Putting my .77 back together after the Cylinder came loose again and noticed the notch in the sleeve isn't lining up with anything. Is this normal? Most engines I've seen it lines up with the head or one of the head bolts.

C,


The MVVS 12.7 (.77) GFS/R indeed does not have anything to line-up with the notch in the sleeve.
There is no pin in the cylinder casing for that purpose, like in some other engines.

The larger bore 15 cc (.91) has clearance notches in the sleeve's rim, that line-up with the head bolts.


All you have to do during assembly of sleeve, is to line-up the exhaust port, with its counterpart in the cylinder casing.
The exhaust port is the tallest one (top lip closest to the top of the sleeve)

Everything else will be where it should be.

Thanks for the info.

Could you tell me what RPM the .77 & the .49 deliver the best power.

Both of them are in Ultrasports and I'd like some options on props I should try for each.

They are great motors but they also tend to be on the loud side.

The .49 has the standard muffler but the .77 has the tuned silencer.

C,


Both engines are optimized for tuned-exhaust usage. Using a normal muffler does not allow them to attain their impressive ability.

The larger .77 is a 'torquer'. Because of its timing numbers and its narrow crankshaft passage, it inclined toward low-mid RPM, with a mini-pipe, or a with full-length tuned-pipe.
Both are offered by MVVS.

It is best propped with a 13x8, a 14x6 or a 13x9 APC, with the tuned-silencer adjusted to support RPM between 10,500 and 11,500 static.
These numbers should be reachable, with the engine in its prime (from 6-10 hours after break-in, onward).

The .49... with the tuned silencer an the header slightly extended, spun a Bolly 11.5x6 at no less than 13,600 RPM.
This RPM may not sound impressive, but it is an actual output of 1.67 HP! For reference, spinning an APC 10x6 at 14,300 RPM (OS.46AX), is just 1.1 HP...

With a normal muffler, you can expect 'normal' .45-.50 performance level, on any prop.

Thanks Dar.
A side note on the cylinder notch. I have read many reports where testers wondered about it.
You can use a 1mm drill to drill a shallow hole through the notch into the cylinder jacket.  When done before disassembly, the drill shank can be used as guidance to slide the cylinder exactly into the same position it was before disassembly.</p>

Can you guys tell me where I can get parts in North America? The header pipe has come apart and my former supplier doesn't carry MVVS anymore.

Dar is in Israel, I am in Holland. I have stock, can't speak for Dar. The world is too small to restrict yourself to Canada.
The one distributer I knew there has been inactive for quite some time now.

None in my stock, Mr Dallas.

Hi!
I have!