Anyone know how to design a program for a calculator to print a flywheel timing tape

[rsss396]

That's a good idea about affixing a permanent indicator. First off, I really want to see where my timing was, when she ran last. Your so right about the importance of the readings.
For example, if the CR flywheel is 4" in diameter, that would translate to .035, for each degree. Not a lot to work with. I will have to make my index marks, much thinner. :pride:

yeah just use a flat piece of 1/8 alum wide enough to span the distance of the 2 old pickup coil threaded holes, drill the holes first and adjust the length so the plate is very close but not touching the flywheel.
Once mounted make a mark on your plate at the point where the flywheel is closest to the plate. Now make to angled cuts from that mark to create a pointer.
Once this is done take a dial indicator and put the piston at TDC, then without moving anything mark the flywheel inline with the pointer.
This now your new timing point that will indicate TDC or "0" , now with your new timing tape that you have made take some clear tape and apply it to the flywheel with the "0" on the tape inline with the "0" on the flywheel.
Now with a standard timing light you can check your timing, but now you should also have a tach of some sort so you can compare the timing/rpm relationship and plot it against my graph.
There may be issues with timing lights that have a advance feature, I am not sure it will be accurate or not, I think the simpler cheaper lights maybe the better choice on a 2 stroke motor

[trxminus]

I'd say use a string and wrap it around to figure out circumference. Then use an online tool like this: http://calcurator.org/circumference-calculator/ to figure out the diameter

[Jerry Hall]

I prefer to paint the outside of the flywheel with Dykem layout die or you could spray the outside of the flywheel with paint.  The tape will often come off at high RPMs and most printers will not print to scale.  The are a lot of ways to find TDC.  The positive stop method is more accurate than using a dial indicator. Measure the outside diameter of the flywheel, multiply the diameter by 3.412 and divide by 360 for 1 degree increments.

Example:

For an TRX250R OEM flywheel, the outside diameter is 111.5mm

111.5 x 3.142 / 360 = .97mm is the distance between marks when 1 degree increments are desired. 

Your 1st mark @ .97mm, 2nd mark @ 1.95mm,  3rd mark @ 2.92mm ..............10th mark (10 degrees) @ 9.73mm,  20th mark (20 degrees) @19.46mm.  As you can see the OEM flywheel mark spacings of 1 degree are spaced approximately one millementer apart.



1. Find TDC and scribe a mark on the outside of the flywheel

2.  Wrap a 1/4 wide metric tape measure tightly around the outside of your flywheel.

3.  Scratch you lines at the degree increments that you chose.


I would make your marks from TDC to no more than 25 degrees BTDC.  All of the good running 250cc to 370cc engines I have had to create/optimize timing curves for, usually fall in the 10 degree to 25 degree range. Anytime the curve falls outside of that range, the pipe and or head is usually screwed up.  The zero to 10 degreed range is only needed to monitor the timing at cranking RPMs.


I use 1 degree marks on the machined degree plate on my ignition dyno because the plate is approximately 7" in diameter which makes it about 1.5mm between marks of one degree.  The RPMs are easier to control on the ignition dyno that a running engine in neutral.  The engine RPMs are also much easier to control on a running engine if you have the bike on a rear wheel dyno and in 3rd or higher gears.

I usually place my marks every 2 degrees because one degree increments are difficult to read on a running engine with a flywheel of 100mm diameter or less.  Some of the small rotor ignition may need 3 to 4 degree spacing between marks

[Hawaiiysr]

Post back from the dead. Great info

[wilkin250r]

It might actually be easier to make an adhesive timing wheel.  The beauty of it is that you wouldn't need to know the actual circumference, and calculations like a timing tape around the outside of the flywheel.  Timing and degree marks would extend outwards as far as needed.

With a printable design, you can buy a dozen shipping labels at Walmart for $3, and print as many as you need.

Forgive the crudeness of the image, I didn't feel like spending more than 4 minutes with Photoshop.  You get the idea.