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ROD¹ said :-
I am no expert, but I would just time the crankshaft and camshaft with the timing marks. The fact that the Haynes manual does not mention the ignition timing suggests to me that the engine fires just before tdc on every stroke,eg a wasted spark.
This can be checked by looking at the rotation of the crank and the ignition timing rotor. If the ignition rotation is half of the crank rotation then there is not a wasted spark and the ignition timing will have to be taken into account. However if the crank and ignition rotor rotation are the same the engine will have a wasted spark.
08/08/2022 14:46:05 UTC
Glyn said :-
That's true for one cylinder Up't, the issue is when the second cylinder fires? Is it the next timing mark on the crank or 360° later ( that must be the 405° spot. I think this is why a Harley has that distinctive sound as the 2 cylinders fire quite closely together. The other thought is, does it matter as the second cylinder will then fire 315° after the first effectively the same thing other than the following cylinder then becomes the leading cylinder. Let's hope that Ren will have some clever answer to this.
08/08/2022 14:52:49 UTC
Ren - The Ed¹ said :-
I can't speak for your machine Glyn but - Shirley surely Haynes has the answer? I'd figure there's ONE mark for TDC. It matters not if it's the front or rear as long as all the other marks (crank, cam) are in agreement.
A very quick search suggests there's a "T{" mark for TDC and a "{" mark for the firing of the "other" piston. If the "T{" is in the right place and all the camshafts are aligned with their marks you should be about right.
I think ROD will be right - if there's no sensor on the camshaft then there's no way for the computer to know if it's at TDC for firing or TDC between blow and suck.
I would think... T on the crank is TDC for the front piston. The camshaft at the front will be marked for TDC too, that's the TDC between blow and suck. The rear piston's camshaft will have it's mark at TDC for the front piston too but there'll be an offset. Hold the camshafts both at TDC - I bet there's a 70 degree offset.
08/08/2022 17:00:59 UTC
Glyn said :-
I'm not sure there's a wasted spark Rod as there's two coils. I remember that the Yam RD had a wasted spark but a single coil fed both spark plugs. In that case the crank offset was 180° so one piston at the top and one at the bottom but the plug fires at both top and bottom dead centres. However, I've found out something on you tube that shows a mark on the crank not mentioned in the Haynes manual. When this Mark is aligned with the oval casting above, then that's the TDC for the firing on the front cylinder and so I deduce that the ignition timing can be out as the next full revolution will show the camshaft to be 180° out and starting the suck part of the cycle. You can just see the mark on the cog on the end of the crank. Ren,s "how to time the camshafts" is correct but unfortunately starts with the rear cylinder and so I'll have to put it together to check that the front cylinder aligns with this Mark after I've done the rear. If it doesn't, I'll have start again 360° later. Just to confuse things even further, Yamaha refer to the rear cylinder as No.1.
08/08/2022 17:32:47 UTC
Glyn said :-
Good grief this is mental torture for me and just torture for a lot of poor readers not interested in the finer points of ignition / cam timing on a 70° V twin. Finally I think I've got it. Haynes say set up rear cylinder when the mark shows in the little window of the cover. That mark is at about 10.30 on the rotor in the picture below. Then set up the camshaft sprocket to TDC. Then move the crankshaft clockwise ( very important) until the mark, seen in the picture at 1.00 comes into the window and set the camshaft on the front cylinder to TDC. This looks to be about 270° apart on the rotor. The problem will be if you miss the mark or go past it and think " it'll be ok as it'll come round again in a few seconds". Apparently there are strong warnings about turning the crankshaft anti clockwise which would encourage you to do just this if you went past the mark. There's another mark on the rotor between the two timing marks, this is to set up the ignition timing. All the papers I read about this assume that I'm just checking the camshaft timing and not staring from scratch. Sorry to be a bore gentlemen.
08/08/2022 18:10:22 UTC
Upt'North ¹ said :-
Not a bore Glyn. It's either this or lifting and levelling slabs! Or fitting a new door threshold strip, or cutting lawns, or.....
It seems Haynes has you covered?
Timing is one of those mysterious arts that once you know it, it couldn't be simpler. I wonder how long it took the Yamaha tech to put those cams in during the initial build.
Good luck fella.
Upt'North.
09/08/2022 08:33:30 UTC
Ian Soady¹ said :-
Re wasted spark: if the triggers are on the camshafts then I'd expect no wasted sparks (ie once per 2 revs); if they're on the crankshaft then there will be. There have to be 2 coils as otherwise you'd be having sparks half way up / down the stroke on one cylinder. Think of it as 2 separate singles.
By the way I'm impressed with your progress so far!
09/08/2022 10:12:57 UTC
Ren - The Ed¹ said :-
My CBF125 is a single - and it only has one coil obviously. And yet it is a wasted spark. Unless there's some (really really) clever computation I don't know of, the sensors that tell the computer where the engine position is are on the crank. The crank runs at twice the speed of the camshaft. As such my computer does not know whether the TDC it senses is the TDC between blow and suck or between squash and bang. So - it assumes TDC is the TDC between squash and bang each time and fires the spark.
This also means the injectors don't know when the suck is due. Super modern cars with cam sensors could possibly time the injector to squirt when the engine is sucking, but mine, well mine will just squirt some fuel that will hang around until it's sucked in.
I suppose it would be possible to work out suck on the cycle by monitoring the inlet pressure (MAP) but I doubt my basic 125 requires this and probably not my more modern 500 either. I doubt MAP sensors are sufficiently rapid enough to do this.
And stop worrying about "being boring". This stuff is fascinating and I concur Ian, he's doing splendidly well.
09/08/2022 11:04:39 UTC
ROD¹ said :-
I think Ian's point about two coils is relevant because the Yamaha is v twin.
The 4 cylinder Kawasaki I owned had two coils and used a wasted spark.
09/08/2022 16:01:28 UTC
Glyn said :-
I should have mentioned it earlier but there are no sensors on the camshafts. That would suggest that any sensor is set within the wiring inside the stator that goes inside the rotor. This would support the wasted spark theory mentioned by many of you.the wiring is very basic with only the stator cables, a neutral switch wire, carb heater plugs and the 2 spark plug leads actually attached to the engine. There is no oil pressure warning device or rev counter either.
09/08/2022 20:25:51 UTC
Ian Soady¹ said :-
The Td5 diesel engine on my demised Land Rover Discovery had a crankshaft pisition sensor but nothing on the camshafts. I understand that it used the timing between pulses to work out which stroke it was on (no idea how) and therefore fire the injectors at the right time. No spark plugs of course. I also remember that the Triumph 955i had only a crankshaft sensor for its 3 cylinders used for both the injectors and sparks. It must somehow have known which stroke each cylinder was on but I never found out how.
10/08/2022 10:29:57 UTC
Glyn said :-
It's all together,timed and torqued. I decided to put the clutch on, that was just as well because this was when I found that, following it's travels around various workshops, pullers and presses, the threads on the end of the input shaft had become damaged and the clutch final nut could not be fitted. It took me almost 2 hours of thread filing, junior hacksaw rendering and filing a small taper on the end of the shaft until the nut could be wound on, torqued up and the lock tab bent over. This was a tricky job and much easier 1 metre above the floor than bent over when the engine was back in the frame. There are some rust issues on the frame that need sorting before the engine returns to it's rightful place but it's getting there.
11/08/2022 20:58:46 UTC
nab301 said :-
Glyn, I'm guessing your next project will be a humble 2 stroke !! Excellent progress by the way.
@ UPT Quote "It is strange too how a lot of the car industry went completely in the opposite direction with service warnings rather than a set schedule. It is fairly routine for large diesel burners to go 20,000 miles before the dash lights up with warnings of imminent wallet emptying."
I don't have a modern car but I thought modern car oil change intervals were determined ( by the ECU) via various inputs , especially the number of cold starts and also by the sometimes optional use of longlife oil ?
Nigel
11/08/2022 21:24:41 UTC
Upt'North ¹ said :-
Nigel.
That is what I was referring to friend, the lights come and it's time to service. The BMW X1 is like this although Er'Indoors Seat of a similar age isn't. That's still yearly. The BMW does run LL spec oil, I don't trust it though. But that's just me.
Upt'North.
12/08/2022 09:37:52 UTC
Upt'North ¹ said :-
Glyn, I don't know if you did or you didn't, if you have or you haven't, but proper guage thread files are worth their weight in steel filings.
Upt'North.
12/08/2022 09:39:47 UTC
Upt'North ¹ said :-
Glyn. Cantilever toolboxes never die.
Upt'North.
12/08/2022 10:07:56 UTC
Ian Soady¹ said :-
No, they only get filled with stuff you never use except that very special tool which hides in the bottom.....
12/08/2022 11:40:56 UTC
Glyn said :-
Sadly, no to the proper thread guage files. That particular cantilever toolbox holds all my files, punches, pullers and specialist spanners such as 3 different size plug spanners. It's one of 4 toolboxes but the others are plastic and all broken unlike the 40 year old red cantilever. I'm not rushing out to buy a 2 stroke Nigel although i might like the simplicity, I think I shall deserve a rest after this one is all finished.
12/08/2022 16:18:56 UTC
Upt'North ¹ said :-
These are my little beauties Glyn. They come in very handy, especially if you're cutting down fasteners to size. One is imperial and one metric. These are over 40 years old.
Upt'North.
14/08/2022 23:08:00 UTC
Ian Soady¹ said :-
That reminds me I lent mine to my brother a year or so back and he hasn't returned it.... I must admit though I generally use a three-square file for bigger threads as you're only removing material where it's been deformed. The thread files can be a bit over the top.
Cutting down to size? I run a nut onto the thread below where I want to cut, cut with a fine hacksaw blade and file flat with a slight chamfer. Then unscrew the nut so it half leaves the thread. Run it back down again and it will have left some rags. Chamfer off with the file again (or use a fine wheel in the grinder) and repeat till the are no rags produced. A purist may then finish off with a die.
15/08/2022 10:19:25 UTC
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