jamesroutledge

Hey Freakingfast.

Sorry about the delay. Checked my telemetry with 2 other tachs and it seems to be spot on.

The ST tuned pipe is one I bought back in the mid 80's

Upped my max speed to 186 km/h a week ago with some more tuning.

Super08

My Feedback: (2)

May as well add mine.

1500' asl
70F
APC 11x7
Omega 15%
OS #8 plug
Stock muffler

12,200rpm

Ernie Misner

Have you tried the mac's extra volume (just for the 55AX, etc.) black one piece muffler? Way lighter than the stock muffler and will add a ton of rpm's and power. I'm running a couple of them. Many other mac's black one piece mufflers do not add power though so they get a bad rap.

airraptor

My Feedback: (66)

Ernie does that mac muffler really give more RPM? all the ones I seen lost power over the stock muffler.

Ernie Misner

Hello Airraptor - I said it adds a ton of rpm's and power over the stock muffler, and you said does it really give more rpms? Maybe you didn't read what I said but from what we knew about the old mac's mufflers I don't blame you for asking. The extra volume muffler for the 55AX is a complete different animal. Here are the specs: https://outlawhobbyproducts.com/airp...ance-exhausts/

Ernie Misner

Hello Airraptor - I said it adds a ton of rpm's and power over the stock muffler, and you said does it really give more rpms? Maybe you didn't read what I said but from what we knew about the old mac's mufflers I don't blame you for asking. The extra volume muffler for the 55AX is a complete different animal. Here are the specs: https://outlawhobbyproducts.com/airp...ance-exhausts/ Keep in mind this is not their std. 55AX pipe. We are talking about the extra volume version which is the 6720. If you buy it in the "profile plane" version the number is 0723. Only difference there is it is angled to get it a bit further away from the wing and fuselage. I am actually using the profile version on my GP Razor 3D plane. The engine is inverted and with the profile pipe on it, the muffler tucks under the wing really nice!!! I can not emphasize enough how this muffler wakes up the 55 and makes it scream.

airraptor

My Feedback: (66)

How much more RPM is it getting over the stock muffler?

Ernie Misner

Did you follow the link to Outlaw Hobby's test? Looks like about 1,380 rpm increase over the stock muffler. I can tell you that when you bolt one on, between the lighter weight and the huge power increase, you'll be amazed if you were running a stock muffler.

Super08

My Feedback: (2)

I just happen to have a brand new one but have not tried it yet.

Super08

My Feedback: (2)

To add to my post above my 55 has loosened up some more and I think it is completely broke in now. I checked it today at the end of the days flying and it peaks on the ground at 12.600 now. I richen it up to 12,300- 12,400 for flight. This is still on the factory muffler and the same prop, fuel etc as above.

Ernie Misner

It sounds strong!!!

Super08

My Feedback: (2)

It is, I am more than impressed with it. My 61FX runs 12,900-13k even. This is not far behind and weighs much less.

Ernie Misner

Hi Super08 - your 61FX weighs much less than a 55AX?

Super08

My Feedback: (2)

No it came across wrong, the 55 weighs way less than the 61FX. Something like 3 ounces or so.

rcjunky67

hi ya boy's, just wanted to get this thing rolling again.I have 3 of these little jewels and love'm. 2 are new just slightly ran for break in, which isn't done yet. They've only had about 4 tanks each of omega 15% ran through them. Still need more time,which I've not had. The 3 rd , which was actually my first one, was bought used and had already rode a twin into the ground. Then I'd put it on a seagull decathalon, flew it for about 9 months, then cartwheeled it on take off. Not enough ground speed!

Anyway, I'd always had trouble with that engine around mid throttle settings, so when I finally got it out to run again, I'd took it apart and changed the bearings and cleaned everything really well. I payed real close attention to the carb, and did a little mod that seemed to fix the problem.

As y'all know , the LSN is part of the throttle barrel,and the seat for it is screwed into the carb housing. Well, when I was using my pin vise drillbits by hand to clean the passages out in the carb, I went ahead and gentley opened up the hole in the seat bellow the taper to 0.635 , I don't have equipment to change the taper accurately so I figured if it didn't help , I'd just get another one.

WALA, no more midrange problems. she rev's up just as clean as can be and I can hold it at half throttle as long as needed and open it up and she rev's right up. SWEET!!! hopefully no more deadstick's with this engine now.

rcjunky67

By doing this mod, I'm able to turn the LSN in almost 1 full turn. Which put's it more in the middle of the carb throat. Using a 11x7x3 blade apc prop , omega 15%N 20%castor, 86F relative humidity at aprox 77% on a test stand, she'll turn 13,400@300 rich with nice clean transition from anywhere between idle and WOT. No more loading up in the midrange like before. Nice and smooth...

That's with a stock muffler from one of my new engines!!!...
Don't know if I'll need to do the same to the new engines as like I said there not broken in yet. And I've not used this prop on them yet

Super08

My Feedback: (2)

I haven't had any mid range issues with my 55's. I have with my 75 and 95. By the time I get the low end lean enough the mid range becomes too lean and begins to rattle. I ran into this with my 1.60FX years ago and corrected it with more back pressure to increase the fuel pressure.

rcjunky67

this one is an earlier 55, the club member I'd gotten it from had it for aprox 3 years, and it had been involved in a crash on a twin. then after sitting for quite some time , he sold it to me. that was 5 years ago. not sure how to tell the date of manufacture,as I'm sure o.s. has made some small changes along the way. but I honestly don't know if they had did any updates to the carb or not.

I'd read an earlier post near the beginning of this thread, in which the poster was having kind of the same issue,and he'd wondered if the "spraybar" was to close to the side of the carb throat,so that it was shrouded by the side of the carb.

this one would load up and get rich at extended mid range running , but now , like I'd said, is fine. I've ran my other two new 55's with the same prop set up and the same fuel from the same bottle and they didn't act this way.

maybe o.s. changed the taper or the seat in the LSN because they do seem to be more in the middle of the carb throat than my older engine.I don't know. But it seemed to do the trick for this one.

next , I'll mount it on the plane it's going to be ran on , but with a pitts muffler and mounted on it's side. hopefully it'll run the same. I know that style of muffler well and the problems their known to have with pressure to the tank.my cure for that is simply to dill a hole through each outlet tube and install a bolt and nut of whatever size it takes to restrict it enough to give it good tank pressure. we shall see Thanks for your reply Super08. what are you running your 55's in?

Super08

My Feedback: (2)

Right now one is in a 40 size Stik and the other is in the it's box. It was in an Escapade MX that was destroyed on the maiden flight. Something let go or it was an electronic failure of some type. I was making a high speed pass and it just went into a fast roll, pitched down and re-kitted itself. The plane never responded to any inputs. The receiver was one that I had put an "X" on the back as it was suspected to be faulty from a previous plane that was doing funky stuff. Needless to say it is in the trash now never to be used again.

rcjunky67

that suck's man... I've got a seagull models ultimate.46 to .55 size that I'll be putting one of the new 55's in. And I have an older Sig Kougar kit that I'm gonna build for the other new one. I don't really have anything to put the older 55 in . it did die on me quite a few times in the two different planes it's been mounted in. So that's why I went ahead and tried this modification . It really just moved the LSN seat about a turn more in towards the carb throat , and opened it up just a hair. I'm guessing the needle is coming off the seat sooner,mechanically, as the throttle is opened. but it really did make a huge difference in how easy it is to tune. It'll sit at idle, aprox 2200 rpm, as long as you want and opens right up. No lag at all...

Now, that being said , I'm still gonna try a couple of bigger prop's to see how it does. After some thought, I think I'll scratch out a stick type plane for testing it in flight. I also have a .52 2c tiger shark and an asp .61 2c that I've recently picked up that I need to get running and it'll be a good test bed for all of them as well. Better to crash something like that instead of a new plane, right?

Ernie Misner

An interesting mod, thanks for sharing. My 55's tend to have a rich gurgle at about 1/4 throttle. That can be mostly tuned out by going almost too lean on the bottom end. Also both of mine really make some serious power with the 50 size Mac's muffler. A huge difference, huge.

Question: One 55 has quite a bit of time on it using Omega type fuel and needs bearings finally. Should I clean any carbon build up off of the piston skirts or leave it there? If I do clean up the piston how should I go about it? My fear is that I will increase the piston/liner tolerance too much.

rcjunky67

Me personally, I don't want to do anything on one of these engines as far as the piston or liner is concerned, unless it's really needed... the one I've just modded had sat up for a long time,at least two year's , and when I broke it down the bearings were in bad shape. Rusty would be the best way to describe it, and didn't turn to well. But the rest of the component's looked good and I already had a new set of bearings for it anyway and planned to change them. As far as the piston and liner, surprisingly , they only had minimal scoring that I couldn't feel with my finger nail , so I left as is.

I believe the carbon build up your referring to is a build up of castor, which unless excessive , is what you want to help lube these parts. Once hot it'll loosen up and act like thick oil. without it if you run lean,you will cause damage. So it is what you want, that's why you'll see it recommended to not run straight synthetic oil in 2 strokes. It won't leave that protective layer like that.

As stated in an earlier post, this was a stab in the dark due to frustration with this particular engine. I didn't feel like it was a big deal. If it was a problem, I was gonna buy a carb for a 46ax for it. I'd read were some guy's were having success doing this and it would eventually be what O.S. did anyway when they came out with version two of this engine.

The pin vise set I have came from snap-on, the next smaller bit fit down in the seat without touching anything and the 0.635 just didn't go down the hole past the taper at all, so I took my time , using just the bit in my fingers and slowly turned it in. All told it probably only cut .003 to .005 out of the hole under the taper. That way it didn't change the taper of the seat.And like I'd said before, I was able to turn the seat in almost a full turn more into the carb body. I think by doing this it positions the seat a little more in the throat and I'm sure it changed the flow rate of fuel through the seat, which I figured might make things worse, fingers were crossed when I'd gotten it running. I'd cleaned everything and installed the new bearings and ran the engine on my test stand a couple of times before I'd done this mod to the carb. It was honestly out of frustration more than anything because cleaning it out like new didn't change anything with the engine.

If you try this trick, you may notice also as I did, that it tightens up the tuning range of the HSN a little. Seems like the difference between rich and lean on the HSN is quite a few clicks less now. Not exactly sure how or why that changed,unless it's because the LSN seat is, like I said , more in the middle of the carb throat. If you do this mod, I hope it makes the positive changes for you that it did for me. I'm gonna run some bigger prop's during the next test session and see how it does.

I'll post the results using APC 11x8, 12x6 and 13x4w props . Hopefully , it will run the same . If it Does, only then will I call this modification truly be successful . Blue skies and soft landings.

rob

Ernie Misner

Good information Rob, thanks a bunch. The reason I asked about cleaning the dark deposits from the piston skirt is because of an article by MAN magazine people on the internet. They were saying that the piston skirt deposits will eventually cause the engine to run hot and loose power until it is removed. They went on to say they use Lava hand soap and, I think, a scotch brite pad to clean the piston skirt. I'm with you though.... with my luck I would cause a loose fit. They used to use tooth paste to hand lap in a tight piston fit too. I tried that and went too far!

aspeed

I use laquer thinner or acetone with Scotchbrite for cleaning the piston/cyl. Smaller motors varnish up quite often and sound like they are almost seized. Some of the really old ringed motors seem to need the varnish for compression :-). 1200 sandpaper of finer works to polish the bottom skirt of a piston. I have used Silvo or Brasso to lap really tight new motors. It has to be done very carefully, and cleaned and checked often to make sure it has not gone too far. New ABC motors seem to be fitted better lately with the advent of good CNC equipment.