Hobbico Avistar ARF
 

Hello. I have bought two of these planes, and the first one we crashed of what we thought was piliot error but as we built the second one we found that the engine had trouble getting fuel to the carburetor. We believe that the fuel tank is to low and that the carb is too high. This could or couldnt be the problem but this is an ARF and we have built the same plane twice with the same outcome...
What do you suggest I do to fix it? Thanks

RE: Hobbico Avistar ARF
 

I have owned 2 avistars with OS 40LA and OS46FX. Easy planes to fly, good quality, no fuel problems ever. Brain failure was their demise.

RE: Hobbico Avistar ARF
 

Sorry, I guess my previous reply didn't help your problem. I don't believe there is any design problem with Avistar. More likely you are doing something wrong when assembling your fuel tank etc. Possibly the cap or clunk line. Too loose or too tight on the tank cap will cause your symptoms. How does the engine run, good or bad transition, full throttle?

RE: Hobbico Avistar ARF
 

Got a picture? Show us how you've mounted the engine.

It would be possible to mount the engine higher than the tank. If the appropriate clearances are cut into the cheeks, the spinner should be at the point of the cheeks and your carburetor will be aligned with the tank.

Best wishes,
Dave Olson

RE: Hobbico Avistar ARF
 

ok i will work on getting a picture. The engine that i have is a .46 Tower Hobbies abc engine, that is what is on the box. Has anyone had any problems with this? The engine runs great on the ground but when you lift the nose upwards you lose the power and it is a dead stick not 3 feet off the ground.

RE: Hobbico Avistar ARF
 

Sounds like adjustment problems to me. Find some one that KNOWS how to adjust it. ENJOY !!! RED

RE: Hobbico Avistar ARF
 

Here are the pics....We have tried tuning it and we got some others at the field to try without luck, this is my first plane but my dad has had many. So i am up for any ideas on how to fix it.

RE: Hobbico Avistar ARF
 

I have a GMS .61 that did the same thing that you are describing. I tried every thing I could think of and it wasn't until I switched to a fuel with less nitro in it that I was able to get it to run. I went from 15% to 10%. Also check that your fuel tubing is good and not cracked.

RE: Hobbico Avistar ARF
 

Do you have foam around your tank? If not, put some extra under it to raise the throat of the tank to be square in the hole. It sounds like either its just too lean, or your fuel is just foaming. I forgot to ask, do you have a spare engine you can drop in it. To test if its the tank or the engine.

RE: Hobbico Avistar ARF
 

i will try the foam to raise it but i think that it is all the way up... Umm i do not have an extra engine to put in.. This is really frustrating because i want to fly but i cant think of a way to fix it.. if the fuel tank was a little high and the engine a little lower it would be perfect.

RE: Hobbico Avistar ARF
 

I have to agree that it sounds like tuning. When you go nose up does it die at any throttle setting, or just wide open? I'm guessing that you're running the engine too lean.

Look for someone at the local field or hobby shop that knows how to tune engines and get some help.

Cheers,
Graham

RE: Hobbico Avistar ARF
 

Ok thanks for all of your guys' help... I think i will just end up taking it to my local hobby shop to see if they can help.

RE: Hobbico Avistar ARF
 

I have had three Avistars over a two year period and not had any problem with flame outs. I have used Thunder Tiger .46 Pro, OS LA .40 and OS .46 FX. If you have an airtight fuel system, (no leaks) and good muffler pressure you should have no problem with the stock tank position. I have one friend that had a GMS .46 and it had air leaks around the carb mount, sucked air, and would not run except at high throttle settings. Why three? you ask...one mid air and two trying things I shouldn't have tried to do. If you look at SIG LT-40 it's tank sets low also and there are three at our field flying with OS .46's with no problems. Great airplane for the price.

RE: Hobbico Avistar ARF
 

Ok thanks for the advice... How should i check for air leaks??

RE: Hobbico Avistar ARF
 

bmannrcflyer , i would remove the fuel tank with the lines , block off the pressure line from the muffler and blow in the fuel line(clunk line) to pressurize the tank , with pressure in the tank pinch of the fuel line (now both lines are sealed with pressure in the tank ) now submerge in water and look for bubbles.
I would also check the clunk line in the tank to be sure that it is properly connected and also make sure that the clunk line is the line going to the carb. and the vent line is going to the muffler for pressure

RE: Hobbico Avistar ARF
 

I would do the pinch test. Start your engine, and carefully pinch the fuel line at the carb. The engine should rev up for atleast five seconds before it dies. If it does not rev up and just quits, you are too lean. If it revs longer than 7 or 8 seconds then you are too rich. That will set the low end. After thats set, open it up to full throttle. slowly lean it out until it quits gaining rpm. If it dies, richen it up 2 turns and start again. Once you get the peak rpm, richen it up so till the engine losses 400 rmp, or once you hear the engine change to a lower pitch, make it about a little less than a 1/4 turn richer. That will give you a starting point. Another test you can do it take out your fuel tank and with all the lines attached, put the tank underwater, while keeping the ends of the lines out. Pinch off one line, and blow in the other. Look for bubble coming out of the tank or tank neck. That will show you if you have a sealed tank. I hope this helps.

I forgot to mention, make sure you dont have the clunk and the vent reversed going to the engine. That could cause the problem also.

RE: Hobbico Avistar ARF
 

My Avistar runs great with the tank in the stock position also. The only problem I had was the original tank sprung a leak at the seam around the stopper. Once I replaced it with a Sullivan seamless tank, I've had no problems at all. I'm running an OS 46FX in the stock mount with no other modifications. You might want to check the forward seam for leaks. Good Luck!

Don