Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Rolfbulmer on May 11, 2022, 08:50:09 PM
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Hi guys,
So my bike currently has no battery, ignition switch or power. But, I want to check the ignition timing and was wondering if it is in any way possible to do this without any ignition or power.
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Use a multi meter
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The "Fag paper" method is simplest without anything special to do it.
Open the points with your fingers, put fag paper in between, let points clamp paper. Then lightly pull on the paper while turning crankshaft until you feel the paper just start to release as the crankshaft lobe begins to lift the points. This is the firing point of the ignition literally as the points start to lift and should line up with the F mark on mechanism.
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Thanks odd job.
Simple lad that I am could you explain exactly how to do this with a multi meter please.
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Thanks k2-k6.
I will certainly give that a try.
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Multi meter method ;- set to continuity with "beep" to confirm the circuit, remove wire from points to coil and attach one lead to that, the other lead to engine cases (earthing) all the time the circuit is connected it will beep, meaning not firing, as soon as the beep stops when turning crankshaft that's the firing point of timing.
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Multi meter method ;- set to continuity with "beep" to confirm the circuit, remove wire from points to coil and attach one lead to that, the other lead to engine cases (earthing) all the time the circuit is connected it will beep, meaning not firing, as soon as the beep stops when turning crankshaft that's the firing point of timing.
That's how it's done. If your multimeter does not feature 'a beep continuity' position, select Ohm and observe the digits go from 0 (closed) to I (open) or the dial move (analogue). Important is to disconnect the wire from the breakerpoints to the coil.
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Thanks guys. Just what I needed, a clear set of instructions. I am looking forward to giving it a go.
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Here's my high tech version
(https://imagizer.imageshack.com/img924/3661/RuZPOU.jpg)
Cheers
Den
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If the adjustment range on rotating the back plate won’t seem to accommodate the firing point, it’s often just a question of adjusting the points gap (to smaller I think) as this makes a sizeable difference to the firing point.
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I found a good picture of my setup on my Z1-A rebuild thread, although the meter face isn't visible due to glare. I'm so glad I ditched those allen screws on the engine, they make my OCD scream when I see them now (actually I'd rather have CDO, same condition but with the letters in correct alphabetical order) ;)
The motor has been turned so that the pointer aligns with the 'F' firing mark, which you can just see through the oval window at the top of the points plate, red wire is connected to the feed wire to the right hand set of points (white wire). The other lead on the meter goes to earth on the engine, anywhere handy will do.
(https://i.postimg.cc/2SmChDz2/IMG-5116.jpg)
First set the points gaps, as doing it later will beggar up the timing again.
The meter is set to 'resistance' - when the points are closed no resistance, when open infinite resistance. I then turned the points plate to get the needle bouncing around as the points just open. Tighten the back plate. Switch the red probe to the other set of points (black wire), turn the motor 180 degrees to the 'F' mark for the other set of points, and repeat the process but using the individual adjustment for that set of points rather than turning the backplate.
Do double check afterwards, as things can change slightly when you tighten the screws up. Once I'd finished the bike, I checked the timing with a strobe, but it didn't need any further adjustment, so I'd got it spot on. :)
I had three pre unit BSA twins over the years (a glutton for punishment, I know), no timing marks but used a suitably marked pencil in the plug hole to find the firing position, and then the fag paper trick to set the magneto to where it was just letting go of it. Tighten the magneto onto its (tapered) shaft and I was good to go.
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I use one of these for most things https://www.ebay.co.uk/itm/303777478353 and have a couple, one in my general service rucksack pocket, one in an old car just in case diagnosis is needed :) often used when on a campsite to diagnose non starting from people flattening batteries etc .
Brilliant design and size, only complaint is that the built in leads aren't over long, but mostly you can reach things to test.