stevie2107

Fellows,
It's been carefully run in,is using specified fuel,soft glow plugs,19x8",usual BCM baffled pitts silencer with pressure,large bore pipe right through to clunk. Everything is tight and free from blockages. The instructions state that the idle needle needs to be 1.5-1.8mm from the spraybar,well mine needs to be at least flush with it or the idle and pick up is far too rich. Do this and the main needle loses all control. The motor is screaming,cannot be richened for flight even if you back it out until the 'O' ring is visible. Tune the low speed for a poor over rich condition and a degree of useability is restored to the main needle but not much. As it is the carb would suit a pylon racer only and is basically an on off switch I have noted that the venturi is a whopping 15mm and that is much larger than even my moki 2.10! I need useful adjustment for club flying,don't require maximum horsepower but I definately want to send an engine skyward slightly rich. Shall I forget the original device altogether and consider something else like a perry 'mega' carb with a venturi of approx 11mm or can anyone suggest another carb? The aviastar uses an 18mm spigot so I'm expecting to have to make a sleeve.Any input would be much appreciated,the engine has only been bench run and I'm quite sure it's a carb issue.
Thanks to anyone with handy suggestions.

loughbd

What is a soft glow plug and a 19x8" prop?? What is a spigot?

w8ye

My Feedback: (16)

Sounds as though the idle needle is too small or the spray bar OD is too large?

loughbd

What is a soft glow plug?

eddiec28

Hi
I had the same problem.I send the carbie back to Aviaster,at the moment they are looking at the carb
Here is a link you might find useful
[link]http://www.rcuniverse.com/forum/m_5682246/anchors_5682246/mpage_1/key_aviastar/anchor/tm.htm#5682246[/link]

majortom-RCU

My Feedback: (40)

I got an AV1.50 a few years back, slightly used by a guy who got tired of trying to get it to run. I had a heck of a time trying to get it tuned, finally got a few flights out of it that showed some promise, but never got to wring it out before the canopy hatch blew off and disappeared in the woods. That was all the discouragement I needed to retire that plane, but I still have hopes for the engine. Now re-mounting it on a 1.20 size CAP, putting a Perry pump on it to see if I can stabilize the fuel draw. Nice to know that Alvin has a solution, just in case the pump doesn't solve things. Do I understand that Alvin is in China somewhere? I wonder if Sig, who now has US distribution, is up on all this?

eddiec28

I tried a perry vp30 on my av2.00 made no difference
Here is some information,might come in handy
Alvin So
Aviatronics Limited
Room 105 , Carnival Commercial Building
18 Java Road, North Point
Hong Kong.
[email protected]

majortom-RCU

My Feedback: (40)

OK Eddie, thanks for the forewarning. I really look forward to getting this thing flying right.

ruggie

hay there guys , alvin from aviastar has come up with a bit of a fix , he has done some needle mods for the carb's
but still not the best , i have got my 150 running ok, on the bench , with alvins patch up , but still not the best , i woundn't fly anything good with these engines , just don't trust them, if they would idle and transition just like my os 160 fx and moki engines alvin would have a winner with his engines , i have been working with these engines (all sizes )for 14 months now , and about to give up,

majortom-RCU

My Feedback: (40)

Update my 1.50 installed in a H9 CAP 1.20 size: hasn't flown yet, have spent several days trying to get the carb tuned with a Perry pump. I will say the pump at least stabilizes the 'tank' pressure, which is better than running off muffler pressure, but the carb is still a hopeless case.

My problem is basically the same as Stevie's at the top of the thread--the only workable setting on the idle needle is with it almost completely closed. At that setting, I can start it easily, get a stable idle of 2000 rpm or less, and reasonable transition--not a quick & smooth transition, but workable. This is with a bypass installed on the pump, and the pump pressure screw backed out for low pressure fuel feed. Without the bypass, the fuel pressure is too much, even at a lean setting.

With that usable low needle setting, I have the high needle as far out as I can get it, basically to where it should be giving no restriction at all to fuel flow. With that high needle setting, I can run the throttle up to maybe half-open carb valve and still have adequate fuel feed to give me a slightly visible exhaust stream, enough fuel & lube to run steady without overheating (cowl off, static). That gives me about 6000 rpm with a 16x8 Mejzlik. I also tried a re-shaped Zinger 18x8 and at the same setting that gave me about 5300 rpm.

If I open the carb any further than that, it starts to sag or quits outright, and the engine is very hot (>300ËšF).

This is the best I can get after playing with all other settings up & down the scale, adjusting pump pressure with and without bypass (more fuel delivered w/o the bypass) from high pressure to low, adjusting high speed needle in & out, low speed needle from way open to way closed and everywhere in between.

If I back out the low needle to leave a gap of 1-2 mm or more from end of needle to end of fuel inlet with throttle wide open, I can get enough fuel coming in to run with carb valve all the way open, and that gives me 9200 rpm on my 16x8 Mejzlik--BUT the low end is hopelessly over-rich, engine has to be started at something like half-throttle, and if you try to back off to an idle, it's drowning in fuel. (This is with an idle-bar plug, by the way, glow ignition ON).

I will try again to call Perry tomorrow, and order their 4601 Hi-Pro carb. This carb has a neck of .625", which compares to .630" (16 mm) that I measure on the stock carb, so it will drop right in. The big difference is in the throat diameter, which on the Perry carb is advertised as .375", vs .540" on the stock carb. That's almost exactly half the area of the stock carb, corresponding pretty well to the ~1/2 open setting on the stock carb that gives me the best usable top end.

What remains to be seen is the interaction of the idle needle with the fuel jet as the Perry carb is opened up. If the stock Aviastar low needle would open at a higher rate than the stock, that would allow more fuel coming in as the throttle opens up, which would improve the high end.

I agree with Stevie, the stock carb behaves pretty much like an on/off switch. You can have full throttle or you can drown your engine in fuel. Or you can have a nice idle, but no top end. I would love to hear from anyone who has this engine with stock carb, who has been able to get wide open top end combined with stable idle below 2500 rpm plus clean transition & mid-range.

I will say this, I have learned a lot about how not to make a carb with all the putzing around I've put into this NFG product. (The sad part is the engine is a real beast at the top end, power to spare!)

ruggie

hay guys , you are all starting to find out wot the carbs are like on these engines, (bloody hopeless), i have tryed perry pumps cline regulators the lot , i have tryed ever size engine and they are all the same , it's a real same if they had a good carb they would be a great engine , i know alvin from aviastar has mad new needles for the engines witch he sent to me , but still no better, i have given up after 2years of working on and with alvin on these engines , just buy moki or os engines around these sizes at least they are reliably,
i don't wont any more to do with them ,,i have wasted to much time and money in fuel on them,

majortom-RCU

My Feedback: (40)

Well Ruggie, it's a bummer you haven't got these engines to work. I thought there was another Aussie in another thread who found his engines worked well after Alvin's new needle fix, so I e-mailed and have the new idle needle on its way to me as of earlier this week. I have the engine mounted on a model, everything ready to go to test the new part when it arrives.

What I am hoping for is that I will at least be able to find a setting that will give me a clean idle, smooth transition and a usable top end. By usable top end I mean I am willing to adjust my throttle servo for something less than full open carb, because the engine has a ton of grunt before it starts to lean out and overheat at wide open throttle.

I'm eager to compare the new needle, once it arrives, to the old. I've been trying to figure what could be changed in the needle design that would make the whole thing workable. The only possibility I've been able to imagine is a longer throw as the low needle backs off the fuel tube sprayhead (can't call it a spraybar), and that would involve more in/out movement of the barrel as the valve turns from closed to open, which would mean changing the angle of the channel cut in the barrel. I don't believe that's what the mod consists of, from what I've read. We'll soon see.

I tried calling Conley Precision, by the way, the Perry pump people, to order a replacement carb. Their product listing shows one that should fit, but its venturi opening is just about half the area of the stock Aviastar carb (as noted above). I think whoever handles the phone is stressed out, because the first call he was rather abrupt, wouldn't even let me say I wanted to order a carb, just listened to my opening words and insisted I try a smaller i.d. version of the bypass plumbing. I tried that, found no essential difference, called again to order a carb, and before I got ten words out, he hung up on me! This is from an outfit who say on their website they want you to call rather than order on-line, so they can be sure you are ordering the right solution! I know what it is to have a constantly ringing phone drive you crazy, so I sympathize to some degree, but HTF am I ever going to order a carb if they hang up on me? They provide no other contact information, no e-mail, no street address, only a phone number which answers and then hangs up on you.

kenny44021

Folks, i just mounted my Aviastar .046 on the bench and found I have superior power at top end and good idle but no transition. I have played with this carb for two days and no one could get it to have any transition at all. I called sig and talked to (Bob-R&D guy #641-623-5154) went through the pinch test and settings etc...he had me send it in and I just called him. ahe said he was sending me a carb that woked. When I asked him what was wrong with mine, he just said he was sending me a carb that worked. I have to belive that they put the wrong spray bars in some of these .046's I had my hobby shop send me another one and this one is defective to. I'm waiting to get my carb back to see if it works any better. saty tuned.

majortom-RCU

My Feedback: (40)

I can report that I eventually did get through to Conley Precision, ordered one of their carbs, installed it with one of their pumps, and my problem was solved. It took a little tuning, but nothing more than usual, and I was able to tame what had been a beast of an engine. I had to give up some of the top-end power in order to get a smooth idle and mid-range, but I expected that, and I still get ample power and no headaches, so I'm happy. (But no thanks to the stock carburetor, which sucks more air when wide open than can be balanced with fuel flowunless you open both the high and low needles all the way, in which case you can run the top wide open, but you can't idle down without going way too rich and drowning out any attempt to come back up.)

Broken Wings

My Feedback: (20)

Dubb Jett makes some carbs for the large Super Tiger engines. I wonder if one of his carbs would work for you.

www.jettengineering.com


click on Jett stream mufflers and scroll down.