I too have been watching the dollar sink to the Euro, but because I am interested in the (still more expensive) UL 315is. Hopefully the cycle will reverse and towards the end of 2014, I'm hoping it will be much more reasonable.

As mentioned before, I threw the LF 26 out of the mix for my consideration as it simply doesn't have enough UMPF for me. However the LF 39 does and compares very closely to the 315is.

That said, I have looked further into the D-Motors and still have the following concerns (applies to either D-Motor):

Weight; I know virtually all manufacturers don't include all of the items required to operate an engine in their weights listed. Knowing that, I still can't see an operating weight near 125 pounds. Maybe for the core engine "with liquids". But this also has a radiator, oil cooler, oil reservoir, cooling reservoir, ecu and fuel pump, all mounted separate from the engine. I'd really like to see some users post actual firewall forward installed weights - my guess would be between 150 and 160.

Extended testing/reliability: There is still very little info about the LF 26 in operation and virtually none on the LF 39.

The above being important (besides the obvious reasons) because - after looking past the cool flat head design - it finally dawned on me that the INTAKE IS MOUNTED ON THE BOTTOM of the engine!

Has anyone ever seen a bottom mounted intake? If so, I'd like to know how well and how long they worked. Anyway, I've never seen one and so (being an ex engineer) it got me wondering - what could go wrong there?

Hmm:

It's next to and above the exhaust and muffler - MIGHT add some heat to the intake air - never good for efficient combustion. Maybe negligible though.

D-Motor says and I quote "When a valve of a sidevalve engine is not closing, you continue flying with less power and there won't be expensive repair cost"

What happens when the rings, valve seals etc. break in and over time wear and allow oil seepage? Where does that oil go? Where does the oil and/or water go if a gasket fails (head or intake)? Or head or block crack? In a conventional top mounted intake - it mixes fluids till it overheats and/or drips off outside the case and keeps running until there is not enough fluid left and/or it overheats and then it fails. IF water and/or oil can get into the bottom mounted intake (likely as there is a direct path) - I'd bet it would stop running pretty quickly.

So, I'd really need to see an extensive amount of time built on either of these engines before investing in one.

Just my 2 cents!
Greg