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please help-rotax 447 single carbie,breaker points----BOGGING DOWN?

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flyerme

New Member
Joined
Apr 6, 2012
Messages
4
Location
australia
on the way home from picking the new super cat I encounted engine failure.whilst cruising for around 20 mins the engine back fired,3 times then started running rough ,i looked for a place to land then I gave it full thottle and it ran fine again,when dropped back to cruise after a few minites it ran rough again ,full throttle applied and ran fine,so flew home at full revs (10 mins) and dropped revs for approch and ran fine landed no issues,but when broght the revs back up for taxing ran rough again. NOTE:noticed full leaking from air filter right before start up and when taking off noticed a slight miss , checked the float level,needle and seat,fuel tap removed inspected,plugs checked (brown) air filter cleaned and oiled NOTE" float level sits about 4mil below bowl top., ran up the engine and runs fine when applying revs up slowly but always runs rough when pulling back the throttle ,push the throttle forward fast and cough and slutters.? thinking I may need to overhaul the carby (jets)? any ideas????????????? should mention was told after,that its happened before! and noticed it come with a spare(old)carbie.?




Update, suspect its the electric fuel pump ,over pressure! as the fuel tank is mounted high (up front under dash like an ag hopper) and gravity feeds to carby,plus has the mechanical fuel pump, we believe the electric pump (always left on) is over pressuring the float needle and seat. will run another test tomorrow with NO electric fuel pump turned on,keep you posted
(no pressure reg fitted.

Nope not fuel pump!ran the same with no electric fuel pump, ran engine70% then switched off in that position and removed plugs,both ceramic,s light brown but 1 plug electrode black,will buy 2 plugs and see if not will pull down carbie and inspect and clean jets

NO ,BUT STILL RUNS ROUGH WHEN BACKING OFF, AND IF THROTTLE ADVANCED FAST COUGHS AND SPLUTTERS


Update,had a new carbie put on and No different...so just bought a newer 447 with carbie and put that in and no change(rough bogging down and rpm fluctuating) so put new prop,no change removed all wiring,no change by pass fuel system no chabge fresh fuel nope,so only leave 1 other thing that remains origanal from purchace,,exhaust ,,ah hello whats this???????????// NO elbow.and exspansion chamber cut and has a 10 inch car exhaust sleeved in and welded ,so longer than standered and now only 2 piece)no elbow) Im guessing that this would upset the tuned pipe??

Ok now getting real peeved!!!!! new exhaust fitted,still bogging doen? should mention with airfilter off it doesnt bog down? it appers to flood when throttle opened fast? I found a old forrum where a feller has the exact same prob,and has not fixed either, every thing I have tried= new engine,new carbie,new exhaust.seperate fuel tank gravity fed to carbie,new carbie rubber,new airfilter,leak test all gaskets,new gearbox,new prop,new engine mounts,DROVE 11 HRS with whole plane to mechanics,he looked at it for 2 days trying everything I have done,No change so mechanic flew in 5 min long circuit and noted a backfire,and revs surge,but said ran fine other than that,he flew again 10 min reported engine slightly surging No back fire an assured me she good to go? So I lined up the runway sat at idle did my departing call ,opened the throttle and she bogged? so quick back off to idle where she cleared opened throttle to full SLOW,and away I went flew a short circuit but definatly revs moving up and down 100-600 rev drop?
PLEASE PLEASE PRETTY PLEASE SOME ONE HELP ME????????????????
I am a carrer for my Pa so dont have $$$$$ to do any more but what eles could I possibly do? I will offer anyone who can solve this 3 month mystry a $100 reward,,I really want to fly my new plane been 3 months and only got to fly it home ...
please help Me,dessperate and very frustrated,,need sleep!
take it easy guys

 
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