform well for a long time. It is quite possible to damage an engine during the first few runs which are the most important ones for an engines longlivity.

Thanks for the responses. I will try again tomorrow and i will let you know what happens.

You have said nothing about where you have set the initial needle setting either the main needle or the bleeder screw.

The first I would do is screw the main needle all the way in (makes no differance with this carb if the throttle is open or closed) then back it out two full turns as an initial setting.

Next is illustrated a simple trick for setting all the OS bleeder type two stroke carbs mid range screw. Insert a modelers straight pin into the bleeder hole on the very front of the carb and back out the screw to allow the pin all the way in. Then just screw the screw in untill you feel it touch the pin and that is a good reliable starting point for initial settings.

Then after adjusting the main needle for a peak and then backing off a bit, now just accellerate the throttle and if the engine stumbles heavily just rotate that mid range screw counter clockwise a tad. No more than one eight turn each time untill it accelerates smoothly.

Remember this mid range screw leans the mixture when you back it out.

All the LA series except the .10 uses this same type carb. The .10 has no mid range. Also all the FP series which was the predecessor to the La's used bleeder carbs too. The pictured engine is the .10FP

Agine you need hands on help for operating the engine and flying, failure to seeks mentorship is the number one reason for not realizing the dream. Get Help.


John

A brand new LA can be cranky to get running for the first time when hand flipping. It sounds like its getting caught up on the ABC "pinch" at TDC. That tight fit pinch is what makes an ABC type system work properly. Once its been run for about 15 minutes it will become a lot more civilized and likely start with one or two flicks.

Keep your initial breakin runs short (about 2 minutes) and on the rich side.

The ABC type metallurgy wants TDC to be fairly tight when cold, the cylinder's are made with a taper machined into them.

Using a leather glove helps for the first hour or so until things loosen up.

I have a .46 LA with over 6 hours on it that still has a fearsome TDC pinch that needs a good thwack to get the prop past, but it starts on the first stout flick every time now.

Dittos to what cutaway just posted concerning the cylinder pinch and this is another reason for new folks I aways recommend an electric starter and not a chicken stick, Something your mentor can help with if you do not have one.

John

Yes that is something to consider. I just cant get it to stay running to adjust the high speed needle. I could get it to run for about 2 mins on half throttle (If i go to full throttle it dies) and the optimum setting seemed very rich at about 2 to2 and a half. I am going out to it later to try and get a good setting on the main needle and work from there.

This is the classic case in what happens when you do not read the instructions that came with your new engine or do not seek experianced help (mentor).

The optimum setting is Not "2 to 2 and a half" or even the two turns I suggested in my earlier post. This is the starting setting to be used to be used anytime with a new engine or anytime the whether has changed after the engine has been previously adjusted.

Yes it is a very rich setting and this is deliberatly done to avoid starting the engine with a setting that is to lean.

The engine must be leaned some after starting and possibly even before attempting to open the throttle.

The process is spelled out in the operation manual or I beleve You can download the manual for that engine at hobby services the Tower hobbies or hobby services the US distributor for OS.


John