BX2670 runs badly at high RPM

jmcmul2

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Equipment
bx2670
Dec 16, 2024
15
1
3
mccomb, ms
After my BX2670 has gotten nice and warmed up, when operating at high RPM and under load, it will suddenly start running extremely rough. Shakes so bad it will make your fillings fall out. Stopping and taking PTO out of gear doesn't help. Backing off the throttle doesn't help. Only completely stopping the engine and restarting will get it to run smoothly. If I continue at a lower RPM (< 2000), it will continue on. BTW, have changed the two fuel filters, air filter, and fuel pump. Don't know what to do next!
 

RCW

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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
Apr 28, 2013
9,274
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Chenango County, NY
How much fuel is in the tractor? Less that 1/2 tank by the fuel gauge? (BX fuel gauges are notoriously inaccurate...)

If so, fill it FULL and see if the same thing happens. A BX with a bad electric lift pump will run fine until tank gets low. Then runs poorly.

Do you hear the Lift Pump "clicking" when you turn the key to the first/glow position?

A Lift Pump is a cheap and very simple replacement. It's also a simple troubleshoot to make sure it's pumping by pulling fuel line off the inlet to the front pump and turning the key.

What did the fuel filters look like? Really dark/black?

Do you use a biocide in your fuel?

A fuel tank plugged up with microbial growth can restrict fuel flow.

Always start with the simple stuff, and fill the tank FULL first..... ;)
 
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North Idaho Wolfman

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Sounds like you might have a propeller shaft issue.

1734398715301.png
 

85Hokie

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After my BX2670 has gotten nice and warmed up, when operating at high RPM and under load, it will suddenly start running extremely rough. Shakes so bad it will make your fillings fall out. Stopping and taking PTO out of gear doesn't help. Backing off the throttle doesn't help. Only completely stopping the engine and restarting will get it to run smoothly. If I continue at a lower RPM (< 2000), it will continue on. BTW, have changed the two fuel filters, air filter, and fuel pump. Don't know what to do next!
When you turn the key to the first position - DO YOU HEAR the ticking noise? That would be the fuel pump running.
 

BX'r

Member

Equipment
BX2370
Jun 13, 2020
84
18
8
ipsc
Remove the fuel line from the tank to the first filter and check the flow.
These lines get plugged up at the tank and can be cleared by blowing compressed air back into the tank with the fuel cap loose.

The filter fills up with fuel slowly and when you start it everything works until the fuel in the filter gets used up and then it starves for fuel and runs rough.
 

madplanter

Member

Equipment
2620 w loader/backhoe/mower
Jan 8, 2024
33
10
8
Pa.
After my BX2670 has gotten nice and warmed up, when operating at high RPM and under load, it will suddenly start running extremely rough. Shakes so bad it will make your fillings fall out. Stopping and taking PTO out of gear doesn't help. Backing off the throttle doesn't help. Only completely stopping the engine and restarting will get it to run smoothly. If I continue at a lower RPM (< 2000), it will continue on. BTW, have changed the two fuel filters, air filter, and fuel pump. Don't know what to do next!
check and make sure its not pulling air into the fuel line/filter/etc somewhere. IE loose fitting.
 

jmcmul2

New member

Equipment
bx2670
Dec 16, 2024
15
1
3
mccomb, ms
How much fuel is in the tractor? Less that 1/2 tank by the fuel gauge? (BX fuel gauges are notoriously inaccurate...) I can't say. Just now it is 1/2 full. Will give this a try. If so, fill it FULL and see if the same thing happens. A BX with a bad electric lift pump will run fine until tank gets low. Then runs poorly.
Will give this a try...................

Do you hear the Lift Pump "clicking" when you turn the key to the first/glow position? A Lift Pump is a cheap and very simple replacement. It's also a simple troubleshoot to make sure it's pumping by pulling fuel line off the inlet to the front pump and turning the key.
Have replaced pump, didn't seem to help...................

What did the fuel filters look like? Really dark/black?
Fuel filters did not look dark but did have some yuck and discoloration...........

Do you use a biocide in your fuel? A fuel tank plugged up with microbial growth can restrict fuel flow.
Yes...........
Always start with the simple stuff, and fill the tank FULL first..... ;)

Good advice. Another way to put it, start with the CHEAP stuff first.... LOL
 

Russell King

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Sounds like you might have a propeller shaft issue.

View attachment 144331
@North Idaho Wolfman - why do you point to a propeller shaft as a possible issue? What issue is there that makes the engine run poorly or shakes the tractor? Enquiring minds want to know!

It is just such an “odd” diagnosis for how I read the problem statement. Not saying it is wrong just can’t see a good cause and effect since I have never seen a similar tractor.
 

North Idaho Wolfman

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Jun 9, 2013
30,739
6,786
113
Sandpoint, ID
@North Idaho Wolfman - why do you point to a propeller shaft as a possible issue? What issue is there that makes the engine run poorly or shakes the tractor? Enquiring minds want to know!

It is just such an “odd” diagnosis for how I read the problem statement. Not saying it is wrong just can’t see a good cause and effect since I have never seen a similar tractor.
What leads me to believe it's a balance issue more then a fuel delivery issue is in his statement.

Stopping and taking PTO out of gear doesn't help. Backing off the throttle doesn't help. Only completely stopping the engine and restarting will get it to run smoothly. If I continue at a lower RPM (< 2000), it will continue on. BTW, have changed the two fuel filters, air filter, and fuel pump. Don't know what to do next!
 
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jmcmul2

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Equipment
bx2670
Dec 16, 2024
15
1
3
mccomb, ms
Fuel pump, fuel tank cap not venting properly or clogged fuel tank. Clogged fuel tank is common on the bx.
So..... I am thinking the first things to check are the fuel tank and whether the cap is venting properly. Not exactly sure how to tell if the fuel cap is venting properly, but it did have a lot of congealed dust.....
 

Mountainman

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L2501, B7100, B6000, B21, B1750, B2400, B7200
Jul 10, 2022
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Attalla Alabama
mossycreekoutdoors.com
So..... I am thinking the first things to check are the fuel tank and whether the cap is venting properly. Not exactly sure how to tell if the fuel cap is venting properly, but it did have a lot of congealed dust.....
When your having the problem just unscrew the cap a little and see if it resolves itself. If so you have a cap vent problem. If not your cap is probably fine. Would definitely clean the crap away from the cap though. Its a good source of debris getting in the tank everytime you open the cap
 

jmcmul2

New member

Equipment
bx2670
Dec 16, 2024
15
1
3
mccomb, ms
So..... I am thinking the first things to check are the fuel tank and whether the cap is venting properly. Not exactly sure how to tell if the fuel cap is venting properly, but it did have a lot of congealed dust.....
Well, I disconnected my fuel line at the first filter and fuel stream was maybe pencil lead size. Blew into it with my air hose and then fuel stream went to pencil size! Now running great. Of course not ideal since I apparently blew yuck that was blocking fuel tank back into tank. cleaning out that crazy shaped tank seems near impossible without some major work. Toying with using my wet/dry vac..... but that sounds dangerous. For now, I am going to cross my fingers that the yuck was dispersed and will enter fuel line to be caught by filter. Will keep you posted.....
 

North Idaho Wolfman

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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
30,739
6,786
113
Sandpoint, ID
Well, I disconnected my fuel line at the first filter and fuel stream was maybe pencil lead size. Blew into it with my air hose and then fuel stream went to pencil size! Now running great. Of course not ideal since I apparently blew yuck that was blocking fuel tank back into tank. cleaning out that crazy shaped tank seems near impossible without some major work. Toying with using my wet/dry vac..... but that sounds dangerous. For now, I am going to cross my fingers that the yuck was dispersed and will enter fuel line to be caught by filter. Will keep you posted.....
Treat the fuel with some biocide and you might get lucky.
 
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85Hokie

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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
Jul 13, 2013
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113
Bedford - VA
Or you might not get lucky and if that is the case - well the fun begins! Tank removal!

Hopefully you get lucky!!!!!!!!!!
 

GreensvilleJay

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BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Apr 2, 2019
11,767
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Greensville,Ontario,Canada
In my case( BX23S, similar tank...) it was a sliver of black plastic that got lodged into the exit spigot so the ONLY option was remove/clean/reinstall. It's a 3 hr dealer job that I took 3 days to do. Not in a hurry and ONLY me so getting seat off---grrrrunt, getting fender tin off---grrrrrrrrrrrrrrrrrrrun, at least NO bandaids !!
 

eserv

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BX24, A1000 Kubota Generator
May 27, 2009
2,179
162
63
Hardisty, Alberta
I have had good luck siphoning the fuel out of Kubota fuel tanks with a large hose ( 3/4 heater hose) to clean debris from the tanks. I did it just last year on my BX24d successfully. I then installed a strainer in the fuel cap port to catch anything that might get in there. I have done on many other Kubota's as well from M135's to zero turns. I posted about the fuel strainer I used a year or so ago. ( might be longer! times goes so much faster as I get older! LOL) This is the strainer I used on mine https://www.amazon.com/dp/B075L531TR
 
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