By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale-Ultrasonics

Ignition coils for small engines

All Topics | Latest Posts

Search for:  in Thread Title in  
John Wood129/05/2009 16:05:47
116 forum posts
As a relative newcomer to building small i/c engines and, having built three so far, none of which can I get to fire! I am obviously still on that part of the learning curve before success is achieved. I would like to get a better handle on typical ignition systems which others use and actual practical information on their use.
I have been talking to Jan Ridders (see previous thread here) who has given me much valuable information however, I do need to be able to source a suitable ignition coil. Reading through articles such as the Recycle Engine and Presure Controlled 2-stroke engine - both from recent ME magazines - one gets the impression that a dig into the workshop's 'odments' box will invariably turn up a suitable old coil which does the job nicely, I DON'T HAVE SUCH A BOX!
I presume that suitable items can be had as spares for such things as mowers, strimmers, chain saws and the like but, on searching around for these there are probably hundreds to choose from and, without the experience how does one determine which are appropriate. Could anyone out there point me at suitable coils which I can easily get in the UK please?
I also see solid-state replacements for (say) Briggs & Stratten engines advertised on websites, any milage in these? What about the Hall Effect system as detailed in Hemingway's catalogue, this seems a good, modern and relatively small system which looks ideal for fitting under small engines. 
Any advice would be most welcome.
Thanks, John
David Clark 129/05/2009 16:27:15
3108 forum posts
99 photos
11 articles
Hi There
Rudy Kohupt suggest using a coil from an old magneto.
You can trim the iron laminations to tidy them up or leave as is.
regards David
Dougie Swan29/05/2009 17:57:10
129 forum posts
38 photos
Relativly cheap coils are available from motorcycle shops, These are available in 6 or 12 volt, you might get on even cheaper from a breakers yard
Sandy Morton29/05/2009 18:37:03
104 forum posts
Try Hemingway at
JasonB29/05/2009 19:32:26
6903 forum posts
687 photos
I went for a CDI ingnition from MjN Fabrication (but he's not selling at the moment) when I built my hit & miss engine
It uses a hall effect sensor which makes it very easy to advance & retard the ignition by having the magnet or sensor on an adjustable mount. And being quite small can easily be lost under an engine rather than having a large wooden box for a buzz coil & large battery
Several of the Builders in the US are now using the following systems while MjN is out of production

Edited By JasonB on 29/05/2009 19:33:30

Henri van der Riet03/06/2009 15:21:52
3 forum posts
Hi John
I am also busy building the IC engine by Jan Ridders - my first engine, i've completed all the brass components so far.
I have already built the ingition system based on the TIM-6 from and  My system uses all the components mentioned on the sites plus the following:

- Second hand 6V ignition coil from a Yamaha motorcycle  (C2T4) - Nice and small.
- NGK CM-6 plug.  Also has a 10mmx1mm thread.
- 6V 4.2Ah Sealed Lead Acid battery
- 3mmx2mm rare earth magnet.
I've tested it up to 5000 rpm using a DC motor in the place of the engine.
I will keep you up to date if it works on the engine.
John Wood104/06/2009 15:07:49
116 forum posts
Hi Henri, thanks for the gen on your ignition system, it sounds just the job and I will certainly look into trying it out myself.  I am waiting to try out some ideas on initial starting of my Jan Ridders engine but am building a tapping and staking stand at the moment so will have a go when that's finished.
Good luck with your engine and do keep us posted on its progress.
Thanks to everyone else who has made suggestions re ignition components, I am gradually getting it all into my head!
regards to all, John
MichaelR05/06/2009 16:02:01
186 forum posts
14 photos
Hi John,
A UK supplier for ignition systems here
At the moment I am using the Jerry Howell Buzz coil circuit on my RLE Hit and Miss engine, these circuits had to be made up from components, the systems on the above site are ready to go which sounds good.

Edited By David Clark 1 on 26/06/2009 08:11:52

mgj06/06/2009 13:41:36
1007 forum posts
14 photos
I was going to suggest Just Engines. I bought a MVVS 30cc aero engine from them and the ignition system for that is tiny. There is a hall effect sensor in a little pastic mount, so that is a ready to fit unit, a box of electronics about  1.5 x 1 inch as I remeber, and you can run it off a model aircraft nicad pack (4 AA cells or equivalent).. Very reliable. The output is, I can vouch, pretty stunning. 
Bob Dennis10/06/2009 14:21:05
5 forum posts
John I would highly recommend the Hemingway hall effect and their small coils.  I have recently built my first IC engine and played with motor cycle coils and bits, to no avail.  Bought the Hemngway kit and the engine started first time and runs well.  I have used radio control type plugs so that it can be connected to other engines as they are completed.

Regards Bob 
John Wood112/06/2009 16:37:18
116 forum posts
Many thanks Stick for the gen on JustEngines and from Meyrick as well, I have been on their site and the modules look perfect so will have a go as soon as I get a bit of time.  Thanks to you Bob for your comments, from a user I find such information invaluable so I will press on with the Hall Effect system. I have looked at Hemmingway's kit which looks excellent and I would have no problem building it (I'm a Radio Amateur) but having looked at the ready assembled modular items from Just, and considering they have the leads and plug cap as well, I am tempted to take the easier option first.
Another point which is that by using Hall effect sensors you do away with the mechanical drag on the cam caused by having to operate contact breakers, this will reduce the overall friction on small engines which seems to be important.
All the best
steamdave24/06/2009 20:35:27
136 forum posts
2 photos
Posted by Stick on 05/06/2009 16:02:01:
At the moment I am using the Jerry Howell Buzz coil circuit on my RLE Hit and Miss engine, these circuits had to be made up from components, the systems on the above site are ready to go which sounds good.

 Unfortunately, Jerry Howell doesn't produce the buzzcoil circuit kits any longer.  They are now available from

but at a huge increase in price.

Or you may want to go the deLuxe route and try



The Emerald Isle

Henri van der Riet25/06/2009 17:26:02
3 forum posts
Hi guys
I am planning to add two "features" to my Tim-6 circuit:

1. An electronically adjustable dwell angle.
2. A safety feature that will protect the coil from possible burnout in the rare event that the engine stops with the magnet over the Hall sensor. In this situation the coil will be charged with a continuous 6V – surely it wil be bad for the coil.

I’m thinking of using a HEF4538B IC “dual retrigger rable -resettable monostable multivibrator” – don’t ask about the name

It would be able to have an output high for a specified time after the Hall sensor fires, with even a single small magnet, which would give the dwell angle effect. The dwell time/angle can be changed/tuned on the fly with a potentiometer and capacitor combination.

I think it would also be able to have a maximum time that the output will stay high to effectively shut off the coil when the magnet gets “stuck” in front of the Hall sensor.
Hey, I just thought of another idea - it can be used to have a adjustable timing if it is used to set a variable time to "wait" after the sensor has fired.

I will post the schematic as soon as it works,– If I can just get some more time to spend on the hobby!!

Thanks Dave for the links above – the warning about testing the coil with a too large gap is very true – luckily my Hall sensor has very good ESD protection and only needed to be powered down to reset it after the spark leaked through and zapped the whole system.

Cheers - Henri
John Wood130/06/2009 13:32:14
116 forum posts
Hi Henri
Very interested in your proposed modifications to the Hall ignition system, it all sounds perfectly feasable to me and should provide a very versatile system indeed.
As a Radio Amateur myself I am reasonably familiar with the circuit details you outline and, as my brother is an electronics engineer as well should have no trouble in putting such a system together once the schematic diagram is available so, I shall look forward to hearing your results when you can find the time, this is my problem as well, a business and family to rum leaves little time for messing about in the workshop.
I have bought the system from Just Engines (mentioned above) and so far I am very impressed with its performance. My Jan Ridders 2-stroke engine is now firing well but I havn't yet got it to keep going under its own steam, ah well, press on!
All the best,  John
popsie04/08/2009 17:09:40
2 forum posts
I'm working on a high voltage (100 - 200 volt ) supply for the capacitor to discharge into the coil, ultimately to be derived from redundant flash circuits in disposable cameras.
So far i've had sparks of 10 - 20 kv from a 150 volt supply and a car ignition coil.
Those wishing to investigate these circuits MUST BE CAREFUL as DANGEROUS VOLTAGES are generated from a 1.5 volt battery!!
Ian S C04/08/2009 17:37:31
4599 forum posts
150 photos
There was a small buz box described in Model engineer a few years back,very simple,if I find it I'll tell you where it is.Ian S C.
Ian S C22/08/2009 02:40:46
4599 forum posts
150 photos
Found it,Building a "BS" Buzz Box by Jim Service ME Vol 190 no., 4196 (June '93)page 624.A neat little box.Ian S C
Bowber16/11/2009 20:28:06
155 forum posts
22 photos
Just a little extra info on the different coils off bikes.
Battery and coil, with points or electronic control, use the points opening to collapse the field when the points open, this uses the battery voltage.
The other is energy transfer, magnito and CDI, and these tend to work at much higher voltages. CDI usually operates at 300 volts.
So make sure you get a coil from the 1st type as you won't get the secondery voltage from just a 12v battery.
dixie04/12/2009 09:53:23
31 forum posts
Hello Have you tried    I purchased a coil from them at a reasonable price. worth a look any way.
Regards brian
dixie04/12/2009 09:53:33
31 forum posts
Hello Have you tried    I purchased a coil from them at a reasonable price. worth a look any way.
Regards brian

All Topics | Latest Posts

Please login to post a reply.

Email News - Join our newsletter

Love Model Engineering? Sign up to our emails for the latest news and special offers!

Latest Forum Posts
Support Our Partners
SPG Tools
Advertise With Us
G and M tools
Eccentric Engineering
Allendale Electronics
TRANSWAVE Converters
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

Visit the Model Engineer
Exhibition website

Model Engineer Exhibition