Okay All, Here we go again!

Last winter, I posted here an issue that I was having with my 2 year old 46FX. It was having "Mid-range" issues (would not transition from idle to full throttle w/o stopping). I was given instructions on how to try and fix the issue from BAX (which I still have in my field box) and after trying them, with no success, I ordered a new OEM piston/liner from Tower.

I installed the new parts and anxiously awaited the first day of flying season. After getting it set at slightly rich, the engine ran like it was new (what else did I expect?). I ran it with no resetting of the needles for the entire summer, running a gallon and a half of cool power (15% w/Benol mixed in for extra protection) and Omega (also 15%, but w/o the extra Benol) by the Columbus Day Weekend this year.

At the field, I'm starting up the plane to take off, and it doesn't sound right. I check to make sure that it transitions correctly and I discover that it's starting to have the same issue AGAIN as it did with the old liner/piston set-up. I try to get it straight, but it will not take a set, nor will it run past 1/2 throttle. Since I'm by myself, and I don't have an experienced modeler(my Instructor) available, I pack it up and go home.

Last weekend was our Clubs Closing Season fly-in, and I had my Instructor and another member (with 30 years of experience), attempt to get the engine to run right. At first I was asked if I checked for any and all airleaks, which I did, and found that the upper left screw in the backplate wasn't staying tight in the crankcase. The reason for this was that the first half of the internal helicoil had come off (?!?!). I get a longer screw, fill the hole w/JB Weld and screw it together. I also replaced all the fuel tubing. I also was asked if I changed the glo-plug, which I did, going from a new #8 to a new Tower plug, both with the same results, bupkus! My Instructor took out the Fox idle-bar plug he was using in his engine and placed it in there and tried to get it to start, it would start, but once again, no matter what he did, it would not transition from idle to full, stopping at 1/2 throttle.

It was at this point that he said "It looks like it's doing the same thing it did last Fall. You might have to replace the piston/liner again" You have got to be kidding! Well, I haven't had a chance to take it apart yet (work and other commitments)but I get a feeling that I'm going to find the same thing I did the first time. I'm not running this engine lean, on the contrary, I'm putting in MORE lubricants than ususal, with the associated mess, and still it's not acting right.

On the other hand, my other 46FX (same amount of time on the engine and amount of fuel)that also developed the SAME problem at almost the same time as the other, and that I went one step further and replaced the piston/liner with an ABC setup from Performance Specialties, is not having any problems, and if anything, is running MUCH BETTER than the OEM one was. It sounds funny, but man does it SCREAM! One thing I must ask though, I looked at the PS website, and it looks like they no longer make the ABC parts any longer, at least they are not listed there as of todays date. If I can find someone who's selling the ABC parts, I'm changing to them!

So my question is, should this have happened in this amount of time? How about it Hobby Services...............

Don

You could convert your 46FX to the Heli version piston/ring and sleeve and get away from the ABL technology. It would'nt cost any different than a ABL piston-sleeve.

G'day Mate,
OK first things first, running a motor rich, does not mean adding more lubricant, to the fuel,
I run all my engines on 18 to 20% coolpower oil, no castor, 2 strokes use #8 OS plug.
Your 46 FX should be running an 11x 6 or7 prop.
When you changed the piston & liner, did you run the motor in again? Because that is like having a brand new motor, after all, these are the things that need to be bedded in when a motor is new.
What size prop are you running, what amount amount of oil, you said 15% Coolpower & 15% Omega, is that oil content or nitro content?
If it is 15% oil, you need more, 18 to 20%.
From reading your post, you said, it would not run past half throttle, that means it is too lean on the main needle valve.
Ok how to check & see if you have a problem,
Start the motor, run it up to full throttle, if it won't run past half way, open the main H/S needle, 1/2 turn anti clockwise, keep turning it out until it WILL run to full throttle, then, hold the plane nose high, & listen to the engine, it should pick up revs as the nose is raised, if it does not, it is too lean, richen some more & try again until it does speed up slightly, with the nose raised, if you can't get it rich enough, then there is a blockage in your needle valve or fuel system, clean it out & try again.

Why don't you call them and ask?

Performance Specialties - CONTACT INFORMATION

Business Hours:

Monday thru Thursday
8 a.m. to 5 p.m. (Pacific Coast Time)
You might even catch us on the weekend and if we are in the office during non-business hours, we will answer the telephone.

The FAX is on 24-7, and don't forget the e-mail, we try to answer our mail at least a couple of times daily.

Performance Specialties
P.O. Box 3146
Gardnerville, NV 89410
NOTE: Please contact Performance Specialities for return shipping address.

Office Phone: 775-265-7523
FAX: 775-265-7522
E-mail: [email protected]

When a motor acts like it's worn out before it's time, and you've been using castor in your fuel, is might be varnish in the engine.

There was a recent magazine article in either Flying Models (probably) or Model Airplane News (maybe) or FlyRC (not likely) about that very issue. It's actually very easy to do. Back when we ran lube that was 100% castor almost everybody who flew a lot did it. I'll look for the issue tonight.

You would think that the castor that is now a small percentage of the blend would be less prone to varnish, but it seems to do the deed more often when the engine is being overlubricated or not run hot enough. You'd expect that to not provide the opportunity, but it must.

From the way I understand it you've eliminated the glow plug as the culprit and the fuel seems to be fine if your other engine still runs great on it. I'll have to ask this because it may be possible but have you pulled the head to check for any peeling? If the engine starts easily (hand starting is the best way to check it out), draws fuel easily for priming and holds compression well at TDC then basically the piston/liner should be in good shape. If all of this seems to be OK then my first suggestion would be to swap the carb over from your other engine and give it a try.

G'day Alan!

I'm running an 11X6 APC on the engine, and the nitro content is 15%. In the Cool Power, oil content is 17% (synthetic) and the Omega is 30/70 castor/synthetic for a total of 17% lubricant. I did run a tank throught the engine prior to flying it after the replacement. It ran fine with no glitches or hiccups and I left the needles alone.

My Instructor was trying his best to get it to run super rich, up to the point that he took the main needle 1 turn away from comming out of the housing, and he did take it out once as well, still with no luck. We went ahead and blew out the lines and also replaced the needle to the carb fuel line again, just in case the other one was collapsing on itself from the suction. He also did the carb needle (the one on the right side of the carb) and still got nothing past 1/2 throttle. The only thing we didn't do was take the carb off and clean out the orifices or take the head off to look at the piston(which I'll do this weekend).

Downunder,

The engine starts easily, but takes a few primer flips to draw fuel easily. Once it's in, if the engine stops, the fuel goes back towards the main needle. This is what made me think of a hole in the tubing somewhere and I replaced it all. This was when I also discovered the bad helicoil on the upper left bolthole in the backplate. Also, it doesn't feel like there is any compression at TDC, so that's why my Instructor and the other Member thinks it's the piston/liner again.

w8ye,

Thanks for the info! I'll try calling tomorrow. I really liked the service I got with the last one I bought. As a matter of fact, I just found the invoice (#110579) and I can't believe that I bought it almost 1 year ago! (Nov 29 05) Something strange here!

As for varnish, none that I can see, at least on the inside.

Thanks for the suggestions Guys! I really appreciate the extra help and knowledge. I'll keep you all updated with what I find.

Don

To convert the engine to a ringed version....

Cylinder sleeve
http://www2.towerhobbies.com/cgi-bin...?&I=LXCK96&P=Z

Piston
http://www2.towerhobbies.com/cgi-bin...?&I=LXCS54&P=Z

Ring
http://www2.towerhobbies.com/cgi-bin...?&I=LXCT20&P=Z

I'd use a ring from Frank Bowman. They are half the price.

Then the next time the compression gets low, you just put in a new ring.

Frank Bowman
1211 N. Allen
Farmington, NM. 87401
505-327-0696 (6 pm to 9pm MST weekdays)
Email: [email protected]

Without actually seeing the engine, it's of course difficult for us to say what the problem may be. If the rear cover was somewhat loose, then it's possible the piston/liner fit has been ruined by a lean run caused by air leakage through the loose rear cover. Usually, though, a bad piston/liner fit will show up with a lousy idle and reduced top-end power. Not being able to accelerate past 1/2-throttle is something that is not at all common. You should be able to get the engine to full throttle if you leave the glowplug battery connected. If the engine will do that, but quit when you remove the glow plug battery, then the plug is the most likely culprit, though that should happen at low throttle, too.

If all else fails, the engine should be put onto a test stand with everything in the open and ideally positioned. If the engine has the same behavior, then the engine has a problem somewhere and needs to be opened up and checked. If the engine runs properly on the test stand, then the engine's not the problem, and you have to examine the airframe/engine/mount/fuel system combination to locate the cause. Fuel foaming is a distinct possibility, though why the engine would be OK for quite a while and then go bad is a mystery...unless combined with damage caused by a leaking rear cover, you have now added causes that result in the current behavior of the engine.

donhef wrote:

"I ran it with no resetting of the needles for the entire summer"


-----------------


Do you mean this literally? This could be the cause of the failure of the two piston/liner sets, or the loose backplate that you mentioned caused it to run lean.

The needle valves are there for a reason. Otherwise, OS, and all other engine manufacturers, would eliminate them by replacing them with cheaper to make and impossible to set wrong fixed jets.

Sometimes we don't type exactly what we mean to type. It happens to me a lot. Is this the case in this instance?

I like W8YE's suggestion of converting to a steel sleeve and ringed piston set up. I won't buy an OS engine without a piston ring. Once bitten, twice shy.


Ed Cregger

Another option would be to order a new piston & sleeve from http://globalservices.globalhobby.com/part/21075602.asp
check out Part number S46203 and use them instead and get what OS should of done in the beginning. The cost is not bad either. Yes these are the Magnum parts for the XLS 46A Engine.

Hi Flyer!

That sounds like a great idea! I didn't know those parts were interchangeable. Thanks for the heads up!

Hey Ed,

Right, I was a little loopy last night while writing that (bad storm in the NE and a large dog with an adversion to thunder kept me on my toes). We (my Instructor and I) had re-run it in for a tank full on the ground by adjusting the needles, and after getting that done, adjusted them to the slight rich setting and from there I didn't have to touch them, at least not so much as a 1/4 turn forward or back as the temperature and humidity conditions dictated. Like I said, it ran like a champ.

Bax,

I'm thinking the same thing in regards to the problem stemming from the loose backplate. I was just surprised to see that happen to this quality of product. Since I've gone ahead and "corrected" that issue, I'm hoping that once I replace the piston/sleeve assembly that will be the end of the ills on this engine. Since it is my original engine, I'm a little attached to it and I'd like to keep it in the stable.

Once again all, thanks for the inputs! I'll keep you up to date.

Don

Okay, update........I finally received my new piston/liner from Hobby People (great service BTW!) and the Magnum parts fit perfectly! I only had to use one piston pin retaining spring also, as the Magnum design only lets you put the pin in one way. Not too shabby and for a total of $47.00 (S&H included there) I'm quite happy with the results.

Upon looking at the OEM parts, the peeling that happened to the interior surfaces of the liner was VERY apparent, and I'll post a photo of it when I get home from work. Also, it looks like the piston was also scored, which I didn't notice in the first two set's I replaced. So, I'll wait for a nice day and take it out to the field to run the new parts in and see how it goes.

Stay Tuned.......

Well, I took this advice and got the parts, which I said above, fit perfectly! I also was able to repair the missing helicoil in the hole on the back of the block where the backplate fits with JB weld. I had to wait for a good day that I was able to get out for the test and 12/30/06 was the day.

Jerry (my Instructor and Friend) and I put the Avistar on the stooge at the field and got it ready for start up. On his recommendation, I replaced the OS #8 plug with a Fox idle bar plug before fire-up. As soon as we started to choke the engine to draw fuel into the carb, I noticed an immediate difference. The fuel was drawn up very quickly and it stayed in the line instead of going back towards the needle assembly. Jerry also noticed that the engine turned very smoothly, much better than the last time.

We hooked up the glow driver and gave the prop about 7 flips before it caught and ran up. Jerry richened up the setting due to the cooler temperature that day, and it stayed running very well. I tached it at idle with 3500 RPM's and when we WOT'd it we got 13700. Not bad with an 11X6 prop. After verifying it would run, we took it off. What a great flight! Even with the rich setting, we had lots of power for it to do rolls and loops. Jerry also tried to get it to hang on the prop, which it almost did, but slid down into a beautiful stall turn. It even sounds different, more like a full scale A/C engine.

Anyhow, I think that this was definetly the way to go! I'll never go with anymore ABN parts for the internals on either of my 2 46FX's. Now I have to wait for the nice days to fly.

All I want to know now is..................does Magnum have a chrome set up for my 40FX?

These pesky little model airplane engines are not SET and FORGET. They require continuous maintenance and tuning. Screws get loose, fuel lines develop chafe and holes, trash accumulates, adjusting screws get bumped or vibrate loose etc.

Learning to troubleshoot and touch up the needles occasionally will save many dollars. Fuel systems always accumulate some dirt and trash and occasionally need cleaning. Air leaks will happen. A good tuner will recognize a change in operation before damage has occurred.

Bill

hi, im glad to hear the magnum parts worked well, i went through the same problems a couple of years ago with my 46fx ,i bought 2 complete pistons and liners just to have them both peel over a 2 month period. i then bought the steel liner and ringed piston and havent looked back, it has been performing as you would expect, very good! i now have just under 2 years on it and it still amazes me!
greg

Donhof,


This is the [link=http://globalservices.globalhobby.com/part/210750.asp]parts page[/link] for the .40XLS, which I believe is, like the .46XLS, also an OS clone, but of the .40FX.

Make sure it is.

The cost is identical.

The part is 281148 S40203.

I'll throw my hat in the ring with Ed and BillS....you must insure that your engine is runing
correctly at all times by adjusting the carb. That doesn't mean every flight, but it does mean
often enough to insure that it is running right and not overheating....

....or, you can replace the burned out parts like you have been doing. Take yer' pick.

FBD.