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Re: Top Dead Centre
Posted: 12 Apr 2010, 10:26
by ghost123uk
From another post re this a few weeks ago =
ghost123uk wrote:Take all the plugs out.
Stick your thumb firmly over number 1 cylinder.
Get a friend to turn the engine over with a spanner (not the starter motor
)
Stop when you can feel compression building up against your thumb.
Then get a large "Tie Wrap" or similar plastic bendy thing.
Carefully insert it into the plug hole until it touches the top of the piston.
Then gently turn the engine over (slightly back and forth if need be) till you get to the position where the Tie Wrap is as far out as it can go. = TDC on the firing stroke (works for all 4 cylinders of course too)
Don't insert anything into the plug hole that might jam up and damage threads, pistons, valves etc - Like don't use a screwdriver, or anything that might break off, like a pencil or Biro !!
~~~~~~~~~~~~~~~~~~~
p.s. = I did it on an old BSA 500cc single motorbike once, with a pencil, and it did break off.
I though flip it, and fired it up anyway. It ran, coughed a few times (wood stuck in the valve seats) - chucked a few bits of mangled wood chips out of the exhaust, but was non the worse !!
Re: Top Dead Centre
Posted: 12 Apr 2010, 11:21
by albertramsbottom
Cheers
I have just had a look and will try tie wrap thingy in a while
However, looking at my Dizzy with the cap off I was wondering what the little line is on the side of this dizzy case. Is this supposed to be TDC mark becuase if it is then somthing is wrong
See pic below with the rotor arm over Cylinder 1 HT Lead, note the red line on the dizzy case. What is this for. Currently I would have thought that with the position of the rotor arm over ht lead 1 and would have thought that I should be at TDC (if everything is right).
IMG_0184.JPG
Also there is a small triangle mark on my dizzy cap, on the bottom lefthand clip goes as opposed to the top righthand clip. What is this for? Could it be posible that the dizzy cap is 180 degs out? I dont think so as the cap only seems to fit properly in its current position
Cheers for everyones help
IMG_0185.JPG
Re: Top Dead Centre
Posted: 12 Apr 2010, 12:03
by Red Westie
As you say.....when No1 piston is on TDC the rotor arm SHOULD be pointing roughly at the line you have marked in RED.
You plug leads and distributor shaft must be wrong.
As for the cap....there should be a detent lug one side of the cap that fits into a corresponding indent in the distributor...as long as these are together?
Sounds like things are a little messed up and you need to start from scratch with the distributor/leads and TDC markings on the crank pulley/and or flywheel.
You mention a plastic dial on the flywheel....do you mean plastic dial on the front pulley?
Martin
Re: Top Dead Centre
Posted: 12 Apr 2010, 12:40
by albertramsbottom
Red Westie wrote:
You mention a plastic dial on the flywheel....do you mean plastic dial on the front pulley?
Martin
Yes i did. So things are a little messed up here then. It allways run before as it is currently set up but I have had serious overheating issues which I feel could be due to the timing being to far retarded or advanced.
So I def need to find TDC then?
I must admit im have issues with this as with the rotor arms current position which should be TDC, if i put a screw driver in clyinder 1 and turn by hand a little something gets caught (Easy does it abert, dont wanna damage anything). Its this geting cuaght issue suggets that its the valves that the screw driver is catching. They should a shut on compression stroke so it shouldnt be possible to get my screw diver stuck
Cheers, gonna try the cork idea this afternoon
Albert
Re: Top Dead Centre
Posted: 12 Apr 2010, 13:18
by bigherb
To get the basic set up remove the rocker covers from both sides, turn the engine over until the valves on number three cylinder are rocking, i.e one valve has just closed and the other valve is just opening. that point is close to TDC for number one cylinder. Confirm by checking the valves on number one cylinder if you rotate the crank backwards and forwards around this point the vales should not be moving. If you still can't find a TDC mark on the belt pulley To find the exact TDC, the centre of the woodruff key in the crankshaft that holds on the fan is inline with TDC when that is exactly 90 deg to the right of the crankcase centre line number one is at TDC. It is easiest to remove the fan to check then you can easily see the crankcase centreline.
Re: Top Dead Centre
Posted: 13 Apr 2010, 08:12
by albertramsbottom
Thanks bigherb ill give it a go
