rotax 447 engine failure
in 2 Stroke Technical Questions
14 years ago
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by tim HEYLBUT » 14 years ago
Hi Bill , egt has stopped working? and cht was a little colder than ussual, ussually reads 8,today only read 5?,,waiting for the rain to stop so I can drag her out and run again,with new plugs,NOW plugs? replaced with standered ngk plug (as was allready in it)but noticed package shows not to use in aeroplane? should I use the aridium plugs?price $26ech standered plug $4.50ech...big difference
thanks
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by bill martin » 14 years ago
Standard plugs are fine. Iridiums will last twice as long at five times the price. Not good economics.
That notice on the box is just lawyer boilerplate. It's on all their plugs.
It still sounds like a too rich condition. a smaller main jet will lean out the top end. Lowering the jet needle will lean out the midrange without affecting the top end or idle.
You really need the EGT gauge to work if you lean anything. Lean too much and you start melting stuff. You can't really use the cyl. head temp. to judge piston temp. You might risk lowering the needle because the midrange temps don't run as high as the top end but I definitely wouldn't risk a main jet change without an EGT gauge.
You might check any spade connectors between the EGT probe and the gauge for corrosion. Most of the time this is what causes the EGT gauge to malfunction. Just unplugging and replugging usually fixes the problem.
Bill.
Thank you said by: tim HEYLBUT
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by Nick Axworthy » 14 years ago
So is the carb bowl still over filling???
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by tim HEYLBUT » 14 years ago
NO ,BUT STILL RUNS ROUGH WHEN BACKING OFF, AND IF THROTTLE ADVANCED FAST COUGHS AND SPLUTTERS
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by mike hallam » 14 years ago
When I bought my 447 powered Rans S4 some years ago it too ran rough backed off to cruise power. Checked the main jet and needle numbers and positions correct to the 'book'.
Finally put in new carb needle, old one's profile worrn after not too many hours.
Reason ?
Unlike Amal motorbike carbs, the aero Bing needles are made from a soft brassy material. Near the cruise position where it mostly sits, it wears thinner, ergo mixture over rich !
BTW. Don't arbirarily change carb settings from Bing recommendations, especially if you've little know how, they have experience of thousnads in service so they DO know !
mike hallam (England)
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