Hello,

I have an older MVVS .49 with a red head. I bought this new quite awhile ago and never used it. It has the original glow plug it came with, which I believe is a rossi plug. What would be a good alternative plug to use with this engine.

Thanks!

Dai,


All MVVS engines .40 and larger, originally came with a Novarossi (not Rossi) C-6S glow plug.

It is a long-reach plug with a medium-cold heat range.


These original plugs can still obtained. But if not, the Rossi R4, the K&B-1L, the Enya #4, a Long Cold Fox and virtually any other long-reach, medium-cold plug, will serve you just as well.

The OS #8 and the Tower-Power plug have the same heat-range, but are not as good, since they have too short a threaded part...
The plug's 'face' will remain recessed in the combustion chamber, after it is screwed fully into the head.

But I have seen customers using them with no consequences (except maybe a slight RPM drop).


As to the identity of your engine... As far as I know, the red anodized head was only installed on the .45 size engine...

The .45 and .49 engines share the same bore.
The .45 and .40 engines share the same stroke and con-rod length.

So the head is different... Lower for the .45, which is a more compact engine.


Please check the stroke of your engine, to make sure what displacement it actually is (maybe they had a 'red' batch of .49 heads, that I am not aware of...).

Dar,

Thank you for the information. I was searching around the internet and all I could find was information on the MVVS .49 so I was assuming that is what I have. I will check the engine as you instructed and will probably be using a Fox glow plug since that is what I mainly use in all my other engines.

Dai,


The appropriate Fox plug, as I wrote, will work OK.


The stroke of the MVVS .45 (and the .40) engine is 19.6 mm.
The stroke of the MVVS .49 engine is 21 mm.

Both the .45 and .49 engines have the same 22 mm bore diameter.


Since I believe they never made any 'Red Head' .40s either, it is enough to ascertain the stroke dimension, to know what your engine is.

Dar,

You are correct that it is a .45. I checked the stroke and it is 19.6. Thank you again for the information. I am now looking for a replacement o-ring on the needle adjustment. Please let me know where I could find this.

Dai,


I will need you to post a couple of clear photos of your carburettor.

There were a few models.

Dar,

Here are some pics of the carb.

Thank you

Dai,


This is the oldest carburettor...

This engine must have been produced about 20 years ago, when 3D flying was non-existent.
It has a blunt-ended low-speed needle, which has an adjustable effect at idle, but is very non-linear from just above that.

If adjusted for a perfect idle, in the 10%-70% throttle range the engine will be running very rich, loading-up heavily; to the point of stumbling and cutting-out, if you suddenly open the throttle, following a short period around ¼-½ throttle.


If you only fly at full-throttle and close it to idle just to land (or can limit your flying to this regime), you can get along with it and your idle-to-full transition will be great!
But you cannot be anywhere in between - no part-throttle flying...

This carburettor is virtually a two-position switch; idle, or full power.

Unfortunately, there is no upgrade kit available for this carburettor...
For the 'in-between' carburettor design, that had virtually the same body, with a rigid high-speed needle, with an external thread, there was such a kit (#3216-0253), but it will not fit onto the carburettor that you have.


On the positive side, this carburettor has its O-ring located at the bottom of the insert - below the draw-bolt, where it potentially precludes all leaks from affecting the engine...


If you intend to run your engine reliably, at varying throttle settings, you will need to replace that carburettor with the new one #3216 (see photo), which is probably the most linear glow carburettor you can get (several members here can attest to that).
Thankfully it is not very expensive.

This engine seems very clean and in good condition, so the investment is probably worth it.