Coolie ignition timing

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seagull101
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Coolie ignition timing

Postby seagull101 » Sun Sep 24, 2017 8:50 pm

Where should the baseplate be on the crankcase for the timing to be correct, i get a good spark and have a clean carb but no luck starting.

Jacob

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Charles uk
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Re: Coolie ignition timing

Postby Charles uk » Sun Sep 24, 2017 9:57 pm

Try the HT lead 20 degrees in front of the tiller arm, Jacob.

If it won't start then try another 10 to 20 degrees in 5 degree increments.

Put a length of masking tape all around the flywheel base, attach a pointer to a crankcase bolt & mark top dead centre on the tape/pointer, measure the flywheel diameter (183.5mm) multiply by 3.142 (576.5mm) divide the total by 36 = (16mm), 16mm of flywheel rotation = 10 degrees, mark the masking tape with 4 marks either side of the top dead centre mark 16mm apart, your points should start to open about 25 degrees before top dead centre when the timing is in the rightish place.
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Oyster 49
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Re: Coolie ignition timing

Postby Oyster 49 » Sun Sep 24, 2017 10:49 pm

A children's plastic round protractor is quite useful :P I have made one with a brass handle to use on my classic motorbike. As Charles says mark TDC on both the flywheel and baseplate, then mark the correct advance using the protractor on the top of the flywheel. Turn the baseplate so the points just open at that point.

Does your SD not have the dimple on the crankcase? Mine does.

I have never tried to put accurate timing marks on a seagull and use a strobe, that might be an interesting excercise!

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Re: Coolie ignition timing

Postby Charles uk » Sun Sep 24, 2017 11:16 pm

I had labels printed for CDI flywheels so I could measure with a strobe how much built in advance the CDI's had.

Perhaps we should explain how to find exact TDC, take a dead 18mm sparkplug, break out the centre electrode & weld in a length of 1/2" bar so it hits the piston about 90 degrees before TDC , round off the end of the bar so it doesn't damage the piston, use the same pointer & tape, rotate the flywheel until it hits the spark plug stop, mark the tape at the pointer, rotate the other way & mark again, half way between the marks is BDC & the other half way is TDC.

It's difficult finding exact TDC by measuring as the piston is stationary for about 7 degrees at TDC & BDC.

SD's didn't have crankcase dimples as coolie/JM baseplates have an inner steel split collar, so the locking screw doesn't protrude.
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Re: Coolie ignition timing

Postby AusAnzani » Mon Sep 25, 2017 12:55 am

Charles uk wrote:Try the HT lead 20 degrees in front of the tiller arm, Jacob.

If it won't start then try another 10 to 20 degrees in 5 degree increments.

Put a length of masking tape all around the flywheel base, attach a pointer to a crankcase bolt & mark top dead centre on the tape/pointer, measure the flywheel diameter (183.5mm) multiply by 3.142 (576.5mm) divide the total by 36 = (16mm), 16mm of flywheel rotation = 10 degrees, mark the masking tape with 4 marks either side of the top dead centre mark 16mm apart, your points should start to open about 25 degrees before top dead centre when the timing is in the rightish place.


Great post Charles. Thanks for sharing.

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seagull101
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Re: Coolie ignition timing

Postby seagull101 » Mon Sep 25, 2017 7:37 pm

Got the motor running today after fiddling with it for a while!

Thanks everyone!

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Re: Coolie ignition timing

Postby headdownarseup » Mon Sep 25, 2017 10:47 pm

For what it's worth, myself and Jeremy have done some comparisons with slightly later villiers magneto's and we came up with some quite varying results.
Worth mentioning that these "experiments" were carried out with baseplates that have a dimple to securely locate its position and not strictly the same as a coolie mag.
Guess what we found.......
a lot more than 25 degrees before any spark took place. Most of the 102's i measured with smaller 167mm diameter flywheels seem to fire anywhere from 40-55 (ish) degrees BTC. I measured this by using a strobe light that works on 1 pulse of electricity and 1 flash. An old aluminium flywheel cover was painted black and then carefully scribed the marks showing TDC and increments of 5 degrees either side of TDC right round to 90 degrees before or after this point.Simple. For a power source to make the strobe light function i connected a 12v car battery to the strobe light. Press the button on the strobe once your outboard is running in the bin and you get "disco lights" that fire in unison with each firing of that single cylinder. It's then very easy to see where abouts the timing is set. 40-55 degrees BTDC on the test subjects i had to hand at that time.
To double check my findings i used the "points opening" method, again using a TDC mark on the flywheel (a tiny blob of black paint) and a fixed pointer made from stiff wire and found pretty much the same results.Where the points begin to open (i used a very thin piece of paper between the points) the paper is released from between the points and a second mark made on the flywheel with some more black paint. The difference was then measured between those 2 points using a protractor and the results seem to tally very well with either a strobe measurement or the "heath robinson" way. Anywhere between 40-55 degrees BTDC.
Jeremy found pretty much the same results with his 40 series FV motors.

I then took a visual reference as to where the HT lead was positioned on my 102's. As a ballpark figure, if you imagine the flywheel as a clock face (12 o'clock being the spark plug) most of the time the HT lead would be in roughly the 4 o'clock position. (with a dimple fixing) This would be more or less what you'd find in most of the manuals as well referring to a 4 o'clock position for the HT lead.

But even this isn't good enough it seems. If you're lucky your engine might fire at this setting provided your coil hasn't gone south by now.
At the beginning of my "fiddlings" with 102's i started to use a different point of reference on the crankcase to use as a "ballpark" setting with the HT lead, and this was the crankcase stud/nut on the tiller side of the crankcase closest to the cylinder base and keeping the baseplate locking screw directly above this stud/nut i seem to get a fairly good starting point whenever i remove a baseplate from a motor that hasn't got a dimple.
4 o'clock for the HT lead seems to work quite well for century's as well, mind you they've got a dimple so you can't really get this wrong, but even so it's not quite 25 degrees btdc. More like 40-50.
Just saying.


Jon

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Charles uk
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Re: Coolie ignition timing

Postby Charles uk » Tue Sep 26, 2017 12:00 am

When I checked the timings with Keith, Jon, as I found it very difficult to believe that the FV/FVP was running a timing so far in front of TDC as Jeremy was saying, & Keith had an FV that seemed to be running better than all the rest, so that was the one I measured.

Keith's FV timing was 45 degrees before TDC, shooting me down in flames & proving Jeremy 100% correct, I set TDC in exactly the same way I posted in earlier in this thread. It was only in the FV series that I've ever seen timings above 30 degrees BTDC, the only reason that I thought that could justify this was a particularly slow burn!

It's only usually the racers who will apply this much effort in measuring exactly what's happening inside their Seagull, I would be fascinated in seeing your results & which motors you measured & how you set TDC, Email me them, if you don't want them public.
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Hugz
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Re: Coolie ignition timing

Postby Hugz » Tue Sep 26, 2017 1:51 am

Two different JM base plates

Later JM11731 without split ring and locating screw all the way through:
jm mag baseplate.JPG



Earlier JM2438 with split ring and locating screw all the way through:
jm mag baseplate1.JPG


Dimple on SD9242
sd dimple.jpg


Any chance of a photo of the underside of a Marston JM mag?
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Oyster 49
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Re: Coolie ignition timing

Postby Oyster 49 » Tue Sep 26, 2017 12:11 pm

Yes, the SD I own, and several I have sold on have had dimples in the crankcases. This could have been added later of course.

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Charles uk
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Re: Coolie ignition timing

Postby Charles uk » Tue Sep 26, 2017 6:27 pm

Jacob here's a picture of the 18mm sparkplug with the welded in piston stop for find TDC. & a CDI timing label.

The sparkplug also work as protection for the plug hole when painting cylinders.

As it's so difficult because of the flywheel shape to affix a 360 degree protractor to the Coolie/JM flywheel, the masking tape method is the cheapest accurate method, certainly well within your ability, let me know what figure you arrive at.
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Re: Coolie ignition timing

Postby headdownarseup » Tue Sep 26, 2017 11:48 pm

I'm not as technologically advanced as some of you out there, but i measure TDC in pretty much the same way as Charles has explained before.
I use a wire pointer fixed to a component on the cylinder that will hold the wire in place for example on the 102's i remove the fuel tank and use a tank cradle BOLT HOLE as such a point for securing the wire that is now wrapped around the same bolt that holds the cradle bolt in position.Nice and secure. I then use an old spark plug with the central electrode bashed out from the middle EXCEPT i use a length of soft welding rod in place of the central electrode that slips easily in/out of the middle hole. Now although this method is not as accurate as i'd like it to be, it's good enough for me. It's then a simple case of marking the flywheel with either a small punch mark or a blob of paint where the pointer is now showing TDC to be (with a plus or minus of around 5 degrees allowing for the heath robinson method)
Then i can start to find where the points begin to open by reversing the flywheel going back towards BDC and somewhere here is where i insert my thin piece of paper. Carefully and SLOWLY i then start to move the flywheel back towards TDC to the position where the points begin to open and the paper is released from between the points. A mark is made on the flywheel using the wire pointer as a reference point and the difference between the 2 marks i use a protractor to find the degrees.
At this point i should mention that all the 102's i measured which range from C's & AC's to later TC's and THC's have a dimple fixing so i'm pretty much governed by where this dimple has been stamped/drilled into the crankcase. Most if not all of them fell into a ballpark in between 40-55 degrees BTDC . Quite a big difference from 25 degrees i know, but it's how many of them are and it's all down to where the dimple has been positioned in the first place. Without a dimple i'd refer back to the manuals and use the 4 o'clock position for the HT lead as a starting point and go from there until you reach that sweet spot where everything is just right. A bit here or a bit there on the baseplate positioning until i can then get the engine to fire consistently and easily every time. Works for me anyway

With that said i then looked at a few 40's i have kicking around (FV,LS,SJM,SJP,FP) and carried out the same procedure as before and came up with similar results as to what Jeremy had found. Slow burning maybe..... i'm thinking more along the lines of compression values being low and having to start the fire earlier to get the job done and not necessarily a heavily worn cylinder or rings either.
No big secret as to how i do things, pretty similar in fact. Not quite as accurate but good enough for me to see what's going on.

Now i do know that Jeremy has since "altered" some of his FV's to run a bit better by gently moving the baseplate round a bit (probably closer to 45 maybe 40 degrees BTDC) The slightly risky bit in all this is making a new dimple position for the locking screw to sit into.I also know that he's doing some work on compression values with smaller 40cc & 55cc seagulls. Some of these smaller engines have got a very large "squish band" if you want to call it that with the resulting low compression value you'd expect with such a large gap. It's possible that this large amount of advance in the timing was an effort to combat this and some FV's will run slightly better than others in this respect.(slow burning) I've found the same sorts of things with a lot of 102's and since started concentrating more on compression as being a bit more important than ignition timing(with dimples) with some of these motors. Without a dimple you can set the timing wherever suits the engine best but it can be a time consuming process going back and forth till you get it just right. No 2 motors will be exactly the same as they will each have their slight differences. Near enough is good enough for many of them now.

I can well imagine that some of you racers have probably increased compression somewhere along the line, and so the ignition timing can afford a bit of a tweak to help keep things running sweeter. I used to do the same thing when i was racing mini bikes.


I'd be interested to see if anyone else has measured a Marston or anything with a JM magneto to see whereabouts the points begin to open and then maybe we can start to get a handle on where things lie with some of this older machinery. It's all very well saying that 25 degrees BTDC is the be all and end all of everything, but sadly it's not. But it is somewhere to start from and not to aim at.

To try and prove this i tried starting my little OA this weekend. Points set at 18 thou, plug set at 20 thou,(although it's a very old plug in this engine) HT lead at 4 o'clock. Fantastic......... don't you believe it. 1 hour later of frantic rope pulling all i could get out of it was a half hearted cough and a couple of puffs of smoke :cry: and yet nothing had changed from the last time i ran the engine when i was with A-J a few weeks back.The last time it ran sweet as a nut and started easily which i find slightly confusing now though :shock:
Off came the magneto and try it on my test rig with a dimple, not that this has any effect with this baseplate and how it's secured into position.HT lead positioned at approx. 4 o'clock i get a great big blue spark from the same very old plug, woohoo so the coil is still alive at least, but refitted onto the motor it's a different story. So i resort to the points opening method of timing this old girl back up again.It likes a fairly good amount of advance before she consistently produces a good enough spark which seems to be around the 40 degree mark(very similar to later 102's) which puts the HT lead very roughly between 4 and 5 o'clock. Not tried it again yet, but i've got everything crossed for another attempt soon.

All good

Jon

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Re: Coolie ignition timing

Postby skyetoyman » Wed Sep 27, 2017 7:22 pm

seagull101 wrote:Got the motor running today after fiddling with it for a while!

Thanks everyone!

Well done on getting it assembled and running in such a short time. Nice to see the younger generation taking charge of classic engines.
LLS c 1961 on a crescent 42 boat c 1980 + wspcl c 1976 + 102 SD8561 c 1944 + 102 ACR 1948

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seagull101
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Re: Coolie ignition timing

Postby seagull101 » Wed Sep 27, 2017 7:36 pm

Thanks Terry! I will have to email over some pictures of it and a link of it running soon.

Jacob

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Hugz
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Re: Coolie ignition timing

Postby Hugz » Thu Sep 28, 2017 2:13 am

I note on my SD125 the split ring on the base plate is visible without removing magneto. If you guys can look at yours in your own good time it would be appreciated.

jm mag 125.JPG
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