Automotive Forums .com - the leading automotive community online! Automotive Forums .com - the leading automotive community online!
Automotive Forums .com - the leading automotive community online! 
-
Latest | 0 Rplys
Go Back   Automotive Forums .com Car Chat > Engineering/Technical > Small Engines ATVs Go Karts and Lawn Mowers etc
Small Engines ATVs Go Karts and Lawn Mowers etc From ATVs to Watercraft, Go karts to Lawn Mowers, discuss your small engines here.
Reply Show Printable Version Show Printable Version | Email this Page Email this Page | Subscription Subscribe to this Thread
 
Thread Tools Search this Thread
Old 08-11-2011, 12:53 PM   #1
jdmccright
The RustBuster
 
jdmccright's Avatar
 
Join Date: Feb 2006
Location: La Plata, Maryland
Posts: 2,290
Thanks: 1
Thanked 51 Times in 50 Posts
Lawn mower running weak after hitting a large chunk of wood and stopping

This is a subject covered in many other forums but didn't see it here, so I'll summarize.

Earlier this week I was mowing the backyard when I went over a hidden piece of wood. It stopped the engine dead and bent the blade about 3" out of plane, enough for it to drag on the ground. Focusing on the obvious, I set out to replace the blade and found one at Sears (Craftsman brand mower).

After replacing the blade, I pulled to restart it, and pulled, and pulled. After about the 15th time it barely caught and started to run but much slower. Just cutting the lawn caused the engine rpms to drop and since I had some high grass, it made for very slow going. I then noticed that the muffler was glowing red and said, "that ain't good"...as if everything else that happend before was normal, right?

So, I figured I'd killed it and in my excitement and frustration went to search for another mower to replace it which I did and brought it home.

The next day, I got my wits about me and searched the Internet for similar situations. Turns out that this is quite common after hitting an imovable object and the damage can range from minimal to severe.

If you are lucky like me, then all that has happened is the flywheel that also triggers the ignition coil has moved (advanced) in relation to the crankshaft. They are kept in sync by a small aluminum key that gets sheared when the engine stops abruptly but the flywheel's momentum causes it to continue turning. It had become offset by about 30 degrees. All it takes to fix it is a new $3 key.

More severe cases will bend the crankshaft and render it useless. This can be checked by tipping the mower up and having someone pull the cord with the spark plug disconnected. If the center bolt wobbles, then the crank is bent.

Other sites go into detail on how to replace the keey but it is as simple as disassembling the top of the mower, and removing the large nut (23mm in my case) that holds the flywheel to the crankshaft. I used a large 3-jaw puller to pop it loose but a steering wheel puller would work too.

Clean the broken pieces out, scuff the surfaces with emery paper and replace the flywheel, lining the cuts up with the crankshaft keyway. Drop in the new little key (made of aluminum) and retorque the retaining nut. Reassemble, refuel, and give it a yank. Hopefully, it'll be good as new.

Hope this helps!
Attached Images
File Type: jpg Sheared key.jpg (97.0 KB, 2 views)
__________________
Current Garage:
2009 Honda CR-V EX
2006 Mazda 3i
2004 Chevrolet Silverado 2500HD
2003 GMC Envoy XL
2000 Honda ST1100
2000 Pontiac Sunfire

Vehicle History:
2003 Pontiac Vibe AWD - 1999 Acura Integra GS - 2004 4.7L Dakota Quad Cab 4x4 - 1996 GMC Jimmy 4wd - 1995 Chevrolet C2500 - 1992 Toyota Camry LE 2.2L - 1992 Chevrolet S10 Ext. Cab 4.3L - 1995 Honda ST1100 - 1980 Yamaha XS400 - 1980 Mercury Bobcat.
jdmccright is offline   Reply With Quote
Old 08-11-2011, 02:47 PM   #2
90civicrider
www.DecepticonRacing.com
 
90civicrider's Avatar
 
Join Date: Dec 2001
Location: Calgary
Posts: 2,607
Thanks: 1
Thanked 9 Times in 8 Posts
Re: Lawn mower running weak after hitting a large chunk of wood and stopping

Damn, that must have been one big piece of wood
__________________
||JEFF| |
Candy Orange 1990 Honda Civic H/B
90civicrider is offline   Reply With Quote
Old 08-11-2011, 04:17 PM   #3
Moppie
Master Connector
 
Moppie's Avatar
 
Join Date: Jun 2001
Location: Auckland
Posts: 11,781
Thanks: 95
Thanked 101 Times in 80 Posts
Send a message via ICQ to Moppie Send a message via AIM to Moppie Send a message via Yahoo to Moppie
Re: Lawn mower running weak after hitting a large chunk of wood and stopping

Cool, so now you've got two mowers, one for you and one for the wife?


I just wish cars where this easy to fix.
Even if you had broken the crank, it's often very easy to replace, or just bolt on a new motor.

My mower came from a shop selling them second hand, and is a combo of best bits from two or three different trade ins.
__________________
Connecting the Auto Enthusiasts
Moppie is offline   Reply With Quote
Old 08-30-2011, 01:11 PM   #4
jdmccright
The RustBuster
Thread starter
 
jdmccright's Avatar
 
Join Date: Feb 2006
Location: La Plata, Maryland
Posts: 2,290
Thanks: 1
Thanked 51 Times in 50 Posts
Re: Lawn mower running weak after hitting a large chunk of wood and stopping

Didn't get to follow up on this since I had to leave town suddenly. Replacement of the key was easy as pie and it started on the first pull! I ended up keeping the new one and sold the 8-yr old Craftsman *sniffle* for $100 before I left. I literally got it running hours before the guy came to see it...was that easy...and had it all shined up for him! Dang I hated to see it go, but the new one is bigger and has key start. I just hope this one will be as trouble free.
__________________
Current Garage:
2009 Honda CR-V EX
2006 Mazda 3i
2004 Chevrolet Silverado 2500HD
2003 GMC Envoy XL
2000 Honda ST1100
2000 Pontiac Sunfire

Vehicle History:
2003 Pontiac Vibe AWD - 1999 Acura Integra GS - 2004 4.7L Dakota Quad Cab 4x4 - 1996 GMC Jimmy 4wd - 1995 Chevrolet C2500 - 1992 Toyota Camry LE 2.2L - 1992 Chevrolet S10 Ext. Cab 4.3L - 1995 Honda ST1100 - 1980 Yamaha XS400 - 1980 Mercury Bobcat.
jdmccright is offline   Reply With Quote
 
Similar Threads
Thread Thread Starter Forum Replies Last Post
Modded Lawn Mower?!?!?!?! RaceMySS_454 COMPLETELY off-topic 13 06-03-2003 05:32 PM
if paranoia boats made lawn mowers paranoiaboats Graphic Manipulation 1 11-14-2002 10:55 AM
racing lawn mower patate Car Modeling 5 05-18-2002 11:11 AM

Reply

POST REPLY TO THIS THREAD


Bookmarks
Go Back   Automotive Forums .com Car Chat > Engineering/Technical > Small Engines ATVs Go Karts and Lawn Mowers etc

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -5. The time now is 11:16 AM.

Community Participation Guidelines | How to use your User Control Panel

Powered by: vBulletin | Copyright Jelsoft Enterprises Ltd.
 
 
no new posts