re: odd Lawnboy issue

Reply

  #1  
Old 06-08-04, 07:07 PM
Member
Thread Starter
Join Date: Dec 2003
Posts: 105
re: odd Lawnboy issue

Hello:

I'm hoping Cheese, Puey or others can help on this one.

I have my Dad's Lawnboy here now as he had some problems with it.

Last season I replaced the magneto and CDI and tweaked it all. Also rebuilt the carb

Last week he took it to my local parts supplier as he could not wait 2 hours until I got home from work to have a look at it. Leaking fuel pet****, no problem.

Anyway, he has been complaining it started fine, but if he ran it for 20 minutes mowing the front lawn and let it sit while he took a break for 30 minutes or more it would not start again--with or without priming.

I doubted this at first as both he and my brother seem to have some sort of magic on making mowers not run. In this case Dad is right, as I've replicated the problem here at home.

The mower is a Lawnboy Gold series with the 4.5 HP motor, self propelled and electric start.

Commercial on the motor it says and has the 22" aluminum deck. Dad thinks he bought it about 10 years ago but is not sure and can find no manual or documents (nothing new there.)

I've hunted for a serial number everywhere and can't see one. I suspect it was on a label that fell off.

Anyway, all I wish to do is solve the starting problem--and should mention I discovered that it WILL start on one pull in this situation when it will NOT with the electric start.

I'm thinking after 9 or 10 years it may be the battery but hate to spend the $$$ if it is something else. I tested the battery with my VTVM and it looks OK.

Tomorrow I'll pull every electrical lead and both battery leads and clean and coat with some lithium grease.

Any tips will be appreciated

Kindest Regards,

Snowman53
 
Sponsored Links
  #2  
Old 06-08-04, 11:26 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,818
Hi Snowman53!

If it will start fine with the rope, but not the starter, then I would go with your idea of either electrical contacts or a battery. The starter could be a possibility too. You might take the starter apart and clean the armature, commutator, brush holder, and lubricate the bushings to make work more efficiently. You'd be surprised how much better that can make a starter work, and with drawing less amperage too. Does it turn slowly?
 
  #3  
Old 06-10-04, 04:08 PM
Member
Thread Starter
Join Date: Dec 2003
Posts: 105
re: Lawnboy problem

Hello Cheese:

I went through the electrical system today abd it appears good. One thing I'll not do is waste money on a battery as it cranks fine and is so close to original specs that can't be the problem.

Also pulled the starter and it definitely does not need any rebuilding, looks like new and tests well.

As I mentioned before I replaced the magneto last season. Only thing I suspect now is the CDI (which I also replaced last season) or a carb problem.

Thing is the darn thing runs like a beast and I also rebuilt the carb last summer.

Only thing I can think of now is that it's a weird issue with the key switch, so will bypass that next time and see what happens.

Gotta go as I need to get the Mikuni type 2 carbs for my Yamaha triple.
back together, then get to a snowblower carb I have in the ultrasonic.

Yeah..I can dream on on getting that one together tonight. Will be lucky to get the Mikunis done.

Cheerio,

Snowman53
 
  #4  
Old 06-10-04, 09:32 PM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,818
Sounds like fun . I can't think of how a CDI could let the mower start with the rope, but not the starter. I figured maybe the starter was dragging or over-amping. It sounds like you know enough about starters though and have eliminated that as a possibility. Does it have spark when trying to start it with the elec. starter?
 
  #5  
Old 06-17-04, 07:45 PM
Member
Thread Starter
Join Date: Dec 2003
Posts: 105
re: odd Lawnboy question

Hi Cheese:

I had some time and went through all the electrics again today.

Will go tomorrow and buy a new battery; it is 10 years old so a replacement will not be a waste of money, and they are not that expensive.

I KNOW it is not logical the the battery is the issue but I've seen weird issues like this before on my Volvos.

Sometimes it's best to keep it simple. A new battery is probably overdue and MAY solve the problem. If not I'll at least know where NOT to look.

Speaking of batteries...went to start the rider tonight and it was dead. Put a quick charge on it and it fired right up. Took a break and it was dead again when I went to do the back yard--ubt fired up after a 5 minute charge.

Looks as if I'll be buying three batteries tomorrow..one for the Lawnboy, another for the MTD and then one for my Triumph Bonnevillle--but I knew that one neeeded replacement, so no big deal.

I'd love to be in the battery business!

Regards,

Snowman53
 
  #6  
Old 06-19-04, 09:53 AM
Otoe
Visiting Guest
Posts: n/a
Battery I/R Drop

It could still be the battery. What is the voltage across the battery
terminals when starting the lawnmower? The battery can build internal
resistance and cause an I/R drop that limits the current. Measuring the
battery without a load isn't much of a test; especially after recharging.

Let us know if the battery solves the problem,

Otoe
 
  #7  
Old 06-19-04, 09:54 PM
jughead's Avatar
Member
Join Date: Oct 2003
Location: Davenport, Iowa
Posts: 597
It sounds like a strange situation. The motor's ignition system shouldn't run off of the battery but from a self contained (i.e. magneto) spark generator. During the starting process the battery only turns the starter motor that produces enough rpms in the engine for it to start. I'm not there so I can only make certain assumptions about how fast the battery/starter motor cranks the engine while attempting to start it. My assumption is that the engine is cranking normally from the starter motor.

I'm thinking that the problem will involve the key switch. Normally, you would ground a wire to the frame to kill the engine. If your engine has a key you would have a grounded wire in the 'off' position and an ungrounded wire in the 'run' position. There would be a third, momentary, contact on a key start motor that would energize the starter solenoid. If in the 'start' position the magneto wire were to be grounded for some strange reason the engine could never start. On the other hand, if the wire were to be ungrounded in the 'run' position you could pull start the engine fine.

If this condition were to exist on the engine you could verify it easily. Just disconnect the battery, start the engine by hand, and turn the key to the 'start' position with the engine running. Since your battery is disconnected the starter will not engage. If the engine dies that means that the key switch is grounding the mag wire in the start position.

Let us know if the new battery is the fix for this problem.
 
  #8  
Old 06-20-04, 06:27 PM
Member
Thread Starter
Join Date: Dec 2003
Posts: 105
re: Odd Lawnboy Issue

Hello, and thanks for the replies

I've been VERY busy and look forward to Winter.

Anyway, I went through everything again but have not had time to go get a battery.

That said, I like what Jughead suggested:

"If this condition were to exist on the engine you could verify it easily. Just disconnect the battery, start the engine by hand, and turn the key to the 'start' position with the engine running. Since your battery is disconnected the starter will not engage. If the engine dies that means that the key switch is grounding the mag wire in the start position."

Doh.... I should have checked that but seem to be in the clouds these days.
Thanks Jughead.

I'm quite sore tonight as I did a vintage race yesterday, flat tracking.

Old motorcycles and men 50 and older. I took second, lost first place to a 68 yr old guy. I'm back into this now and in training at the gym daily. I hope to whip his butt in the next Baja 500.

Regards,

Snowman53
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes