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Stihl 32 cc 4 mix conversion

Old 10-06-2015, 01:31 PM
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au117
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Default Stihl 32 cc 4 mix conversion

Thought i would share my 32 cc 4 mix conversion. I have been messing with the 32cc and 64cc for the last 2 years . I am using a walbro WT 891 and a inline pump made from the stock zama carb. The 90 deg. intake is copper with steel flanges high temp soldered, i used low temp solder and brass tubing to port match the inside of the intake. The prop hub holds a ring with the magnet and a set screw secures it in the key way with a C & h ignition, the whole setup weights 3.5 lbs, It is swinging a menz 21x8 at 5400 the nieuport 28 weighs 16.5 lbs.

https://www.youtube.com/watch?v=cFxm2Tgdz5o https://www.youtube.com/watch?v=K6x3LfZj3gg thanks for looking.

Last edited by au117; 10-06-2015 at 03:57 PM.
Old 10-06-2015, 08:47 PM
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av8tor1977
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Very, very nice. I have converted and sold several of the 32cc Four Mix engines, and have a 36cc converted that I saved for myself. I also sold a bunch of the 65cc models unconverted.

That prop sure seems big for that engine. No problems with overheating?? You might pop the valve cover off and check for signs of oil coking. The Stihl engines like to rev, including the Four Mix. The Four Mixes tend to run a bit warm anyway, and I've seen numerous exhaust valve failures because of it.

Great job though, on both the engine and the plane. Nice wheel landings too! What ignition timing are you running, and what oil ratio?

AV8TOR
Old 10-07-2015, 06:38 AM
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au117
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Hi Av8tor. It is a large prop for a 32 cc Im getting 220 deg. wot and 175 at low. I have about 40 flights now on that prop. It would swing the 20 x 8 zinger at 5800. the 21 x 8 menz pulls the 28 nice. I replaced the ring. so i have been using 32 to 1 lawnboy. i am going to pull it apart this winter to inspect it . what do you think of a wt 38 for the 32cc the 891 is an 11mm venture and the 38 is an 9.5. thanks Sean

Last edited by au117; 10-07-2015 at 06:49 AM.
Old 10-07-2015, 09:20 AM
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Well, first the prop. The Zinger is nowhere near as good as a Menz prop, so that's not a quite fair comparison. Zoar props are good, but are a heavy load, so not a particularly good choice if you want to run a big prop on a little engine. You might try a 20 x 8 wide blade Top Flite on it if you can find one. I'm running a Top Flite on my big Fokker triplane and I'm quite happy with it.

Now the oil. As I mentioned, I've seen a lot of problems with carbon and oil coking with these engines, so I would definitely switch to Red line Racing or Stihl Ultra UP oil at this point. Oiling is always a little "sketchy" with "oil in the fuel" four stroke engines, so you want to run the best oil you can. Stihl specs a 50:1 ratio, but I run at 40:1 for a little better oiling.

As for the carb, I would say "If it works don't fix it". However, if your setup is being finicky about adjustments and/or throttle up transitioning, then I would try the smaller carb. I doubt that you will lose any power, as your airflow requirements are pretty low at the rpms you are running, plus it's a four stroke which can use a smaller carb. Some of the 9.5mm Walbros have an accelerator pump in them, which would be a great thing to try too, specially on a four stroke engine.

What degrees of ignition timing are you running?

AV8TOR

Last edited by av8tor1977; 10-07-2015 at 09:24 AM.
Old 10-07-2015, 11:57 AM
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au117
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Im sorry i was not trying to compare the zinger to the menz it was a prop that i had and was using it on the stand i also ran a zinger 18x8 on the stand i think it was 6300. I fly menz props on all my ww1 stuff, i like the low end pull of the menz.. i do think the low end could be better so i will try a 9.5 mm carb this winter when i do an inspection, i will look to see if the 38 has a pump. The timing is at 30 deg. 32 was a little hard starting 28 did not seem to make a difference.
Old 10-07-2015, 10:56 PM
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Well done, very nice ...

I also have a 36cc 4 Mix currently stripped and waiting for conversion, no time now but the festive season is soon upon us...

AV8TOR - I thought you once mentioned you have some useful information and diagrams for the 36cc? you still have this info?
Old 10-08-2015, 06:31 AM
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Yes. Since then I had a computer crash, but I should have the info in my back up and will look for it when I get a chance. Please send me a PM with your e-mail address.

Stihl only wants their licensed dealers to have the technical info, and prohibit it from being posted on the web. That's a REALLY crappy attitude in my opinion, but they make great engines. I kept at it until I lucked into tech info for the Four Mix engines. (A person doesn't even need tech info for a two stroke....)

AV8TOR

Last edited by av8tor1977; 10-08-2015 at 06:39 AM.
Old 10-08-2015, 06:38 AM
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au117
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Thanks prigai. I would like to know more about the 36cc also. Av8tor have you ran yours, if so do you have any numbers and tell me more about the fokker. Thanks Sean
Old 10-08-2015, 11:30 AM
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The last 32cc I did had the magneto ignition, and it turned a 16 x 8 prop at 8300, and an 18 x 8 at 7200. It has been a while since I ran the 36cc of mine, but if I remember right it turned the 18 x 8 at around 8000 rpms. Really very respectable power for a four stroke!!

Here's a couple of pics of my 36cc Four Mix. In these pics I had just set it up for test running without bothering with detailed cleaning and painting, etc. When actually done, it will be much prettier!

I've got a short video of the 32cc running but I can't post it. You have to do so via YouTube, and I don't want to get into that.

AV8TOR
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Old 07-25-2020, 02:55 PM
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I wish av8tor1977 would pop in once in awhile. I have a 4mix 28.4cc (FS90R) I need a few tips on. Id like to put this into my newly acquired Seagull Extra 260.
His knowledge is undeniable on these conversions!!

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