Scintilla Mag Problems

N12HR appears to have a problem with the impulse coupling on the Lycoming O 320 engine. Does anyone have a repair, overhaul or parts source? The part number is Scintilla 84LN-21.
Thanks
G Harben

I'm guessing you mean S4-LN21, not 84-LN21. If so, it's a common mag. AC Spruce has overhaul kits. I don't know any particular shop to recommend, maybe someone else will.

C. Smith

It actually is:
84LN-20 OR 84LN-21
https://www.dropbox.com/s/ax2tgh05x2mzsyu/Mag Close up.png?dl=0
https://www.dropbox.com/s/bwh32e3zr96znrh/Mag1.JPG?dl=0

It may be the same as B4LN-21
Thanks

Just talked to Columbia Aircraft Services Inc. They said to send it it and they could test it and hopefully repair it.

That data tag has been mis-stamped. It is a S4LN-xxx. No such thing as a B4LN or 84LN Bendix mag model number.

Columbia will figure it out however. I'd make sure they correct the data tag for proper future reference.

George

Magneto Part Numbering

That 8 at the front end is likely an S, for single magneto. S4LN would stand for Single, 4 cylinder, Left hand rotation, and the N is for Bendix (no idea how Bendix got the N for their identifier. I’d guess B got used got used earlier for something else.

Thanks to every one!
Yep Bendix S4-LN21. That "8" confused me. Doesn't take much apparently. Now on to the problem.
The 0 320 is very old SN 193-27. First log entry 12/31/55.
The engine is very difficult to crank. The mag will fire two plugs weakly when they are removed and laying on top of the engine. The primer appears to go into the bottom of the cylinder on one cylinder on each side. The carburetor has a accelerator pump.
Gas or Spark? One is missing during normal cranking.
Any Thoughts?
G Harben
N12HR

starting problem

You need to provide some more information. You say it’s difficult cranking. Does the engine eventually start? How long has it been since the engine has run? You say two plugs fire but are weak - all 4 need to fire. If the spark is weak it indicates a problem with the mag or the impulse coupling (as you stated in your original post). How long has it been since the mags have been serviced? Does the engine sound like it’s trying to start? Does it backfire?

The primer is easy enough to check. Disconnect the line where it goes into the cylinder, put something on the end of it to catch the fuel, and pump the primer a few times (assuming it’s a manual primer).

You may want to post your question in the General Discussion/News forum. Starting problems are not unique to the RV4. My guess is that you’ll get many more responses.

C. Smith
RV4 serial #68

N12HR fly's about once a week. I have owned it about 2 years. It has always taken too much twisting to crank. I have disconnected the primer and it appears to be working. After a lot of cranking it suddenly bursts to life. Never a pop or crack! It feels like there is no gas or no spark. When you turn the propeller and as the impulse coupling spins ahead there is a weak spark about every 3rd try. I don't believe the mags have been overhauled in the last 800 hours.
It also appears very ez to flood.
Thanks for your reply. I will look at the General Discussion section also.
G Harben
N12HR
S/N 1664