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Small Air Cooled Gasoline Engines Briggs & Stratton, Clinton, Lauson, Maytag, Nelson, Wisconsin and other small air cooled engines. Sub forums for mowers, scooters and powered eqipment.

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Jacobsen 4 acer mower


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  #1  
Old 08-03-2005, 02:56:52 PM
Dan Hodge Dan Hodge is offline
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Default Jacobsen 4 acer mower

I see a lot a talk about these old Jacobsen mowers and thought it was time I asked a question about mine. I have a 1930, 4 Acre it runs good but I do not know the correct color to make it when I do a restoration. Do any of you folks know the correct color? Also It has a bracket for an oil can does any one make a replica of the original can? Last I see in the owners manual a cycle bar attachment was available has any one seen one of these on a 4 acre mower?
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  #2  
Old 08-03-2005, 04:59:31 PM
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Default Re: Jacobsen 4 acer mower


Dan,
I've got one of these motors (but unfortunately, not the whole mower).
The color I painted it when I started restoring it is as close as I could 'find off the shelf' to the color it was when I got the engine. I can't say for certain that it was the original paint, but it had been that color for a very long time..... I used DupliColor Engine Enamel from my local Auto Zone store called New Ford Gray. I'm still not finished with it, but it is all painted.
Would it be possible for you to make a copy of the owners manual that you have? I would pay for your time & effort (and postage). I have several manuals for various engines that I have made copies of. If see any you like / want / need, I'm sure we could work out a swap. You can see some of the manuals I have available on this web page Engine Manual Copies
John Newman, Jr.
Saint Louis, MO
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Old 08-04-2005, 12:16:23 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Jacobsen 4 acer mower

I have had several of the 4 acre mowers. The earliest was painted dark green, with black accents (flywheel rims and head cooling cover were black), with the mower itself being painted silver. The other 2 engines were painted silver, as were the entire mowers. They all had the screw on round muffler, seperate starter hand cranks, and gear driven mags - off one end of the crankshaft. The one pictured in the previous post is a later version, with the bolt on muffler. I have seen only one of these later engines, and it too was silver in color. The Johnson-Jacobsen engines were painted a medium grey, and the earliest of these also had black accents (1934). I have one of these- very early, with a 3 digit serial #. The mower I currently have (about 1027-8 vintage), has a small box mounted on the deck, that housed tools, as well as a clip that holds the starter crank. I also had an early type 4 acre engine that was set up as a power unit by Jacobsen This unit had the same bosch mag as the mowers, but it was direct drive thru a coupler on the crankshaft of the engine. The unit was started by a wrap a rope starter, built into the drive flat belt pully (similar to the Maytag model 82 set up) The power unit was also painted in the green and black scheme, with the steel base being painted black as well. One neat thing about the power unit was that you could idle it until it nearly stopped, and if you released the throttle, the engine would run up to about 3/4 throttle, and maimtain speed at that setting, no matter what the load! It seemed to use engine vibration as a governor! It maintained speed to load better than one of my modern engines! The 4 acre mowers also had a sulky attachment, and were available with rim extensions My mower has the rim extenders.
Andrew
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Old 08-04-2005, 12:43:36 PM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

Andrew
Thanks for the info. I will see if I can get some info out to you as far as manuals. Give me a few days and an address.

John
I have a bolt on muffler and my mower was dated as 1930. What is your best guess as to the correct paint arangment. Do I need the black stripes? Do you have any photos of you mowers? I will try to post some soon.
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Old 08-04-2005, 07:56:14 PM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

Let me see if I can get a photo of my 4 acre in here. The serial number is 7881 I think

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Old 08-04-2005, 07:58:33 PM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

I should of put this in the last post but I forgot. I have a small vidio of it running but was unable to load it in photobucket. If you would like to see it send me an address. Thanks
Dan
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Old 08-05-2005, 01:01:16 AM
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Default Re: Jacobsen 4 acer mower

Here is another view of mine showing the other side. These pictures were taken shortly after I painted it and had just started putting it together. You can see that the backing plate is missing behind the flywheel in the front of the picture and the lower shroud part is not there either. They have since been installed, but I am still hung up by the lack of a good piston. The one that was in it had rusted through (it is a cast iron piston) where it was exposed through the exhaust ports. So basicaly, its all got to come apart again. This one has a flywheel magneto (HOT!) I picked up another one of these that originally had an external mag (missing) hoping to use the piston out of it, but it is around 1/8" different in diameter (I forget at the moment if it was bigger or smaller, but I know it didn't fit.....)
Dan:
I'd like to see and hear yours running. Did you mean you could send this clip in an e-mail? I would also like to get a copy of the manual that you have.
E-mail me - link is in my name, just click on it.
John Newman, Jr.
Saint Louis, MO
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Old 08-05-2005, 07:05:35 AM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

I have not had my engine apart yet but I will when I do a restoration so I can look at the rings. It has low compression. If your good piston is larger than your bore maybe you could get it turned down to fit and just grind the ends of the rings to get them in the bore. or if things are loose maybe you could sleeve the painted engine. I will send the vidio file to you this weekend. It shows a lot of smoke. I was running rich and not all the noise is from the mower, other engines were running near by.
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Old 08-06-2005, 12:29:01 AM
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Default Re: Jacobsen 4 acer mower

I had a chance to go over the 2 Big Jakes I have and this is what I found:
The one of mine shown in the pictures above has an ID tag and it says it is serial # HM-6-1478. It has a 2.750 bore. It has an aluminum head and cast into it in raised letters / numbers between two of the fins just under the sparkplug hole it says "LYNITE" and has the number 1602 (might be 1802 its not very clear & sharp) All 4 of the studs for the head are 3/8" . As previously noted the cast iron piston has holes rusted through it - shown below. This piston has (had) 3 rings all at the top - two of which are still stuck tight in the grooves and one missing
The other one that I have does not have an ID tag - in fact, it doesn't even have the sub-base under the crankcase at all. It was bolted down on a piece of 2X4 lumber with a flat plate of 3/16 steel about 12" X 12" under that. This one has a bore of 2.830 - which is a rather unusual size in my opinion... The head on this one is cast iron and has cast into it around the outside perimeter in depressed numbers / letters is 1602B. Two of the studs for the head are 3/8" and the other two are 7/16"
I don't think I can turn the bigger piston down to fit the smaller cylinder, because I would have to turn the ring grooves down to maintain the same relative depth and I have a feeling that I wouldn't have much of a wall left after doing this. Here are a couple of pictures of this other engine. The piston for this motor has 3 rings as well, but two are at the top and one is at the bottom of the piston. The bottom one has a broken segment stuck tight in the groove while the rest of that ring floats free. The top ones are intact and free.

If anybody has a 2-3/4" Jacobsen piston available, I' sure like to make that one old boy run.
John Newman, Jr.
Saint Louis, MO
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Old 08-06-2005, 09:18:26 AM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

You have a .080 difference in size. That is a lot but it could be an over bore.
I would make some close measurements on that cast piston. It might be possible to only slightly cut those grooves and put in new rings that fit your grooves. Remember you only want it to run. You are not going to make a living with it.
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Old 08-08-2005, 12:58:34 PM
Ned L Ned L is offline
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Default Re: Jacobsen 4 acer mower

OK, I'm going to ask a 'stupid' question. Why couldn't the rusted though piston be used? If all the holes are below the rings you won't loose compression, the skirt area is intact so the alignment in the bore won't get off or cocked. (Does the skirt area leave the bottom of the bore on the bottom of the stroke? If so it won't work) If the rest of the piston material is pretty solid I should think it would work ok. I'd chamfer the edges of the rust holes so the cylinder can't get scored. As has been said, it just needs to run (reliabley & well), not work nonstop. -- Just wondering??
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Old 08-08-2005, 03:46:57 PM
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Default Re: Jacobsen 4 acer mower

Remember, this is a 2-stroke engine. The piston covers & uncovers ports in the cylinder wall to admit the fresh fuel / air mixture and exhaust the spent (burned) gasses. Plus it has to be able to be able to suck in a fresh mixture charge through the crankcase on the piston's up stroke. With holes in the piston, the ability to seal off these ports is lost and the system simply doesn't work.
If it was a 4-stroke engine, your theory would probably work.
John Newman, Jr.
Saint Louis, MO
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Old 08-08-2005, 09:17:51 PM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

Maybe some JB weld on the inside and the outside of that rust spot a quick trip through the lathe and it is as good as new. I'd give that a try. You dont really care what the inside looks like and I don't think the extra little weight will do much.
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Old 08-09-2005, 01:20:45 AM
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Default Re: Jacobsen 4 acer mower

Not a bad idea....
But, I still don't like the idea of J-B Weld sliding directly against the cylinder. So what if I J-B Weld a patch or two inside the piston so there is at least metal showing at the holes instead of epoxy. I'll have to look inside the piston to see what kind of surface I have to work with. Another thing to put on the 'to do' list. There is still the issue of the two remaining rings that are stuck tight. Do I just pry (break) them out and hope OTTO can match them, or can anybody tell me a way to free them up for possible re-use?
John Newman, Jr.
Saint Louis, MO
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Old 08-09-2005, 01:28:18 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Jacobsen 4 acer mower

Another approach would be to have the holes in the piston brazed over, You do not need structural strength, you need to fill the opening! Chances are that JB weld would not stand up to air cooled 2 cycle engine heat, and heated gasoline vapors. These engines are not high compression engines - if you get 75 PSI on a comp test, I would be suprised! A good test on the old 2 stroked , is 'The Bounce Test' Do the following: engine cold - spin the engine up against compression, and let the crank coast - watch the crank. If it just mushes to a stop, remove spark plug, squirt oil into bore, replace plug, and re-test! If the piston bounces back, and rocks back and forth between compression strokes on the first try, then compression should be OK to run the engine. If the pison just mushes thur the compression stroke; with no bounge back, and after the addition of oil, it does need a re-ring job. If the engine still mushes thru, then a re-ring, and possibly other work may be needed
Andrew
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Old 08-09-2005, 06:34:33 AM
Dan Hodge Dan Hodge is offline
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Default Re: Jacobsen 4 acer mower

I am not sure about that patch on the inside. You would still have thin parts that coule get loose in the engine when running then. You could braze as said before. The heat will help get those rings loose.
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Old 08-09-2005, 12:40:31 PM
Ned L Ned L is offline
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Default Re: Jacobsen 4 acer mower

Yep, wasn't paying enough attention to the pictures to notice it is a two cylce engine, sure won't work with holes in the skirt.
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