Top dead centre?

[sharky]

How do you get TDC on a ZXR400?

[howdamnhard]

Remove the sparkplugs, put a thin stiff piece of wire/rod down the hole and turn the engine over slowly until the wire sticks out the most. If you have a shop manual use that to line up the timing marks.

[bogan]

Remove the sparkplugs, put a thin stiff piece of wire/rod down the hole and turn the engine over slowly until the wire sticks out the most. If you have a shop manual use that to line up the timing marks.

I wouldnt use the wire methode, sounds pretty inacurate, there should be timing mark on the stator somewhere, obtaining a shop manual is always a good idea.

[zx rider]

The ZXR family of engines usually has the timing marks (on the ignition rotor) on the r/h end of the crank. See the small black cover there, remove it and there are 2 marks on the rotor. The first is the firing (advanced 5-10 deg) and the 2nd is TDC. Happy tuning

[sharky]

The ZXR family of engines usually has the timing marks (on the ignition rotor) on the r/h end of the crank. See the small black cover there, remove it and there are 2 marks on the rotor. The first is the firing (advanced 5-10 deg) and the 2nd is TDC. Happy tuning

Sweet. I'm doing valve clearances. Says position "#4 piston TDC at end of compression stoke" How do I know when that is? Also do I just put a socket on the end of it and turn it over by hand?
Previously I have just put it in a position so that the cam lobes are pointing up - is this a safe method?

Cheers

[Taz]

Compression stroke is when the cam has finished opening and closing the intake valves and has yet to get to the exhaust valves. Make sure you're turning the motor forwards.

[CookMySock]

Previously I have just put it in a position so that the cam lobes are pointing up - is this a safe method?

I, too, am interested in an answer to this question.

Steve

[Hoon]

Yeah thats all I do. Just measure the clearance when it's off the lobe.

[bogan]

yeh if you are just doing valve clearances it doesnt matter exactly where the piston is, as long as its on no movement part of the lobe.

[Naki Rat]

Many moons ago I had an RD 400 that required the spark at 19 thou' before TDC, (twice as it had a set of points for each cylinder). We used a dial guage which is a way fancier version of the 'bit of wire'.

We found TDC (to the nearest thou') and then backed up 19 thou'. Then same for other cylinder.

First time we tuned it that way the RD all but put me and pillion over the back as we mono'ed up the road after State of tune only lasted a few days though

[craisin]

a piece of wire is fine as long keep it at the right angle a skinny scewdriver maybe easier to handle

[pete376403]

There can be quite a lot of crank rotation while the piston appears to be not moving at TDC. Also factory provided marks may not be exactly accurate. To check to true top dead centre, make a stop that will contact the piston a bit before it reaches the top of its travel (eg a 5 mm down the bore). You also require a reference pointer at the edge of the flywheel. Rotate the engine untill the piston contacts the stop. Mark the flywheel in line with the pointer. Now rotate the engine in the opposite direction until the piston touches the stop. Mark the flywheel again. Measure the distance between the two marks. Halfway between the two marks will be true top dead centre. A bit of work but if you want accurate ignition or injection pump (diesel) timing this is a way to do it.