Briggs opposed twin 20hp Craftsman LT1000 bogging down

[bkenobi]

I have a 2000 Craftsman LT1000 DLT lawn tractor that had the engine swapped from a V-twin to an opposed twin at some point. It seems to run ok for the most part with plenty of power. I ran it the other day to mow my grass which is mostly brown at this point so just cutting down the few high spots of green. After an hour or so the motor seemed to bog down a bit as though it was low on fuel. I finished the section and headed back to the shop but it was running ok agian so I finished the last section in 15 minutes or so. I checked the fuel quantity and I've still got lots in the 3.5 gallon tank.

When I got the mower earlier this summer I changed out the fuel, changed fuel filter, checked the spark plugs, checked the air filter, changed the fuel line (from the tank to the filter only). I spoke to the mower place and they suggested a few things but the primary things that seemed plausible were: a faulty/plugged filler cap, a crack in the fuel pump vacuum line, or a fuel jet blockage.

I pulled the panel on the left side of the engine when I got it to see if that's how the rockers are accessed but didn't notice a fuel pump. Since the fuel line goes under there, I assume that's where it would be. I don't have a part number for the fuel pump though so I'm not sure if they can be replaced or rebuilt. As for the fuel cap, I'll just crack it and see if that helps before I mess with the fuel pump. If anyone has a P/N for the fuel pump and/or any idea about sourcing or rebuilding I'd appreciate.

B&S 461707-0145-E3
Craftsman 917.272201

 

[Richard001]

You didn't say, but i assume that the engine is air cooled. Have you checked for a mouse nest on top of the cylinders or head ?

Overheating will cause what you described.

Richard

 

[oldnslo]

Briggs has a very good parts break down website. I would suggest looking there for the fuel pump location

Have you verified spark & compression when engine is warmed up?

 

[bkenobi]

I can't find a spec for the compression on this engine. I have a parts breakdown for the engine but it's kinda mediocre compared to others that I've seen. If you have a link I can use to search for a better one, I'd certainly appreciate!

I looked in that and found one diagram that suggested the pump was located on the carb so I went back to the tractor this evening and cleaned it up a bit better. There does appear to be a rectangular part on the front of the carb that has the main fuel line feeding it as well as another fuel type hose coming from the engine block. That has to be the fuel pump but even after removing the majority of the debris I do not see a part number. The vacuum line does not appear damaged but it does run right past a metal bracket so it could become torn at some point. I think I'll go ahead and replace the remainder of the fuel line (fuel filter to pump) and the vacuum line since I have extra from replacing the other portion of the line.

I pulled one of the side shields off and did not see anything on the head but I'll check the other side tomorrow.

 

[jaxs]

There does appear to be a rectangular part on the front of the carb that has the main fuel line feeding it as well as another fuel type hose coming from the engine block. That has to be the fuel pump but even after removing the majority of the debris I do not see a part number. The vacuum line does not appear damaged but it does run right past a metal bracket so it could become torn at some point.

THAT IS THE FUEL PUMP. The secoud line coming from crankcase delivers a pulse each time piston goes up then down. Inside cap w/4 screws is a thin rubbery diaphragm that can stretch or get a pin hole. The diaphragm is fairly generic and interchangeable so you should be able to find one locally. To see if pump is the problem,temporarlly connect fuel line to a tank elevated above carburator effectivlly makeing carb gravity fed and pump unnecessary. I keep a couple old push mower tanks around for this very purpose and for temporary replacement while waiting for new tank to replace one that has sprung a leak.
If this test confirms bad fuel pump and your mower mechanic plays dumb on part # for new one,order a low pressure 12 volt pump off Ebay.

 

[Richard001]

bkenobi​

This is from your first post:

I have a 2000 Craftsman LT1000 DLT lawn tractor that had the engine swapped from a V-twin to an opposed twin at some point.

You have not told us what engine you have in your machine. Can you please identify the manufacturer and the model number of the engine.

Richard

 

[tomplum]

It might be as simple as some water or debris floating around in the bowl. There is a bolt on the LH side of the bowl that when removed will drain it. Use a clean catch pan. Drain is 3/4" on a 4 screw pump model and 5/8" on a 3 screw model. You can take a straw from the carb clean spray can and spray around in there and actually straight in will be the main. Won't hurt a thing. Put the drain bolt in and try again. Also a good way to see if your pump has filled the bowl.

 

[bkenobi]

Good idea. I'm hoping to have time this weekend so I can try these ideas.

 

[bkenobi]

I replaced the section of fuel hose between the filter and the fuel pump as well as the line between the case and the fuel pump. Neither seemed to be a problem, but they are old so why not. The fuel pump vacuum line was really short and was rubbing on a bracket as well as the output line from the carb. I don't know if it would have worn through, but I didn't like it so it's fixed. I did notice an issue with the inlet side of the fuel filter though. The fuel line had slipped off of the larger diameter of the fuel filter and was only on the smaller diameter. I suspect this could have cause a fuel feed issue though I didn't see any leakage.

The fuel tank cap seems ok. I cracked it when the motor stalled on startup but it didn't make any difference. In that case, the issue was really the choke setting because the engine hadn't warmed up yet. My old mower didn't have a choke so tweaking the choke is new to me. Anyway, I'll keep watching the fuel cap if it is an issue or not.

While the lines were disconnected, I tested the fuel pump by sucking/blowing on the vacuum line and it seemed to hold pressure fine. I don't think the pump has an issue.

 

[bindian]

Still sounds like a small pin hole in the diaphram that expands when the engine is hot. Try the electric fuel pump.
Then again, the Briggs could have a worn keyway on the flywheel. I haven't messed with twin B&S engines in years. Is this engine electronic ignition?
hugs, Brandi

 

[bkenobi]

It has a key so i assume that would be considered an electronic ignition? If it was a pin hole in the diaphragm wouldn't that mean it wouldn't hold pressure on the vacuum side? Seems like i would have felt that when i tested.

 

[bindian]

It has a key so i assume that would be considered an electronic ignition? If it was a pin hole in the diaphragm wouldn't that mean it wouldn't hold pressure on the vacuum side? Seems like i would have felt that when i tested.

Oh boy. Maybe you will be better if you take it to a small engine repair shop.
Having a key means it has an electric starter. Electronic ignition means it does NOT have points and condenser to make a spark, but an electronic module to fire the spark.
hugs, Brandi

 

[tomplum]

Your filter being loose, then tightened again- did it change anything?

These engines definitely had their share of coil problems for a hot stall. Sometimes the CD would be wiggy and begin to throw the spark at the wrong time. The thing to know before you replace a coil is that these machines are old, harnesses brittle and you should confirm that there is never any power getting to the coil. Crank, run, stop. wiggle this an that. The OEM replacement coils are really sensitive when it comes to stray power hitting them. AN aftermarket coil could be better.

 

[bkenobi]

The tractor is a 2000 model year. I didn't think there was a motor made with points since the 1980's. This model has an ignition coil which is what i thought all modern engines used.

 

[bkenobi]

FWIW, I checked the compression and found that the two cylinders were 78 and 82 psi. The best I can find suggests that is within the normal range for opposed twin Briggs motors though the range I found was 60-100psi. So long as they are within 25% the concensus seems to be it's good to go.

 

[oldnslo]

78 to 80 PSI seems low unless that model had the compression release that kicks out at higher RPM.

 

[bkenobi]

My 17.5hp Briggs was around 50psi with a blown head gasket and holds closer to 120psi after repair. That seemed low but without published specs from the mfg I can't say other than what I found searching forums. Yes, it was lower than I'd have expected too.