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Can't adjust ignition timing enough - belt a tooth off? - Engine & Ancilliaries/Gearbox - The Lotus Forums Jump to content
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Can't adjust ignition timing enough - belt a tooth off?

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Need some advice folks. Just finished changing the timing belt on my Eclat. Fired it up and didn't hear any sounds of pistons against valves so was happy with that! Brought it up to operating temperature to check the timing.

With my distributor fully adjusted one way, I'm only getting ignition timing at 0 degrees TDC, when I know it should be around 8-9 degrees at idle. Am I right in thinking that the ignition sprocket is likely a tooth off, and is there any way to adjust for that without taking the belt off again? For reference, I'm using Powerspark electronic ignition timing in my distributor instead of the regular points.

Thanks in advance for any advice you can offer. Was all going so well until I checked the ignition timing with a timing light :(

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Before you adjust the belt, make sure the advance module hasn't been disconnected (by knocking a vac pipe).

If you have to adjust the belt, you don't need to remove it completely, Get some plastic (about as strong as a credit card, or a little less rigid) approx 6 inches long and 1.5 inches wide. Feed it into the gap between belt and dissy sprocket, by turning the engine over by hand (using spanner on crank). Once in, put the car in gear and gently rotate the dissy sprocket with a spanner. The belt will naturally turn with the sprocket until you put eh extra force into play, then the plastic should give enough for it to slip that tooth (or 2). Once re-aligned, take it back out of gear and again rotate engine to get plastic out.

I was thinking two teeth, 40 teeth (IIRC) per engine rotation, so 9 deg = 1 tooth but you don't want to be right at the end of the adjustment, so two should get you back to the middle of the range that the dissy can be rotated (and still get he cap on and off).

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36 minutes ago, andydclements said:

Before you adjust the belt, make sure the advance module hasn't been disconnected (by knocking a vac pipe).

If you have to adjust the belt, you don't need to remove it completely, Get some plastic (about as strong as a credit card, or a little less rigid) approx 6 inches long and 1.5 inches wide. Feed it into the gap between belt and dissy sprocket, by turning the engine over by hand (using spanner on crank). Once in, put the car in gear and gently rotate the dissy sprocket with a spanner. The belt will naturally turn with the sprocket until you put eh extra force into play, then the plastic should give enough for it to slip that tooth (or 2). Once re-aligned, take it back out of gear and again rotate engine to get plastic out.

I was thinking two teeth, 40 teeth (IIRC) per engine rotation, so 9 deg = 1 tooth but you don't want to be right at the end of the adjustment, so two should get you back to the middle of the range that the dissy can be rotated (and still get he cap on and off).

That's a nice idea! Thanks. And I've got too many credit cards anyway, so this will be a good use for a couple of them.

In the centre of adjustment my ignition timing was after TDC, so that would mean I'd need to rotate... anticlockwise by a couple of teeth??

Will have to find some way of getting  purchase on the dissy sprocket as the end is rounded so a spanner wouldn't work, but I should be able to think of something 

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A round bar through one of the holes, to a place on the engine, and it will act ass a lever.

 

If you had a manual tensioner, I'd have just said slacken and do it that way, but the semi-auto is a PITA but at least it does allow that extra bit of belt movement.

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Forgot to follow up on this. That credit card trick worked a treat (although I'm dubious if the cards will now work contactless anymore!)..I went too far at first but then got it back around. Most difficult part was getting a lever on the gear so it would turn. Managed it in the end and timing now spot on.:)

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