Strange goings on with an FP40

[Doug Lawrence]

It is now Phil! Cheers!

[Nigel R]

"an OS F st plug"

I'd be interested to see if you also get a good result from a warm or hot 2 stroke plug.

[Doug Lawrence]

Nigel, how did I guess that someone would raise that question! Maybe I will try it sometime but having spent so much time on getting the thing properly operational (not to mention the hassle of removing the cowl.. remote glow) I am very happy with the status quo and would like to enjoy flying the thing before I muck about with it again! If I ever try I will post again! Cheers!

[Peter Christy]

You may find its more a question of long reach plug vs short reach plug. Most modern 2-stroke engines are designed for a short reach plug, whereas older engines - particularly European ones - are designed for long reach.

The old OS max 40 I referred to in my earlier post is designed for a long reach plug. Whilst it will run quite happily on a short reach (OS 8, Enya 5, etc) when upright, it doesn't like it when inverted! Because the plug doesn't reach the bottom of the threaded plug hole, when inverted, it tends to trap liquid fuel and extinguish the plug. This is less likely to happen with a long reach plug, and an idle-bar will also help to stop liquid fuel "pooling" in the plug.

Its a long time since I looked at an OS 4-st plug, but I have a nagging feeling it may be long reach. It is also a much hotter plug, so not so easy to extinguish!

--

Pete

 

Edited By Peter Christy on 07/09/2017 15:59:33

[Doug Lawrence]

Hi Pete, I guess there are two aspects involved, a longer reach ( which it is with the os f) and a hotter plug to keep it all burning nicely. Nigel R in the previous post said he wondered how it would perform with a warm or hot 2 str plug, well I don't know whether the os8 is a hot plug but it seems to be the recommended plug for that engine. Unfortunately, it didn't work with the engine inverted so with everything up and running with the os f I'm going to stick with it!

[Denis Watkins]

And Doug, the F element is thicker with more glow surface area.

Edited By Denis Watkins on 07/09/2017 17:46:49

[onetenor]

One person said the engine is ABC another not .Which is it please Jon are you listening?   BTW Manuals are available here  https://www.google.co.uk/search?q=os+max+fp+40+manual&oq=o.s.+40+fp&gs_l=psy-ab.1.0.0i71k1l4.0.0.0.15739.0.0.0.0.0.0.0.0..0.0....0...1..64.psy-ab..0.0.0.jyoW4l3v0ak.

Edited By onetenor on 07/09/2017 19:39:42

[BackinBlack]

OS 40FP is listed as ABC, see: http://www.osengines.com/parts/engine-specs-discontinued.html

[Nigel R]

Early FPs were plain lapped steel piston. They got "ABC" later on (alu/brass/nickel).

 

" I don't know whether the os8 is a hot plug but it seems to be the recommended plug for that engine. "

OS #8 is a medium. Rule of thumb, for low power / small engines, go a bit hotter. Lots of nitro, go a bit cooler. Cold weather, go a bit hotter.

I would mostly choose a warm plug (enya #3, OS #3, firepower f6) on anything sub 10cc.

And maybe even a hot plug (firepower f7) for something like this FP.

But. If the engine runs well on the OSF plug, stick with it

Edited By Nigel R on 08/09/2017 09:03:23

[Doug Lawrence]

Thanks Nigel, yes, I will stick with the OS F. It does the trick which is all I am concerned with at the mo but the info you have given is useful so..thanks!