What's normal drive shaft vibration on BX24?

[ibnxe]

BotaBX24er,
Your thread had me curious enough to go down and start my BX23 to see if there was any visable vibration in the drive shaft. At idle, and all the way up to full throttle, no noticable vibration was seen or felt.
I think there is a small amount of runout in the shaft at all speeds. Maybe 0.050" or so. So far, I've been lucky enough not to have broken the fan, so everything is original.
As fast as the fan runs, it is rather important to have it well balanced.

 

[CHDinCT]

Possible KISS solution for your consideration. Assuming the fan is out of balance, perhaps try putting a sheet metal screw or two into one of the blades. Problem is you won't know which one to weight, but with some trial and error you might smooth it out enough to be acceptable. If it doesn't work, worst your out is another $10 for a new fan.

 

[BotaBX24er]

Possible KISS solution for your consideration. Assuming the fan is out of balance, perhaps try putting a sheet metal screw or two into one of the blades. Problem is you won't know which one to weight, but with some trial and error you might smooth it out enough to be acceptable. If it doesn't work, worst your out is another $10 for a new fan.

I have screws in addition to the epoxy, however, the screws were installed when the epoxy was wet, so I know that they are secured to the fan hub. However, I'm pretty weary about putting screws into the blade because at 3500 rpm, those things are essentially little bullets. And being that it's only plastic between me and the fan, I'm not too comfortable with that. I'm going to remove that setup and try a different one. You're right though, worst is I'm out another $10.

To slide the engine forward just enough to get to the fan bolts, requires a lot of work: grill guard, fenders, floor board, hood, etc all have to come out. I'm not that mechanically inclined nor challanged, however I cannot come up with the consecutive amount of hours to do it. I don't have a place for storage, so once I start with it, there's no stopping and I wouldn't like to leave it open in my yard.

 

[Berniep]

I have screws in addition to the epoxy, however, the screws were installed when the epoxy was wet, so I know that they are secured to the fan hub. However, I'm pretty weary about putting screws into the blade because at 3500 rpm, those things are essentially little bullets. And being that it's only plastic between me and the fan, I'm not too comfortable with that. I'm going to remove that setup and try a different one. You're right though, worst is I'm out another $10.

To slide the engine forward just enough to get to the fan bolts, requires a lot of work: grill guard, fenders, floor board, hood, etc all have to come out. I'm not that mechanically inclined nor challanged, however I cannot come up with the consecutive amount of hours to do it. I don't have a place for storage, so once I start with it, there's no stopping and I wouldn't like to leave it open in my yard.

Are you cutting the fan into two pieces?
A couple of posts I read they just cut one side so as to leave the fan in one piece and pry it open enough to go around the shaft. Yours is the first I read about having too much gap. Which might make sense if you sawed it completely in two so you would have two saw kerfs that could add up to a pretty good gap

 

[tommu56]

we use to use hose clamps on car drive shafts we would put 2 on in line with each other and move one around till vibration settled out by eye.

took a lot of trial and error mostly error but it would work.
tom

 

[BigD23]

Slight vibration at idle on my BX23...I rarely let it idle though. I'll back the throttle off all the way then bump it up a touch.

Don

 

[BotaBX24er]

Thanks for all the feedback...
I went to remove the fan so that I can try to get another on there. In the process, I took 1 screw out and figured to give it another shot. Well, with the 1 screw removed the vibration got reduced DRAMATICALLY...even at idle, the most vibration noticed was less than 1/16 of an inch (if even that)...even less than that at half to full throttle. Vibration wasn't ever completely gone, but much less.

Oh, the reason why there was so much gap was because the new fan hub is slightly smaller than the original also. And it's a much thinner plastic and doesn't feel as durable. It appears they may have changed their supplier. The only way to get it perfectly circular is to cut the old fan cup out and simply leave the disk just enough so that the new fan fits snuggly over it. Then yes, only one slit would be enough.

With that resolved...now on to getting a skid plate on there...This is the repair...with the exception that the screw in the middle has been removed. It's a little half inch self tap metal screw, amazing that it caused that much vibration.

Thanks again everyone...

 

[DavidAubke]

Maybe it's different on a BX24 but on my BX2350, the drive shaft could be unlocked from the transmission spindle and pulled back about two inches. Not enough to clear the spindle and remove the shaft but plenty of room to get a wrench behind it to unbolt the fan. The old fan comes out and the new one gets to use the mounting bolts.

 

[BotaBX24er]

Maybe it's different on a BX24 but on my BX2350, the drive shaft could be unlocked from the transmission spindle and pulled back about two inches. Not enough to clear the spindle and remove the shaft but plenty of room to get a wrench behind it to unbolt the fan. The old fan comes out and the new one gets to use the mounting bolts.

that is correct...the older styles BX's allowed you that little movement to get after those bolts. the "improved" newer models do not give any movement and therefore you have to move the engine forward just to get to those bolts.