Old Jacobson Commercial Hand Mower question

JWFilips

Well-Known Member
My Son just picked up an Old Jacobson Hand Mower with "power burst" & rear drive: It is so old that No literature can be found online for it.
Sometimes it starts and runs great and other times it refuses to start & We tracked that down to "no spark" !

It appears that if you monkey with the throttle ( Before stating, by pushing the throttle to Power burst and then put the throttle in the mid speed setting) and also to fully disengage the rear wheel drive a few times ..... 50% of the time it starts!
What else "spark wise" should we be looking at?
 
Last edited by a moderator:

JWFilips

Well-Known Member
Popper....Thank you ! With what you sent above I was able to get the whole 3 parts of the manual and a ton of other helpful links
Jim
 

Bret4207

At the casting bench in the sky. RIP Bret.
Agree with Popper. Take a look at whatever the kill switch is connected to and you'll likely find something is worn, loose or misadjusted and causing your lack of spark. If it's not that, then use the diagnostic progression above to figure it out.

Jake made good stuff back in the day!
 

JWFilips

Well-Known Member
Going with a

"Electronic Transistorized Ignition Module"​

Can't beat the price and no monking with removing the flywheel!
Cut the magneto and Splice in the Module!
Just have to secure it to something that is not the engine to avoid direct heat!
 

Bret4207

At the casting bench in the sky. RIP Bret.
From your description in the OP, I think you may have a ground problem. The "Atom" modules and other like them usually work fine, but you may have a bad/intermittent ground that's causing the spark issues. Generally, if a coil is bad it's bad when it gets hot. Or if it's a condenser, it's bad- period. What you describe sounds like either corrosion, maybe a bad wire or end attachment or something sticking someplace. Some machines had a mechanical "OFF" switch in the throttle linkage. I'd check it all over if it we're me.
 

JWFilips

Well-Known Member
Finally got to put the Transistorized Module on the old Jacobson Mower!
Started on the first pull and purred like a kitten! ( great deal for $18) Cut the lawn in my "local" back yard today! Mower ran flawlessly!
Actually with the magnesium body it was so light, it was a real pleasure to use! Probably the best hand mower I have ever used!
Son was out cutting the back 4 with the big zero turn! 4 Acres of over grown grass gone!
 

Bret4207

At the casting bench in the sky. RIP Bret.
If it works, it's all good! From what I've read, only having used a couple of those Atom type modules myself, it's a good idea to keep a spare on hand. When they die, they die completely. OTOH, some last forever. Just make sure it's well grounded.
 

JWFilips

Well-Known Member
Have another question to throw out here:
I have been using my Old Jacobson "Power Burst" from the early 1970's the past few weeks & it has been starting & running great with the Transitorized ingnition.
This season I noticed that the rear wheel drive system has been acting up, off and on. The drive pretty much works going forward ( I do get some squeeking from time to time....figured it is the drive belt slipping!) But what I noticed more is that when you release the forward drive handle and try to pull it backwards....it is difficult to get the rear wheels to spin especially if it is cold. Once it gets good and hot it works fine!
I took a look at the gear box today and there dosen't seem to be a way of adding grease or oil to it....that I can see.
I'm posting some photos to see if any of you have seen anything like this.
It is impossible to get a manual on the mower deck itself anywhere and Jacobson's manuals on their site, do not go back that far.
It appears someone is selling one on eBay but for what they are asking for it, It is not worth the money to me. At least I have the engine manuals!
Will need them when I do a Ring job on it in the winter.
First photo is the straight down view:
mower1.jpg

Next photo shows the gear box :
mower2.jpg
The orange coil spring is the self tensioner for the belt drive. The silver spring is the go between fot the hadle cable and the actuator arm.
 
Last edited:

358156 hp

At large, whereabouts unknown.
Your belt looks kind of glazed. That could cause the condition you're describing. It could also be the wrong profile for your pulleys, but your pulley wear appears to be normal. I think I'd try a new belt.
 

fiver

Well-Known Member
i was looking at that belt too.
it looks original equipment, still with the bias ply construction.
it also looks to be rubbing on that spring
 

JonB

Halcyon member
did you try to remove any of the bolts?
Sometimes, a bolt hole doubles as a oil filler hole/drain hole.
 

Bret4207

At the casting bench in the sky. RIP Bret.
Agree the belt looks aged. I'm a bit surprised Jake didn't have a fill hole, but it's entirely possible you are supposed to lay it over on it's side, pull the cover in the pic and fill to capacity that way. There may be a clutch mechanism that's hanging up when you try to go backwards. Got any more pictures?
 

popper

Well-Known Member
If anything like Honda, trans has a couple 'shoes' inside that control a clutch type mechanism. Shoes wear and trans needs repair. Honda doesn't have a drain/fill plug either.
 

JWFilips

Well-Known Member
Man you guys are great observers!
Belt is OEM Probaly not going to fing one of those for a 1975 machine! Yes it is glazed and the spring only touches it sightly when you release the drive handle You can see the spring is lightly polished in that area! I believe if I could get a new drive belt it would not be so streched which would roll the gearbox forword causing the spring to sit lower away from the belt!
I guess I shall start my quest for a new drive belt. Don't have any more photos because those pretty much show everything.
Thanks for your input!
 

Bret4207

At the casting bench in the sky. RIP Bret.
Take the belt to any decent auto parts store, or Tractor Supply for that matter, and match it up. Keep in mind it's probably stretched a good 1/2-3/4" over the years. It will likely be narrower than the new one too.
 

RBHarter

West Central AR
I can't remember now which way it is but the belt numbers are either length in inches and width in 16ths or the other way . It's a standardized number system just like bearings that gives length , width , drive shape , and thickness . It's width first , then length . Then something like V,U,W , R and S maybe it was a particular number code of the last digit . Roughly translated to 60° , 45° , wide 45° where the width exceeds depth , ribbed for 2 or more drive Vs , and serpentine types . If it is a number in the last place instead it's per drive faces.......that may not be wholly correct but it's pretty close it's been a very , very long time since I had to pass that test . I hate it when the stuff is right there and I can't get at it .......