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Ignition timing

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wikkadoo500
Crotch Rocketuer
Crotch Rocketuer

Posts : 33
Location : Leicester

Ignition timing

Post by wikkadoo500 on Thu 07 Feb 2013, 4:49 pm

Need help!!

Recently replaced head gasket and began reassembly.

Like an idiot, I moved the crank several revolutions before refitting the camshafts.

I know there are 2 rotations of the crank per ignition cycle.

I have lined up the "O" and refitted the camshafts, but I don't know if I should have turned it another revolution until the "O" appeared again in order to maintain the timing.

Is there any way I can determine if the timing sensor is in the correct place.

Obviously, if it won't start (Not fully assembled enough to test yet.) then I suppose I have refitted the camshafts incorrectly.

Would swapping round the HT leads help, so at least then I would know to realign the cmashafts?
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eternally_troubled
Admin
Admin

Awesome!
Posts : 3639
Location : 'ere be fens. (near Cambridge)

Re: Ignition timing

Post by eternally_troubled on Fri 08 Feb 2013, 1:30 pm

Firstly, don't worry.

Secondly, I assume that you have (or have downloaded) the Haynes manual? If not, then get one (there is a link at the top of the workshop section).

As suggested by Haynes, replace the camshafts in the 'O' position, making sure that you can see the 'O' through the timing inspection cover.

Replace the cam chain tensioner.

Rotate the engine so the 'T' mark is visible and check that 'IN' and 'EX' line up as per this diagram:





This is the valve clearance checking point for no 1 cylinder and hence is near TDC (top dead centre).

So if your no.1 cylinder isn't near TDC with the cams in the position shown above, you've got it wrong.

I think I have got this right from my memory of doing my valve clearances - everyone else agree? (I could be wrong! I have been before...)
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teamster1975
Admin
Admin

Posts : 2455
Location : Woking, Surrey

Re: Ignition timing

Post by teamster1975 on Sat 09 Feb 2013, 1:57 pm

Looks good to me, I'll sticky this one ET!
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jimt_thenoo
Newbie
Newbie

Posts : 4
Location : Motherwell

Re: Ignition timing

Post by jimt_thenoo on Tue 21 Oct 2014, 11:05 pm

Another tip for finding the correct top dead centre.

In between bikes I have rebuilt two 3Litre V6 essex engines for two Reliant Scimitars. If the distributor was removed its easy to refit it 360 degrees out, and therefore it will never fire. The hard way to find which is the correct top dead centre is to take the rocker covers off and with a pencil down the spark plug hole confirm when both inlet and exhaust valves are closed at the top of the stroke then you have got top dead centre. Having done this once too often and not wanting to go to the bother of doing it all again to find TDC I came up with this easy way to find out.

At the wrong TDC there will always be a valve(s) slightly open due to the overlap at end of exhaust stroke. 360 degrees later both inlet and exhaust valves will be closed at TDC for the firing stroke.

If you get a short length of 25mm or so radiator/ heater hose and push one end up against the spark plug hole so that it seals it, then blow in the other end one of two things happens. Either you blow through with no resistance, i.e valve open therefore the wrong TDC, or you blow and get resistance as if trying to blow up the hose like a balloon, therefore valves are closed and the correct TDC for the firing stroke and ignition.

The example given was for a car engine but should translate for the CB500 engine or any 4 stroke engine.

Hope this helps,
Jim

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Beresford
the 900
the 900

Posts : 1408
Location : not that far from Kirkistown

Re: Ignition timing

Post by Beresford on Wed 22 Oct 2014, 1:10 am

@jimt_thenoo wrote:Another tip for finding the correct top dead centre.

In between bikes I have rebuilt two 3Litre V6 essex engines for two Reliant Scimitars.
Jim


This takes me back. I've been through a Reliant phase and survived with my sanity. In the dim past I've done engine and gearbox rebuilds on 4 cylinder Consul engined Sabres, 6 cylinder Zephyr/Zodiac engined Sabres and Essex engined Scimitars. Even a Robin gearbox once. Also Mays headed racing Sabres with their ZF gearboxes. We were all mental once  Shocked    
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jimt_thenoo
Newbie
Newbie

Posts : 4
Location : Motherwell

Re: Ignition timing

Post by jimt_thenoo on Thu 23 Oct 2014, 9:43 pm

Beresford, you need to get an se6b scimitar with the cologne V6 engine, rebuild it and that will be complete set!

Sorry forum - off on a reliant tangent here!

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