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Anyone Still Doing Conversions?

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Old 11-07-2017, 11:19 AM
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mmattockx
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Default Anyone Still Doing Conversions?

I have a Poulan 46cc that I would like to convert to aero use. I previously had talked to Ken Lambert about getting parts for the conversion, but his website hasn't been updated since 2015 and my last email from him was in 2014. If anyone is still offering parts or even can offer details of what I need so I can make it myself that would be very appreciated.


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Mark
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Old 11-08-2017, 11:10 AM
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I still do them. I ocassionally build an engine for sale, or do one to order for a past customer. I don't generally do parts for sale though, as I don't have the time and energy, plus there is just no way it is worthwhile. By the time you hand craft individual pieces for a conversion, you can't charge anywhere near what they are worth. That's one of the reasons nobody makes the conversion parts any more.

The influx of cheap Chinese engines has all but killed engine conversions, though I personally still feel they are definitely worthwhile as you get the satisfaction of creating something yourself, but more importantly, you get a much better engine.

At the moment I have a Poulan Pro 42cc in the works, and a real nice Kawasaki 50cc. They will be for sale, but progress on them was held up due to a fairly recent back surgery.

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Old 11-08-2017, 06:01 PM
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Quote:
Originally Posted by av8tor1977 View Post
I still do them. I ocassionally build an engine for sale, or do one to order for a past customer. I don't generally do parts for sale though, as I don't have the time and energy, plus there is just no way it is worthwhile. By the time you hand craft individual pieces for a conversion, you can't charge anywhere near what they are worth. That's one of the reasons nobody makes the conversion parts any more.
Yeah, that's what I am finding out. If I had a lathe and mill it would all be done already, but I don't so I will be working on a couple of machinist acquaintances to build the parts I design for beer money on the side or at home.

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Old 11-09-2017, 02:25 PM
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I will try to help out. With the configuration of the Poulan engines, they are most often mounted by making plates that bolt to the crankcase screws for the crankcase halves, and extend outwards to the sides. These plates then mount to a large size, standard beam type engine mount.

However, this makes for a rather wide mounting footprint; too wide in fact for some firewalls. In this case, I cut down the original crankcase bolt spacers, and size the crankcase half bolts to a length that will go all the way through the beam mount. The engine then sits directly on the beam mounts themselves, making the mounting width much narrower. The crankcase bolt spacers, made shorter, space the crankcase off the beam mounts, allowing space for the large rounded crankcase half to fit between the mounting beams.

Hope that all made sense.... If you are going to go with the side PLATE style mounts, send me the exact center to center distance (fore and aft) of your crankcase screws. I think I have a template for that engine and if I do I will send it to you free.

Next is prop hub and ignition. That model Poulan can be run either with the magneto ignition, or be converted to electronic. Which way are you going to go? (Personally I much prefer losing the heavy mag and going electronic.) Anyway, if you go with the magneto, the prop hub is pretty straight forward with no tricky machining involved. If you want to go with electronic, here's a trick I often use. I use a hole saw and the drill press to cut the center out of the magneto. I then dress this down on the lathe, and either install the sensor trigger magnet in it, or machine a rotatable collar for it with a magnet. This precludes having to machine a matching taper in the prop hub, plus provides a keyed location for the sensor magnet so that if the prop hub happens to shift, it doesn't throw off your ignition timing. Then the prop hub itself is the same as would be used for a magneto engine; just a simple screw on affair.

Lastly, if you go with the rotatable collar for around the magneto center that has the magnet for the sensor, (which I recommend), I found a place that sells set screw collars for around 4 bucks each. I don't know about you, but for only four bucks, in most cases I just buy them and "pass" on that particular time spent bending over the lathe...

AV8TOR

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Old 11-12-2017, 11:56 AM
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I have right now life has got in the way(work house, ect.)I'm doing a stihl 4mix( thank you av8tor) hope to get it done soon.There are a lot of engines out there it's a part o
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Old 11-14-2017, 05:16 PM
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I haven't really seen the conversion businesses around for awhile now. I still do conversions on a limited basis, mainly for my own enjoyment or use. Sometimes I'll trade one off, or sell/trade a plane with a conversion in it. I almost never keep the magneto these days and use either an rcexl or an EI module from hobby king.
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Old 11-14-2017, 06:34 PM
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Quote:
Originally Posted by av8tor1977 View Post
I will try to help out.
That is very appreciated. Here are a few pics of what I have:

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It looks to me like I can use the beam mount flanges directly, without the adapters you mention. No magneto as you see. The prop will be on the shorter, tapered end of the crankshaft and the other end gets cut off.

EDIT - Why don't the full size pics work when a thumbnail is clicked on?

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Old 11-15-2017, 10:19 AM
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As you have by now probably realized, the hard part of converting the Poulan 46cc is dealing with the carb mounting situation. Once done though, it does make a quite nice conversion engine. This engine was the base for the (now defunct) Brilleli 46cc, and he did a very nice job on them.

For some hints on dealing with the carb mounting problem, see the old "rcfaq" website, plus have a look at my "Stihl 62cc" thread in this forum. (The Stihl is easier though, as the port is round instead of oval, and has more "meat" to work with.)

Whatever the solution you come up with, don't neglect the necessity of having the carb AND carb mounting screws thermally isolated from the engine. Not doing so will lead to incredibly frustrating tuning and operational hassles. (Yes, ask me how I know....)

It might seem arcane or silly, but using epoxy soaked plywood of good quality can be a viable part of a carb mounting setup. Diluting the epoxy with acetone helps the epoxy penetrate the wood. (I prefer acetone over alcohol for this as it evaporates faster and allows the epoxy to cure completely faster.) Another good option is the material called "G-10". Try McMaster Carr for that. (A bit pricey.)

Good luck with it and keep us posted,
AV8TOR
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