BX24 over revving engine or tach accuracy
- Thread starter tcrosby
- Start date
85Hokie
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Equipment
BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
What does it show at idle? and or what DID it show before at idle on the old engine? Did you have any experiences with the old engine? In other words can YOU feel in the seat of the pants the rpms????
If I push my BX from 3k to 3.4 I can FEEL a big difference, at 3.9 I would think I would want to get off the seat!
Daren Todd
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Equipment
Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
I'm with 85hokie. How does the tach read at an idle? With the throttle backed off till the motor is just barely running smooth, the idle should read about between 700 and 900 rpms.
When slowly increasing the rpms, do they slowly climb on the tach? Or start jumping higher then would seem normal? For example a very slight increase in engine speed and the tach rises 300 or 400 rpms.
Is the tach electical or mechanical (cable driven)?
If electrical, it could be a simple pulse count adjustment on the back of the tach. It's either pins with a jumper, a dip switch, or push and turn dial. With brief instructions written near the adjustment. This would be if at low rpm and reading other then 700 to 800 rpms. Say 1 rpm or showing an rpm of 1500 and the motor is barely idling for examples.
If mechanical it may be the ratio on the tach versus controller that bolts to the block could be off. Say showing 700 to 800 rpms, and slight increase in throttle and rpms on tach make a drastic change
Or it could be that if rpms seem to increase properly, the max rpm limit may not be adjusted. Which is the set screw where the throttle linkage connects to the injection pump. One set screw is low idle, the other is max throttle
When slowly increasing the rpms, do they slowly climb on the tach? Or start jumping higher then would seem normal? For example a very slight increase in engine speed and the tach rises 300 or 400 rpms.
Is the tach electical or mechanical (cable driven)?
If electrical, it could be a simple pulse count adjustment on the back of the tach. It's either pins with a jumper, a dip switch, or push and turn dial. With brief instructions written near the adjustment. This would be if at low rpm and reading other then 700 to 800 rpms. Say 1 rpm or showing an rpm of 1500 and the motor is barely idling for examples.
If mechanical it may be the ratio on the tach versus controller that bolts to the block could be off. Say showing 700 to 800 rpms, and slight increase in throttle and rpms on tach make a drastic change
Or it could be that if rpms seem to increase properly, the max rpm limit may not be adjusted. Which is the set screw where the throttle linkage connects to the injection pump. One set screw is low idle, the other is max throttle
I think the low idle reads around 1500 rpm but I will need to double check that. The tach is just one of the digital hour meter/tach combo units. It seems to me like the tach is just off. I don't know how the digital tach gets the signal from the engine or if there is a way to adjust it.
Daren Todd
Well-known member
Lifetime Member
Equipment
Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
A digital tach works off a pulse count from either the altenator or a magnetic sending unit on the fly wheel. Should be a screw in sending unit that excepts a quick connect harness if on the fly wheel. If the tractors barely idling and it's showing 1500 rpm, then it's probably a pulse count setting is off. Now i'm not sure how kubota does it with the electric tach. I've just dealt with the aftermarket tachs. They may have it mated for a certain sending unit, with no adjustment. Or there may be an adjustment on the back of the tach. You would have to check the back of the tach to verify what your working with. In this case, a picture of the back side of the tach would help out greatly