Kubota engine RPM drops after a few minutes of operation

[dave53]

I have Kubota BX18 that started having sporadic huge RPM drops when the mower deck was engaged. At first it was just when I was going uphill. RPM would drop from 2500 to 1250 and the whole tractor would shake. Would disengage the deck and the RPM would come back up and then I could mow again. By the end of last season it was happening frequently. Went out today and it was fine for 10 minutes then the RPM drop and the whole shaking thing happened but regardless of how many times I would disengage the deck, the same thing happened. Could barely drive it back to the shed with the deck disengaged. Fuel filters are fairly new, fuel is fresh. No problems with the front loader, only the mower deck before today. Any ideas? Dave

 

[Jerry/MT]

Check for fuel delivery from the tank to the filter. Oftentimes the strainer at the tank bottom gets clogged.

 

[doxford jim]

Might two or more things happening at once. Blades running true (balanced) on mower deck ? Transmission in good condition ?

 

[Leejohn]

Fuel Filter, tank vent, and air filter.

 

[dave53]

I guess I will revisit fuel delivery. No noticeable problems with tranny and serviced mower deck last fall. Air filter is good, but I don't know where the tank vent is located.

 

[SSdoxie]

Fuel vent is probably in the cap. When tractor starts dropping RPM after it is warm, loosen or remove the cap while it is still running. If RPM comes back up you know it is in the cap vent.

 

[dave53]

So I guess I will start with the tank vent and work downstream from there. Thanks for the ideas. I will update.

 

[RalphVa]

Is this a new BX18? Think the new ones have a tiny fuel filter right off the tank, like is on my new JD 1025R. Apparently, both Kubota & JD (and maybe others) got surprised by tier 4 requirements that required a finer mesh filter. The in-bowl one apparently doesn't come fine enough; so, they stuck a siny little filter in the fuel line.

Ralph

 

[dave53]

Thanks for all of the suggestions. I sorta feel like an idiot...I have a BX 1850 not an 18. Nevertheless, the problem was both of the fuel filters that I replaced last mid-summer. I end up with a good bit of dust and dirt on the tractor and I try to keep the fuel area clean (kinda) but after this, it's getting washed down before I re-fuel. By the way, there is no screen in the tank. Fuel is straight to the first filter and then the pump.

 

[Pepsiboy]

I had a similar problem with my BX2350. I changed BOTH fuel filters. Still had problem, usually in colder weather (Below freezing). Turned out that electric fuel pump was failing. A check valve in the pump was sticking in cold weather. Kubota pump was over $150 at dealer. I found an aftermarket one with a slightly higher output pressure and slightly higher flow rate for $50. Got it put in, and no more problems. Also found that changing BOTH fuel filters at every oil change helped also.