Mag check on rotax 912 uls

Hello, the kitfox s7 is almost ready, started the engine, everything is ok, motor runs smooth, but on the mag test I get little drop on rpms on one side (200) and the other too much like 1000+, changed the plugs and still same drop, did everything by the book on the installation.
Checked the cables from the switch to the modules several times and they seem to be ok, also switched from left to right and the drop changes from left to right meaning that the ignition switch is ok I think.
Will be nice to hear some input on this matter if someone had the same situation as me or knows what could be the problem.
Thanks
Leonardo

Leonardo,

Congrats on closing in on your build on your S7.

The 200 RPM drop is within the normal drop a person would expect with the ULS....1000 is a crazy number.

Question...when you say you switched the left and right and the problem moved with this change, are you saying that you switched the modules L/R? Or, did you switch something other than, or in addition to, the modules L/R? Thinking some additional info would help with figuring out what the problem is.

Second question...is this a brand new factory ULS; or, is it's history other than new?

Hello Dave, thanks for reply so soon, on the change I mean the cables on the ignition switch, very easy to change that, first the drop was on the L now after changing cables is on the R. And yes is a factory 912 uls, bought it in 2013 dough.

Quote:

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Originally Posted by silvaleonardo

hello dave, thanks for reply so soon, on the change i mean the cables on the ignition switch, very easy to change that, first the drop was on the l now after changing cables is on the r. And yes is a factory 912 uls, bought it in 2013 dough.

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Leonardo,

One strategy is to first check the easy to see stuff first......sounds like you have dealt with the plugs (and plug wires & connections to the plugs?)

Another item to check is the module grounds - there should be one black wire coming from each module with each anchored to its separate bolt on the top of the right intake manifold - make sure both are solid and tight to the manifold. There should also be a larger black ground wire running from one of the manifold grounds back to the clamp on the back of the manifold. If one of the manifold grounds is loose or intermittently open that could be (but no guarantees) one possible cause of rough running or a big rpm drop on one side - if one is completely separated that module will not work at all but if it is loose it could cause the module to behave erratically.

I'd double check the two sets of connectors on the back of the modules to be sure all of the connectors are completely seated into the receptacles.

A person might consider rechecking each wire going from the ignition switch to each module with a meter to be sure there are no intermittent shorts or opens.

There are others on this list who have had significant experience with Rotax ignition 0issues. Probably one of the best things you could do, if you haven't already, is to go to the search function near the top of the page and search on "ignition" or "912 ignition" - you'll find a lot. There are a lot of experienced people on this list who have placed a lot of information in the archives and reading the search results might trigger some useful strategies.

I did not wire my KF3 with a 912, however... I do believe that the recommendation is to wire the ignition modules with off/on toggle switches. The keyed switch is used only for engaging the starter.


The wireing diagram is for an engine with magnetos (i.e. O-200).

Thanks again Dave for all the input....I will get on it today.