Oil & Fuel Popping & Sputtering

Gregster613 · Apr 1, 2019

Hi Guys, A little helpful advice requested. This could have gone in the yard & garden spot also, but since I own and operate this machine; I thought I'd put it here.

Here's my dilemma. Scotts 2048 riding lawnmower, 20 hp B&S twin cylinder Intek engine. Two weeks ago I was mowing grass, mower running just fine. Then out of the blue it starts surging terribly, I had to fully choke engine to limp it into the garage. I immediately thought it was fuel related.

I replaced the fuel filter, air filter [regular and pre] , spark plugs, check the valve lash (cold engine, piston at top dead center - plus just a tad more - when both valves closed- as instructions say) valves at a snug .005. During this process I discover my positive cable has corroded through. So I made new Positive and Ground cables also. I thought "Ah haw, I've found my problem." Start it up and it is better some but still slightly surging and now is popping and slightly backfiring through I believe the carburetor.

Next; I disassembled and cleaned carburetor with spray sea-foam and carb cleaner and used air pressure to blow out the jet and passageways. Everything looks clean and good inside. No change in performance. I disassemble and clean it again. No change.

I buy two of those spark checkers that go between the plug wire and the plug. I run it and both seem to be brightly lit. Although the one on the right side of engine (from sitting in seat) "could" be just a "Tad" dimmer than the other. Really hard to tell and could be just an illusion. So now I "probably" can rule out an armature failure?

I'm at a loss here now. Just can't seem to discover any reason it should be popping & sputtering and not running at full strength? I can order a carb repair kit but don't want to just throw $$ at an unknown fix. It now seems like it's an electrical issue, but I just can't seem to discover where.

So I hoped someone here had had a similar issue and had found the cure. Any helpers out there? If so, my sincere thanks!! Greg

tomplum · Apr 2, 2019

The popping and sputtering sounds like you have a lean side in the carb. Especially if the choke helps to smooth it. As you are unfamiliar with the carb, you may want to compare the kit vs complete cost. If the jets have come loose in the pipe assy, they have to be replaced (or hunt for the tiny oring) and do not come w/ the kit. You could try replacing the moth gasket and oring that seals around the pipe at the bowl. If the jets were in place and you would like to try something simple, pull the shroud and remove the top plate (3 screws) and flip the gasket after cleaning the body. You will see two holes that enter the brass fuel pipes near the center. A quick burst of carb spray down each, quickly screw the cover back on and give it a quick start to see if it has improved.

Al that being said, if that doesn't get you where you want to go- get back under the valve covers. You will want to know that the valve guides are not migrating and beginning to touch the valve and that rockers are staying tight. So compare the 4 guides and they should protrude from the head close to the same. Next compare valve lift by cranking the engine. Should you have a worn cam lobe, you'll see a big difference. .004" intake and .006" exhaust 1/4" PTDC

Thomas · Apr 2, 2019

Check to air leaking around head gasket.

Gregster613 · Apr 2, 2019

Tomplum, Thanks for the advice. It looks as if I will need to disassemble the carb again and be "far" more through in cleaning it. Mine has the black pipe housing and does "not" have the jets inside the top of the pipe; which is why I referenced only the main jet just above the backfire solenoid. However, I did not use any tiny pieces of wire to clean the holes in the pick-up tubes. I've watched several more you-tube videos on Inteck carb cleaning and believe I just wasn't through enough. I do use sea-foam mixed in each/every tank fill up and have tried running lots of it through the carb but I just don't seem to be as lucky as others are for whom it has cleared up their problems! I'll try again and this time I'll really look on the carb itself for any numbers as to which it could be replaced with if I get no good results.

Thomas, Thanks for the thoughts also. I'll try squirting some carb cleaner around the head gaskets also to see if it sounds as if leaking. This just happening out of the blue is what has had me puzzled. It's run swell for years and I've done nothing different suddenly to cause anything that I can think of. I'll keep plugging away at it and see if'n I can't solve the puzzle. Greg

big bubba · Apr 2, 2019

in the future go ethanol free fuel, you probably already know this best regards

tomplum · Apr 2, 2019

You may find this helpful: Disassembly, Cleaning and Repair of Briggs Intek V-twin Two-Barrel Nikki Carburetor - Part 1
SO yes, the jets are in the plastic fuel pipe and that slides over the brass fixed ones in the carb body. Keep track of them should you remove them as they are slightly different.

woody · Apr 2, 2019

have you checked the gas for water, drain and replace the fuel.

IH3444 · Apr 3, 2019

Have the Scotts 2554, same issue. I cleaned the gas cap vent, it was plugged up with dust. Problem fixed. See if this could help you also.
There is also a small diaphram fuel pump which connects with a line to the crankcase. Be sure the line is good, and check the pump for pumping.

Gregster613 · Apr 3, 2019

Tomplum, Thanks for the link. I've looked at a lot of those videos and haven't yet seen one that's just like mine. Will check it out and see. I have found a complete replacement carb that costs "less" than just the darn repair kit! I plan to completely disassemble the carb once I catch up on a few other projects the wife has me focused on at the moment. Now that I can just replace the carb, I'm not so worried about screwing something up during disassembly.

Woody, Fresh gas in tank. No issues there.

IH3444, Thanks for the tip. I haven't cleaned out that tiny vent hole in awhile and that just might be the culprit! I'll check it ASAP and hopefully that was the issue!! My fuel pump is pumping gas through it, there is a vacuum hose from the back of the intake to the crankcase and it is/was cracked. I black friction taped it while awaiting a replacement and it made no difference. The replacement came in and I will put the new one on and again recheck for issues. I'm not holding my breath in chance of success on that one though....

Once I get it fixed I'll be sure to report back the issue -- I'll be just so happy.

searcyfarms · Apr 6, 2019

the best thing i ever invested in for cleaning carbs is guitar wire, stiff, flexible and will root out places and unplug those tiny holes that you thought were flushed out - fixed many over the years that way, an old guy working on deere carbs taught me that

Gregster613 · Apr 7, 2019

Success finally...I just wish I could take or give credit where it might have been due. IH3444 I made sure to check that tiny vent hole and yes indeed it was slightly plugged; I thought "oh my this might just be the ticket" to freedom from sputtering; and it helped - a lot - but did not completely stop the problem. I should have thought of checking that myself, I didn't though. I did "write" it in my troubleshooting portion of the manual, for future events to remember to check it! Thanks for the reminder.

I had grass to get cut and decided pop, sputter, and/or gasp for air this machine is going to get some work done today. I scraped my deck, put on new blades to give it the best chance at living through the mission, poured about 3/4 of a bottle of sea foam into the fuel tank and began cutting. She popped a few times and ran ragged for about 3/4 of an acre of cutting, then I went over some rough spots in the yard and a pop or two later then she just began to purr smoothly!! Just like when she started to run roughly...out of the blue, and my troubles are gone!! It must have been something plugged deeply in the inside of the carb is all I can guess and when I went over that rough patch it must have jogged loose and got gone.

I did learn a lot this trip around though...fuel // electrical symptom/problems can often seem the same. I began this adventure believing I had a fuel issue problem - and it appears I was correct. But the popping/misfire quite quickly had me checking all electrical also. I was getting ready to buy 2 new armatures as this "I thought" could only be the source of the misfires. If it hadn't have cleared up, they would have been ordered tonight.

Tomplum, you were right on it being in the carb and I was prepared to order a replacement carb also - I have found a replacement for only $40.00! Hard to believe that a complete carb is cheaper than a repair kit - but it's true. I would have torn a gasket or 2 whilst doing a complete tear down & cleaning of old carb and the repair kit is listed at about $80.00! I would have tried that anyhow had it not cleaned itself out. I'm glad it did tho!

At any rate, my old girl just reminded me that she's just like me - old and sometimes gets sick and stumbles around for a few days or (weeks). Give her any medicine that you have on hand and hope that she gets better on her own. With faith and luck, she will.. My most sincere thanks to all who helped me troubleshoot this mysterious aliment. I looked at/used everyone's advice and yet my aliment worked it's own kinks out by itself. You've just got to love a machine that gets sick, but then just gets it own self well!! Thanks to all, One happy mower owner now -- Greg

denchen · Apr 7, 2019

It might not be very environmental friendly, but I always put a bit of two stroke oil in with the petrol (gas). My reasoning is that todays petrols do not contain any form of lubricant. Anyway, I`m satisfied that when doing heavy work my motor seems to run a lot better.

tomplum · Apr 7, 2019

Excellent news. The vent was great call. Should you install the carb in future, give us updates. I've not seen aftermarket carbs used in this application before. I will say that I've seen a few walk behind mower carbs that were cheap, lasted only a short while as an FYI.

fried1765 · Apr 7, 2019

denchen said:
It might not be very environmental friendly, but I always put a bit of two stroke oil in with the petrol (gas). My reasoning is that todays petrols do not contain any form of lubricant. Anyway, I`m satisfied that when doing heavy work my motor seems to run a lot better.

Marvel Mystery oil would likely be a better choice than two stroke oil.
MANY professional mechanics believe that Marvel Mystery oil is effective.

tomplum · Apr 7, 2019

fried1765 said:
Marvel Mystery oil would likely be a better choice than two stroke oil.
MANY professional mechanics believe that Marvel Mystery oil is effective.

I even comb my hair with the stuff! Frees up those stuck thoughts ya know

woody · Apr 7, 2019

It was the seafoam I run a little in everything I got with a motor on it.

Gregster613 · Apr 8, 2019

Hi TBN'rs, I ran it again today with the same perfect purring engine as in the past!! I am just mystified as to how anything could have gotten into a closed fuel system?? I always use the same brand of fuel (Exxon 87 octane); and I add 2 oz of sea foam, 2 oz of stabil, and quite often [not always but when I think of it] 1 oz of Marvel mystery oil to each gallon of gas.

That is my routine and why I was so stymied when she started acting up. I admit it's been at least a year since I changed the fuel filter, but I don't run it all that many hours per season - with the past drought I've hardly run it at all! I've got 470 hours on it in total. The old filter was a clear plastic type that showed fuel flowing through it at the time of issue, but it got changed along with everything else. Old fuel filter went into trash can, but I've put my old champion brand plugs back in and they are working just fine. I am baffled as to how this happened or why, but sure am glad it sorted itself out!

Topplum, I hadn't yet bought that replacement carb, it was sitting on my Amazon screen if I thought I'd need to give the carb another clean out and messed up a gasket or something. If I ever do need a carb though it's there and cheaper than a gasket kit! Although what you say is probably true - cheap but how long will it last? and will it actually fit? Looked like an exact replicate - but that's on the computer screen and not in hand! If I ever have the future need to go that route I will give an update as to if it really works!

Woody, I added quite a bunch of sea foam this last time around and I don't know for sure but it might/must have helped!! All I know for sure is that it didn't hurt!! And I'm back in a smoothly running saddle again.

IH3444, Once again thanks for the reminder to check the gas cap vent!! I wrote that into my manual just to jiggle my mind in the future if I ever have this dilemma again. It helped a lot and may even have been the turning point for my machine to get it's act back together! I'll never really know for sure but it is something to always keep in mind!!
Thanks again to all you guys for the thoughts and suggestions...Helped me keep my own mind intact as I was really confused this trip. Greg

tomplum · Apr 8, 2019

To think of this differently, it is not a closed fuel system. A carburetor is always vented or it wouldn't work. Externally or inside the bore, it's always vented. Why that is important to know is that there is a relatively small amount of fuel with a decent amount of surface area that will allow the fuel to lose key constituents that aid in starting and preserving the fuel. On these especially, and really just about anything else- I suggest that they are run at least monthly. This engine seems to have the quality of fuel actually evaporating to where if it sat, and you remove the solenoid (on the new style) you won't get any fuel and the pump at crank speed won't fill the bowl on its own.

My guess is some gel or ? was stock in one of the brass fuel pipes that fit inside the pick up tube. Note too that the fuel cap on yours is vented, but there is a much larger volume of fuel so it deteriorates not as quickly. Stay up with stabilizing the fuel and run it frequently.