Oil & Fuel Popping & Sputtering

[Gregster613]

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]

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]

Check to air leaking around head gasket.

 

[Gregster613]

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]

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

 

[tomplum]

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]

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

 

[IH3444]

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]

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]

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