Topic: 550F sluggish tach

[centerpunch]

My new low-mile ‘77 550F has a sluggish tach. I assume since it’s working at all the cable is ok, and the problem is with the tach itself. Is that correct?

Also, I assume the instruments are identical on K and F versions, right?

[jlh3rd]

instruments are the same,( faceplate colors are different for different years).....are you positively sure the cable is not binding up inside?......To take that tach apart to see if anything can be done requires taking off that crimp ring, no easy task...and then putting it, or a new one back on....even harder..
    also, i took one apart and added a new faceplate and aside from making sure the mechanics were clean , i saw no way to re oil it........some say there is a way.......anyway, it can be disassembled...that'd be my last resort...

[seanbarney41]

The reason why your low mile bike has low miles is the same as why your tach is sluggish.  So use may help, either that or it wont...then you must repair or replace.

[Maraakate]

Mine was sluggish.  I took it apart and found that the grease the bell spins on was completely dry.  I heated it up and wiped off the excess and redistributed the grease.  It works OK, but it is a bit off.   Seems to be about ~500RPM too high, but at least it works now.

I had the same problem with the speedo and again, it works but is about ~5-7mph too high.  Did not try adjusting the needles.

[jakec]

instruments are the same,( faceplate colors are different for different years).....are you positively sure the cable is not binding up inside?......To take that tach apart to see if anything can be done requires taking off that crimp ring, no easy task...and then putting it, or a new one back on....even harder..
    also, i took one apart and added a new faceplate and aside from making sure the mechanics were clean , i saw no way to re oil it........some say there is a way.......anyway, it can be disassembled...that'd be my last resort...

Why is putting on a new set harder than using the old one? I just ordered a set of new ones.

[Maraakate]

instruments are the same,( faceplate colors are different for different years).....are you positively sure the cable is not binding up inside?......To take that tach apart to see if anything can be done requires taking off that crimp ring, no easy task...and then putting it, or a new one back on....even harder..
    also, i took one apart and added a new faceplate and aside from making sure the mechanics were clean , i saw no way to re oil it........some say there is a way.......anyway, it can be disassembled...that'd be my last resort...

Why is putting on a new set harder than using the old one? I just ordered a set of new ones.

I think he means putting a new chrome ring around it.

[jlh3rd]

instruments are the same,( faceplate colors are different for different years).....are you positively sure the cable is not binding up inside?......To take that tach apart to see if anything can be done requires taking off that crimp ring, no easy task...and then putting it, or a new one back on....even harder..
    also, i took one apart and added a new faceplate and aside from making sure the mechanics were clean , i saw no way to re oil it........some say there is a way.......anyway, it can be disassembled...that'd be my last resort...

Why is putting on a new set harder than using the old one? I just ordered a set of new ones.

i said  putting the old crimp ring or a new one back on is harder than getting it off.......especially for someone who hasn't done it before........

[jakec]

Ah gotcha. I’ve already rebuilt my speedo before. And the rings go back on easily in my opinion. But the old ones will have more flexibility than a new one, I’d assume. I only bought new ones this time around because it’s a restoration so I wanted nice ones.

[1976cb750f836]

Take an old cable, hook it to a drill, lock it on in high, and walk away. If it's needing used, that will warm it up.

[Maraakate]

Take an old cable, hook it to a drill, lock it on in high, and walk away. If it's needing used, that will warm it up.

I've thought about doing that.  I guess eventually the grease will warm up?

[centerpunch]

I found a restored tach on ebay for $50, so that fixed my problem.

https://www.ebay.com/itm/1977-Honda-CB550K-Tachometer/143429211438

[1976cb750f836]

Since I changed my faceplates, my tack seems kinda the opposite of slugesh?  From idle to bout 5k it is right, but then from 5k to 9k it flies ? Now this is a mild 836 with cams, but the tack seems to out accelerate the bike in the upper end? It was very clean inside, so i did nothing except change face.

[Maraakate]

I'd imagine the tachs were never fully accurate except in a certain range?  Was it always this way?  Might be possible that you disturbed something when you took the needle off.  I don't know if they have jeweled bearings in these for the needle?  If so, that would make them easy to break with pressure, but you can usually feel where it catches on the crack of a jeweled bearing.  Maybe the spring too?  Check the bell it rides on.  I had problems with mine with the grease getting funky in there and had to wipe the excess and redistribute the grease.  Mine aren't dead accurate and I never expect them to be.  I'm unsure what type of grease it is in there.  I'm guessing silicone?  However, for the plastic gears you can probably use this: https://www.ebay.com/itm/280646126932

In case that link expires some day Dow Molykote EM-30L.  It's meant for plastic gears in VCRs and things like that.  Good stuff.

[kerryb]

I remember reading about sluggish needles on here.  The fix was to put a cotton ball soaked in kerosene in the hole for the illumination bulb and leave it overnight at least,.  The fumes thin out the grease in the tach or speedo to allow the needle move more freely. 

http://forums.sohc4.net/index.php/topic,171559.msg1996641.html#msg1996641

[Maraakate]

I remember reading about sluggish needles on here.  The fix was to put a cotton ball soaked in kerosene in the hole for the illumination bulb and leave it overnight at least,.  The fumes thin out the grease in the tach or speedo to allow the needle move more freely. 

http://forums.sohc4.net/index.php/topic,171559.msg1996641.html#msg1996641

Pretty sweet idea if it actually works.

[1976cb750f836]

Wonder if the fumes would fog the glass?