914 rough running

by Greg Regan in 912 / 914 Technical Questions 11 years ago

Hi
Still unsure what's wrong with my Sabre have not as yet balanced the prop but this morning on run ups at 2500 to 3000 the mag drop is only 50 or so revs but at 3500 on it drops by 200 and starts to run rough putting more pitch on the prop seems to make it worse carb balance looks ok could it be blocked jets
Greg

Re: 914 rough running

by Rob Seaton » 11 years ago

Rob Seaton

3 1.32k 251

Greg,
You are right to keep your focus on the carbs/induction. I doubt you have a ignition problem.
Try going one notch richer on the needle, see if that helps.
then check the float bowl are not distorted by overtorque; the float pins should be perfectly upright (don't just straighten then; replace the bowls)
Check the airbox for oil; you may have a leaky checkvalve or scavenge system problem and oil is being ingested into the carbs.
Rob

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Re: 914 rough running

by Greg Regan » 11 years ago

Greg Regan

25 75 31

Just talking to my lame reckons it could be plug gap as I replaced the plugs hoping that was the problem but didn't set the gap so I have set them to 23 thous they were wider than that out of the box got my doubt's it will make any difference the carbys were checked by our rotax service people about two and a half years ago just checked the air box and no oil the carbys are a bitch to get off so trying the easiest things first
Greg

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Re: 914 rough running

by bill martin » 11 years ago

bill martin

10 757 0

Could very well be the plugs. If they were installed right out of the box without gapping, the gap was probably way too wide.

Have you tried it yet with the .023 gap?

Bill.

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Re: 914 rough running

by Greg Regan » 11 years ago

Greg Regan

25 75 31

Hi Bill
Thanks for your interest While I had the cowls off I dropped the float bowls off and blew out the jets the bowls were clean seems it is running ok now still rough at 4500 revs but I think it was always that way ran rough at those revs when I done a mag drop It was windy when I flew and it seemed to make a difference when I changed direction so I hope it must have been the plugs
Greg

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914 rough running

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