Onan BFA 4Kw genset, "Des Moines"

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asavage
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Onan BFA 4Kw genset, "Des Moines"

#1

Post by asavage »

I seem to be in a genset-acquiring phase over the past six weeks. This one I got from the Des Moines/Shoreline area, suburb of North Seattle.

Acquired 28-Oct-2006
Model: 4.0 BFA 1R/16004A
Serial: L78xxxxxxxxxxx (built Oct-1978)
120v only, 30a breaker, 33a max.
1800 RPM

Onan made a lot of horizontal-opposed twin engines (CK, CCK(x), BF, BG, NH), and they're all different.

Previous owner bought it for about $700, paid $278 to have a "doghouse" constructed for it -- I have the receipts. I paid PO $300 and took his word that it was working OK. Bought it two weeks ago. These are the pics from the CL ad:
Image Image
And the CL text:
ONAN Cummings Push Button Start GENERATOR, DUAL EXHAUST - $350
Reply to: sale-225212317@craigslist.org
Date: 2006-10-24, 2:24PM PDT

4KW ONAN/CUMMINGS Push Button Start GENERATOR, DUAL EXHAUST

This is a 4KW, or 4,000 watts Onan/Cummings Gennie. It's been used at our house only once, and is in AMAZING condition. It's push button start and dual exhaust system make it a REALLY NICE (and quiet) unit. The house that we built for it has cedar shakes and a great roof so it won't get wet if you are putting it outside.

Please call (xxxxxxxx) to come and get it!

* this is in or around Des Moines
Some explanation: the PO had it very close to his neighbor's garage, so he had it plumbed with two mufflers ("dual exhaust"), but in series. The muffer you see laying upon the (removeable) roof above actually sits vertically behind the doghouse, and plugs in to the OEM muffer that exits horizontally out the back.

Loading it was a bear: it's heavy! But I had help of the PO and his son.

However, at my end, I was alone -- and it began to rain, of course. The engine hoist would pick it up, but just barely, and then only if I provided ballast (ie I had to sit on the back of the hoist).

First order of business was to casterize it: build a piano dolly for it so I could work on it in our shop and be able to stow it out of the way during this phase.

Image Image Image Image Image Image Image

And even with the piano dolly, it wouldn't clear the legs of the engine hoist, so I had to get creative . . .
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Believe me, that was not fun doing alone.

So, it sat in the corner for the past two weeks, while the electronic ignition conversion parts arrived from eBay. Actually, a Pertronix 1181 kit for SB Chevy. This particular path has already been beaten for me, by two others, though neither did a BF series.

CCK: Vaugh Simon
NH(?): Ken Henderson

So, armed with their photos & notes, I ordered a couple Pertronix 1181s (I have more than one of these beasts). Today, I got serious about doing something about installing them.

For now, I'm just going to throw a bunch of photos up. Later, I'll edit them and include dimensions and such.

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No mufflers; heat shields still installed.

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Heat shields off.

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Carb, with points box below it (points cover removed).

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Stock points setup (cover removed).

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Exhaust wye pipe removed, fan shroud removed. Crank turns clockwise, and despite the forward curvature of the fan fins, air is pulled over the engine and expelled out the fan shroud. This is the Onan "Vacu-Flo" system for RVs.

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Timing marks: 25° (presumably for Natural Gas or LPG) and 21° (for gasoline). The divot in the flywheel is stock, I just put a little silver paint in it. Connected a timing light, with the stock points I get two readings: about 23° and about 20°, alternating regularly. Seems there's a bit of slop in the engine and mechanism that triggers the points. One cylinder gets 20°, the other gets 23°.

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That's gonna change!

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A picture to show that the OD of the flywheel is not perpendicular to the shroud's backing plate, nor parallel to the crankshaft. This is important, and impacts the Pertronix installation and magnet mounting.
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The SBC Pertronix kit comes with a ring of eight magnets embedded in plastic. I Dremeled one of them loose for this project.

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Fire up the Chinese bandsaw. Cut off a section of 1/8"x1.5"x1.5" anodized aluminum angle.

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A bit of crude measuring and I was able to trim the first leg of the bracket, good enough to be able to know where to lop off the excess mounting plate from the 1181.

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Then I cold rough-cut the leg that mates to the fan shroud backplate. Note the unequal height: about 1/16" difference matched the OD of the shroud circumference fine. I could have just hacked it off square to the shorter dimension too.

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Time to match drill the new bracket to the 1181's trimmed mounting plate. Two 8-32x3/8" pan head screws, SS of course. Locktite + split lockwashers.

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Note the non-parallel fit. I bent ("re-aligned") the 1181's mounting to match the flywheel's OD taper. More or less.

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The yellow dot is where the magnet needs to pass by.

Now for the real fun: mounting the magnet.
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A bit of Dremel work again, created this nice furrow in which the magnet will be epoxied.

Image Image Image Image

I epoxied the magnet in tonight; more pics later.
Last edited by asavage 14 years ago, edited 5 times in total.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.
pbknowles
Posts: 95
Joined: 17 years ago
Location: Illinois, USA

Genset

#2

Post by pbknowles »

Looks like a good deal Al.....those old Onans were good machines. I built a 20 KW out of a Chinese ST series generator end and a Isuzu diesel out of a Thermo King semi refrigeration unit when I was once on an "off the grid" kick.
SD22 powered '85 Chevy S-10
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asavage
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#3

Post by asavage »

So, when last I'd typed, I'd just fab'd a bracket for the Pertronix 1181 and glued a magnet into the flywheel's edge. In the morning, after a minimum of work with the bastard file, this is what the magnet looks like:
Image

With a working magnet installed, I could then static time the engine. In constrast to the method detailed by Vaugn Simon, I connected the test lamp as if it were the coil load.

I connected 12V+ to the test lamp (lead No. 1) and the Pertonix Red lead. Then the test lamp (lead No. 2) to Pertronix's Black lead. What provides the ground? Yup, the Pertronix's case. The lamp won't light if the Pertonix isn't well grounded, and that threw me for a while, because I was using welding clamps to temporarily jig the position:
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and the ground wasn't sufficient; I had to run a separate ground jumper for the setup during testing, until it got bolted down permanently.

The goal is to get the magnet to run right under the yellow dot on the Pertronix's belly:
Image Image

Ideally, you want it no more than .060" from that dot. Something was preventing me from doing that: casting flash on the flywheel. Out came the Dremel again. I had to clearance three high areas on the rim's edge (only one shown):
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Then it was just a matter of applying power and watching the test lamp, which remains ON (Pertronix completes ground of lamp, simulating points closed) until the magnet is moved under the Pertronix. A bit of fiddling with the welding clamp, moving the flywheel back and forth a bit, and I was satisfied with the bracket position. That took almost 90 seconds.

With the welding clamp still in place, I used clip leads to temporarily connect the Pertronix to the ignition coil, disconnected the points & condensor, and started it up.

The following two pics show "before" (running on points) and "after" (running on Pertronix). The left pic is the unit running on the points system. Note the 4-5° spread. It's firing one cylinder several degrees different than the other. The right pic shows the Pertronix timing dead on -- Yippee!
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OK, so I thought I'd go to mount the Pertronix permanent-like, but I wasn't happy with the fit. This is the mount I'd created:
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But I wanted more and wider clamping. So I started over, and built a different bracket (I was up to Rev. 5 by now):
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(Good thing I had a 4' chunk of alum. angle and a new bandsaw blade!)

I also moved the Pertronix inboard (closer to backing plate) a bit, to better position the yellow dot above the magnet. This meant trimming even more off the Pertronix's base plate:
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Some assy. views:
Image Image Image

The gap I settled on:
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The new bracket allowed more-robust mounting bolts (1/4-20, Gr. 5).
Adding a grommet brought it to this:
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A nylon wire tie added as a strain relief, and some split loom to protect the harness, a cable clamp or two.
Image Image Image
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.
aaronrodg
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Joined: 8 years ago
Location: Pleasant Prairie, WI
Contact:

Re: Onan BFA 4Kw genset, "Des Moines"

#4

Post by aaronrodg »

http://asavage.dyndns.org/ftp/Onan/BFA/ ... _16-1b.jpg
http://asavage.dyndns.org/ftp/Onan/BFA/ ... _76-1b.jpg
http://asavage.dyndns.org/ftp/Onan/BFA/ ... FA_17b.jpg

can someone help me find a manual that will help me repair my generator? it doesnt have any spark going to the plugs and I want to try to repair myself before turning it over to a mechanic.
how do i "change the points"?
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asavage
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Location: Oak Harbor, Wash.
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Re: Onan BFA 4Kw genset, "Des Moines"

#5

Post by asavage »

Hello, Aaron:

I've deleted your signature link to a website, as it looks suspiciously like advertising.

The service manual for the Onan BFA gensets is 900-0337, and I have a page-by-page accessible version online here.

You can also buy it from several places. Cummins may even have a PDF online now -- ISTR seeing that a while back. Of course, mine was online in 2006 :)

If your genset isn't a BFA, then I'll need to know more to be able to help you.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.
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