Small Engine Repair Guidance? (1 Viewer)

[NewlyRetired]

I have a old (1997) 36 inch Bunton Bullet lawnmower.

It has a Kholer Command 12.5 Pro Series engine.

The engine is sputtering. Low idle to fast idle to low idle.

Can anyone recommend any steps and/or videos for how I could go about fixing this issue without having to send it in for a full tuneup?

 

[Officer Pete Malloy]

https://www.youtube.com/results?search_query=Kholer+Command+12.5+Pro+Series+engine

 

[Foosball God]

First thing I would check is the fuel filter

 

[NewlyRetired]

Thanks guys.

My knowledge level is very low (I don't even know where the fuel filter is), so I printed out the manual for the engine to get started.

 

[NewlyRetired]

OK I located the fuel filter. It looks to be inline between the gas tank and the carb, with an arrow pointing away from the gas tank.

I have shut off the gas flow from the tank to the fuel filter so that I can remove it.

I have taken off the clips but the filter itself appears almost molded to the black tubing. I feel like if I yank hard enough it is just going to rip the plastic on the fuel filter and leave the part inside of the black tubing.

Is there a trick in how to remove this from the black tubing?

 

[psychobillies]

OK I located the fuel filter. It looks to be inline between the gas tank and the carb, with an arrow pointing away from the gas tank.

I have shut off the gas flow from the tank to the fuel filter so that I can remove it.

I have taken off the clips but the filter itself appears almost molded to the black tubing. I feel like if I yank hard enough it is just going to rip the plastic on the fuel filter and leave the part inside of the black tubing.

Is there a trick in how to remove this from the black tubing?

Just twist and pull. It'll come loose.

 

[Fat Nick]

So I just taught myself a lot about small engines...I'm not an expert, but I can tear down most small engines and rebuild them now. When you have a sputtering engine, it can be a few things, but simplistically, an engine needs air, fuel, and spark. If it's running, but not running smoothly, you can usually rule out a lot of things like bad compression, broken parts, etc.

Some things to try if they're easy and you think you can do it:

-Drain all the old gas and replace with fresh gas. Get in the habit of using both Stabil and Ethanol Treatment in your gas for small engines. I get premium gas, and put some Stabil Marine in every 5 gallon can. Stabil Marine is blue, and covers normal gas stabilization, removes Ethanol, which is really bad for small engines, and also has a dry fuel to absorb any water.

-Remove the air filter. Spray some carburetor cleaner into the carb via the air intake. I do this while it's running. It will likely stall out the engine. That's OK. Once it's stalled, let it sit. This will break up some of the gunk that may have built up. After it's sat for 10 minutes or so, go through the normal process to re-start it.

-If your engine has carb adjustment screws, try adjusting them. Read your manual or google to find out the procedure for your engine. Some engines don't have them. Some have one screw. Some have an idle and a high-speed. Just depends on the engine.

-If you know where the spark plug is and have a proper socket, remove it, make sure it looks OK (not completely covered in black crap), and put it back. Don't over tighten and strip the threads...that would be very bad.

-The last thing to check that is relatively easy is the throttle. I think most lawn mowers are all the way on or all the way off...i.e. no throttle. The throttle is controlled by the governor, which is usually some combination of springs and things around the throttle. If you can see that, try revving it by hand and see if you can hold it at a constant RPM. Some of the older flywheel controlled governors would cause a surging action where the spring would just kind of bounce back and forth instead of finding a steady state. If holding it by hand smooths it out, then that might be your issue as well...You might need a new governor spring or something.

Those are the main things I know to check for. Again, not an expert...just tinker on occasion.

 

[NutterButter]

One thing I'll add which worked great for my backpack leaf blower is that if the engine starts but stalls pretty quickly, there's a good chance the carburator needs to be cleaned out. What this involved in my case was just taking the carb apart and letting everything dry out. Apparently, old gas or water just gets stuck in there and just screws everything up. I never did anything like this before and it was pretty simple. Just take a bunch of pics while breaking everything down so that you can reference them when it comes to putting everything back together. I'd essentially pay the local small engine repair place like $70 to do the exact same thing.

 

[3C's]

First thing I would try. http://www.homedepot.com/p/Mechanic-in-a-Bottle-4-oz-Synthetic-Fuel-Additive-2-004-1/202580655

 

[SWC]

brohan it sounds like a carb problem to me sounds like she is getting gas in spurts and burning it off which is the revving and then when that gas is gone is sounds like it stalls out until the next spurt of gas comes along some dudes call it lopeing but i just call it a hey your carb is messed up you probably just need it adjusted and one more thing if it is firing the gas is probably ok or at least good enough because if it was really shot she would just not go but it could be the filter if it is making the gas come through in spurts and check the fuel lines if they are cracked or shot they could be letting air in or stopping the carb from pulling the fuel along basically just check for wet looking spots and splits on the lines that is what i have to add on this take that to the bank brohan

 

[SWC]

one more thing bromigo if the old workhorse has a vented gas tank cap clean that off because if it is clogged up it might cause lock and prevent gas from getting to the old carb bam let us know what got her running right i bet a lot of brohans would like an update take that to the bank brohans

 

[Ned]

one more thing bromigo if the old workhorse has a vented gas tank cap clean that off because if it is clogged up it might cause lock and prevent gas from getting to the old carb bam let us know what got her running right i bet a lot of brohans would like an update take that to the bank brohans

Shtick aside, this is a great little known tip.

 

[NewlyRetired]

OK I got the fuel filter off but I mangled one of the sides since it just would not come lose.

It was pretty filthy so I replaced it with a new one.

The problem remains.

I took a quick peak at the air filter and it was pretty clean.

I am going to read the new posts now to see what I should try next.

 

[NewlyRetired]

OK after reading, this is what I have tried

1) Let all gas run out and refilled

2) replaced fuel filter

3) cleaned out air filter

4) Added http://www.acehardware.com/product/index.jsp?productId=20790516&KPID=15718058&pla=pla_15718058 to the new fuel and let it run through an entire tank*

5) I have adjusted both screws as suggested by the manufacturer near the carberator

* At the VERY END of this tank, the engine ran pure and smooth for about 30 seconds and then the gas ran out. When I refillied it the problem came right back. Does this give us any clues?

 

[3C's]

I'm telling you that MIB is great stuff. All others are pretenders. You have to follow directions though. Add it, run for 10 minutes, let sit overnight.

 

[NewlyRetired]

I'm telling you that MIB is great stuff. All others are pretenders. You have to follow directions though. Add it, run for 10 minutes, let sit overnight.

This will probably be my last attempt since I am not making any progress.

I will go to Home Depot tomorrow and pick this up and try it before calling for repair.

 

[Fat Nick]

* At the VERY END of this tank, the engine ran pure and smooth for about 30 seconds and then the gas ran out. When I refillied it the problem came right back. Does this give us any clues?

My initial reaction to this would be that it indicates your mixture is too rich. As the tank ran out, your mixture leaned out and it ran better. That means too much gas or too little air.

-Could be a blockage in the air intake - Check air filter (again) or get a new one. Also check intake openings/passages for blockage from grass, leaves, etc

-Could still be the carb adjustment. I know you said you adjusted it, but does it smooth out if you lean it out more?

-One last thing to check - make sure you have your choke OFF and that the choke switch is actually fully closing the choke. An open choke can make the mixture too rich.

To 3C's point, I'm guessing MIB is similar to a fuel-additive Carb Cleaner. If this is your 1st time running it after the winter, I would echo doing some sort of chemical carb cleaning, either MIB or via the method I posted above using aerosol carb cleaner. These things have really strong solvents that will break up fuel gunk.

 

[NewlyRetired]

* At the VERY END of this tank, the engine ran pure and smooth for about 30 seconds and then the gas ran out. When I refillied it the problem came right back. Does this give us any clues?

My initial reaction to this would be that it indicates your mixture is too rich. As the tank ran out, your mixture leaned out and it ran better. That means too much gas or too little air.

-Could be a blockage in the air intake - Check air filter (again) or get a new one. Also check intake openings/passages for blockage from grass, leaves, etc

-Could still be the carb adjustment. I know you said you adjusted it, but does it smooth out if you lean it out more?

-One last thing to check - make sure you have your choke OFF and that the choke switch is actually fully closing the choke. An open choke can make the mixture too rich.

To 3C's point, I'm guessing MIB is similar to a fuel-additive Carb Cleaner. If this is your 1st time running it after the winter, I would echo doing some sort of chemical carb cleaning, either MIB or via the method I posted above using aerosol carb cleaner. These things have really strong solvents that will break up fuel gunk.

Thanks. I need to locate the air intake. I am unsure what to look for.

The mower was run at least 10 times after the winter storage before this problem occurred.

When I adjusted the screws near the carb, the problem only seem to get worse (almost stalling). But as I have mentioned, my knowledge level is below zero and I could be doing something completely wrong.

The air filter looks easy enough to replace so I will try that. It looked pretty clean though and I vacuumed it.

The problem occurs whether I am at full throttle (near the choke line) or at very low throttle (far away from the choke line). I will trace the line to see what is happening when I move it.

Thank you to you and everyone for your suggestions.

 

[3C's]

if it were a clogged air filter you could try running with it removed.

 

[Nathan R. Jessep]

Good answers in here thus far. I had a similar problem and it turned out to be the gas I was using. It wasn't old, so I don't know if maybe it was dirty (like maybe the fuel truck had just refilled the tanks at the station and stirred up crud in the tanks) or just too much Ethanol for the small engine to handle. At any rate, I bought a fuel additive (one of the Ethanol treatment products... there's several on the market) and it seems to have fixed the problem for me.

 

[Mile High]

There should be a metal bowl at the bottom of the carb held on by a bolt under it. Take out the bolt there should be a couple of small holes in the bolt, take a bread tie strip the plastic off the tie and use the wire to make sure that the holes are not clogged. Clean the bowl to. Might help might be a hole in the shaft that was covered by the bowl clean it out to

 

[SWC]

brohan they put different carbs on the kohlers can you read a name on the carb because there are normally at least two adjustment screws one is for idle air gas mix and one is for high speed air gas mix sometimes there is a third which is for idle speed adjustment tell us if it is carter a kohler a walbro you name it that would be good to know so we can help you take it to the bank and not to a small engine repair place brohman

 

[Funkley]

Take the carburetor off, clean it then boil it in hot water. Put it back on. Should run fine.

Eta: clean with a carb cleaner, add some vinegar to the water when boiling.

 

[NewlyRetired]

I know nothing about carbs. I will try and watch a video on youtube to see if I can find one that looks similar to what I have. I don't feel comfortable trying to take it apart right now blind.

I will report back tomorrow on updates from the air filter testing and what I can learn about the carb.

 

[NewlyRetired]

brohan they put different carbs on the kohlers can you read a name on the carb because there are normally at least two adjustment screws one is for idle air gas mix and one is for high speed air gas mix sometimes there is a third which is for idle speed adjustment tell us if it is carter a kohler a walbro you name it that would be good to know so we can help you take it to the bank and not to a small engine repair place brohman

It was very dark and I could not see a name on it. I did see two screw adjustments though. I will try and clean the surface first to see if I can get a name before trying to take it off.

 

[3C's]

* At the VERY END of this tank, the engine ran pure and smooth for about 30 seconds and then the gas ran out. When I refillied it the problem came right back. Does this give us any clues?

My initial reaction to this would be that it indicates your mixture is too rich. As the tank ran out, your mixture leaned out and it ran better. That means too much gas or too little air.

-Could be a blockage in the air intake - Check air filter (again) or get a new one. Also check intake openings/passages for blockage from grass, leaves, etc

-Could still be the carb adjustment. I know you said you adjusted it, but does it smooth out if you lean it out more?

-One last thing to check - make sure you have your choke OFF and that the choke switch is actually fully closing the choke. An open choke can make the mixture too rich.

To 3C's point, I'm guessing MIB is similar to a fuel-additive Carb Cleaner. If this is your 1st time running it after the winter, I would echo doing some sort of chemical carb cleaning, either MIB or via the method I posted above using aerosol carb cleaner. These things have really strong solvents that will break up fuel gunk.

MIB is basically a carb rebuild in a bottle. Unlike any other carb cleaner I've come across. When left to sit overnight as directed it softens up gaskets to like new. I was all ready to replace or rebuild a carb on a nice backpack blower I picked up for next to nothing and was doing a little surfing and ran across a small engine mechanic who posted about it. He says he always tries it first now on the small stuff before going on to tearing the carb apart.

Not the post I had found but definitely a similar sentiment: Our shop just started using it and sea foam goes to the back of the line. I am a buyer. I put two carb in ultrasound cleaners with the stuff and they came out and worked. I had taken them apart and cleaned them with carb clearner and put them in the machines and still had problems. Ran them thru that stuff for 2 hours put them on and whal they worked. I ordered the stuff and the ultrasonic cleaner. I watched the mechanic do the water absorption test and it was the only one that held water in suspension for half a day. Sea foam failed that test big time. But time will tell it sure looks good for dealing with water.

 

[SWC]

okay brohan i found a parts catalog for the old bunton bullet walk behindd and it looks like you might have a fuel shut off valve under the gas tank make sure that sucker is open and maybe open and close it a few times to make sure it is working right and letting fuel through

 

[SWC]

on the air filter it looks like its got a foam cover over an internal element the kohler manual says to check that baby every time you start it or daily which is sort of ridiculous but hey they write the book not me the filter is a paper one if i am looking at the same manual so you could spent ten smackers and get a new one and here is a tip sometimes if you have a real dirty air filter the engine will blow black smoke because the gas is not burning all up but that could also be from to o rich of a fuel to air mix at the carb but i will get there is a second

 

[NewlyRetired]

on the air filter it looks like its got a foam cover over an internal element the kohler manual says to check that baby every time you start it or daily which is sort of ridiculous but hey they write the book not me the filter is a paper one if i am looking at the same manual so you could spent ten smackers and get a new one and here is a tip sometimes if you have a real dirty air filter the engine will blow black smoke because the gas is not burning all up but that could also be from to o rich of a fuel to air mix at the carb but i will get there is a second

I have been looking for the black smoke but I don't see any.

I am going to get a new air filter tomorrow. The current one does not look bad to my eyes but it was last replaced in March of 2012 so it has gone through two full seasons+.

 

[SWC]

the manual i found says that there are two types of carbs on this bad boy either a nikki that has only one setting screw and a walbro that has two so it sounds like you ahve the walbro from what you said and i am not going to just type out he manual for you but here is the link http://www.kohlerengines.com/onlinecatalog/pdf/12_590_01.pdf the stuff about the carb is on pages eleven and twelve and actually a lot of what everyone else in this thread says is in there so hey man good luck and let us know what you find out take that to teh bank brohan

 

[NewlyRetired]

okay brohan i found a parts catalog for the old bunton bullet walk behindd and it looks like you might have a fuel shut off valve under the gas tank make sure that sucker is open and maybe open and close it a few times to make sure it is working right and letting fuel through

I was thinking of checking that closer.

I have to turn it off every time I shut the mower off (if I don't I can get oil and gas mixing which makes it near imposdible to start the next time).

I have turned it on and off at least 20 times in the past two days while tinkering.

I can see fuel very clearly flowing through the new fuel filter I added today.

 

[NewlyRetired]

the manual i found says that there are two types of carbs on this bad boy either a nikki that has only one setting screw and a walbro that has two so it sounds like you ahve the walbro from what you said and i am not going to just type out he manual for you but here is the link http://www.kohlerengines.com/onlinecatalog/pdf/12_590_01.pdf the stuff about the carb is on pages eleven and twelve and actually a lot of what everyone else in this thread says is in there so hey man good luck and let us know what you find out take that to teh bank brohan

I printed this manual out today. I think I do have the Walbro.

I am just not confident in removing it.

 

[SWC]

and hey one moore thing if you are not comfortably screwing around with the carb then do not do it just take it in and get a small engine guy to tune it up becuse if you run it too hot which means with too much air you can burn up the motor so just do what you are comfortably with and do not wreck it and do not get hurt either take that to the bank brohan

 

[SWC]

and last but not least on the fuel filter kohlers are finicky about that you need to get a real oem kohler fuel filter for reasons that i do not understand but read on a small engine forum so i am just telling you what i read

 

[NewlyRetired]

SWC,

The manual tells me to make sure the grass screen is clean and that the air intakes are not blocked (this was mentioned earlier in thread).

The manual does not point out where those two things are. Do you see them in the pics in the manual?

 

[SWC]

i am looking at this http://www.kohlerengines.com/common/pdf/kohlerengines-accessories-parts-catalog.pdf and it looks like the grass screen is part of the blower assembly and the air intake is just the whole air filter assembly i think but i do not have anything to support that in terms of a link or whatever

 

[Fat Nick]

and hey one moore thing if you are not comfortably screwing around with the carb then do not do it just take it in and get a small engine guy to tune it up becuse if you run it too hot which means with too much air you can burn up the motor so just do what you are comfortably with and do not wreck it and do not get hurt either take that to the bank brohan

I'm leaning this way. You've learned a lot about engines from this post most likely, and tried a lot of the basic, easy-fix things...removing and taking a part a carb isn't novice engine work. Not doubting that you could do it, but you have admitted that you're a novice. Probably worth just taking it in at this point.

 

[NewlyRetired]

I replaced the air filter this morning. As expected it was quite easy, but unfortunately the problem remains.

I am down to my last chance now assuming I don't get the guts and find a step by step video on how to remove the carb.

The store I bought the air filter at did not have the Mechanic in a Bottle in stock so I will have to look elsewhere.

I guess at worst now I can make sure the repair shop does not over charge me for replacing the fuel and air filters.

 

[3C's]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

 

[NewlyRetired]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

yeah I went to Lowes and they were out of stock.

I have a small Ace near me I will check else it is in stock at HD a little drive away.

I don't have a lot of hope for this since I have already tried a similar product but for the price it is certainly worth a shot before I call.

 

[3C's]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

yeah I went to Lowes and they were out of stock.

I have a small Ace near me I will check else it is in stock at HD a little drive away.

I don't have a lot of hope for this since I have already tried a similar product but for the price it is certainly worth a shot before I call.

Trust me, what you used is not all that similar. It might not fix it but for the price it's certainly worth trying.

Rather than drive, maybe you can check online if they say they have it or call them. No sense in wasting gas and time driving around looking for it.

 

[Fat Nick]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

yeah I went to Lowes and they were out of stock.

I have a small Ace near me I will check else it is in stock at HD a little drive away.

I don't have a lot of hope for this since I have already tried a similar product but for the price it is certainly worth a shot before I call.

Trust me, what you used is not all that similar. It might not fix it but for the price it's certainly worth trying.

Rather than drive, maybe you can check online if they say they have it or call them. No sense in wasting gas and time driving around looking for it.

Man...you REALLY love this stuff. I'm going to have to get some to try on some of my older stuff just out of curiosity now. I've got an old edger that I got in a trade that maybe I can try some out on. It surges pretty bad.

 

[3C's]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

yeah I went to Lowes and they were out of stock.

I have a small Ace near me I will check else it is in stock at HD a little drive away.

I don't have a lot of hope for this since I have already tried a similar product but for the price it is certainly worth a shot before I call.

Trust me, what you used is not all that similar. It might not fix it but for the price it's certainly worth trying.

Rather than drive, maybe you can check online if they say they have it or call them. No sense in wasting gas and time driving around looking for it.

Man...you REALLY love this stuff. I'm going to have to get some to try on some of my older stuff just out of curiosity now. I've got an old edger that I got in a trade that maybe I can try some out on. It surges pretty bad.

I know it sounds like I'm in sales for them, right? Read the reviews from people who have (actually) used it and they all say the same thing. I was impressed for sure.

 

[avoiding injuries]

MIB is available at most hardware stores like Ace, Lowes, Home Depot, Tractor Supply. Think I got mine at TS.

yeah I went to Lowes and they were out of stock.

I have a small Ace near me I will check else it is in stock at HD a little drive away.

I don't have a lot of hope for this since I have already tried a similar product but for the price it is certainly worth a shot before I call.

Trust me, what you used is not all that similar. It might not fix it but for the price it's certainly worth trying.Rather than drive, maybe you can check online if they say they have it or call them. No sense in wasting gas and time driving around looking for it.

Man...you REALLY love this stuff. I'm going to have to get some to try on some of my older stuff just out of curiosity now. I've got an old edger that I got in a trade that maybe I can try some out on. It surges pretty bad.

What did you trade?

 

[SWC]

brohans ccc loves that stuff so much i think i might drink some and see if it takes care of my ulcer just kidding take that the bank brohans i am pretty sure this is a carb adjustment issue with the low speed gas and air mix but hey that is just my gut reaction take that to the bank broahns

 

[Fat Nick]

Man...you REALLY love this stuff. I'm going to have to get some to try on some of my older stuff just out of curiosity now. I've got an old edger that I got in a trade that maybe I can try some out on. It surges pretty bad.

What did you trade?

Long story...I bought a used snow blower off a guy a few years ago. 22" MTD. Rusty piece of crap, but it ran and was better than shoveling. I managed to find a lady last fall who had a 26" Craftsman blower with a busted engine. She ran it sans oil and cracked the rod. She gave it to me for free. Everything was pristine except the engine. I looked into fixing the engine, and realized that the Harbor Freight 212cc Predator engine was a direct-bolt on replacement, and I could get one for $90 with a coupon. Cheaper than even buying a new rod and bearings for the busted Briggs. So, I bolted up the new engine, and it was back into working order. I even made a few modifications to make it run even better.

That left me with 2 snow blowers. I took the old rusty MTD blower and traded it for 3 gas edgers. I didn't need 3, I only needed 1, but the guy had 3 and offered me 3. One of them was a newer Yard Machines edger that was in 100% working order. I use that one regularly now. The other one was a 1978 King 'o Lawn edger. It was made out of some super heavy gauge steel, had very solid parts, and the engine ran. The finish was all rust though. I found some pictures of what it could've looked like, and made it a project, so I took it apart and used electrolysis to strip the rust, refinished and repainted it, and I'm rebuilding the engine now. The 3rd edger was a 1990's Green Machine edger. It was missing the blade, belt, and recoil. I found an old recoil and managed to get the engine running. I'm not putting a lot of work into that one, but I may try and sell it at some point. I'll eventually finish the King 'o Lawn and then decide if I want to keep it as a nostalgic piece or just sell it. I've literally rebuilt it from the ground up, so it'll be like new old stock once I'm done. I won't ever get my investment back in it, but it was a good project.

So...like I said, long story. 1 old snow blower + 1 HF Engine = 1 better Snow Blower + 3 running edgers

 

[NewlyRetired]

I picked upthe MIB today and the mower has been running for about 20 minutes with the MIB mixed in with the fuel.

The symptoms have changed a bit.

Instead of the constant up and down idling in a regular heart beat type pattern, I now get about 1 minute of light sputtering and 1 minute where it is barely staying alive. It has not fully stalled but has been on the absolute verge a few times.

When it is near stall, plenty of dark grayish smoke is coming out.

I would not doubt my tinkering with the screws on the carb might have something to do with this change.

After a few more minutes I am going to shut down the mower and let it rest over night. Tomorrow I will try running again but if it does not improve I will call a repair shop.

I am bummed, I was really hoping one of these fixes would have been the trick. It is hard to gain any confidence in this type of stuff when always faced with failure.

 

[3C's]

20 minutes is more than enough, 10 is all that's needed. Shut it off and resist any temptation to try again for 16-24 hours.

 

[berndog]

I am bummed, I was really hoping one of these fixes would have been the trick. It is hard to gain any confidence in this type of stuff when always faced with failure.

You are looking at this wrong. The timing of a broken lawnmower is almost perfect with the start of the World Cup. Without the lawnmower you can't cut the lawn so you have no choice but to watch the games, well played.

 

[NewlyRetired]

I am bummed, I was really hoping one of these fixes would have been the trick. It is hard to gain any confidence in this type of stuff when always faced with failure.

You are looking at this wrong. The timing of a broken lawnmower is almost perfect with the start of the World Cup. Without the lawnmower you can't cut the lawn so you have no choice but to watch the games, well played.

I have a back up mower . My yard is large and the grass is very thick. I have to cut at least 2 times a week to keep up

The back up mower is a small push one so it takes me about 3 hours or so.