Followup from an earlier thread, I checked the gap on our DU 6 and it was very narrow (probably .12 or less thousandths).
To change the gap I have to remove the cover and "cone", so gapping is a bit of a guess (and hard to get at with a mirror and too big of hands and fingers).
Now the gap is .24 thous, and it runs better, but still dies at idle. An old manual says the gap should be .19 (plugs too). Before I try to change it again, should a narrower or wider gap work at low rpm. The mag was recently rebuilt by a magneto "expert" so the magnets and windings should be good.
Thanks for any help,
Sometimes (USUALLY) you have to play with the points gap to find where you get the best spark.
The recommended gap is 1/64" or .015-.016".
what are you trying to change, the points gap, or the air gap under the porcelain cap? if it was rebuilt by an expert, shouldn't you ask him?
I didn't have it rebuilt. The person I bought it from had a receipt from a magneto rebuilder that I have heard of, but don't know personally.
I'm just trying to determine if a bit more or less point gap might improve firing at low RPM.
I was confused by your question because the points on a DU mag are about the easiest things in the world to set. The air gap, not so much. The air gap will only spark if something is wrong, anyway.
The points should be set to .04 of a millimeter OR 1/64 OR .0156 I don't think there would be a benefit to setting them differently than that. Remember, you must set the spark plugs tighter when using a high tension magneto. .017-.019 The book states a mag will burn up if plug gap is too wide.
Just to clarify Tim's post, 1/64" = 0.40 mm (or 0.39768..)
^ (or 0.39768......what?)
1/64", if you want to get down to brass tacks, is .015625 of an inch.
Rob.......if the, so called, rebuilder didn't replace the condenser that would explain the weak spark.
The downside to the otherwise terrific Bosch mags is the condenser and windings are on the armature......in the armature to be more correct.......and it's a complete PIA getting to the condenser but it can be done because the condenser end, fortunately, is opposite the commutator end.
You need to remove the screws that hold on that end, remove the condenser "box thingy".......unsolder that box and toss the condenser material.
Then you sub a modern replacement capacitor in the box, solder it shut and slap everything back together.
It sounds worse than it really is.......MAYBE........
Thanks guys. I just found these instructions on the net (1937). They also say 1/64 gap. I tried to change the gap last evening, however my "cheapie" ignition tool set have too much offset and now I'm unable to loosen the locking nut.
Hopefully I can find a better set by tonight and try setting the points closer. Craig, if that doesn't do it, it's off the car for another rebuild.
Thank you again,
Rob-I tried to bring up your pdf, but cannot. Any suggestions? Thanks, Bill
The link worked for me, I use Google Chrome.
I took it to my drop box. Try this:
There is a guy who lists reprints of the original back-in-day DU2 on eBay. http://www.ebay.com/itm/Bosch-Type-DU2-DU1-High-Tension-Magneto-1-2-Cylinder-Bkl t-/330937908518?pt=BI_Heavy_Equipment_Parts&hash=item4d0d6fbd26
I have an original DU4 manual from mid teens, as is this reprint. The two, relative to timing, install steps, gaping, are virtually identical, as well they should be since the only difference would be the number of terminals. For folks with the DU4, it is a low cost way to get a manual
And of course this, which has a whole chapter on the DU
http://www.amazon.com/dp/0982173369/ref=as_li_qf_sp_asin_til?tag=tractordata-20& camp=14573&creative=327641&linkCode=as1&creativeASIN=0982173369&adid=1P8PP4HYPN0 QA4QQWGFV&&ref-refURL=http%3A%2F%2Fwww.tractordata.com%2Farticles%2Fbookreview%2 Frestore-tractor-magnetos.html
thanks Roger for the correction..... 1/64 is easy for me to remember.
Thanks guys. Now to find a set of ignition wrenches. I've stopped at several places in Lincoln, no luck.
Get a set from Sears.......I've had mine for YEARS and wouldn't even think of working on a mag without them!