I have been lurking here for a few years. So far all my questions have been answered. Now I have a new one. My wife has a 14 touring with a bosch mag without an impulse coupling mounted on a bosch triple gear drive. The car has a starter and starts well, but will not start by hand cranking. We have a freshly rebuilt du4 with an impulse coupling. I have put the new mag in position but it is a tight fit. The mounting holes do not line up and the stock intake manifold is close to the secondary terminals. Also the drive is a mis match. I have seen pictures of this instalation so I know it can be done. Any advice as to how would be appreciated. Thanks Pete
What front plate for the Mag are you using. A photo or two would help.
I tried to send photos from my ipad but they are too big. When my IT person gets home maybe we can send some. Pete
Lets try this again
New mag on the left original on the right . in the previous photo
Peter, See who on this previous bosch front plate thread might be able to help.
I am in the beginning stages of playing with one of these and also found that things get close when an impulse coupler is added. If you are willing to seek out either a "Duplex" or "Dual" that makes spark from a separate battery / coil arrangement, I believe you can forgo the impulse coupling and save the space.
Pete: I sold my '13 Speedster to Ron White & he added an impulse to the same DU4 setup that you have. The trick was fabricating a custom coupling that kept the mag as far forward as possible. I had cut the output terminals short & put rubber caps on them to insulate against the intake manifold. Of course, you could go with a non-stock manifold to get clearance as well.
Jay I see the base in the link you sent has two sets of mounting holes. That tells me someone has done this before
Walt. I think I might look for one of those at chikasha.
Bill,I had not thought of shortening the terminals that would give room for a thicker drive adapter.
Thanks to all. Pete
Hey Pete! I'm glad to see someone else with a Bosch Triple Gear front plate and a DU-4 Magneto. I have this setup on my speedster and absolutely love it. I don't have a starter but mine starts right up with the impulse coupler.
Here is a picture where I had the engine out.
You can't see it in this picture but my base has another set of holes for the mag that is maybe an 1/8 of an inch or a bit more towards the rear (that's the distance between the edges of the holes) compared to where your original holes are located. It's just like Jay's pictures in the AoTD thread he linked.
Here is my input, for what little bit that it is worth. If you look at my picture you will see there is a black plastic ring between the impulse coupler and the drive part of the front plate. It has a groove that matches the impulse coupler teeth on one side and then 90* out to make an X or + sign, on the other side. If you use really short bolts the same depth as the two teeth sticking out on the impulse coupler you can have the whole mag unit pretty far forward and still be okay.
Here are a couple pics of the ring.
Someone like Steve at www.mainelymagnetos.com will be able to supply you with the black plastic ring. It's a really tough plastic, but the idea is that if something were to happen with the magneto the plastic will shred instead of the engine forcing the mag around anyway. I tried to make an identical piece with some rubber I had and it wasn't strong enough, same thing with wood. Just get 2 or 3 rings from Steve.
If you want I can take some more pictures and give you the measurements on exactly where my second set of bolt holes are, as well as how thick the plastic ring is between the drive and the impulse coupler.
What I found was that more than the spark plug terminals being close to the manifold, the ignition terminal to kill the mag would like to rotate around and ground itself against the manifold - which would kill the car, very annoying. Working the spark lever up and down as I drove would eventually walk the contact around. I ended up zip-tying the wire to the frame so that the contact couldn't go very far. Works great now.
Someone may know another way but once you actually get the magneto mounted on there correctly, you're basically going to have to start from scratch on timing the mag with the engine. Best thing to do is have the radiator off the car and the front plate cover off. Get engine cranked around to just before TDC. Then take the big gear off of the camshaft and spin the mag slowly, by hand, until it's about to be spring loaded before #1, then put the big gear back on. Before you try to hand crank it I'd mark the big gear and the middle gear teeth with a Sharpy so you know where you are starting. Then make sure spark advance is fully retarded and use the starter to see if it'll crank. It might start right there, might not. If it doesn't, then slowly advance the spark to full and see if it does. I found that I could start mine the first time with full advance, so I ended up moving the mag timing forward by two teeth from where I started and then car would crank and run with spark advance fully retarded.
Hi Seth thanks for all the information. I think I will give Mainlymagnetos a call tomorrow. I was just looking through the McMaster catalog today for some Delrin or something to make a coupling. I thought somebody had already invented that wheel.
My wife bought the touring car last spring and we have been on two tours and daily icecream runs with nieghbors last summer.i have been pleased with the Bosch magneto except it would not start with the hand crank. Also it does not have the timing advance lever hooked up . I think I may copy your linkage. It just has a spring to hold full advance now.
Yeah you are definitely missing out on a big part of the magneto's drivability if you have the spark always advanced. The car will idle much slower and drive much better if you can advance and retard the spark as necessary.
The lowest picture above is how I had everything setup for when I had the stock exhaust manifold (I have the dual manifold now). I just used a straight rod from the spark advance lever behind the fan. Where that front brass rod connects to the middle pivot I used a threaded eye bolt so that I could make it longer or shorter as necessary to get a full range of advance. I don't have nuts on the backside of the flat plate, just used it as a washer with the intake and exhaust clamps right against it. The original manifold studs were plenty long to handle an extra 1/8th inch steel plate. This is with the dual exhaust manifold but here I have it all cleaned up and painted, just scroll down a little in this thread. Also has some better detail to see what all I did. If you want some different or specific pics just let me know and I'm glad to help out. http://www.mtfca.com/discus/messages/411944/493893.html?1416118228
Keep us updated as you work on it and let me know how it's going. Post pics of the touring car!
Just one other note for you and any others lurking: whatever your question or issue just type it into google and add mtfca as the last word. If you google "Bosch triple gear linkage mtfca" without the quotes and then hit images - you'll see a zillion different pictures from this forum all related to what you are looking for. There's multiple threads on the subject. Some newer, some older, but tons to pick from.
And of course don't ever hesitate to just post your question. =)
I have a newer Bosch magneto than a DU4, but without any impulse coupling and it's really easy to hand crank even with a milled Prus head on and 5.8:1 in compression. No starter needed. Maybe your DU4 need to be remagnetized?
Roger you make a good point and I didn't think of this until you said that but Pete before you go to all the trouble of fitting the DU4 with the impulse coupler, maybe just try and retard the spark first. Silly I didn't think of this before. Take the spring off and push the spark advance arm on the mag all the way down (clockwise if looking from the back of the car towards the front). If she cranks up now with the starter I bet you can retard the spark and she'll crank right up by hand.
Now, you may still want to add the one with the impulse coupler. The best thing would be to have both DU4's configured the same way so that if for some reason one of them dies on you then you can just plug the other one right in its place. On tours and such everyone has extra coils and usually 2 or 3 folks have a timer, but nobody usually carries an extra DU4. You'll want to give it a good rip, but it should start with the spark retarded.
Also - check your spark plug gap. The plugs need to be gapped much closer for a high tension magneto compared to the stock timer/coils setup. I believe .018" is the recommended gap I've seen and use myself. You'll have to check with Steve at Mainely Magnetos but if you've been running the car a while with the plugs gapped really wide .025"+ then you may need that DU4 rebuilt. Running with the plugs gapped too wide burns up some part of the magneto's windings.
I have DU4 that have been completely rebuilt with no impulse coupler and no retard device. I can hand crank the engine but I need to recharge the magnets every year otherwise it wont hand start. And of course I have always a spare one in the car.
I did retard the timing when I tried to hand crank the car, still would not start. The first thing I did when we got the car was to check plug gaps. They were at least .025 I reset them to .018 like aircraft plugs. That almost completely eliminated a miss at low rpm and higher load, such as the low to high shift. I suspect many years of running with wide plug gaps didn't do the mag any favors.
My plan B is to try the freshly rebuilt mag without the impulse coupling to see what happens. It is interesting that Roger and Philippe have no problem starting one,but it makes sense because the triple gear drive was designed for a non starter car and no impulse. I guess the reason I want one is a friend has a brass Mercer with an impulse mag and he just slowly pulls the crank ,the car starts like magic. Almost as well as a stock T with well tuned ignition.
Seth, I called Steve at Mainly Magnetos,he doesn't have the drive adapters on the shelf. He needs dimensions to make them. I was wondering if you had some pictures and dimensions of yours so I could make some or have them made?
I will be glad to measure mine for you and will take a few pictures as well. Unfortunately I didn't see this last night so you'll have to wait until this afternoon/evening. I set an alarm on my phone so I won't forget.
Would you post pics of your whole touring car as well as the engine?
Here you go! As you can see in pics, outside diameter is 2.5", the inside hole is 1.5", the thickness is 3/8" (actually 3/8+1/64 according to caliper but whatever) and the channels are 1/4" wide and 7/32" deep (a touch deeper than half the thickness of drive adapter). Should be easy for Steve to fab you up a few with that info.
And here is a picture of my base. The extra set of holes are 1/4" from outside edge to outside edge further away from triple gear drive.
Thanks Seth. That should do the trick.
I tried to post a photo of the car last night and also just now, but the picture is too big. I will have to ask my ipad guru and photographer son in law how to resize ipad photos. The previous photos I just cropped and it worked, not this tme thuogh.
Download the app SimpleResize. It's super easy to use on your iPad and works great. It just creates a resized copy of whatever picture you want. Shoot for 196 kb or lower. Just have to test some to figure out what works best for you.
Meant to say it's free and it's how I posted these pictures of the drive adapter. Took them on iPhone, simpleresize and presto, posted from phone. iPad will work identically.
Seth, Sounds like you have quite a bit of experience with mags. I have a 66 Harley running a mag. In dealing with its mag I had some conversations with some old Harley guys. They explained to me that a mag and a set of points ignition act different at the spark plugs. A mag likes a large gap. It seems that most Harley mag users are changing their plugs as soon as they show some wear at the contacts. But the old guys said to leave them alone. A mag will find its "happy place" as soon as the plugs start to erode. They showed me their plugs. They looked awful as far as gap and erosion go, but the bike ran perfect. They gave me an old eroded set to try out. (they wanted them back as they cherished and hoard the worn plugs) I could not believe the difference. The bike ran Ok before, but it just acts different with the old eroded plugs. I can tell the bike is "happier" I do not know if that will apply to the other style mags we use on the Ts, but from their explanitions as to why it works, I believe it will. Just my thoughts, experiences, and opinions, for what its worth.
Donnie that's wild. What kind of mag is it on your Harley?
I will say that the plug gap thing is not something I know a whole lot about first hand. I haven't burned up secondary windings or tried lots of different plugs/gaps. When I got the DU4 for my speedster I was soaking up all the info I could find about it and kept seeing where it was important to set the gap on the plugs tighter than you normally would in a stock T ignition. The reason being that if the gap is too wide you will burn up the secondary windings. Which sounds terrible to me so I set my plugs from .025" to .018" and she runs great. I saw recommendations everywhere from .014" to .019", I ended up settling on .018" cause I saw that number more places, it seemed more on the big end, but within the recommended range.
I haven't driven her long enough to really wear down the plugs I guess. If anything I've been a bit surprised at how little the plugs have worn despite a few thousand miles. I don't know if other magnetos are constructed differently but I wouldn't mind trying a fatter gap if I wasn't worried about it damaging the magneto.
The other thing that is kind of weird about the eroded plugs working better is that everything I've heard is that electricity prefers a nice sharp edge - that's why folks say you want Champion Xs, so it's easy to rebuild them and file the rounded nub back flat so it has a nice sharp edge. The sharp edge being a better/easier place for the electrons to jump from.
All of this to say - I'm just passing on the tiny bit that I can claim to "know" from experience and most of it is what I have heard or read from others. Electricity is electricity as far as I know (that's not saying much) - maybe the exact voltage/amperage/resistance is different, but juice is juice. What kind of compression does your Harley have? And, just as an off the wall question - have you tried running fresh, new plugs but with a much larger gap to mimic the size of the eroded plugs gap? Just wondering if it's the actual erosion or maybe that mag is happier at a fatter gap. Again, no offense or anything. I'd be fascinated to know more about this from someone who knows more than me. =)
I'm in the process of using a DU4 on my '26, with a chain off the crank pulley. Just curious, if someone was able to find a Bosch triple gear plate, what would the going price be?
Seth, My mag is a Joe Hunt mag. It is the same mag as a Fairbanks Morse mag that a lot of tractors use. It is an impulse mag. The only real difference is the mounting and cap. I have tried the new plug thing and there is still a difference. I have no way of explaining the results, as I just barely understood the reasons I was gave for why it works. It has been about 4 or 5 years since I was dealing with the mag on the Harley. The Harley Ironhead forum is a lot like this forum. I got into a long thread discussion on that Forum about what the old guys told me, and some of their very very knowledgeable people explained how it worked. I do remember that a impulse mag was supposed to act different than a T magneto or some of the other styles of mags. Ill try to find the old thread from the Harley forum where we were discussing this. I have very little experience in the use of mags, and was just wondering if you had heard anything about it.. Im going to be using a mag on my speedster project, so I guess I need to start the learning process now...
Jon, sent you a PM (check your email) with more details. There's a Bosch Triple Gear drive exactly like mine pictured above in the classifieds. I think the gentleman is a bit high on his price but not crazy high.
Seth, thanks, I missed that.
Price is about what I thought. Since I'm retired and on a budget, I think a chain and a couple sprockets will have to work.
Yeah - it's definitely cheaper and easier to build your own platform and then get some chain and sprockets. That triple gear drive is also kind of missing the point on a '26 engine. You could just make a base and run the mag in place of the generator. If you're keeping the generator then the chain drive is the way to go anyway.
Have you considered running the chain drive off of the camshaft? Might be easier than making a sprocket/fan belt pulley combo. On the flip side you'd need double the teeth on the cam so you'd have two different sprockets. Just a thought. Check this thread out about another guy's Dixie magneto with a chain drive. http://www.mtfca.com/discus/messages/331880/375902.html?1374535682
Maybe this time
Very nice Pete! What kind of wire wheels are those? I always like the ones with lots of spokes. Whole car looks great.
They are either buffalo or house,which may be the same thing.
Near as I can tell they are from an Overland.
Thanks for the info on resizing ipad photos.
They are Budd.
Ok I finally finished installing the impulse mag. It starts well well with the hand crank now. I did have to shorten two of the output terminals to make it fit with the stock intake manifold. I also made a linkage for the advance mechanism. Thanks again Seth I used your measurements to make a drill jig for the mount and for a delrin drive adapter.
If you have bolted one side of your adapter solidly to the flat drive plate coming out of the mag drive, you have defeated the constant velocity feature of an Oldham coupling. It may not matter, but just wanted to mention that. Both sides of the disk need to be able to float on the drive tangs.
Here is a link to a youtube video. DU4 magneto with no impulse coupler and with no problems starting.
Hi Dan the adapter floats on two pins on the drive end and is a slip fit on the impulse coupling.
Joe the car started just like the video with the starter,12 volt, but was hard to start with the crank. I suspect it would hand start ok with the fresh mag without an impulse coupling because it was designed for that originally.
Hey Pete! Looks great and I'm glad it worked out for you. DU-4 is one of my favorite accessories for a T. I'm glad I could help. I had new gears machined for my triple gear drive and the guys that made the new gears highly recommended that I figure out a way to run them with oil in the case instead of grease. Well, I sealed up the faceplate of the case and it holds oil no problem. Except that once I got it full it runs out like crazy because of the gap between the case and the big gear that goes on the cam. I need to mic the shoulder of the gear as well as the opening of the backside of the case and see if there is a modern seal I can add. If so - it'd let me run oil in there without making a mess. I'm thinking something just like the modern cam seal we use on timer cover would be perfect - just some different diameters.