ragingbeaver

my new os 25 la engine has a really hard sticking TDC. I know the cylinder bore is tapered, but it seems to reaaaallllyyyy stick. is there some way to make it a little looser so I can actually start my engine for the first time?

Thanks for the feedback!

downunder

Most new ABx engines will seem to lock in the pinch if you turn them over slowly but this isn't a good thing to do, especially if there's no fuel in it yet. Just about all engines that seem really tight will turn over easily with a good fast flick and you won't even notice any pinch. I presume you have the glow plug fitted because that actually makes it easier to flick completely over TDC.

ragingbeaver

it was really easy one time, and the engine ran for like 1/2 a second, then it seemed to get really stiff again. the glowplug came with the engine, its a nice fit. i have a 12 volt starter, and its so hard to turn than the rubber started to tear off.

carl24bpool

Have you tried putting a little fuel in the cylinder through glow plug hole? Just a couple of drops to lubricate it.

downunder

OK, starting to need more info here. Is the engine in a model or a test stand? Upright or inverted (inverted could be a hydraulic lock)? Is it easy to turn until getting into the pinch or hard to turn everywhere? Does the crankshaft slide easily back and forwards by a very small amount?

ragingbeaver

its in a stand. its upright for now, until I get it running then it goes upside down in my plane. its really smooth up until the TDC. yes crankshaft does move a wee little bit, with no to little resistance. Ill try putting some fuel on top of the piston, hopefully that'll get'er lubed enough to make that flip easier.

JohnBuckner

My Feedback: (1)

Rotate the propeller backwards completely up to TDC before pulling the starter trigger every single time this is imperitive and have someone hold the airplane it is important that you use two hands on the starter to maintain correct alighnment with the crankshaft and push hard aginst the propeller before pulling the trigger.

Have you properly charged your battery for the starter and this usually means all night before?

John

Ed_Moorman

My Feedback: (1)

Oh for heaven's sakes!

With a really tight new engine, if you pop it with a strong starter you take a chance on bending the connecting rod, especially with the smaller sizes of engines. Take your heat gun with a long extension cord out to your test stand and heat up the cylinder all around. This will open the sleeve up and allow you to start the engine. Rev to full power and lean out to just into the 2-cycle range. If it starts slowing down, open the needle up for 10 seconds, then lean out again. Normally, after a single run the engine will be loose enough to start by starter or by hand.

ragingbeaver

thanks for the tip ed! it worked good. unfortunately I flooded the engine (I think) and it wasn't starting, it was spurting a little fuel out the exhaust, so it definitely was trying. I removed my glow plug and spun it over a few times to get the remaining fuel out. I tested my glowplug and found it wasn't glowing at all, it was about 5 minutes prior. maybe my battery was dead for my igniter or maybe I burnt out my glow plug and I don't have a replacement. the glow plug came with the engine and I don't know what it is.

Anyone know what kind of plug is prime for a OS 25. LA?

JohnBuckner

My Feedback: (1)

Oh for heavens sakes! Right back at ya Ed.!

There is nothing wrong with with having the gentleman make sure his starter battery (whatever it is) is fully charged. And there sure as heck nothing wrong with telling him to simply back the engine up before pushing the switch, Good Griief! Now poping the starter i.e. hitting the switch first and then banging the starter into the propeller is certainly not what I wrote and perhaps you choose to think that is what I wrote if so perhaps you should reread my post before you go on the attack.

I am no stranger with that size engine and currently have lost count with something like 16 or 18 all mounted and flying in single engine, twin engine, four engine airplanes and one six engine airplane, all twenty fives Oh and one three engine airplane just happens to have three LA 10''s Guess what I have never bent or damaged a rod or crank. None of this takes into account my 428 racing engines which have the heaviest choke I have ever ran across and I never had the need for a torch.

Please do not misunderstand I agree with you and a torch can work and does work but On the other hand I would never tell someone new who seems to be on his own to take a torch to his engine. Better he get experienced help as always before the torch.

John

jester_s1

I think it was a heat gun that was recommended, not a torch. And it's not a bad idea. Not absolutely necessary, but it will ensure that the pinch isn't ruined by cranking an engine that isn't primed right or is just hard to start for whatever reason.

bikerbc

Lets rember we are all trying to help and get along..John knows an awfull lot about what it takes to start an engine and nobody dedicates more time and effort to the hobby .. I have seen much the same from Ed.. Anyway this is supposto be fun ..

ameyam

ragingbeaver,

is it still tight at the tdc with the plug removed? If not, you flooded the engine. Simply use the starter to turn the engine over with the plug removed. Be careful, there will be a spray of fuel out of the plug hole. Run for a few seconds, then install the plug and try it again, first by hand with the driver removed and then with the starter

Always remember, when using the starter, move the prop back all the way till it hits compression. Then apply the starter in the forward direction. Doing this way, the prop gets sufficient momentum that it doesnt hurt the spinner cone or the rubber insert. Never bang a running starter on the spinner cone to start the engine, you will end up damaging something

Also, make sure the prop is installed tightly. In some of the OS engines I have overhauled, I found that the crank rubs against the backplate or the recess in the crankcase when the prop is not installed. This is because, once the prop is installed and tightened, the crank moved forward just a bit. That much is enough to clear the rubbing on the rearside. Without the prop installed you can hear the rubbing and if you take off the backplate, the marks are clearly visible. Just my observation

I have come across a couple of "tight" engines at the field. They are usually the older engines that havent been cared for properly- you know, just gunked up for several months or years. Not saying anything about you, just what I saw one day. I started one which, just like yours, ran for a second, then got stuck at TDC. But it ran fine after it warmed up a bit

Ameyam

ragingbeaver

thanks for all the advice! I my little os .25 running for the first time today, I burned through about 1/2 a liter of fuel, hopefully that's sufficient to break it in. I was running it without the prop installed, and just the spinner on to start. I found that sometimes the nut the holds on the crankshaft sometimes loosened, and I would have to remove the spinner and retighten the nut so I could get it to turn over when I applied the starter, is this normal or what...?

downunder

I won't be the only one to say this, but WHAT???

jester_s1

Yeah, that's totally wrong. You were probably turning 25k rpm with no load on the engine and may have damaged something. The fix for a prop nut that comes loose is to tighten it better, not to take the prop off!

And on a helpful note, are you using a plastic backplate on your spinners? They are prone to slipping and letting the prop nut get loose. If you'll put a piece of open mesh plumber's sandcloth or sheetrock sanding screen between the prop and spinner it will fix it. Alternately, you can buy spinners with aluminum backplates which will grip the prop enough to not let it loosen. You also need to tighten down the prop nut pretty hard. If you are using one of the little 4 way wrenches to do it you probably aren't tightening it enough. Put a box end wrench on it and you won't have any trouble from now on.

ragingbeaver

well now that's something that's good to know. yeah its just a cheapo plastic backing on the spinner. I will try the plumbers cloth or something to make It catch better. I just use a normal wrench and tighten it. but I think that's all for this thread.

Thanks for all your help! and take care!

JohnBuckner

My Feedback: (1)

Here is the best solution for the new fellas when learning:

http://www3.towerhobbies.com/cgi-bin...&I=LXE158&P=RF

They are called spinner nuts, fit your starter perfectly and lot a whole lot better that the cheap plastic spinners that typically are included with many arfs.

The big advantage of course is as a beginner you will be frequently breaking props on occassion (always keep spares on hand when going to the the field) and fooling with full spinners can be very time consuming when changing the prop. The spinner nut can allow you to change the prop very rapidly however with less loss of flying time.

This is a photo of how they look installed below: Some suggest that its harder on your engine in the event of a crash however I think that is a rather rare occurance perhaps with a direct vertical arrival into concrete. In that case not much of anything is going to be left.

And yes as noted above the propellor is a vital part of the engines operating system and the prop is the all important flywheel as well a a vital part of the cooling system. Not a great idea to run any engine without a prop ever

John

bikerbc

Make sure you haven't lost the little spacer that goes on the prop shaft.. Check the expolded view to see where it goes and what it looks like.. I remember that happening to me once and everything would seem fine till I torqued the prop nut then it got hard to turn over.. Just a thought...When I found the spacer and replaced it all was well . I believe it looks like a black washer..

ameyam

Spinner nuts ar good but I would suggest you get a nylon spinner with a metal backplate. What happens to the plastic backplate ones is that when you tighten the screws, the backplane no longer remains flat but forms a dish shape. This shaple lets it slip off the hub. It doesnt happen with the metal backplate spinners. I have even run that a nylon spinner with metal backplat on a dle20 and it gives no issues

However, running without a prop is plain wrong

Ameyam