No Timing marks on flywheel

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jamiefixit
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No Timing marks on flywheel

#1

Post by jamiefixit »

OK, so my attempt at installing the electronic ignition got interesting today. I pulled the inspection plug to align with the full advance front cylinder mark and guess what, there isn't one. There is only one set of marks that look like they've been made by hand with a punch when the motor was disassembled in the 90's. It happens somewhere before TDC on the front pot but that's all I know. So.... I got to work out a way to find out exactly where 35 degrees before TDC is right? Cos as I understand it that is the full advance point and that's where the Electronic Ignition needs to be set to apparently.

So given my dliemma, I was considering doing the following and then seeing if anyone has any other suggestions.

1. Turn the crankshaft (I have open belt primary) until the front cylinder is at TDC on the compression stroke, which I should be able to ascertain by poking a screwdriver into the spark plug hole and waiting until I feel it stop going up... ?
2. Line up a peice of card that I've already made which has a line for TDC and another for 35deg BTDC, on the crankshaft and with some other fixed point on the bike so I can track movement.
3. Rotate crankshaft back about 45 deg or so and then forwards until the 35 deg mark I drew lines up with the fixed point on the bike. The flywheel should now be at 35 deg BTDC on the compression stroke.
4. take a drill and make a mark on the flywheel through the inspection hole (because hitting it with a punch from the side probably not a good idea for the main bearing etc).
5. Set the Electronic Ignition to that point as instructed.

Can anyone improve on that? Obviously I don't want to take the engine out. It would help to know at how many degrees the normal fully retarded point on the flywheel is too.
nmaineron
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Re: No Timing marks on flywheel

#2

Post by nmaineron »

Don't use a screw driver to find TDC,use something soft like a straw...you really don't need to mark the flywheel,you can use the alternator shell,makes it much easier when you use a timing light,no more oily mess ...
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Re: No Timing marks on flywheel

#3

Post by jamiefixit »

Heythanks. Notsurehow to use rhe alternator shell though... will it be obvious once i have fiddled a bit?
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Re: No Timing marks on flywheel

#4

Post by kitabel »

The concept is sound, but piston movement around TDC is really small, only a few thousandths of an inch per degree.
jamiefixit
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Re: No Timing marks on flywheel

#5

Post by jamiefixit »

Hey thanks. Any other inspiration for finding TDC?
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Re: No Timing marks on flywheel

#6

Post by john HD »

kitabel wrote:The concept is sound, but piston movement around TDC is really small, only a few thousandths of an inch per degree.
Correct! A straw or a screw driver is not going to give you a good reading.

You will need to find a way to get a dial indicator mounted in the spark plug hole. Back in my 2 stroke days I used to hot rod Yamaha RD400s I set the timing with a metric dial indicator inserted in an adaptor in the spark plug hole. Timing on those bikes is set in 100ths of a millimeter BTDC.

I would imagine an enterprising individual could replicate this. There may be kits available.... fire up the google.

Once you find your TDC then you can use a degree wheel to do it in degrees. Mount the wheel on your drive sprocket, used modeling clay to hold a pointer and reverse the motor until you hit 35 degrees. Mark your flywheel and set your timing.

john
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Re: No Timing marks on flywheel

#7

Post by RUBONE »

Find the end of upward travel (with a degree wheel fitted and note the reading) and then find the beginning of downward travel (once again note the reading). Subtract the smaller number from the larger for a total number of degrees between those points. Divide in half. Move crank to the halfway point. You are now within a couple degrees of actual TDC. Set the degree wheel to zero. Rotate in the direction of engine rotation just past 35 degrees. Rotate backwards to take up gear lash and stop at 35 degrees. Set timing. Put a paint mark or something on the alternator rotor to align with zero for future checking. You may need to tweak a couple degrees one way or the other to make your particular engine happy.
Have fun!
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Re: No Timing marks on flywheel

#8

Post by 58flh »

You can also use a Degree-wheel With the Dial-indicater & Get all your marks! From TDC,BDC,35 degrees & so on.As a plus you can tune exactly by measuring your cam absolute lift & BOTTOM-overlap of intakes & exhausts.But I think at this stage GO SIMPLE!!.GET it started,Thats most important!.You asked if you would mess anything up by marking your front Pully!--Short answer is NO!/Just make sure your where you want to be & take a file-small millsmooth & just V-it where the pointer is at!---The olny thing that will see it is the Strobe when setting your timer.Its simple & fast & CLEAN!----Richie
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