B&S Engine problems

[Pepsiboy]

I have a 2000 MTD Yard Man tractor with 46" mower deck. Tractor is fine, BUT engine is not. Last season it started to run rough at idle. It sill surge constantly until I open the throttle about half way. This season it is still doing the surging at idle, and now will not start after running for more than 5 minutes. It starts great when engine is cold, but when warm it will not start. I have tried to adjust the carb, but there are no adjustments for mixture. It also seems to have a lot of blow by coming out of the crank case vent into the air cleaner area. It does not appear to be starving for fuel, as when the top of the carb is removed there is a FULL fuel bowl. yesterday I used it to mow our front yard and after about 4 minutes of mowing it back fired once and died. I could not restart it. It will crank, but no fire. I went out there today and it fired right up. Again, when warmed up would not restart. The engine does not use any oil and does not smoke. Engine information listed below. Thanks in advance for any help.

Dave

B&S I/C 20 hp Twin II
Model 461707
Type 0143E1
Code 0009205A
Family YBSXS.7482VE

 

[jaotguy]

grab an old set of booster cable and a spark plug .... connect one cable end to the frame of the tractor , the other clips on the base of the new spark plug ....

start and run the tractor till it dies on you ... then pull the plug wire and clip it on the new plug on the booster cable ... crank and check for spark ...

if you have a good spark , you've eliminated 1 possibility ( or found your cause )

next check the air breather and clean it

last thing to check is the fuel system .... get an old can , pull the fuel line from the carb and drain into the can ... should flow freely and have no water at the bottom ... drop the carb bowl and check for dirt , corrosion , and clean the main jet ... re-assemble

 

[Mysfyt]

Lots of possibilities here and people are going to give you some good advice. Start with the simple/no cost stuff first before you start swapping any parts is my advice. Your problem sounds electrical to me, very similar to my neighbors lawn tractor. Turned out to be a corroded ground wire to the chassis. Looked perfect until you took the bolt out and looked underneath the terminal.

A coil could be your problem also, but again, do the simple wiring check first.

 

[Walt 2002]

Well this is the one B&S ignition coil which gives trouble. As said above, check for spark when it dies. Your surge problem is something else.

Walt Conner

 

[Pepsiboy]

Walt,
Thanks for the tip. I think I have cured the surging problem. I disassembled the carb, cleaned what I could, and put it back together. No more surging after resetting the throttle stop for idle rpm and readjusted the governor. When I checked the coil, the gap was WAY off. Spec calls for .008 to .0133 inches. It was set at about .025. I reset that and took it for about a 1 mile run to our mail box and back. It ran just fine. I shut it down and went inside to get a drink. When I came back out after about 5 minutes, it would not restart.

Dave

 

[Pepsiboy]

Mysfyt,

That was one of the first things I checked. ALL of the grounds have been removed and cleaned before reattaching. Thanks.

Dave

 

[Pepsiboy]

joatguy,

It has plenty of spark any time I crank the engine. There is also plenty of clean fuel (maybe too much when hot). Air cleaner is new this spring. Only thing I can think of is that I may need to replace the carb float and needle valve, and rebuild the fuel pump. Both will have to wait as budget is VERY tight right now on our fixed income. Thanks for the advice.

Dave

 

[Fawken]

I have an old Craftsman with a 2-cyl Briggs that was doing the same thing. I've actually had the mower since 1990 and what I discovered is in spite of periodic cleaning of the foam air filter element those filters degrade and pass less air volume over time. Now mind you, less air on a cold motor is a good thing, but obviously not so much on a nice and warmed up motor. Instead of buying a new filter I found you can just throttle all the way back to the turtle and it cranks right up.

 

[Walt 2002]

Suggest you shut gas off before stopping. Gas may be leaking past float needle flooding engine and has to evaporate before starting. No shut off, pinch gas line. Also gas line on some of these ran thru the cooling shroud, IF so, may be vapor locking. Did you check if it had spark when it stops as suggested above.

Walt Conner

 

[Mysfyt]

Check your gas tank cap to make sure it's breathing properly.

The backfire that you mentioned still points to ignition IMHO. Were the flywheel magnets rusty? According to theoretical physicists, it shouldn't matter. But unfortunately, the rest of us live in the world of reality. Honestly, I've seen this fix a no spark issue. Weak magnets in the flywheel get weaker when they get hot for another theory to keep in mind.

Good luck and please post what you find! I have the same mower from the same year.

 

[Walt 2002]

You can polish the magnets all you want, won't matter, polishing the coil mounting surfaces will.

Walt Conner

 

[bindian]

If this is a twin cylinder opposed B&S engine, you have a vacuum fuel pump. It's getting vapor locked. Take the pump apart, clean and replace the diaphram.
hugs, Brandi

 

[Pepsiboy]

Fawken,

Air filter element was new this spring. Foam prefilter was just cleaned about a week ago. So far, it looks like the main problem is the coil and / or fuel pump. Being on a tight fixed income, the $50.00 coil is off the page for now.

Thanks for the tip.

Dave

 

[Pepsiboy]

Walt,

Fuel line does NOT go through the cooling shroud. I'll try pinching off the fuel line next time I get it running and see if that helps. I can put a valve in line if it does. As in my last post, It looks like either coil or fuel pump at this point. Budget says nothing expensive for repairs at this time.

Thanks for the tip.

Dave

 

[Pepsiboy]

Mysfyt,

Fuel cap was one of the first things I checked. It is venting properly. I did clean the dirt off the magnets and coil. I did not POLISH them, just removed loose dirt and rust flakes, then PROPERLY set the air gap between the coil and flywheel. As above, I think it is in the coil, fuel pump, or possibly carb float valve.

Thanks for the suggestions.

Dave

 

[bindian]

I mis read your posts last night. I just re read them. After running it after a few minutes , shut it off, remove one spark plug at a time....connect the plug back to the spark plug wire and while the spark plug threads are touching metal on the engine, try to start the engine. This works best in a dark area. You should see blue arcs from the electrode gap of the plug to the engine. No spark.............coil is hot and shorting out internally. Need new coil. If you got good spark when checking above on both plugs...............fuel line is vapor locked from the heat. Try dripping fuel straight into the carb. and try to start it. If it starts, or tries to start then...........it for sure is vapor locked from the heat and the fuel pump can't overcome the vapor lock.
hugs, Brandi

 

[Pepsiboy]

bindian,

Well, I think I have found the problems (YES, plural). The coil gives no spark when warm, AND intake manifold appears to have raw fuel under the carb when warm.

SOOO, I need to get a new coil and a rebuild kit for the carb / fuel pump combination. Cost will be just over $110.00, so will have to wait until budget allows it.

Dave

 

[bindian]

bindian,

Well, I think I have found the problems (YES, plural). The coil gives no spark when warm, AND intake manifold appears to have raw fuel under the carb when warm.

SOOO, I need to get a new coil and a rebuild kit for the carb / fuel pump combination. Cost will be just over $110.00, so will have to wait until budget allows it.

Dave

Glad I could help.
hugs, Brandi