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 Post subject: otto and minis (help!)
PostPosted: Fri Aug 10, 2007 11:20 pm 
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848cc
848cc

Joined: Wed Jun 29, 2005 11:51 am
Posts: 464
Location: North East melb
Realllly basic question here guys. I'm a little embarrassed to be posting it, but i am completely baffled!

When cylinder 1 is at TDC, its valves should be rocking ? ie. one valve has just closed, the other is just opening, right?

Thats what I've been reading, i would have thought that at TDC cylinder one would have both valves closed, because its just had the intake cycle and has just sparked.

I am completely baffled, i even started to think that maybe the cylinder closest to rad was cylinder 4 instead of cylinder 1, and i have had it wrong all these years. All this time i've claimed that there were no timing marks on my flywheel, but I've taken the cover off to check, and they are there! (just in a completely different spot to what i expected). Perhaps I'm wrong!

As it stands, I've just pulled my engine out and have redone the timing chain because i wasn't confident it was spot on. When the dots are aligned, cylinder one (rad side) is at its top, the crank key is @ 12 o clock, and the camshaft key is approx at 1 oclock, the gears dots are lined up. The rocker gear on top of cylinder one has just closed one valve and is almost about to open the other valve. Is this correct??

It can be no other way in order for the dots to line up on the timing gear, but i thought maybe my camshaft had been keyed in the opposite spot or something.

Please help confirmed or deny!
its all reassembled again and ready to drop back in.

THANKS


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 Post subject:
PostPosted: Sat Aug 11, 2007 9:51 pm 
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1098cc
1098cc
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Joined: Mon Sep 12, 2005 11:48 pm
Posts: 1842
Location: Hobart, Tasmania
Its a 4 stroke so there's two TDCs one at the end of the compression stroke/start of the combustion stroke, when both valves are closed. The second TDC is at the end of the exhaust stroke/start of the combustion stroke, where the exhaust valve is closing and the inlet valve is opening.

Tim

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 Post subject:
PostPosted: Sat Aug 11, 2007 11:28 pm 
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Bimmer Twinky
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Joined: Mon Sep 06, 2004 4:36 pm
Posts: 8606
Location: Brisbane
Deleted, the way you`re doing the cam timing is right & yes at the point where you set "Doit to Dot" it will be firing on #4 cyl

The marks on your flywheel being in the wrong spot is most probably because some goon has pulled the 2 pieces of the flywheel apart at some stage & has bolted it all back together in a diffent orientation.

Now tell me that you have a one piece flywheel & i`ll just shut right up :-)

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

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 Post subject:
PostPosted: Sun Aug 12, 2007 12:49 am 
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848cc
848cc

Joined: Wed Jun 29, 2005 11:51 am
Posts: 464
Location: North East melb
some goon indeed!
thanks guys, its running bootiful now :)


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