Riding Mower Engine Overheating

[KrashnKraka]

I picked up a head gasket the other day.

Is anyone else agreeing that my 30 year old mower could be carboned up in the head/piston area and this could be the problem?

Doesn't read as such to me, a lot of variables in 30 years of time.
Like only 40 hours of operation 'cos each year it is used the engine
appears to overheat so back in locker it goes till next year, year in
year out.
:laugh:

Srsly, other symptoms would have appeared long before serious
carbon buildup. You only report one consistent symptom.
Buuuuut... as a test you can try getting the unit hot, at night.
In the dark you will see loose burning carbon particles flying out of
the exhaust. If in numbers it is best you strip and decoke.

I still don't believe that is going to fix your problem - it may just prove
another symptom.
My money is on a timing issue, or wrong plugs.

-- flipping cards an ' readin' sign

 

[Rick'sToro8-32]

"My money is on a timing issue, or wrong plugs."


Appreciate it!! :smile:

When I get some time to work on it this week we will find out. I could see the chuck key being an issue too as mentioned above. I do get a slight backfire when I shut it down. It's never had a valve job in 30 yeears for that matter.

Thanks again!

PS Just to be clear this issue started about 2 years ago. You are right though, since then it has been back in the shed at the end of the mowing season.:ashamed:

 

[KrashnKraka]

"My money is on a timing issue, or wrong plugs."


Appreciate it!! :smile:

When I get some time to work on it this week we will find out. I could see the chuck key being an issue too as mentioned above. I do get a slight backfire when I shut it down. It's never had a valve job in 30 yeears for that matter.

Thanks again!

PS Just to be clear this issue started about 2 years ago. You are right though, since then it has been back in the shed at the end of the mowing season.:ashamed:

This is all good info in the thread... you should appreciate in a workshop environ it would
take some less time to find the problem than write up a post on what the problem may be.
For example when "timing issues" are written? That could prove to be anything from a
dislodged crankshaft key to a camshaft cog worn to the bejaysus. Better to keep it simple
and work on your feedback.
It aint a competition, with your posts being of the most value here, not the assorted
thoughts of those working from experience or logic, or both.
At the end of the day you will be mowing grass, cool.
That outcome should be the only priority.

Cheers...

 

[Rick'sToro8-32]

For all contributors and any who might be interested, because of increased mandatory overtime at work I still haven't had a chance to work on my mower and persue the detonation suggestion. But, I just looked this up before I am going to bed:

"Detonation, often called pinging, is nothing less than a series of small explosions that take place within an engine's combustion chambers. It can be extremely destructive, breaking pistons, rod bearings and anything else from the pistons down that a large hammer could damage. It is best avoided."

I thought I was hearing a rod knocking in my engine when I start to have trouble and start to konk out, but again this makes perfect sense and sounds right.

So, I will pull the head and clean any carbon and make this my first attempt at a fix, hopefully this week, and again report back. I'm only working in theory here like the rest of you even though the mower is in my shed, but in theory based on what I have explained above in this thread, my money is on detonation suggestion right now.

 

[KrashnKraka]

[...]
"Detonation, often called pinging, is nothing less than a series of small explosions that take place within an engine's combustion chambers. It can be extremely destructive, breaking pistons, rod bearings and anything else from the pistons down that a large hammer could damage. It is best avoided."

I thought I was hearing a rod knocking in my engine when I start to have trouble and start to konk out, but again this makes perfect sense and sounds right.

"pinging"... low octane fuel in a high compression engine.
Ask any "hot-rodder" or "very fast bike" (in a straight line) rider about it.

Something to think on.......?

KK

 

[Rick'sToro8-32]

"pinging"... low octane fuel in a high compression engine.
Ask any "hot-rodder" or "very fast bike" (in a straight line) rider about it.

Something to think on.......?

KK

I'm not sure what the point is here, it sounds like you saying detonation can only occurr in a high compression engine with low octane fuel?

In other words it sounds like you are saying it is not possible for a small engine to experience detonation.

 

[KrashnKraka]

I'm not sure what the point is here, it sounds like you saying detonation can only occurr in a high compression engine with low octane fuel?

Nope...I am saying it takes a combination of circumstance.
Like not one single thing will cause pinging on it's own.

In other words it sounds like you are saying it is not possible for a small engine to experience detonation.

That is a separate issue, see my response above.
However I would go as far as saying low octane fuel in a small engine would not
cause "pinging"... the design simply does not develop the pressures required.

Maybe advanced timing in an engine with excessive coking might "detonate"
some fuel as the engine gets hotter. The heating being caused by the timing or
poor air circulation.
Anyway...enough theorising.
Let's wait until you have time fo spanner work, yeh?

KK

 

[Rick'sToro8-32]

Gotcha! Understand, thank you! :smile:

 

[Honda Tech]

Thanks very much for all of the posts! :smile:

If I am hearing things correctly it seems as though the consensus is that my mower is konking out after about 40 minutes of run time because of a timing issue.

It occurs to me that this mower has never had a valve job. It think poorly seated valves can mess up the timing. I wonder if this could be the 'cause' of the problem.

Also, in the back of my mind, I think I remember something about a vapor lock in the gas line that creates a situation like mine from a mower when I used to work at a local cemetery. It seems like we had a mower that would run until it heated up and then konk out and then run again when it cooled down. I think I remember the mechanic there saying it was a vapor lock or something like. Does anyone know anything about this?

That is the 'symptom' of my mower: simply put, it runs great until it heats up then it konks out--and when it cools down it runs great again until it heats up and konks out again.[I think you are on the right track. 30 year old engine that has never had a valve job? It not going to effect the actual timing, but will affect the cooling and power.] ]

 

[Rick'sToro8-32]

I think you are on the right track. 30 year old engine that has never had a valve job? It not going to effect the actual timing, but will affect the cooling and power.

Very good, thank you!!

I can appreciate that now looking back to a job I had a cemetery when I was younger. Each winter I would tear down small engines that quit running or had problems (mostly trimmer mowers), on these I would take the coke / carbon off the underside of the head with the wire wheel on the grinder (which was often pretty thick crust of carbon) and mill the heads, and do valve jobs as needed, and in the majority of the cases they went back out the next spring running strong like new.