View Full Version : Blown motor ?

Bunton Guy
10-29-2001, 09:25 PM
I see alot of ads in the classifieds of all sorts with mowers with blown motors. What can these people possible do to blow the motors ? is this from a lack of maintnence & abusing it ?or is this normal problems ? what usually breaks when the engines " blow" is the usual case a rod that lets go ? or a crank that cracks ? or maybe piston sticking/seizing?

John DiMartino
10-29-2001, 09:36 PM
If most of these have blown motors,I feel the rest of the machine is shot too,or else they would have invested the money to fix them.I only buy them when they are so cheap,that i can use them for parts.I see a seroius lack of maintance everytime i look at what is on LCO's trailers,golf courses typically take much better care of equipment,and it usually lasts a lot longer IMO.

10-30-2001, 06:13 AM
Blown motor is a widely used and abused term, and means
little until the engine has been inspected. If a mower starts
smoking badly, people might trash it, not knowing the problem
could be a flooding carb, or blown head gasket{OHV}. I
stopped by the local hardware store and the mechanic was
uncrating a new Briggs twin shortblock, saying that is was
for this one tractor that was not even torn down at all.
I ask him why, he said the rod was knocking very badly. I told
him a chunk of carbon can do the same thing, it has fooled
me before. The next week I came by and the customer had his
mower back, with a new shortblock, and the mechanic had a used shortblock for sale. Oddly, he never did find out why it
was knocking[wink]. "The rods looked good", was all he said.
So a motor that is "blown", may be not so bad. And you
may buy something that is a good deal.

Bunton Guy
10-30-2001, 08:38 AM
The term "Short blocking " is that refering to taking the block off another mower to use it on your ? or is because the block is really shorter ? please enlighten me. I hear that term very often to:blush:

10-30-2001, 08:47 AM
After 35 years of working in small engine repair related fields, in my humble opinion, most small engine damage is caused by lack proper preventative maintenance.

The most overlooked item on these engines is the engine oil level. I continually see engines brought in with broken rods, scored cylinders, oil saturated air filters, and massive oil leaks caused by either too little or too much oil. Too oftem operators fail to check the oil level causing too little oil or check the oil level, find it at or below the add mark, forget the engine holds less than a quart, and add a quart. Overfilling the crankcase on most small engines causes faoming and oil saturated with air adds very little lubrication. Overfilling also causes oil to be forced into the air filter and through gaslets and seals.

The second most overlooked preventative maintenance item is the air filtration system. Most of these engines use filters which are marginal at best and if the air filters are not properly cleaned and installed costly problems will happen. Many engines that are brought to me and are "burning a lot of oil" have air filters that a plugged up. If the engine is running it is sucking air from somewhere and if the air filter is nearly plugged the engine may be getting it's air through the engine by way of the crankcase breather. The air filter must be properly installed to insure all the air coming into the engine is being cleaned by the air filter. It takes very little dirt in a small engine to cause major damage.

Other items that cause damage in lesser degrees are dirty fuel, failing to let the engine warm up and cool down properly (many blown head gaskets are caused this way), wrong spark plugs (moslly in two cyle application, improperly mixed two cycle oil, wrong type of oil or fule, and equipment abuse.

Again these are just my opinions.

Thanks for your time, Bill

10-30-2001, 02:22 PM
A shortblock is the core of an engine, it is replaced and the starter
carb, muffler, coil, etc, is transferred from the old engine to the
new one, which can have problems by itself. A "longblock"
is a complete engine that is bolted on, hooked up, and ready to

10-30-2001, 03:11 PM
In the small engine area the two items normally found are short blocks and complete engines
In the automotive end of it there are short blocks which are blocks with crank, rods, piston and rings, camshaft with lifters, timing chain/gears, and gaskets.
Long blocks are the above with heads installed, push rods, and timing cover gaskets.

10-30-2001, 04:07 PM
You are correct. I do not work on cars, but was trying to use
that terminology, which I failed. I do not work on cars, so I defer
to your take on the matter.

11-01-2001, 02:00 AM
I agre with Justractors. I find that most major engine problems are from a high build up of chaff in the cooling fins and very dirty motor oil. I find this abuse on residential mowers more than commercial. But there are exceptions out there.

12-04-2001, 02:14 PM
I appreciate all of your comments above - I am one of the losers that could not properly read the oil level in my mower. Although I did periodically fill it with oil, it obviously was not enough. This weekend I encountered some very thick grass, and because I was trying to do the final low cut for the season, the engine started smoking, and then the engine started to make a loud knocking noise. I immediately turned it off, checked the oil, which of course was very low. I filled the oil level to the proper setting.

So the problem is - it runs, but knocks loudly. Is this repairable or not worth the expense?

Thanks for your comments.

12-04-2001, 03:56 PM
If the engine is on a $50 mower junk it and start over.
If the engine is on a $5000 mower it is worth replacing.
If the equipment is worth it and if the engine has been ran low on oil and has ran that way for awhile I would seriously consider junking it and putting on a new one or at least a short block.
Most engines that have been ran low on oil have done damage to not only the crank and rod but also the cylinder wall, piston, and valve train.
Just my opinion and like they say everyone has one and the most important one is your own.

12-04-2001, 08:31 PM
is a shortblock job hard to do??, i've seen a lot of "blown motor" deals here

Robert Doubrava
12-07-2001, 10:08 PM
It depends on what kind of work that needs to be done to the engine. Like transferring old parts to the block isn't too hard. You just have to have the right hardware like gaskets, washers, screws, bolts, linkage, so on and so on.

Also, just as most of everyone has said, it's the lack of *Preventative Maintenece* that has to be done. Check the oil, air filter element,clean the carb. etc. etc........

12-11-2001, 04:56 AM
Originally posted by Fish
A shortblock is the core of an engine, it is replaced and the starter
carb, muffler, coil, etc, is transferred from the old engine to the
new one, which can have problems by itself. A "longblock"
is a complete engine that is bolted on, hooked up, and ready to
Fish ummmm you forgot the head....

12-11-2001, 09:27 AM
That is one of those "extra" parts that is leftover and not really
needed anyway.