Engine rpm drop

by William Hicks in General Tech Discussion 8 years ago

Have a 914 on a highlander with a few hundred hours. Drop on one module is 100 and other 500. Changed modules to known good ones and still same problem. Replaced spark plugs. Still same problem. Runs smooth on both modules and seems to make good power in all rpm ranges.

Any trouble shooting suggestions would be appreciated.

Re: Engine rpm drop

by Bill Hertzel » 8 years ago

Bill Hertzel

13 1.95k 7.98k

Wiring is the next suspect.
You can throw money at the problem and change all the wiring.
Or, try this...

Run it in the dark. Really, Really Dark!
Wait for your eyes to adjust 'till you can just barely make out your hand in front of your face.
Any Blue Electrical Corona Glows (Think St.Elmo's Fire) that you see will point to the bad wiring.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Engine rpm drop

by Roger Lee » 8 years ago

Roger Lee

128 5.28k 4.98k

First, easiest and least expensive would be to unscrew the spark plug caps off the plug wire. Trim the plug wire back about 3/8". Apply I tad of dielectric grease the the wire tip and screw it back in the plug cap and start it again. The 400 rpm difference between the two modules isn't indicative of a bad module. That is usually more rpm difference. This suggest a single plug or wire.

What did you set the plug gaps at? They should be between .023 - .027.

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

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Engine rpm drop

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