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Feb 25, 2020, 02:44 AM
Still gassin' it.
You only need to check the master cylinder, #1. That is the cylinder that has the large master conrod, it should be identifyable somehow, check the manual for that.
First make a temporary mark on the propdriver for TDC against a fixed point on the crankcase or bearing seat, and also one for 28 deg BTDC.

Take out the plug from the head, fit the plug into the HV lead.
(keep the other leads connected to the plugs in order to avoid damage to your ignition)

Now turn over the engine, and verify that the spark occurs at the 28 degree mark.
If one cylinder is timed right, they all should be timed right, no need to check the other cylinders.
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Mar 09, 2020, 09:01 PM
Registered User
I don't know if it applies in rc world, however in race world with a magnet in the rotating part... IE the engine balancer, the pickup wiring is polarity sensitive. Meaning, wire the pickup backwards, the engine generally starts, but no idea where the timing will be from one cylinder to the next.
Mar 10, 2020, 04:31 AM
Still gassin' it.
No idea how racing ignitions work but RC stuf seems to work a bit different: The sensor is connected via a non-reversible plug, no wiring errors possible unless you make an effort to...

There is one magnet oriented with North polarity, it serves to indicate the beginning of the ignition sequence, and is place "after the last cylinder, but somewhere before cylinder #1" (usually bang in the middle between those two). Then there are several magnets with south polarity, that each indicate the trigger point for the individual cylinders.
Upon powering up, the ignition fires all plugs simultaneously on the passage of a south pole magnet (or so I am told), until the first time it sees the North magnet. From then on it only fires the next plug in the "crankshaft-order", starting from #1 upon each magnet passage.

It does not actually see which cylinder is in top, it just assumes that when (for example) after the North magnet has passed, the 1st next passage is #1, the 2nd next passage is #2, etc etc.

As long as the crankshaft is spinning in one direction, the correct cylinder will fire at the correct time. Turning the crank over backwards while the ignition is powered up, will confuse the ignition sequence of course, but I have never noticed this to lead to any undesired effects.


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