Author Topic: os .25 la questions (Read 1006 times)

jim gilmore · « **on:** June 25, 2009, 01:08:11 PM »

Ok going to ask a few questions here. What rpm should I look for it to run with a venturi and needle valve for flying the shark 402 ?
I has a leak at rhe back so I used a little red rtv and it seems to be holding.
My tach seems to say it is swinging a 9 4 at 10500 or so, does that seem low ?
Also I'm not running at full lean. Just running some fuel through to see how it runs, it was bought used.

Larrys4227 · « **Reply #1 on:** June 25, 2009, 02:11:28 PM »

That would probably be a good starting point, but its gonna depend on the plane weight, line length and what speed your going for.

Currently, my 25-LA is on a SuperClown. 60ft lines, 9x5 prop and around 10K = approx. 5.2 sec p/lap

Hope that helps! FlySafe! Larry (Larrys4227)

Mark Scarborough · « **Reply #2 on:** June 25, 2009, 02:12:46 PM »

Jim;
short of actually flying it, that sounds really close to what I fly my LA 25s at. Although I have used a 10x4 with very good, actually better success than the 9x4. Might be worth a shot if your so inclined.
You want it to run in a rich two stroke, its not a 4-2-4 motor, its a two two two motor,, it will "break some" but not like a Fox 35,,
have fun,
Pats, Shark 402 is a good airplane for the 25,,

jim gilmore · « **Reply #3 on:** June 25, 2009, 02:22:02 PM »

Ah ok,here is anothr question. Should I use hot plugs or cool plugs or in between?
I use an old cox sure start batter set-up for power.
It tells me if the plug is flooded and has a button I can push to make it run hotter.
I can usually posh the button and get the engine to pop if it's a bit too rich and doesn't want to stay running.
If it is still too rich it will di when I turn the power off. I'm wondering if the glow plugs are too cool.
What do you all think ?

ray copeland · « **Reply #4 on:** June 25, 2009, 07:12:03 PM »

Maybe something is wrong with my tach,, i don't think so . All 4 of my planes with an OS la 25 and APC 9x4 prop launch somewhere between 12,000 and 12,500 and still have room for a little 2 2 break at the top!!

Larrys4227 · « **Reply #5 on:** June 26, 2009, 05:35:02 AM »

Ray - Maybe something is wrong with my tach! LOL! My notes show the last time I put a tach to my 25-LA/9x5 was early May, and it says 10K. I make notes just for reference when experimenting with setups, but one thing I do dislike is my tach. Its very flaky ... sometimes i cant get a reading at all. Once things are the way I like, then its usually just a click or two in either direction depending on the day. Now ya got me wondering where my RPM is at .... :-) ..... this weekend I'll have to tach it to see.....

Jim - I believe a NIB 25-LA comes with an A3 plug. I've got both OS#8's and A3's in my box .... currently there is a #8 in the motor. If yours is like mine, you'll find that the 25 is hard to start when hot. I have to let mine cool down between runs. The way I start mine every time: thumb over venturi and turn prop over twice once fuel reaches venturi. Remove thumb, and flip prop 3-4 times. Attach ignitor, and will start on first or second flip w/chicken stick. I never use electric starter. This motor had the sleeve/piston replaced 3 months ago and probably has 60 runs on it. I dont run muffler pressure and can get 8 minute flights out of 3oz fuel, at a rich 2cycle. Good lil' motor for me!

FlySafe! Larry (Larrys4227)

ray copeland · « **Reply #6 on:** June 26, 2009, 06:49:26 AM »

Larry, my box and motors are also a mix of #8 plugs and A3 plugs, same thing on my fsr 25's. i really need to do some research on performance and durability of the plugs, although i haven't noticed and difference. I do run muffler pressure on all mine, the hayes tanks don't quite hold a full 3 ounces so my run times are between 6 and 61/2 minutes with one exception. On one la i made a homemade nylon venturi with a brodak needle and spraybar, same amount of fuel and with plenty of power my run times jumped to 8 minutes or longer. My first try at a contest with this setup in the Magician and less than 2 ounces of fuel (because this was the beginner pattern) was a flight of 7 min 42 sec , almost an over run.

Also my start routine is the same as yours, works well. Take care,, Ray

Larrys4227 · « **Reply #7 on:** June 26, 2009, 08:04:23 AM »

Ray - Originally, I ran the stock exhaust with a 4oz tank on a Flight Streak, and I could get 10-12 minute runs. I wanted plenty of handle time, and certainly got it! Shortly after, I put a tongue muffler on and the flights dropped to 7 minutes or so. Didn't really think much about it until I moved to a 3oz tank and the SuperClown. Flight times dropped to 5 minutes, which wasn't enough. Couldnt go back to the stock exhaust because of clearance issues with the landing gear, and weight issues. I happen to come across an archived thread, and it was mentioned about blocking some of the holes in the tongue muffler to increase the backpressure. There are 15 holes in the tongue muffler (3 rows of 5) and some simple math between the size of these holes, and the original outlet of the stock exhaust, showed a HUGE difference. I blocked 10 holes (2 rows) with JB Weld. On the same 3oz of fuel, and a readjust of the needle, every flight is right around 8m15s and pretty consistent with no pressure to the standard vent tank. I still find it amazing how much the 25LA likes the back pressure!! My Fox29 lost power when I added a tongue muffler and ended up drilling more holes.

I think the A3 is hotter than the #8? But I haven't noticed any difference between the two. I run out of the jug WildCat 10%, at 18%oil(syn/klotz) .... seems to like it! For awhile, I was bumping the oil to 23% for the 25LA but all it seemed to do was make more of a mess. Hahaha!

FlySafe! Larry (Larrys4227)

john e. holliday · « **Reply #8 on:** June 26, 2009, 09:52:33 AM »

I am still running LA 25's on SIG SKyray, Ringmaster and have had a ARF Streak. Most of the time used 10-4 props. But, seems the kids like the planes better when a 9-6 is put on. I also do not run my engines flat out. My LA 25 restarts easily even after I do get a lean run once in a while. I also use 10% nitro with 22% half/half oil. The LA's are like any other engine. Some run great out of the box and some take a little break in. Most of my engines are put in the air as soon as they run with enough power to fly the plane.

I have a Brodak 25 that was put thru the pattern on its first flight in the air and another one that is still breaking in. Have fun, DOC Holliday

jim gilmore · « **Reply #9 on:** June 28, 2009, 04:17:33 PM »

Ok, I got the la .25 running decent I think it is a 9/4 prop and doing 12.5 . only tank I have is a 1 ounce tank .
Fairly easy to start now. I'm still try to get the .09 to run a few tank fulls.
Thanks to whomever suggested sanding my props sharp edges off. It works well and my fingers will thank you. I hate rubber fingers.

Author Topic: os .25 la questions (Read 1006 times)

jim gilmore

os .25 la questions

Larrys4227

Re: os .25 la questions

Mark Scarborough

Re: os .25 la questions

jim gilmore

Re: os .25 la questions

ray copeland

Re: os .25 la questions

Larrys4227

Re: os .25 la questions

ray copeland

Re: os .25 la questions

Larrys4227

Re: os .25 la questions

john e. holliday

Re: os .25 la questions

jim gilmore

Re: os .25 la questions