Lynn S

I know a few of you have experience with the Norvel .25 Big Mig. I bought this engine last year and it is still in the box.
I have 50 inch span ARF pattern type plane(Lanier Javelin) to start with using this new engine.
The questions I have are: What fuel to use? do I need to run the same fuel as the .049- .074?
What size fuel tank is best? and what size prop?

This plane is for .19-.40 engines so this .25 should be a real powerhouse for this plane,not to mention the light weight.
I was a little bit shy to start out with my 35inch wingspan Tequila Sunrise.
Thanks, Lynn

Andrew

Hi Lynn --

10 to 15% fuel will be fine. 15/16 or 15/18 with an 80/20 syn/castor mix will work well. You really don't need more than 15% nitro and the castor requirements are reduced.

6 oz is a nice middle of the road tank -- 4 oz. would be a little small. 6 oz should give you 16 to 17 minutes, more at reduced throttle.

8-6 to 10-4, but these are the extreme ranges, expecially the 10-4; 9-4 or 9-6 would be a good starting point.

the "other" Andrew

Lynn S

Andrew,
I know the combat flyers use these engines, but I'm not looking for maximum speed at all times. I'll see what the hobby shop has for fuel the next time I'm there. Nice to know I don't have to use this $10 per quart fuel. I have a 6oz tank already.
Thanks Lynn

wild fred

My Feedback: (3)

andrew is right. I've been using bigmig 25's since they came out. I run 8-5 and 9-4 on them and 15% nitro. check the idle stop screw once in a while, as I've had a couple back out and the barrel fall out and get lost. only after a long time, and since I started checking haven't lost any more. they scream! good engines. I run them mostly on ferroplanes, but have had them on LT-25's w/ 9-4 and it flew well on that. if you want to go fast, go to flying z hobbies and get a mousse can muffler for it! they are in sebree just north of murray, and have a website.

Lynn S

WF
It will probably be fast enough as is but nice to know about the can muffler.
Thanks for the tips on the props, idle stop screw and fuel.

buzzard bait

How is the idle and transition on the Norvel .25? The only guy in our club who has one had endless frustration with the carb and finally swapped it out for a different carb. Jim

rrragmanliam

My Feedback: (1)

Not to hijac this thread, but has anyone tried the 15 size motors?. And what has your experience been? I been seriously eyeballing he .15bb and the .15 Mig.


Darren

flyinrog

My Feedback: (1)

I have a .15 ,bought at a swap shop havent fired it up yet....Prole got the BB version it fires up and runs real smooth.......Rog,

He has it on a spad that I've seen him fly twice,1st at Hurdle Mills then here at my flyin it dead sticked the first time, the bb version has the carb needle angled back ..I just realized Norvel goes from .049 to .40 no one else does that , do they?.

loading

Is the carb different on the 25? I have come to hate air bleed carbs, but i have the 15 and it idles great and transitions great. It did take some break in though. I didn't keep track, but I think it was at least a quart. And that is a lot of flying for this motor. I need to add that I did break it in on my test stand first. The quart was flying after the test stand.

Andrew

Hi Loading --

It depends on whether you have the Big Mig or the AME -- for the .15's and the .25's, the Big Mig's have a single needle airbleed carb. The .15 and .25 AME's have the twin needle throttle body. The AX-40 comes in BB only and also has a 2 needle carb.

Some observations (my apologies to Lynn for straying from the .25): I have 2 or 3 .15's that I have not run that are squeaky tight at the top end -- I'm talking tight like a Q40 or Q500 engine. Several have been tight, but not like these. OTOH, my AX-40 will turn thru TDC W/O a plug with less resistance than an .061. The .40 also has 6 steeply angled bypass ports, two of which are elongated like the AME ports.

However, the instruction sheet that came with the AX-40 states, "Instructions for AX-25 and AX-40 Model Engines". Haven't seen or heard of an AX-25, but apparently there is one in the works that may be a replacement for the AME or a more user friendly (more easily broken in) substitute. Another word that was on the sheet was Sliktec -- certainly as the displacement increases, the very tight fit at TDC can become significant (as in my .15's). A .40 with an equivalent fit would be almost impossible to turn over. Sliktec (just guessing here) may be a newer terminology that implies a freer fit -- realistically, unless you are familiar with the smaller NORVELs or have run the pylon engines, the average modeler would probably think that a very tight .25 or .40 had a manufacturing defect or had siezed up. I have seen many used NORVELs with plier marks on the thrust washer [:@]

The market segment targeted for the AX-40 is probably the Sunday flier who is familiar with Thunder Tiger, Super Tigre, TOWER and Magnum engines -- given breakin questions that have come up with the .049 and .061, can you imagine a .40 or .25 hitting the market with similar fits. Guess time will tell -- does the AME .25 stick around or is the AX-25 going to be the new guy on the block?

Sorry to have rambled -- must be the caffine.

the "other" Andrew

Lynn S

Andrew,
I have been using a hair dryer set on high to heat the cylinder and piston before trying to turn them over the first time. I also remove the head and put a few drops of after run oil in the cylinder. It really gets the engine HOT and it then has a normal feel when turning it over. I turn it over by hand 100 times then I spin it over with my electric starter for several short burst.This done while heating with the hair dryer.
I put the head back on and its ready to start and has the feel of a normal engine. I had read about using a heat gun, but the hair dryer seems to work fine. It gets the engine hot enough that it is very hot to touch.
I plan on using this method on my .25. I can't imagine forcing these engines over without heating them first.