Engine Pops at High Revs

[hotajax 223]

Sitting at a high idle, NOT under a load, I get a pop once in a while.  Electrical or lean fuel mix?  When cutting, with the engine under load, it behaves.

Thanks in advance.  Engine is 14 Horse single cylinder. 

Edited July 23, 2023 by hotajax

[gwest_ca-(File Mod) 11,048]

Try adding a shot of Marvel Mystery oil or 2-stroke oil to the fuel. It will lube the valve stems.

[ri702bill 8,345]

Hmmmm... had the head off to decarbon things and look at the condition of the valves and seats...??

If not, a leak-down test may be in order....

[hotajax 223]

48 minutes ago, gwest_ca said:

Try adding a shot of Marvel Mystery oil or 2-stroke oil to the fuel. It will lube the valve stems.

How much MMO?  It's a 2 1/2 gallon tank.  Thanks

[kpinnc 12,098]

If it's a distinct loud pop, it's definitely an issue. 

 

That being said, it's not entirely unusual for a 40+ year old Kohler to have a little "burp" sound every few seconds. Especially when not revved high or no load. Usually a few housecleaning maintenance items will clear that up. Clean carb/ fuels system/ points/ electrical contacts.

 

And also, ethanol-free fuel is the only way to go. No additive on earth or even 95 octane will prevent mediocre results and fuel system damage running ethanol fuel in an aluminum carburetor.

[Rob J. 1,942]

10 minutes ago, kpinnc said:

If it's a distinct loud pop, it's definitely an issue. 

 

That being said, it's not entirely unusual for a 40+ year old Kohler to have a little "burp" sound every few seconds. Especially when not revved high or no load. Usually a few housecleaning maintenance items will clear that up. Clean carb/ fuels system/ points/ electrical contacts.

 

And also, ethanol-free fuel is the only way to go. No additive on earth or even 95 octane will prevent mediocre results and fuel system damage running ethanol fuel in an aluminum carburetor.

Yep ethanol is garbage, it’s worth the extra for non-ethanol. 

[ebinmaine 67,642]

On 7/23/2023 at 12:42 PM, hotajax said:

, I get a pop once in a while

 

On 7/23/2023 at 3:27 PM, kpinnc said:

If it's a distinct loud pop, it's definitely an issue. 

 

That being said, it's not entirely unusual for a 40+ year old Kohler to have a little "burp" sound every few seconds

 

 

@hotajax

 

What kinda pop? 

[Lagersolut 661]

On 7/23/2023 at 1:44 PM, hotajax said:

How much MMO?  It's a 2 1/2 gallon tank.  Thanks

 

I add 2-3oz of Marvel to my 5 gallon can before heading out to fill it - been running a touch of Marvel in my Kohlers for 30 years

[peter lena 8,635]

@gwest_ca  agree with the fuel additive , when doing a base line run in on an  unknown engine , its amaizing to me , to regularly fing TOTAL NEGLECT  EvERY WHARE . have often emphasized a hot oil flushing . gaining on run time and effects . that lead me to trying zink to the oil effect . without a doubt , once you start to clean up the varnish and unknown oil statis , along with a packed fuel bowl of rubber hose . it starts to get better . done this and use it as a  regular set up in my stuff , no smoke , instant starts , regularly check over statis of all areas . you cant do that , pete

[hotajax 223]

I put in a big dose of Marvel, like double the amount on the bottle.  It helped.  It still burps, but not as loud, and not as often.  Today I'll throw some MMO in the oil itself before I cut.  Revs good at high rpms's while it's cutting.  At idle, it is fine.  Thanks for y'all help.. 

[peter lena 8,635]

@hotajax  https://www.google.com/search?q=kroil+fuel+treatment&rlz=1C1CHBF_enUS866US866&oq=kroil+fuel+treatment&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIR nothing creeps like kroil . pete

[ebinmaine 67,642]

34 minutes ago, hotajax said:

I put in a big dose of Marvel, like double the amount on the bottle.  It helped.  It still burps, but not as loud, and not as often.  Today I'll throw some MMO in the oil itself before I cut.  Revs good at high rpms's while it's cutting.  At idle, it is fine.  Thanks for y'all help.. 

When was the last time the carb was rebuilt?

Fuel lines replaced?

 

[hotajax 223]

Carb about 3 yrs ago.

[ebinmaine 67,642]

3 minutes ago, hotajax said:

Carb about 3 yrs ago.

 

If you use ethanol gas it's about 2 yrs overdue. 

 

I've had fuel lines and carb here on a friend's machine go junk after only 4 months. 

 

[lynnmor 7,308]

Just now, hotajax said:

Carb about 3 yrs ago.

It all depends on the quality and age of the gasoline, basically what many call a carb rebuild is simply cleaning out the debris.  On rare occasions additives may help, but I just physically clean out the junk and decomposed fuel lines and don't depend on snake oil.

[ebinmaine 67,642]

1 minute ago, lynnmor said:

It all depends on the quality and age of the gasoline, basically what many call a carb rebuild is simply cleaning out the debris.  On rare occasions additives may help, but I just physically clean out the junk and decomposed fuel lines and don't depend on snake oil.

 

My experience shows me that when an additive does help it's because the system needs to be cleaned out. 

The additive has loosened up some schmootz.  

 

[hotajax 223]

2 hours ago, lynnmor said:

It all depends on the quality and age of the gasoline, basically what many call a carb rebuild is simply cleaning out the debris.  On rare occasions additives may help, but I just physically clean out the junk and decomposed fuel lines and don't depend on snake oil.

I wouldn't exactly call Marvel snake oil.  Last time I cleaned the carb, it was pretty spotless.  Not much to do except replace the rubber ring. If you've ever taken off your heads, look how clean things are.  I use it in my truck, too.  Have never had to replace a fuel injector. 

Edited July 29, 2023 by hotajax

[hotajax 223]

Every time I started it up today ( did 3 cuttings ) it was sounding better each time.  I think the MMO had time to soften up the boogers in the fuel lines for a few hours before a re--start.  That stuff is really good.  

Quote

 

 

[ebinmaine 67,642]

7 hours ago, hotajax said:

Every time I started it up today ( did 3 cuttings ) it was sounding better each time.  I think the MMO had time to soften up the boogers in the fuel lines for a few hours before a re--start.  That stuff is really good.  

 

 

No offense to anyone and I mean this in the the most positive way. 

THAT is exactly why you know it's time to rebuild the carb and replace the fuel lines. 

 

I'm sure MMO is fine stuff and all but the money spent on that could have bought a Kohler brand carb kit and a few feet of fuel line. 

 

It's great that your tractor is running better but that by itself shows there's a need in the fuel system.  

Instead of trusting a chemical to move the dirt or contamination around, replace the parts.  

[lynnmor 7,308]

3 hours ago, ebinmaine said:

 

It's great that your tractor is running better but that by itself shows there's a need in the fuel system.  

Instead of trusting a chemical to move the dirt or contamination around, replace the parts.  

 

Just running an engine might help move the dirt around, with or without additives.  We hear success stories about neglected engines that ran poorly and were "fixed" with their favorite chemical, but it likely was just the fresh gas flushing things out.

 

Some information:

Claims

Marvel Mystery Oil marketing literature claims benefits which include improved lubricating qualities, primarily cleaning and friction reduction capabilities. The product has previously been marketed as a fuel additive in all kinds of engines, including aircraft (although the company no longer markets it for the latter application on their website). It has also been used as an oil additive, corrosion inhibitor, penetrating oil, and in automatic transmissions as a leak stopper and seal relubricator.[5] Supporting evidence for claimed benefits is not provided by the manufacturer.

The lubricant was used as a fuel additive in a Lycoming aircraft engine, which specifically cautioned against oil additives (Service Instruction No. 1014M, which also stated its use would void the warranty), that suffered catastrophic damage during take-off. The NTSB listed the probable cause of the accident as "The improper use of [a] fuel additive which resulted in a power loss."[4][6]

Auto manufacturers Ford[7] and GM[8] recommend against using engine oil additives, stating they are unnecessary in their contemporary engine designs and may void their warranties.

[Handy Don 12,237]

I have long thought that if any of these additives was really as effective as claimed, they would have been adopted/recommended/bought by a major oil company or motor vehicle manufacturer years ago.

[hotajax 223]

Problem solved.  Three tankfuls of Marvel Mystery Oil and adjusting the carb.  Back in biz.  Thanks. I'll think about a carb in the winter time. 

Edited August 7, 2023 by hotajax

[hotajax 223]

On 7/30/2023 at 12:44 PM, Handy Don said:

I have long thought that if any of these additives was really as effective as claimed, they would have been adopted/recommended/bought by a major oil company or motor vehicle manufacturer years ago.

 

Just now, hotajax said:

Problem solved.  Three tankfuls of Marvel Mystery Oil and adjusting the carb.  Back in biz.  Thanks. 

No but lots of guys with small engines will swear by it. 

[ebinmaine 67,642]

25 minutes ago, hotajax said:

Problem solved.

Did you replace the fuel lines and rebuild the carb? 

[hotajax 223]

No.  Carb Adjust and MMO.  Carb comes in the winter when I'm bored of sitting in the house.