Hi, i am back from Prague in Czech.. i bought the MVVS 2.5 DFS/R-R/C, an 2.5 cc dieselengine. In the manual are nothing wroted about the recommented propeller size for break-in and in normal use.

I asked the seller in Peska Modelar (hobbyshop in Prague), they can not some word of english, mostly own Czech language and nothing knowledge about model engines. Unuseful for tourist who are buying the hobbyarticles who want to ask about all thing

Jens Eirik

8x4, 8x5, 8x6, 9x4
for racing, 6x6, 7x5

Thanks! What is recommented size propeller for break-in the MVVS 2.5 diesel?

Jens Eirik

Hi Jens

9 x 4 worked fine for me with Model Technics D1000 and D2000 fuel when breaking in the CL version of the 2.5 diesel.

(oops, I just noticed that this is a forum for support from manufacturers, sorry for sticking my oar in )

The largest that the engine will handle. That is quite opposite to glow engines. Diesels like to turn slower when running in.

2.5 Diesel Thread up from the vaults and revived!

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Pe Reivers recently sold me a new Piston and liner set for an MVVS 2.5 cc diesel I acquired "pre-loved" (from an old gentleman who sadly is very ill). It appeared to have very little use though the piston and liner in it felt awful when turned over and would not hold compression. It was sitting neglected and sad when I collected it

The engine stripped, cleaned and assembled with new piston and liner and placed on a test stand today. Purpose - first start and running in.

Fuel: 25% Castor Oil; 35% Di-Ethyl Ether; 1.5% IPN; balance lighting grade Kerosene.

After a few minutes flipping and gradually screwing down the tommy bar, it started to pop. Open exhaust - no silencer fitted (I do not fit silencers to engines I am running in).

A quick touch of the electric starter - and it was away. Brrrp ....brrrrp .... brrrp running very rich (3 1/2 turns out on main needle)

Several very rich 5 minute runs followed. Complete cool down to ambient temperature between runs. Engine starts to feel "bouncy" as the moving parts bed in. Still can't hand start it though. Compression feels good.

Contra piston is an extremely tight fit. I use my "broomstick" handle compression adjuster to turn in the compression screw. There is no blow by leaking out past the compression adjusting screw. These MVVS engineers and machinists know their business.

Lean out to rich max RPM and adjust compression carefully for best running. Back off 1/16th turn. I lean it out to see if will hold a peak. All is good. Quickly richen up. Try R/C carb. After screwing out the air-bleed adjustment screw to max, it throttles like a good glow engine.

One VERY happy MVVS small diesel owner. Onlookers (mostly electric flyers) are impressed.

Basic data :

+ Temp: 13c

+ Elev. 200 meters AMSL

+ Humidity 65

+ Barometer Not Known

Engine

MVVS 2.5D "Blue Head"

Propeller: Bolly Clubman 8.5 x 4

Fuel mix: As above

Max RPM after several tanks (run in not yet complete): 12,500 on R/C Carb fully open

Min - not checked (engine not run in nor settings optimised)