I have a ZDZ 40 RE.
I am trying to install the ignition sensor.
I have read the instruction and they look pretty easy.
The only question I have is how do I locate exactly TDC on the piston.
I have turn the shaft around, and I can see the piston through the exhaust opening, but it's difficult to locate TDC perfectly.
Is there an easy way to do it, or you have to just "guess" the best you can?

Thanks for all the help

I use a rather crude method of installing a depth gauge through the spark plug hole and resting it on top of the piston in conjunction with a degree wheel, and the lowest measurement on the gauge is TDC. Rocking the prop hub a little each way without any movement from the piston give me a zero point.

I'm quite sure that someone will chime in and give a much more accurate way of doing it.

Karol

You can make a positive stop from an old spark plug by breaking out the insulator and related pieces to leave just the shell. Then you can either weld in a round dowel or thread the inside of the shell and use a bolt screwed into the old plug shell to create a positive stop for the piston. With the degree wheel mounted rotate the engine all the way one direction until the crank stops. Take note of the position on the wheel, then rotate the engine the opposite direction until it stops again. Note the position on the degree wheel again. TDC is halfway between the two points noted on the wheel. There are a number of other ways to make a positive piston stop such as using a lathe to cut one from bar stock etc. They can also be purchased if one desires. I have two, one made each of the two ways I have mentioned using an old plug shell. I made the first using the tap and bolt method and the second by welding in a piece of round stock when I couldn't locate the first in a timely manner. Good luck with yours.

You can also use Jezmo's method with a wood dowl placed in the exhaust port.

Just take a popsicle stick,small dowel,bamboo skewer,anything that will fit down the spark plug hole.Turn the engine over until the stick doesnt move up anymore.Then rock the crank to the left and right and when it doeesnt move anymore your at tdc.(just eyeball it).Youll never get true TDC because the piston doesnt move 2-3 degrees as its rocking or moving to each side of center.Youll be close enough.

I leave the spark plug in /mount the deg wheel, They will be from 10-15 deg of play at top dead center, Rotate the deg wheel both way's to see how much lose play you have and center of that is top dead center, If you have 10 deg of play then you should have 5 deg of play on both sides of zero for top dead center

As mentioned, it's pretty difficult to get TDC exactly unless you use a degree wheel, but it isn't really necessary either...[8D]

Just line up the trigger in the hub with the casting rib that is on the engine's left side as you look at it from the back. Normally I just tell people to use the side opposite the exhaust, but since you've got an RE, that doesn't work!

Now if you've got any kind of an eye for lining stuff up straight, this will get you well within acceptable limits and is the way everyone I know with a ZDZ does it. Works just fine.

Of course you could use variations of any of the methods mentioned, or there is something similar on ZDZ's website.

Doomking,

You do not need to find TDC. The following works well, as recommended by RC Showcase, for positioning the pick-up on a 40 RV. The RE may have different timing, I do not know.

Place the engine on your bench with the prop-drive facing you and the exhaust port down. You will be looking directly down on a web cast into the side of the case. Measure 6mm to the right of the center of the web. Make a mark there. Mount the pick-up centered over that mark.

You got it!!

CH Ignitions has good tips on finding TDC in the "Timing" section of the installation instructions:

http://www.ch-ignitions.com/CHinst.html

M'self, I usually use a dial indicator inserted thru the spark plug hole for finding TDC.

--Bill

Funny that nobody has mentioned using a dial indicator. That's the most accurate and can be obtained rather inexpensively from some of the tool supply houses. You'll find it useful again the first time you crash and you want to check to see if the crank was bent...