thunder tigre f 91s won't idle below 5000 rpm

by Marc Evans
(Reading, UK)

I've adjusted with the carb on this engine quite a bit but it refuses to idle below 5000 rpm unless I leave the glow battery connected.

It appears the glow plug is going cold as the engine idles fine for 10 secs then just quits. I'm using an OS type F plug.

Can I reduce or increase the nitro content of the fuel to make the engine run hotter ? Is this engine suitable for colder climates like the UK in winter (ambient temperatures below 5 centigrade).

My 20 yr old lazer 75 has no such problems and runs fine on 5% nitro fuel in both summer and winter and I can't remember the last time I adjusted the carb or changed the glow plug.

Why don't I get the same performance from my thunder tigre engine.

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thunder tigre f 91s won't idle below 5000 rpm

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Mar 01, 2010
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I'm using 1yr old 10% nitro
by: Marc

The fuel I'm using is Model Technics contest 10, i.e. 10% nitro. However its about a 1yr old and so I might try topping up with some more nitro. The problem is that because we've had a long spell of calm weather, I've done a lot of flying with my electric planes and my fuel stock is getting old. This however does not seem to affect my lazer 75.

I've seen other flyers in our club use a glow driver switchable from the Tx but this hasn't cured their problems so I'm a bit reluctant to try one at present.

When adjusting the carb for idle, I do adjust the low speed needle. I've not done the pinch test yet so I'll look into this next. Reading through the manufactures manual suggests the idle is too rich as the engine cuts out when the glow is removed or coughs and splutters on opening up the throttle and then quits. This originally lead me to beleive the idle needle was lean.

I'll make another attempt at adjusting the carb this weekend.

Mar 01, 2010
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won`t idle below 5000
by: Anonymous

quite common
low end needle adjustment but very little increase there is more and more people turning to on broad glow when correct adjustment will do
but yes it takes a long time to get right and at home could work fine then at patch no go down to damp in air
good luck

Mar 01, 2010
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Engine dies
by: Bill

When you fiddled with the carb, did you adjust the low speed needle? Have you tried the pinch test to see if the mixture is wrong? If all else fails you could install an on board glow driver to come on at low throttle settings.
This "Switch Glow" thing looks like a winner, go here to see it----http://www.switchglo.com/index.html
Copy paste the address above to learn all about it.

Feb 28, 2010
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what nitro percentage are you using?
by: Matt

What percent nitro are you running in your TT?

Maybe try 15% nitro. More nitro does help with idling. It's worth a try.