finding tdc

[ogh11756]

Hi guy's,
I been working on hardtailing a 77 xs650 in my spare time for a few months now.
I have the rolling frame about done and will be starting the engine soon.
I bought the bike as a non runner, it was in a shed for about 15 years before i bought it.
It turned over smooth with the kicker and seemed to have decent compression.
The engine side covers were off and the stator & rotor had been pulled and in a box.
I will be doing the Pma/Pamco/Capacitor conversion but need to know if finding tdc for that conversion is going to be a problem. Does the Pma/Pamco find its own timing?
I did a search but didn't come up with a match to my question.
Thanks for the education i am about to receive.

 

[I am Carbon]

finding TDC is as simple as pulling the sparkplugs
then rotate the engine while looking into the sparkplug hole for the piston to rise to the top. when it gets close to the top you can poke something into the hole and let it rest on piston "a dial indicator setup is the best way to get it perfect" when it gets to the top you will know because after the top it will go back down. If I just want a general idea I use a 12" bamboo rod. the ones for barbeques.
PS only rotate in the normal way the engine turns , not backwards

 

[ogh11756]

finding TDC is as simple as pulling the sparkplugs
then rotate the engine while looking into the sparkplug hole for the piston to rise to the top. when it gets close to the top you can poke something into the hole "a dial indicator setup is the best way to get it perfect" when it gets to the top you will know because after the top it will go back down. If I just want a general idea I use a 12" bamboo rod. the ones for barbeques.
PS only rotate in the normal way the engine turns , not backwards

Thanks, sounds easy enough.
Does it matter which cylinder?

 

[I am Carbon]

well I would use the left side because that the side You will be working on.
but the pistons come up at the same time so it in fact does not matter. Unless You have a rephazed engine then the pistons come up at different times

 

[Paulrxs650]

Hi

Few methods used for finding TDC:

1. Pop the plugs out and put a long screwdriver or rod down the bore, turn the engine over, find the highest point on the piston stroke, then mark that on the rotor against a corresponding (or original mark) on the casing

2. More accurately you can use the dead stop method, for which you will need a degree wheel (google images, download and print) and a spark plug with an 1 1/2" added on the end (you want it to interfere with the top of the piston). Pop both plugs out, attach the degree wheel to the rotor and bolt a piece of hard wire to the casing to act as a pointer for the degree wheel. Screw in your elongated spark plug and GENTLY turn the engine over anti clockwise until the piston bumps into the extended spark plug. Note the reading on the degree wheel. The turn the engine back the other way, clockwise, until it bumps again, note the reading. the, simply half the two readings i.e if one reading was 0 and the second was 40, you would want 20. Pop the plug out and turn the engine to the reading in the middle (eg 20 and that is TDC. Mark up the rotor and casing as above - done

3. Use a dial gauge long enough to go into the bore, touching the piston at TDC. Simply rotate the engine until you note the shortest measurement and mark up as above

 

[Paulrxs650]

And as Carbon says (Hi Carbon by the way ) use the left side (rotor side) piston for TDC

 

[I am Carbon]

Hey Paul , I know you have been riding that Beamer.
Good to know your alive n kickin.
ogh11756 , Here is a degree wheel for you just copy and print pout the size you need it

 

[XSLeo]

If you have the stock rotor install it with the proper key. Install the stock stator. You now have all you need to get to TDC. Turn engine till the stock marks line up. Now remove Stator and rotor without turning the engine.
If you are using a PMA kit with the sticker that goes on the left side cover, install the sticker on the cover.
Install the PMA rotor on the engine, I would use a key so I only had the mark the PMA rotor once.
Install the left cover. Now put a mark on the PMA rotor that lines up with the TDC mark on the sticker.
You now have repeatable timing marks.
Leo

 

[grepper]

Thought this was a cool way too.
http://hughshandbuilt.blogspot.com/2012/12/tdc-and-how-to-find-it.html

 

[Take Warning15]

Not to hijack, but I always see that people say never turn the engine backwards. Why is that?

 

[ogh11756]

Thanks to all who responded.
I have gotten great advice, love this forum.