Mag check roughness both lanes but not equal.

While Plugs and wires might be recommended.
Just to get started pull the plugs and have a look at them.
While they are out give them a cleaning.
Sandblasting might be preferred, but 30 seconds on a wire wheel will also do wonders.

Hi Dave, have a search through this forum, there are a number of threads where there is a wealth of useful information discussing your very problem.

A drop of only 20 shows that one ignition is virtually doing nothing. Are you saying that the logs show that the plug have never been changed? If that is genuinely the case the condition of the plugs confirms this then I would replace them. If the insulation has broken down or the electrode is excessively worn with a large gap then you will never get a good spark.

I've never had a problem with the HT leads, they are just copper core. I have however had many problems with the plug caps which should have about a 5kohm resistance. In a recent thread I described how to easily check them without removing them from the leads.

Let us know what you find.

Thanks all.  Yes. I’m new to the forum and didn’t know if this was unique to the 914 since the manual says a 500 drop is allowed.

I see zero indication in the logs of plugs being replaced despite 800 hrs on the motor.  A little disappointed no annual caught this.  I’ve seen several indications they were removed, cleaned and gapped 

for the cost of these plugs I would think that is cheap insurance.

how do i find your thread Kevin?

Usually a 300 rpm drop is a one spark plug issue. Like Bill said check or replace your spark plugs. Plus I would unscrew each spark plug cap and trim the wire back about 3/8". Apply a dab of dielectric grease on the wire tip and screw the cap ALL the way back down. This will make sure all wires and caps have good contact and checking the plugs will help eleminate them. It is possible to have a fairly new plug that could be bad.

I would download the 914 heavy maintenance manual https://www.rotax-owner.com/en/support-topmenu/engine-manuals#914-series-engines

Look at the second post here: https://www.rotax-owner.com/en/912-914-technical-questions/8883-ignition-failure_1

Kevin