SonexBuilders.net

Hello all,
I've recently purchased a Sonex that needs an engine replacement.
Going back and forth with all of the options, I'm weighing the possibility of a Revmaster 2300 conversion.
As I understand it, the Revmaster 2300 is slightly wider than the Aerovee and that a cowling modification would be required to make the conversion to the Revmaster.
If anyone out there can shed some light on Sonex/Revmaster 2300 set-up, I would love to hear the pros/cons and how difficult the process was.

Thanks in advance...

I can't comment too much on the RevMaster 2300 specifically, however, my VW engine has the Hummel 94x86 cylinders so in theory it should be even wider. The RevMaster are 94x84 which means the emngine is 2mm narrower on each side compared to my engine. (not considering any differences in cylinder heads)
I was able to fit my engine in the standard Sonex "Universal Cowl", but I had to use stock VW valve covers. With the bolt-on covers it did not fit.

Off course, if your cowling was previously fitted to an AeroVee engine, it is very likely the builder cut material away at the center line to just fit the AeroVee engine. On mine there was just enough material on the cowling as it came from the factory to make the cowl wide enough to fit my engine, but I can see on an AeroVee you'd want to cut away some material and make it a bit narrower.
If that's the case, you might have to add some material again to both sides at the centerline to make it fit.

You will have a few more adjustments to make to your cowling/mount if you go with the RevMaster.
- The top bar on the mount will be replaced with a rounded one to go around the electronic ignition unit, there are some pictures of this floating around somewhere on this forum.
- If you keep the RevMaster case breather, you will need to make a blister in that spot as it is too high to fit under the cowl. Alternatively you reuse your AeroVee case breather plate or you can buy a similar low profile case breather plate from Hummel which will fit, that's what I have on mine.
- I'm not sure about the revmaster 4-in-1 exhaust but it is very likely that does not exit the cowl in the same spot as the AeroVee 2-in-1 exhausts, you might need to create a different opening. Of course if you still have the AeroVee exhauast and it is in good condition, there is no reason why you could not put that on your RevMaster and leave the cowl as it is in that area.
- If you decide to go with the RevFlow carb that comes with the RevMaster, you will need to make a ram air intake at the front of the cowl. Of course, if you have the AeroCarb from your old engine and it is usable, perhaps you can reuse it on your RevMaster, I don't see why that would be a problem.

There are probably other things to think about but this is what comes to mind right now.

We have two RM 2300 Sonex's here in Bunbury , Australia.

The RM 2300 is wider and requires a cutout for the tappet covers in the standard cowling ( mine ) , or a simple popout dimple ( the other one ) . Otherwise no problem : also requires the standard mounting mod that RM supplies , no problem again.

However on a related RM issue : we have both had continual ignition problems with their CDI system which we are trying to resolve ( both planes are u/s currently ) . I have also had a total flywheel fracture due to below spec thickness - fortunately no dramas in getting home !

A good value motor , but seriously suggest a visit to RM in CA to satisfy yourself on the QA aspects of their motor manufacture and testing - we would do that except the tyranny of distance prevents that !