BX2670 runs badly at high RPM

jmcmul2

New member

Equipment
bx2670
Dec 16, 2024
10
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
9,244
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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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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
81
17
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
32
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
10
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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L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
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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
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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

New member

Equipment
bx2670
Dec 16, 2024
10
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
253
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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