jacobsen 2 stroke mower..

[Magice]

I picked up an old jacobsen mower last year.. It runs real nicely, starts first pull. I was wondering if anyone could give me any more information on the engine.. It winds out real good.. sounds louder than a chainsaw.

 

[Russ2251]

I have several Jacobsen J-321's which are the horizontal shaft equivalent of this engine. One is totally rebuilt and others pending.

 

[Magice]

any idea the horsepower / rpm / year / how rare it is?

I got this thing for $30.. I've done nothing to it since I got it.

 

[Russ2251]

Pretty much standard stuff as 2 cycles go...
around 2.5 HP, mid to late '50's (?) and Extremely rare.
Finding the right buyer would be difficult at best. Could fetch a couple hundred. Best not to do anything to it. Appears to be original paint which is first thing a collector would look at. Parts are almost impossible to find. Store it in a dry protected area.
If you're interested in value, try Ebay with a high reserve price. I would not settle for less than $200 to $300. Set reserve at $500 or more. You can state that you reserve the right to pull from auction at any time.
I personally would keep it as it can only appreciate in value.
I can post some pics of mine if interested.

 

[Magice]

thanks for the info! A pic of your would be great.

I'm going to keep it.. I lke it

 

[Russ2251]

Jacobsen J-321 2 cycle pics. One of the smoothest running 2 cycles I've owned. Induction system is cross-flow scavenging which features a rather odd looking piston crown still popular in outboard motors. Most high performance 2 cycles use loop scavenging.
Original muffler is cast iron (not pictured) and is unbelievably heavy and super quiet.
I was very fortunate in finding an NOS short block on Ebay which (essentially) makes this engine brand new.
Original oil mix was 16:1 using a straight non detergent SAE 30 oil.

 

[Magice]

Wow that's awesome! I love old engines.

you must have alot of neat stuff.

 

[Russ2251]

Some of my collection goes back to mid 1930's.

 

[Russ2251]

any idea the horsepower / rpm / year / how rare it is?

I took another look at my service manuals and have to make a correction on estimated manufacturing date. I missed the bagging/discharge chute. Could be early '70's. This does not take away from rarity/value.
I also noticed that some sheet metal is missing (lack of orange over-spray on cylinder fins/head) which would diminish value somewhat. See pics in previous post (#6) in this thread.
If you have this metal, I would reinstall it. Possible overheating/seizure could result without it in place. This is especially true of 2 cycle engines.
Check with party you purchased this from. He still may have it (short prayer to Jacobsen gods may be appropriate). If I didn't need mine for a neighbor's restoration project, I would send it to you. Requires removal of 2 head bolts to re-install. Parts for this power-plant have been out of production for a couple of decades. Current Jacobsen's use Briggs, Tecumseh, and Honda engines. No more 2 cycles...Thanx to tree huggers...

 

[Kenny_McCormic]

Wouldn't be hard to make one.

 

[Russ2251]

Could...but would not be original.

 

[Kenny_McCormic]

But it would run without the chance of overheating. I never understood why 3600 rpm 4 strokes dominate the pushmower world when a faster spinning 2 stroke engine will cut the grass quicker/cleaner and be more tolerant to a dull blade.

 

[Russ2251]

2 cycle mowers cut at 3600 rpm. Same as 4 cycles. Difference is that 2 cycles have less trouble getting through grass because they fire on every revolution as opposed to 4 cycles which fire on every other revolution. A waste of potential energy.

 

[Jerryburger]

They're limiting rotary mowers by "blade tip speed", probably the same concerns as a cheap flywheel- don't want that unbalanced, dented worm-burner blade spinning too fast.

 

[Russ2251]

They're limiting rotary mowers by "blade tip speed"

Most manufacturers rate there mower engines at 3600 rpm plus or minus 200 rpm for the very reason you stated. Virtually all governed engines I've checked were on the minus side.
Last year I repaired a neighbors Briggs powered mower.
Before he got it, someone tried to rig up a throttle control and really it up.
I removed all the "add ons" and got it running to factory specs.
He decided engine wasn't spinning fast enough so he wired throttle to full open.
He's still using it that way.
I was going to say something but decided against it.
How do you tell somebody they're stupid.:toetap05:
I've seen mowers throw a blade and it ain't pretty.

 

[I like karts]

...Thanx to tree huggers...

Did you know they're starting to make all 4 stroke dirt bikes and eliminating their 2 strokes?

pisses me off. all this gay global warming stuff everybody's freakin out about

 

[oscaryu1]

But it would run without the chance of overheating. I never understood why 3600 rpm 4 strokes dominate the pushmower world when a faster spinning 2 stroke engine will cut the grass quicker/cleaner and be more tolerant to a dull blade.

Emissions.

How do you tell somebody they're stupid. :toetap05:

You egg his house

 

[Jerryburger]

Yeah, it's pretty frightening to think about (tossing mower blades). We used to have a 3.5hp briggs on 22" mower- with that large of a blade,the engine was just putting along. I was shocked one time, when out of curiosity, I started it without the blade- the motor at full governed throttle was running at not much more than a fast idle! When I asked my power-mech teacher at school about setting the governer for 3600 rpm, he told me I'd be stupid if I did. Knowing how many dog turds, tennis balls, golf balls, and chew-toys I hit on a routine basis, I NEVER upped the speed! Interestingly, most of the noise from a mower is pretty much the blade!

 

[Jerryburger]

Oh- credit for the term "Worm-Burner" (LawnMower) goes to him, at least I heard it from him 1st, back in '79. Something like the HF engine would've been exotic to us back then!

 

[Magice]

Just rezing this thread to ask if you would know where I could get parts to do a rebuild?