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Re: 1948 Iron 4G Coil Ignition

Posted: Wed Sep 25, 2019 2:11 am
by chris.matthews
Good Morning,
I have only ridden 160 miles in 2019 and about 410 miles in since July 2016.
BSA, Velocette and VB have been used.

This year have only ridden the bike about 15 times since the rebuild.
Most of the starts have been 'cold' using BiStarter, even though Japan is a lot warmer than UK (usually over 25C).
When I stop for petrol its a 'Hot' start - I don't use the BiStarter for these starts.
Offhand I can't recall what I would call 'warm' starts (say a lunchtime one hour stop).

Plugs - usually 1, 3 & 4 are dry & sooty, but #2 usually shows damp/wet and sooty.
I really doubt lean running.

On Tuesday I tried to replicate things.
Not a glimmer, this was with every combination of Hard Wired; Permanent Wiring; Old Rotor; New Rotor: BiStarter Full, Half and In.
I had Sparks at the plugs under all tests, so I feel coil is ok (and its ohms were OK)
All this took time and plenty of cuppas.

Paul, The steam engine thing must be infectious to Ariel Owners - I see Simon Holyfield is also into them.
At least they don't have much in the electrics department.

I anticipate the worst so Solex and MagDyno are off and on the bench.
It also gives me the chance to cleanup a few oil leaks from when I plumbed-in a spin off oil filter.

That's about all from here.

Best regards,

Re: 1948 Iron 4G Coil Ignition

Posted: Fri Sep 27, 2019 1:20 am
by chris.matthews
Hello there
I have had the magneto off and on the bench.
For the first time I can really see details of the previous mods to convert to coil.
First off (and most important) the quality of the conversion is astounding - far better than the stuff made by Prince of Darkness.
A New Armature Shaft Rotor has been made and all the old windings slip rings etc are removed.
The shaft runs in the new Lucas bearings. Its beautiful, and everything is new and the screws look like they have never been disurbed..
I was not expecting problems as I have always had sparks at the plugs.
There were two areas of concern.
First the Electrical Pickup wire looked a bit fragile and exposed as it made its way from the contact breaker to the coil.
Continuity and connections were good so I put some nice new shrink wrap on it.
Second thing was a close look at the points cam. A couple of weeks ago John Whiting advised a circular cam with two flats would reduce the coil overheating. I think he is correct and I will be trying to arrange a cam - consensus is that my local machine shop will be very expensive. The good news is that its keyed to the shaft and held on by a 5mm screw. The points are retained by some 4mm screws so I am beginning to believe that this conversion was done in Japan.

The only markings are on the points plate where we find F E W inside a diamond shape.
No-one here has any idea who these folks are.
The points are nonadjustable which will create a problem at some time in the future - lets cross that bridge when we come to it.

I gave it all a wipe over, painted a couple of minor parts and will be refitting it later today.

I'll have another look at the Dynamo and AVR.
My Japanese helper thinks this is the problem (I'm not convinced).

Best regards

Re: 1948 Iron 4G Coil Ignition

Posted: Sun Sep 29, 2019 9:32 pm
by paul.jameson
Hello Chris,

Following your description of the coil conversion, plus the photo you posted earlier, I think it unlikely that this is the cause of the problem. You are consistent in saying that you have a spark. If we exclude jets of the wrong size, or jets fitted in the wrong places (it can be done by mixing them up) then a quick blast from the air compressor through the various passages in the carb should solve any issues there. If your petrol tank has previously been lined with a sealant this could be dissolving in modern fuel which includes ethanol but I would expect you to find some detritus or residue in the carb.

That leads me to fuel supply issues. If you fit the carb without the float chamber and turn on the petrol, do you get a good flow (into the cup you have handy to catch the petrol). Is the petrol clean in the cup or is there detritus / residue?

As a totally different possible cause of problems, take the rocker box cover off and try starting the engine. My 4G ran well for a while after I rebuilt it then started misfiring. Eventually, I found that repeated skimming of the head and rocker box had led to the point where the valves were being held open by the tappets catching on the underside of the rocker box cover. It took some time for the gaskets to bed down enough to make this happen but the bike is now fitted with 2 very thick rocker cover gaskets which has overcome the problem. You will find witness marks on the underside of the rocker box cover if this is happening on your bike. Perhaps unlikely, but very easy to check and eliminate.

Keep us posted, but after some fantastic days on the North Yorkshire Moors Railway I have appointments with one or two other steam engines over the next few days so replies will be erratic.

The photo below is from last year at the NYMR but is the only one suitable to show you on this computer at present.


Re: 1948 Iron 4G Coil Ignition

Posted: Sun Sep 29, 2019 9:50 pm
by john.whiting
Chris,when you say the points are non adjustable,what do you mean?....I see a slotted base under the rear screw...the points would be some Japanese car type if the conversion was done there.They look a bit like the Delco set fitted to Chevs and GMC s,which may be ,as early on Toyota licenced nearly every part to GM.....but I think it was Nissan that used Lucas licensed electrics.....

Re: 1948 Iron 4G Coil Ignition

Posted: Mon Sep 30, 2019 3:40 am
by chris.matthews
Good Morning,
I was very impressed by Paul's photo of the steam locomotive - it smokes more than my 4G (if I can ever get it running).
I also think the converted magneto is nit cause of the starting issues.
But one thing lingering in the back of my mind is that the points mounting plates are magnetized - I wonder if this is a problem ? I hope not, as I di have sparks at the plugs.

As for fuel supply issues, the tank has never been lines and I don't find anything in the float chamber or jets.
I checked the fuel supply; petrol on, supply pipe tank to carb fitted there were no problems with a good supply of fuel.
Solex is on the bench.


John, I hope the photo of the points is attached.
The points have no facility to individually vary the points gap, The points assembly can be moved and this moves the cam follower relative to the cam so the points can be adjusted. But there us no provision to move only one contact.

That's about it from here,

Best regards

Re: 1948 Iron 4G Coil Ignition

Posted: Mon Sep 30, 2019 5:19 am
by john.whiting
To adjust the point gap,turn the motor until the lifter block of the movable point arm is on the highest point of the breaker cam...(max lift),then slightly loosen both screws in the plate,..using the notch in the plate for leverage,open and close the gap by moving the back plate....when its correct (12 thou ,maybe),carefully tighten the screws (so the plate is fixed),then you should have 012 gap each time the point arm lifts per revolution of the breaker......if its a little out,dont generally have two little bumps opposite the notches,to make adjustment easier......In a old style breaker point setup,things like lift,cam dwell ,point gap are somewhat critical ,if the motor is to run properly...........( in a 4 ,its possible to have a working ignition without a distributor by having dual points (cf Honda Dream),and two double ended coils........this will fire two cylinder plugs at once,which many bikes do anyway.......but no distributor required.)

Re: 1948 Iron 4G Coil Ignition

Posted: Mon Sep 30, 2019 5:51 am
by john.whiting
Your points are listed in a forklift parts book as for a Mitsubishi industrial engine.....the ref here is 106TA 6492......which is a Thermote and Van Halst reference no.........Bosch ZPN24657/GM208/GTIN:4047026160444.

Re: 1948 Iron 4G Coil Ignition

Posted: Tue Oct 01, 2019 5:25 am
by chris.matthews
Hello Folks,

I am very grateful to John for a nice explanation about CB adjusting
But especially for identifying the points as Bosch GM208.

I got on the web and I found these were fitted to many engines - particularly Mazda RX3.
Plus as you pointed out Mitsubishi used Mazda engines in Forklifts and stuff like that.
My Japanese supporter is very happy "No wonder its quality points".
He is looking for Japanese source.
When I looked online, the easiest source (in English) was in Queensland - very close to John.

John, can I ask another question ?
You advised Contact Breaker cam could be circular with two flats, to minimize Coil Overheating
Do you have any idea about a source for such a Contact Breaker Cam ?
Mazda ?

Paul - Rocker cover has been off for ages mainly to get the timing set.
So sign of interference of Cover & Tappets.
My cover has a vent on it witch disappears in the direction of the rear chain. - but there has never been any sign of vented oil or oil mist.
There are no leaks from Rocker Box, so it might be working.

We are currently delayed by the most trivial of things.
I had the dynamo off and re-checked it - its fine. But a few days ago I painted it and the Magdyno Strap - new paint reacted with the old and ended up a black sticky mess. The morning session was spent removing it.

When we get the Magdyno fitted we will get serious about setting the timing. No more "near enough" we hope for some accuracy.
We think we can get the Points & Piston relationship set up OK, but we will also give more attention to the Distributor & Rotor.
Before, the rotor drive was rigid - now its been freed off so the fixing screw really does something and the rotor can be set in any position

That's about it from here,
With best regards,

Re: 1948 Iron 4G Coil Ignition

Posted: Tue Oct 01, 2019 12:03 pm
by john.whiting will have to make one.....not rocket science ,for sure......I could make one in a half hour with a does it fit the ignition unit.....there is a screw down the middle,my guess is the current cam is a car unit ,cut off,,,,,,,how does it locate?...anyway it will have to come out.........And as I mentioned ,if you change over to a dual point setup,then you need only one flat on the round distributor cam,and can dispense with the distributor altogether......You would need two double ended coils,as were used on many Jap bikes,,,shouldnt be hard to find there........I used a old Honda Dream coil on my Harley for years,worked perfectly........(as you know ,Harleys were double spark from a double ended coil from 1926 onward)

Re: 1948 Iron 4G Coil Ignition

Posted: Fri Oct 04, 2019 1:19 am
by chris.matthews
Hello Folks
Its Friday Morning and pouring with rain, plus I have a couple of hours escape from Domestic Duties - a good time to go into the workshop for more Ignition Torture.

Game plan is
Set Points.
Retime CB & Piston
Retime Distributor.
This will be with the original CB Cam, which overloads the coil.
But it used to run ok - if I get it to run in present configuration, I'll then get a 'less opening' cam organized.
I'm not sure about John's One Flat Cam and 2 coils solution (and no distributor), that's 'mentally pending"
In the back of my mind is Thorspark Electronic Ignition but that will be a New Topic sometime down the road.

I had a smile about finding parts here in Japan.
I have no language skills and finding parts here is a nightmare - even the Bosch / Mazda Points are proving problematic.
On-line from Queensland is easier.

Best regards