B&S 440000 series V-Twin problem

CWatters said:

I have a 440000 series B&S V-Twin in a Toro Wheelhorse that's giving me some trouble.

From cold it starts fine and cuts quite tall grass ok. However after about 40-50mins or running it bogs down/looses power. If I'm quick and turn off the cutter and drive the revs will come back up. Sometimes that doesn't happen and it will stop. It can be restarted again immediately. Sometimes if I give it a 3 min rest it will carry on for another 15-20 mins and bog again. Sometimes it bogs down again almost immediately and I have to give up and pack it away.

Next day/week it will be fine and do another 45mins work before going on strike again. The thing is it never packs up after say 10 mins so it's not just a case of it failing when warmed up. It takes longer than that.


I think I have ruled out:

Blocked fuel tank air vent.
Coil or Diode breakdown (replaced with new)
Spark plugs (replaced with new. Old plugs look clean, not oiled)
Fuel filter (replaced with new )
Fuel pump (replaced with new, including the pipe from valve cover to pump)
Valve guides moving in the head (They seem fine - all look same height)
Engine oil was replaced last season and still looks quite clean.


I'm beginning to think this is a fuel, carb or governor issue. Got any tips on how to narrow the problem down further?

I've noticed that the transparent fuel filter is never full of fuel, it always has a large air bubble in it. I've tried filling the filter with fuel using a syringe and it stayed full for one session. Today when I looked it was mostly air again. Any thoughts on how air is getting into the filter? I can't see any fuel leaks but perhaps I should just try replacing all the hoses anyway as they aren't expensive?

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Boobala said:

Air in the fuel filter is NORMAL..

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.. you say it runs fine for awhile, .. then your issue starts, seems you have done all the checks but, ... have you removed the engine shroud ( cowling ) and cleaned the engine cooling fins, it may be an overheating problem.. ??

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bertsmobile1 said:

Yes there are really 2 possible causes,
1) overheating as already mentioned
2) loose or floating debris blocking the outlet of the fuel tank

When it starts to play up jump off remove the fuel cap, rip the fuel line off at the fuel pump and blow back up the line.
Hook it back up, if the problem goes away , for anothe 10 minutes of more then time to pull the tank

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Luffydog said:

Or if you have another known good clean tank that you can make an external tank out of and add clean fuel and try to what happens.

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Boobala said:

WHY are you posting the SAME issue several times ........ it makes for confusion !!

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CWatters said:

I'll try that but have already tried disconnecting the fuel line at the filter and fuel flows out of the pipe with no problems.

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