I just converted a new Poulan 42cc using Brillelli conversion parts and an XYZ ignition. Got it set-up and running yesterday and I got 7100 RPM with a Xoar 18X10. I was a little disappointed with that - or does the RPM sound reasonable? What about going to an 18X8?

Thanks - JPR72C

I run a 20/8 Menz prop on my sons Echo 44cc conversion and it turns 6800 RPM or so. He originally had a Poulan 42cc for his first gas engine and we used an 18/8 prop on it. Those numbers are good but if you went to say a 20/8 and lowered the RPM to mybe 6700 or so you should find it to pull as hard or more and slow down better too.

I've got a Poulan 42cc converted to gas/glow. It spins an APC 18x8W at 7700rpm and a Menz S 20x7 at 7000rpm. It has a Walbro carb with 11.11mm venturi and stock chainsaw muffler with spark screen removed and an extra 1/4 inch hole drilled in bottom of muffler. I've got another carb with a 13.5mm venturi on the way that I'll be trying soon. The Menz S prop pulls my 14 pound plane straight up until I back off the throttle.

With a free flowing modified stock muffler, a 13.5 mm venturi carb, and running on Gas/Glow my Poulan 42cc turns an APC 18 x 8 at about 8400 rpms.

When putting it together, I noticed a lip around the exhaust port right at the cylinder. I ground that lip out, which raised the exhaust timing a bit, but not a whole lot. I can't remember for sure, but I think with the lip ground out the exhaust timing came to around 150 degrees.

AV8TOR

AV8TOR, how much did you open up the muffler on your "free flowing stock muffler"? Did you just drill a couple of holes in it or what? I have a quarter inch hole drilled in mine and it increased the power a bit and increased the noise a little also. I have a 13.5mm carb coming in the mail and I want to make sure I have the muffler opened enough to realize the potential of the larger carb. However, I don't want it to be too loud as our flying field has neighbors. Thanks.

For me, a muffler with no baffles nor other obstructions inside, and two outlets of at least 1/2" i.d. would be a minimum setup for a 42cc engine. Larger or more outlets would be even better. That setup might be a bit loud for you though.

I am fortunate to not have a noise sensitive area to fly. What I did on mine was I took a piece of 1 1/4" sink drain pipe, flattened it into an oval, and brazed that into my muffler for an outlet. To me, it's not all that loud, and makes very good power.

I find, and many people agree, that the deeper sound of a gasoline engine turning around 8000 is much less offensive than the higher pitched sound of a normal glow engine turning higher rpms. I don't know if the people at your flying site would agree however....

AV8TOR

av8tor: I was wondering if you liked the 42cc or the 46cc Poulan best? Just got back from vacation...got a lot of yard work & other Honey do,s to do....but I cannot wait to do some engine work!!! Best Regards Capt,n

Hi Captain, and welcome home!

I like my Poulan 42cc, and the reason I chose it over the 46cc when I bought it was to avoid having to make up an intake manifold like you have to do on the 46cc. The 42cc is rather heavy though. I think mine weighs around 4.5 lbs. if I remember correctly. I have been told the 46cc is lighter....

AV8TOR

Well I tried an APC 20X8 and only got 6000 RPM. I think this is low from what others are getting on the forum. I''m using a 13.5 mm carb and I drilled out the stock muffler. The engine starts ok and idels and transitions very good, but no RPM[] Any ideas? I''m considering going gas/glow if I can''t improve the RPM. It is a LE (low emission) model. I wonder if that makes a difference?

Did you take the muffler apart and remove any and all baffles, etc. from inside, or just drill holes in it? You need to remove all the power robbing guts of the muffler, leaving only the support that prevents the mounting screws from collapsing the muffler.

If the engine was new, it will need some time to seat the rings. If it was used, it likely needs a new ring. I recommend rings from Frank Bowman.

AV8TOR

OK - so I tried gas/glow this afternoon and somebody woke up the genie! I got 7950 RPM on a APC 18X8W. It idles good without a glow driver, but the transition is not there yet. This is a new engine so maybe like you said, AV8TOR, the ring need to "seat". (there is only one ring)

Thanks for the Input!!!!

JPR72C

Like Walbro says in their tuning literature, quite often the idle mixture needs to be a touch richer than ideal in order to get a good transition. I have found this to be even more true when running Gas/Glow. It is also important to make sure the engine is completely warmed up before tuning and/or expecting a good transition. They run slightly cooler on Gas/Glow than on pure gasoline, and it can take a couple of minutes or so for them to warm completely.

Congrats on your project, and welcome to "Gas/Glow".

AV8TOR