Rebuilding small engines for longer life 1

[m899nyc]

I’ve had flathead Kohler and single cylinder Honda engines last around 10,000 hours, but I can’t seem to get more than 1500-2000 of life out of a Briggs and Stratton I/C flathead. Is there anything I can do to increase the longevity of this engine, possibly different rings, or cylinder coating? I’m not sure what this particular design is so limited.

 

[enginesrus]

What is failing so soon on the B & S engines?

If its cylinder related, what materials are the cylinders of those other engines made from and how are they lubricated and cooled? Are all these air cooled? Does the B&S have an aluminum cylinder?
Are they all used in the same application, meaning running in the same conditions and type of machine they power?
If one engine is wearing more than the others, do all run similar air filtration and fuel type?
Need more details.

 

[m899nyc]

They are used in generators and outdoor power equipment. The Briggs, even with an iron liner, wears the bore and crank at around 2,000 hours. Kohler powered gensets and lawn tractors are good for 10,000 hours. All are air cooled, single cylinder, splash lubricated engines.

 

[Lou Scannon]

Briggs & Scrapiron

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[TugboatEng]

What is wearing out?

 

[enginesrus]

Must be dust entering some how, or oils used. What viscosity in the B&S? What are the ambient temperatures they all operate in?
Have you ever checked engine cylinder and head temps?
And what does the BS power?
What oil change interval for the BS?

 

[TugboatEng]

Some things that could be done:

Nikasil coating of cylinder.

Piston rings with a wear resistant facing such as moly.

Hypereutectic alloy pistons for better cylinders fit.

Nitriding of the crankshaft for longer bearing life.

Aluminum-tin alloy bearings for longer bearing life.

Nitronic alloy valves for longer valve life in iron guides and seats.

 

[m899nyc]

Thank you for the replies. The engines are used in generators and outdoor power equipment. I’d like to rebuild this old Briggs. The equipment is well taken care of, not overheated. The Briggs powers a generator. I think 2,000 hours seems a little low - 2 cycle chainsaws will last that long. The Briggs is smaller than the Kohler but the oil is changed just as frequently. Don’t know why the bore and crank should wear that fast. If I can have some of the modifications listed above made, I will rebuild it and see how long it lasts.

 

[TugboatEng]

Are the bore and crank wearing? You haven't told us what parts are wearing out yet.

 

[m899nyc]

Both the vote and crank are wearing.

 

[GregLocock]

B&S warranty
There is no warranty for engines on equipment used for prime power in place
of a utility; standby generators used for commercial purposes, utility vehicles
exceeding 25 MPH, or engines used in competitive racing or on commercial or
rental tracks.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[LittleInch]

They're just different products for different markets. B&S is just built to the lowest possible price. They are intended for low use domestic machines. Starting first time is more important than service life.

I have one on my mower. I barely use it for 50 hours a year I reckon. Even a 100hrs would make it last 15 to 20 years. The rest of the mower is going to fall to bits before then.

Trying to make something which is made as cheaply as they do to last longer is a fools game IMHO. Even if you fit new bits etc something else will wear out or fail.

You get what you pay for in this world.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Tmoose]

"wears the bore and crank at around 2,000 hours".

Does "Crank" = rod journal, main bearings, con rod or ??
Got any good clear pictures of the worn components ?
Cranks, rods, pistons and cylinders ?

Did we hear if it is an aluminum bore engine?

Have any of the short lived engines been OEM factory assemblies?

"I’d like to rebuild this old Briggs"
What is the likelihood the old Briggs has been "rebuilt" before?

If an iron cylinder bore is not thoughtfully cleaned after refinishing, ring and cylinder life can be cut drastically.
Many Aluminum cylinders required pretty sophisticated honing methods to create the proper finish with exposed silicon nodules.

Like others asked, are you using name brand oil of the recommended viscosity?

https://www.briggsandstratton.com/na/en_us/support/faqs/browse/mower-oil-type-and-capacity.html

Superfinished crank bearing journals could help if operating conditions are marginal.

Like TBoat said, fancier piston ring facings can reduce ring wear, and often at the same time cylinder wear.

I'd use name brand synthetic oil of the maximum recommended viscosity.
Might have to resort to seasonal oil changes to get the correct, different viscosity for summer and winter use.

A higher level oil analysis ( normal dissolved chemistry PLU wear particles ) after 500 hours or so could provide useful info if dirt entry, gasoline oil dilution, or ??? are issues.
And that information would provide useful direction to improve service life.
Also might suggest more frequent oil changes would have some value.
An oil change on a "fresh" engine after a few hours is often recommended.

 

[NDimitrov]

If the cylinder bore wears, it could be a combination of a short piston skirt and a low rod/stroke ratio. In other engines the low R/S which comes with increasing stroke, results in premature wear due to increased forces on the piston skirt . An example is the kia 1.6 and 2.4 I4 engines .

 

[BrianPetersen]

Briggs engines don't have particularly unusually short rod lengths relative to their stroke, nor are the piston skirts particularly short. They do have pistons and rings running directly in aluminium bores, and aluminium con-rods running directly on the crankpin, no bearing inserts. With that situation, material choices, heat treatment, and surface finishes are absolutely critical, and these engines are built to be cheap, not to be long-lived.

It is possible through careful material selection and surface treatments for aluminium bores to be extremely long-lived.

 

[XR250]

Use a high quality synthetic such as Amsoil and make sure the air filter is working properly.
The newer ones do not even require an oil change. Just adding as needed. What an amazing idea

 

[TugboatEng]

This is why I ask, what wore out? I bought a Honda XR650R motorcycle some time ago. The previous owner told me it was getting hard to start and probably needed a valve adjustment. Modern engines don't need valve adjustments, wear indicates impending failure. I bought the bike and pulled the head without even running it. The valves were so sharp you could cut paper with them.

He had been running an aftermarket air filter. The valves were the only worn part. There was also a score in the cylinder but that wasn't wear.

 

[XR250]

I bought a 2004 XR250 new. The exhaust valves kept getting tight. Apparently it was a common problem with the bikes as the valves would mushroom into the head. Replaced them with stainless KW's and was good for the next 19 years.

 

[TugboatEng]

The receeded valves in my 650R were KW valves. The owner of my local dealership had a major role in the 650R Baja racing era. He did not have kind things to say about KW valves. All of the race bikes, including the factory bikes got Honda valves. "Stainless steel" is a very broad term. I would not want a valve made from 303 stainless steel. Long lasting valves aee likely going to be made from one of the Nitronic alloys, maybe one of the Nimonic alloys for exhaust valves.

 

[Tmoose]

OP bailed May 27