Hey guys I need help
I purchased a new in box avistar46 engine and broke it in per the directions. the problems I am having is,
1 engine wont transition from idle to high rpm
2 then engine will not shut down with the throttle and trim both closed as far as they will go, it takes about 30 sec. to 45 sec for the engine to die with my finger over the carb. When I look into the carb the barrel is closed all the way

The engine idles good and the high rpm is good I am about a quarter turn rich with the main needle setting. I have checked for leaks and found none. What might be the problem.
any help would be great and thanks
rduff55

There is a crankcase air leak or the engine would shut down.

The usual place is around the carburator

Is the air leak also responsible for the poor transitioning, or should rduff55 also be trying a hotter glow plug?

The transition problem needs to be explained in more detail I think?

I think the air leak needs to be addressed first as it may effect the idle mixture. At this point I don't know if the transition problem is one where the engine just quits or is it one where the engine stumbles around before quiting

guys
The problem with the transition is that it will die unless I pump the throttle stick slow, If I try to move the stick quickly it just dies.
I removed the carb. and checked the oring and surface area to make sure it was clean and reinstalled it makeing sure it was seated tightly. I checked the backplate it was tight. I did find that the low end neddle was backed out along ways when I tried the resetting the needle process where you use some fuel line and place it on the intake nipple and blowing into it. the needle was about 7 full turns off of what the actory setting should have been. This is probly what the problem is I will test it sunday weather permitting. I also found the high speed needle had a bure on the end of the needle I was able to clean it off buy rubbing it with my finger the needle now seats and seals properly.
thanks for the help and I will let you know what I find out sunday
rduff55

Be sure and let us know how it did

I'm having the very same problems with my Aviastar .46 purchased in September. I think the air leak is a loose fit
between the carb barrel and body. Both needles are VERY critical, hard to tune perfectly. This engine also likes hot plugs.
Mine transitions a lot better now, but one click either way on the high speed needle could mean four cycling rich or a lean run.
I still can't stop the engine by shutting down the carb. Mine also Knocks at cold startup. I think it's a tight TDC pinch, a little more breakin time will tell.
Good luck rduff55, let me know what you find.

David

hot plugs would be like a OS A3 or Enya #3

Guys
I made it to the field today and here is what I found. I got the engine to idle and transition great but would not shut off I even had a couple of veteran pilots try to set the car and could not. I ended up with exactly the same thing as dmcclendon did in his earlier post here and the conclusion was at our field was the same the the carb body and barrel fit is to loose and the needle settings were very touchy. The motor has great power and pulled my fore runner around great until I feed it to the canyon gods. and put it into about 6" of water. The engine is fine but I cannot say the same for the plane. The gods got feed because of pilot error not an engine problem. Bottom line I will not use this engine on a really good plane nor will I buy another one of these engines.
thanks for all the help and I did learn alot about setting engines. I can use what i learnd on other engines that I have, that have been setting along time.
thanks for all the help and good luck with your engine adventures
rduff55

In the future you may try a different carb on the engine?

Just see if you can borrow one from a friend to see if you can get the engine working like you need it to.

Sorry about your loss

It's an odd size carb. None of my many spare carbs would fit.
I can't remember what plug I finally ended up with, but each time I went hotter, it would idle and transition better.
It now idles great IF you warm it up well, but transition is still iffy. Don't play with the throttle unless you like dead sticks.
After about a gallon and a half of fuel, it still sounds like Thor is trapped in the engine tryin' to get out.
I e-mailed Justin at Sig, and he said to run it awhile and see what happens. I've been using Sig products since the mid seventies and
they have always been great to deal with. I have a feeling I'm gonna have to test their warranty on this one.

If it has internal noise, there is something wrong with a bearing?

Just for reference... a Super Tigre carb from the .40/.45/.51/.61 fits perfectly and turns the AV .46 from a mediocre engine to one that's a real sweetheart to run.

Tis a shame though, of all areas to skimp on an engine, why'd they chose the carb? I have three AV carbs here, and only one is passable (barely) - even then, I had to resort to the ST carb to get the transition/midrange that I desire. (I'd take an as-cast crankcase if I was guaranteed to have a decent runner.)


BTW, the AV carbs aren't really an oddball size - they're 14mm...

probrojoe
I am going to try your suggestion about using a supertiger carb I have acouple of engines I am not using right now and can afford to use them .
thanks for the suggestion and help I will let you know what happens.
rduff55

rduff - do let us know how you make out with that (I suspect you'll be happy with the results).

FWIW, I'm running an OS #8 plug, and 10% Wildcat fuel on my AV, and well.... I'll let the video speak for itself.

Check it out: http://jbwebst.home.comcast.net/CLIP0340.ASF

I mailed mine back to Sig Friday, will let you know what happens.

Ok Guys
I made it to the field yesterday and here is how it went. I put a supertiger 45 carb on the engine and was able to get it started and was able to get it to idle and transition fine but the engine still will not shut down with the throttle closed and the trim all the way off. I tried to pinch the fuel line and the engine would still run for about 10 to 15 seconds before it would die. I tried to lean the low end out till the engine would die after about 4 sec. with the fuel line pinched. The engine would still run for about 45 sec. before it would die with every thing shut down. The carb was sealed in the crankcase with fuelproof silicone except for where the pin and nut that holds the carb in the crankcase. I will now try sealing the back plate and the pin that holds the carb in the crankcase. and will try again in the morning. If there are any other suggestions please let me know what to do. any help would be useful. I am about ready to trash the motor and chaulk it up for lesson learned (dont buy cheap foreign engines) I will let you know what happens in the morning.
thanks for the help and stay tuned for the next round
rduff55

What was the outcome of sending it back to SIG?

Ok guys here is the report. I made it out to the field this morning and low and behold the engine runs and shuts down great. The transition has a slight hesitation but I think it is due to the temp outside, it is approx. 38deg. I have a 45 supertiger carb in the engine and I think the air leak was in the pin and nut that holds the carb in the crankcase. When it warms up in a few days I am going to put the stock carb back in and try it again. I will let you know what happens.
thanks for all the help.
Gypsy56 What was the out come with sending your engine back to sig? I would be interested in knowing how good the service is.

thanks to everybody
rduff55

The transaction with Sig is still not completed, but here's where I'm at as of 1-2-09.
After talking with Bob at Sig, I sent the engine back with a long letter explaining the loud knock, carb problems, etc. Before shipping, I made a very small I.D. mark on both
engine and carb with a carbide scribe. Not that I really care if the engine is replaced or repaired, but just as a reference. In just a few short days, the engine was returned.
Bob's enclosed note stated that all he had done was test ran the engine, put it back in the box and returned it to me! Upon checking for my reference marks, sure enough, they had sent the same engine and carb back with no repairs whatsoever!! Now, keep in mind that I had specifically ask to make sure the engine would shut off with the carb and
transition cleanly. I put the engine on the test stand, started it, and it still knocked like it was flyin' apart! Still could'nt kill it, even by putting my finger over the carb. Still
couldn't tune it. Basically, I paid 8.00 in shipping and insurance just to have them send it right back with no repair at all and no regard to any of my complaints.
BOY, WAS I MAD!!!
But the story is not over yet.
I called Sig the next day and asked to speak to a manager. I explained the entire situation to this man ( I believe his name was Dave, but not sure) He was very nice and understanding and was willing to do whatever it took to make me happy. I decided against his offer of a new engine and instead opted for store credit. This is how it should have
been handled in the first place. I'm no longer upset with Sig, I will continue to do business with them, I just wish they had listened to my problems the first time and saved us both some trouble. At this time I am waiting for the UPS pickup card to show up in the mail.


Finally, a happy customer
David