A DIY & home improvement forum. DIYbanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » DIYbanter forum » Do - it - Yourself » Home Repair
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems.

Lawn Mower Idle Oscillates



 
 
LinkBack Thread Tools Display Modes
  #1  
Old August 8th 03, 04:03 PM
Buck Wheat
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

My Murray lawn mower idle oscillates up and down, I can see the spring
on the carb moving about 1.5".

I there a spring kit or some kind of throttle control that may fix
this this?

I rarely use this lawn mower and am about to put it up for sale, just
thought I'd fix this problem before advertsiing.

Its a Murray riding lawnmower, model 30552x12a w/a Tecumseh 10 HP

Thanks for any input..
Ads
  #2  
Old August 8th 03, 04:47 PM
Stormin Mormon
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

I learned about this in my small engine repair course.

If the spring on the throttle gets a bit hardened (painted, rusty, etc) it
doesn't respond right. So the engine speed "hunts" for the right speed.

Replace the spring between the throttle and the carb.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.org
..
..

"Buck Wheat" wrote in message
om...
My Murray lawn mower idle oscillates up and down, I can see the spring
on the carb moving about 1.5".

I there a spring kit or some kind of throttle control that may fix
this this?

I rarely use this lawn mower and am about to put it up for sale, just
thought I'd fix this problem before advertsiing.

Its a Murray riding lawnmower, model 30552x12a w/a Tecumseh 10 HP

Thanks for any input..


  #3  
Old August 8th 03, 09:31 PM
Stephen Kurzban
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates


Yup, could definitely be a spring. I read a little book on
repairing small engines from the library recently, and it
also suggested it could be any spring or linkage which
connects the governor system with the throttle.

You may have to remove the engine cover to fix this one, but
the good news is that if it's packed with grass or other
debris, cleaning it may resolve the issue for you (anything
that binds or blocks the spring(s) or linkages from proper
operation).

Good luck,

Stephen Kurzban

Buck Wheat wrote:

My Murray lawn mower idle oscillates up and down, I can see the spring
on the carb moving about 1.5".

I there a spring kit or some kind of throttle control that may fix
this this?

I rarely use this lawn mower and am about to put it up for sale, just
thought I'd fix this problem before advertsiing.

Its a Murray riding lawnmower, model 30552x12a w/a Tecumseh 10 HP

Thanks for any input..

  #4  
Old August 9th 03, 01:31 AM
Dr. Doctor
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

hunt or oscillates can be the spring but in all my years of working and
teaching on small engines it is not a common failure. there is a list of
possible here is but a few, air filter plugged, worn throttle shaft carb,
intake manifold leaking, governor problems (worn or misadjust) linkage worn
bent or missing, fuel problems.

as I said the list is long but when one runs into a problem with a spring it
is more common it will either be stretched and the rpms are too low or
modified some how and has too much tension making rpms too high.

good luck



  #5  
Old August 9th 03, 02:04 AM
Chip Stein
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

Stephen Kurzban wrote in message ...
Yup, could definitely be a spring. I read a little book on
repairing small engines from the library recently, and it
also suggested it could be any spring or linkage which
connects the governor system with the throttle.

You may have to remove the engine cover to fix this one, but
the good news is that if it's packed with grass or other
debris, cleaning it may resolve the issue for you (anything
that binds or blocks the spring(s) or linkages from proper
operation).



a spring won't fix it. you have junk in the carb. the idle feed
passage is clogged causing it to try and run off the main fuel
circuit. pull the bowl and clean thoroughly. up in the center of the
carb tube is a asmall passage running at a 45 degree angle towards the
top. this is where the restriction is.
good luck
Chip
  #6  
Old August 9th 03, 02:38 PM
Buck Wheat
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

Actually, it would not start about a month ago, so I took the bowl off
and cleaned out the carb and hoses. I had to turn the bowl little by
little to get it started again, I think maybe the bowl is still not
correctly positioned.

I'll take it off and try to find the right position, I have not seen
any markings to line-up..if there are any(?) I'll check all other
parts for clogging, etc.

Thanks for taking the time to reply, it's a riding mower and I dread
trying to get it to the shop.


"Dr. Doctor" wrote in message news:qpWYa.14434$%T.3973@edtnps84...
hunt or oscillates can be the spring but in all my years of working and
teaching on small engines it is not a common failure. there is a list of
possible here is but a few, air filter plugged, worn throttle shaft carb,
intake manifold leaking, governor problems (worn or misadjust) linkage worn
bent or missing, fuel problems.

as I said the list is long but when one runs into a problem with a spring it
is more common it will either be stretched and the rpms are too low or
modified some how and has too much tension making rpms too high.

good luck

  #7  
Old August 9th 03, 10:32 PM
Bob M.
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

If it's a Tecumseh engine, and there's a flat area in the fuel bowl, this
goes directly under the hinge area of the carb, so the float can drop as far
as it needs to.

Bob
===
"Buck Wheat" wrote in message
om...
Actually, it would not start about a month ago, so I took the bowl off
and cleaned out the carb and hoses. I had to turn the bowl little by
little to get it started again, I think maybe the bowl is still not
correctly positioned.

I'll take it off and try to find the right position, I have not seen
any markings to line-up..if there are any(?) I'll check all other
parts for clogging, etc.

Thanks for taking the time to reply, it's a riding mower and I dread
trying to get it to the shop.


"Dr. Doctor" wrote in message

news:qpWYa.14434$%T.3973@edtnps84...
hunt or oscillates can be the spring but in all my years of working and
teaching on small engines it is not a common failure. there is a list of
possible here is but a few, air filter plugged, worn throttle shaft

carb,
intake manifold leaking, governor problems (worn or misadjust) linkage

worn
bent or missing, fuel problems.

as I said the list is long but when one runs into a problem with a

spring it
is more common it will either be stretched and the rpms are too low or
modified some how and has too much tension making rpms too high.

good luck



  #8  
Old August 10th 03, 05:25 PM
Buck Wheat
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

That's exactly what I needed to know, I tried several positions
yesterday w/the float bowl, all yielded the same result...no change,
I'll correct it today. I was able to cut the lawn as once it is in
full throttle it doesn't seem to oscillate.

What does the screw/adjustment at the bottom of the float bowl do?

Thanks.

"Bob M." wrote in message ...
If it's a Tecumseh engine, and there's a flat area in the fuel bowl, this
goes directly under the hinge area of the carb, so the float can drop as far
as it needs to.

Bob
===
"Buck Wheat" wrote in message
om...
Actually, it would not start about a month ago, so I took the bowl off
and cleaned out the carb and hoses. I had to turn the bowl little by
little to get it started again, I think maybe the bowl is still not
correctly positioned.

I'll take it off and try to find the right position, I have not seen
any markings to line-up..if there are any(?) I'll check all other
parts for clogging, etc.

Thanks for taking the time to reply, it's a riding mower and I dread
trying to get it to the shop.


"Dr. Doctor" wrote in message

news:qpWYa.14434$%T.3973@edtnps84...
hunt or oscillates can be the spring but in all my years of working and
teaching on small engines it is not a common failure. there is a list of
possible here is but a few, air filter plugged, worn throttle shaft

carb,
intake manifold leaking, governor problems (worn or misadjust) linkage

worn
bent or missing, fuel problems.

as I said the list is long but when one runs into a problem with a

spring it
is more common it will either be stretched and the rpms are too low or
modified some how and has too much tension making rpms too high.

good luck

  #9  
Old August 11th 03, 02:11 AM
Bob M.
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

The screw at the bottom is the main jet needle valve.

Tecumseh carbs have three adjustments: idle speed which will be a screw
possibly with a spring wrapped around it, that sets how far the throttle
plate can close off the fuel/air supply; a low speed needle valve which is
often located on top or on the side near the throttle shaft, and a high
speed or main needle valve located under the fuel bowl.

The low speed (often called idle mixture) needle valve is adjusted for
maximum RPM at idle. This is usually about 1-1/2 turns from fully tightened.
Turn it slowly each way, noting where the engine runs rougher or slows down,
then set it in the middle. Do this adjustment first.

Second would be to set the idle speed. This is often around 1800 for rotary
mowers but could be slower for tractors, i.e. 1200 - 1400 RPM. If you make a
significant adjustment here, go back and repeat the idle mixture adjustment.

Lastly is the high speed mixture. Set the engine at idle speed, then set it
to full throttle using the main speed control. Do NOT use a finger to
manually open the throttle at the carburetor as the engine is governed and
should limit its speed to around 3000 RPM. Adjust the mixture so the engine
accelerates without hesitation or backfiring. This will take several tries,
and is also usually around 1-1/2 turns from fully tightened. Usually it will
only take a change of 1/4 to 1/2 turn to get it to smoothly accelerate. You
can do this under load as well. Clockwise will result in a leaner mixture,
i.e. less fuel compared to the air going through the carburetor.

None of these adjustments should be way out unless someone pulled the valves
out to clean the carburetor and didn't pay attention to where they were set
beforehand. If you do need to pull them out, carefully turn each one in
(clockwise) and count how many turns it takes until it seats fully, but do
not exceed that position, then remove it and the spring. Some needle valves
also have a rubber O-ring and even a flat washer at the end of the spring in
the casting, so be careful.

These procedures are most likely outlined in the several good books on small
engine repair. A trip to a local library might give you more detailed
information. I'm going from memory as I usually make the adjustments without
even thinking about them.

Good luck.
Bob
====
"Buck Wheat" wrote in message
om...
That's exactly what I needed to know, I tried several positions
yesterday w/the float bowl, all yielded the same result...no change,
I'll correct it today. I was able to cut the lawn as once it is in
full throttle it doesn't seem to oscillate.

What does the screw/adjustment at the bottom of the float bowl do?

Thanks.

"Bob M." wrote in message

...
If it's a Tecumseh engine, and there's a flat area in the fuel bowl,

this
goes directly under the hinge area of the carb, so the float can drop as

far
as it needs to.

Bob
===
"Buck Wheat" wrote in message
om...
Actually, it would not start about a month ago, so I took the bowl off
and cleaned out the carb and hoses. I had to turn the bowl little by
little to get it started again, I think maybe the bowl is still not
correctly positioned.

I'll take it off and try to find the right position, I have not seen
any markings to line-up..if there are any(?) I'll check all other
parts for clogging, etc.

Thanks for taking the time to reply, it's a riding mower and I dread
trying to get it to the shop.


"Dr. Doctor" wrote in message

news:qpWYa.14434$%T.3973@edtnps84...
hunt or oscillates can be the spring but in all my years of working

and
teaching on small engines it is not a common failure. there is a

list of
possible here is but a few, air filter plugged, worn throttle shaft

carb,
intake manifold leaking, governor problems (worn or misadjust)

linkage
worn
bent or missing, fuel problems.

as I said the list is long but when one runs into a problem with a

spring it
is more common it will either be stretched and the rpms are too low

or
modified some how and has too much tension making rpms too high.

good luck



  #10  
Old August 11th 03, 02:01 PM
Stormin Mormon
external usenet poster
 
Posts: n/a
Default Lawn Mower Idle Oscillates

Increases or decreases the gas jet. Richens or leans the fuel mix.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.org
..
..

"Buck Wheat" wrote in message
om...
What does the screw/adjustment at the bottom of the float bowl do?

Thanks.



 




Thread Tools
Display Modes

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

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


All times are GMT +1. The time now is 09:29 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.SEO by vBSEO ©2010, Crawlability, Inc.
Copyright 2004-2014 DIYbanter.
The comments are property of their posters.