Sorry to say, but I really think you should spring for electronic ignition or go Gas/Glow. I felt my 42cc Poulan was rather heavy even on Gas/Glow. I'm afraid yours is going to be quite heavy and bulky.

The cost has come down on ignition systems. Check www.ch-ignitions.com

Good luck,
AV8TOR

I would like to use the stock muffler. How do I take it apart and gut it? Do I need to drill outlet holes in the muffler for the exhaust and if so, how many and what size?

If you are planning on using the same carb. I wouldn't modify it to much,
especially if you have a one needle carb. or limiters on it.
You will run out of adjustment in a hurry.

Being a chain saw the mufflers aren't all that bad.
A lot of mufflers have a screen over the outlet.
Try removing that and go from there.

Your muffler looks sealed and can't easly be opened and resealed.

I finished up my 42cc conversion and was able to keep the magneto ignition by keeping just enough of the saw case to keep the coil in the proper position. I did a little more trimming to the case since I posted the photos. I’ve test run it twice on a test stand and it runs and sounds great. I have not tached it though. However, it is quite heavy as I did not trim the flywheel or do any of the typical things to loose weight. It has the 11.11mm carb and stock chainsaw muffler. I mounted it to the plane that used to have the flywheel/magneto Homelite 30cc and after adding 5 ounces of tailweight to get it to balance, it came out 2 pounds heavier than with the Homey. I still need to test run it and tach it on the airplane, and if satisfied, I’ll try flying it. However, I’m thinking that I may go with the gas/glow setup. How much weight could I feasibly loose by doing this? Is it possible to get it down to what the flywheel Homelite 30cc weighs? If so, I could remove the added 5 ounces of tail weight. I’m thinking that the portion of the saw case I kept weighs around 5 or 6 ounces also. Does anyone know how much the flywheel/coil/spark plug assembly weighs on a Poulan 42cc? Obviously, what I’m trying to do is replace the 30cc with the 42cc for more power and keep my flying weight the same or very close. I guess I need to order a glow plug adapter, an OS four stroke plug, and try to get some 10/10 glow fuel. I hate to buy a gallon of 10/10 since I have 4 unopened gallons of Omega 15% already, but if I have to, I will. Am I forgetting anything else?

Well she's not going to win any beauty prize, but should work OK. I guess you noticed that quite a lot of support is needed to stop the coil being attracted to the magnets while it's running - so you can't hack too much away there.

You're right, I did see movement in the coil mount as I rotated the magnets past, so I secured it with a steel zip tie around the coil mount and around the back side of the muffler. Now, there is no movement when I rotate the flywheel. I'll run it a bit on the ground to make sure everything is holding up OK before I fly it. Also, I don't think it would be that hard to replace the hacked up saw portion with an aluminum bracket to hold the coil. I think it could be made with small pieces of aluminum L channel to mount the coil in the exact position. I may still pursue this if I don't go the gas/glow route.

The alloy channel route is how the coil is fitted to my McCulloch. Looks quite professional with the corners trimmed and small capheads holding it all together.

Hi plasticmaster, if you can get some methanol try to mix one part methanol with 2 parts 15%nitro glow fuel this should give you a 10% nnitro mixture as for oil if its on a 18% oil content you'll probably end up in the 12% range so probably your mixture will be a 10/12 glow fuel which once you mix with 2 parts gasoline it will give you a 3.3% nitro and a 4% oil content, so go ahead and make a samll batch and try it on your 42 poulan as Gas/Glow mix with an OS 4F plug.

A 1 to1 mix of 15% glow fuel with methanol will give you a 7.5% nitro and 9% oil glow fuel that you can alsomix with 2 parts high octane gasoline and at the end you will have a 2.5% nitro and 3% oil which isn't bad for Gas/Glo fuel either.

I'd mix up a batch of fuel using the 15% flow fuel.

Knowing that this isn't the ideal mix run it to see how is works.
Leave everything in place and give it a shot.

I did this on my first conversion and I knew I was on to something good.
It was a 32cc Mac that was discarded by another flyer when the EI went out.
It ran better on gas-glow than it ever did on EI.

AV8TOR,
How much did your Big Stick weigh with the 42cc on gas/glow, ready to fly?

Hey plasticmaster, regarding the stock muffler depending on how new it is it could have a catalyst. If you have "material" looking stuff inside, I would round up another muffler.

I've only run the Poulan 42cc with the original muffler completely stock. I've taken it apart though and the exhaust goes into a hard metal "cage" with holes in it. This cage is also wrapped with the spark screen and the cage gives support when tightening the muffler to the engine. Once I get it running on gas/glow, I'll try running it again with the stock muffler and then with the spark screen removed. These are the only components inside the muffler shell.