#1 cylinder

by Jesse caudill in General Tech Discussion 7 years ago

I have a new 912 s in a just Highlander with 50 hours engine time. The number 1 cylinder spark plugs carbon up in a couple hours of flight time, all the other spark plugs look very good, with a very light color, I have been running the engine at 5,300 to 5,500 rpms. I ask Billy Payne about this problem he suggested that I just run the crap out of it, but it hasn't solved the problem of carbon building up on the plugs, if anyone out there knows what I should do please let me know. Thanks, jesse

Re: #1 cylinder

by Riley Stevens » 7 years ago

Riley Stevens

1 1 0

I wish I knew the answer... I have 25 hours on my new engine and the 25 hour inspection shows #1 plugs very sooty and oily, 2 & 4 are fairly sooty and dry, and only #3 is the expected light grey. Also, the #1 EGT drops smoothly to the 5-600 range when I throttle back to below 3000 RPM, with the other 3 around 1000-1100 EGT. The plane runs well, smoothly at cruise with good fuel economy.

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Re: #1 cylinder

by Roger Lee » 7 years ago

Roger Lee

125 5.12k 4.53k

Dry black soot is normal for many. This happens from sitting and idling or long taxi's at idle rpms. Run the engine up to 4000 for a few minutes and then immediately shut it down the dry soot should be burnt off.
Make sure your plugs are gapped between .023 - .027.
.025 is a good place to be. The colder the OAT are the narrower the gap.
Make sure the carbs are synced, make sure the plug caps on on correctly. Just had a plane in yesterday that 2 caps were off to one side.

If the plugs in a cylinder are oily black then that is a different issue.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: #1 cylinder

by Jesse caudill » 7 years ago

Jesse caudill

1 1 0

Ok I'll give it a try it takes a lot of time to get the oil temp up to 100degrees for taxi, engine runs good in cruise between 5,300 and 5,500. Thank you for your help. If this doesn't work I'll try giving them a call down in Mississippi. Jesse

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Re: #1 cylinder

by Riley Stevens » 7 years ago

Riley Stevens

0 1 0

Thanks Roger. I only have one cylinder with the oily deposit. The low idle and extended taxi is applicable here because I just finished running the engine for a long time to check propeller pitch and warm it up for an inspection. What are your thoughts on the oily deposit on number one, which is also the one with EGT that drops off below 3000 RPM?

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Re: #1 cylinder

by Roger Lee » 7 years ago

Roger Lee

125 5.12k 4.53k

It shouldn't be oily or wet after a run. Do a leakdown compression check on that cylinder just for grins.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: Riley Stevens

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Title	Category	Replies
Cylinder 1 EGT drop out	915iS Technical Questions	0
912uls cylinders not firing some intermittent	912 / 914 Technical Questions	2
912uls cylinders not firing some intermittent	General Tech Discussion	1
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#1 cylinder

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