How to find TDC easily ?
 

To change a CCT we have to find the "good TDC" for each cylinder.
For one cylinder, the good TDC is when the intake and exhaust valves are closed (no tension on valve spring) : end of compression stroke.
the "bad" TDC is at the end of exhaust stroke (exhaust valve opened).
We can see these two different TDC at the fly wheel (FT mark for the front cylinder).

At 6th gear, turning the wheel, we'd be able to feel the compression stroke (difficult to turn the wheel) of the two cylinders.

If we know which cylinder fires first ccw, we can know which cylinder is at compression stroke and then know which cylinder is at "good TDC".

Checking FT or RT mark at the fly wheel would confirm us that we are right... isn't it ?

Is there a way to find TDC ?
Which cylinder fires first ?
Does the motor run counter-clockwise ?
What is the timing between the compression strokes of the two cylinders ? 1/4 turn, 3/4 turn, 1-1/4 turn, 1-3/4 turn ? cw, ccw ?

Re: How to find TDC easily ?
 

Not to poke fun ....but I had to laugh as I read this.

Which cyl fires first??

Reminded me of a chicken and an egg story I once heard.
Good luck on the timing issue.....seems I'm no help here......


















Mike

Re: How to find TDC easily ?
 

Just remembered....Gerrit did a piston install....he may chime in to help ya out...

Good Luck
Mike

Re: How to find TDC easily ?
 

I mean... I want to know if it goes something like that :

Beeing at the left side of the bike, motor is running ccw at the fly wheel, ccw at the rear wheel, timing is 0° Rear cylinder fires, 450° (1 turn 3/4 ccw ) front cylinder fires.

Based on what I read in other posts, is this the correct timing ?

Rear :
0° : Rear at "good" TDC, both valves closed, end of compression stroke
180° : Rear at BDC, end of explosion stroke
360° : Rear at "bad" TDC, exhaust valve opened, end of exhaust stroke
540° : Rear at BDC, end of intake stroke

Front:
90° : Front at "bad" TDC, exhaust valve opened, end of exhaust stroke
270° : Front at BDC, end of intake stroke
450° : Front at "good" TDC, both valves closed, end of compression stroke,
630° : Front at BDC, end of explosion stroke

Front and rear share a common journal for the connecting rods. So front and rear are always 90 (270) degrees apart.

Engine spins forward, so TDC for the rear is 270 degrees after TDC for the front.

So timing goes like this:
Front TDC at 0 degrees
Rear TDC 270 degrees later
Front back at TDC 450 (360 + 90) degrees after rear TDC.

TDC referring to the compression strokes.

Helpful?

Re: How to find TDC easily ?
 

Yep ! Great !

Re: How to find TDC easily ?
 

So the timing goes like this :

Front :
0° : Front at "good" TDC, both valves closed, end of compression stroke, FT Mark
180° : Front at BDC, end of explosion stroke
360° : Front at "bad" TDC, exhaust valve opened, end of exhaust stroke
540° : Front at BDC, end of intake stroke

Rear:
90° : Rear at BDC, end of intake stroke
270° : Rear at "good" TDC, both valves closed, end of compression stroke, RT Mark
450° : Rear at BDC, end of explosion stroke
630° : Rear at "bad" TDC, exhaust valve opened, end of exhaust stroke

Would it be possible that TDC for the rear would be 270°+360° later than Front TDC with such a V90 motor ?

Re: How to find TDC easily ?
 

Can't you just take off those little plugs on the left side crank case and it tells you through the viewing window?

That gives you a 50% chance of getting it right... 8)

Re: How to find TDC easily ?
 

Then you look down the spark plug hole?

Re: How to find TDC easily ?
 

no still 50% ..... There is 2 different TDC per cylinder, then the spark hole does not help...
You must find the TDC at compression stroke. To feel it you must leave the spark plug.

Re: How to find TDC easily ?
 

Look at : https://www.superhawkforum.com/viewtopic.php?t=1502
:wink: