losing revs slowly at idle

[Silver Wolf]

Not really a problem. I have an OS46 that runs quite happley however at idle it slowly losses revs, any ideas?

 

Kind Regards

SW

Edited By Silver Wolf on 05/07/2018 18:23:34

[Jon H]

could be a number of things.

First off, which glowplug, fuel and prop are you using. Second, as it runs down does it do it smoothly or does it slowly stutter/stumble and cough itself to death.

Also, does it only do this just after startup or does it do it all the time, even after a blast at full power

[Former Member]

[This posting has been removed]

[Denis Watkins]

Exactly Percy, is the motor run in? And as Jon asks, is the motor over propped, the plug tired, the fuel suitable.

Edited By Denis Watkins on 05/07/2018 20:16:58

[Peter Christy]

Is this something its always done, or has it just started?

If its always done this, it sounds like the tickover mixture is too rich and needs leaning a bit.

If its only just started doing this, then the above suggestions are all possibilities...!

--

Pete

[Shaunie]

My rule of thumb which works for almost every two stroke is: - if it idles fast and runs down then it’s lean, if it bogs and then picks up its rich. Make a small adjustment in either direction and see if it’s worse or better. If it’s worse, go the other way, if it improves it carry on in the same direction.

[Gary Manuel]

Posted by Shaunie on 06/07/2018 20:59:30:

Make a small adjustment in either direction and see if it’s worse or better. If it’s worse, go the other way, if it improves it carry on in the same direction.

Even I wouldn't argue with that advice

[Silver Wolf]

Firstly apologies for the late response, short working week but long hours that don''t allow for anything to be done on work days unfortunately.

Plug is enya No3, fuel is model technics Irvine sport 5 and fresh, the prop is a 11x8.

The gradual lose of revs seems to happen all the time. Pick up from idle is not to bad maybe a little rich but only at the very end of the transition to full power. Only really notice this behavior due to setting up throttle in new model. As I have said it is not really to much of a problem, just wonder if i have been a bit tardy with setting the secondary needle.

Thanks for all the replies.

Kind Regards

SW

[TartanMac]

11x8 is too much load. Is it an LA, FX, AX, or SF series of O.S ? 10x6 is what I would try before you do anything.

[Denis Watkins]

Have you mistyped an 11 x 8 prop SW? should it read 11 x 6, as normal on a .46.

The plug and the fuel are spot on

Edited By Denis Watkins on 09/07/2018 21:08:02

[Steve Hargreaves - Moderator]

An OS46AX will turn an 11x8 no problem Denis...if it's an LA then I'd agree...an 11x6 is as big as I'd go...

An interesting trick, if you can reach the fuel line feeding the engine safely is to pinch it at idle & see what happens....if it cuts out immediately it's a bit too lean.....if it revs up & then dies it's a little rich....if the revs increase a little & then die then it's a teeny bit rich & just about perfectly set.....you need it a little bit rich just coming off idle to help the motor accelerate.

Have you checked the head & back plate for tightness too...? A tiny air leak can give the symptoms you describe...similarly is the carb tight in the crankcase with the 'O' ring compressed a little?

What happens when you open the throttle as the engine starts to fade? Does it speed up OK or cut dead or splutter back up to speed?

How old is the engine BTW..?

[Silver Wolf]

Tried the intresting trick, however could not get the engine to cut, so presume that the fuel line is thick walled.

I have leaned the bottom end out just a small amount and engine seems a little happier and more than adequate for flight. Just for the record it is an AX and swings a11x8 and the engine is around 3 to 4 yrs but as not had a great deal of running in fact it looks almost new. I also put a few drops of after run oil in and model is stored nose down.

Thanks for all the replies.

Kind Regards

SW

[stu knowles]

You need to squeeze the fuel line just before it enters the carb and hold it until the engine stops. My guess is that eventually you will see a significant increase in rpm before it dies, indicative of a rich setting on the idle jet. A modest increase in rpm and then dies soon after is the goal, just on the rich side of spot on.

Unless you are using some form of fuel tube that I have never heard of, it is not strong enough to stop a squeeze with the fingers cutting off the fuel flow. You just haven't held it and waited long enough.