Topic: Tach stopped working

[smccloud]

Ok,

While changing the rear tire on my '72 CB750K2 Friday night the tach decided it would stop working (I know they aren't related).  Pulled the cable off the tach and it will only spin if I push down on it.  My guess is the gear stripped out (since its the hardest to fix ) since it has been jumping around a lot (and a new cable didn't fix it).  It will also sometimes show 1000 rpm going down the Interstate when it should read 6000-7000rpm.  Is it just time to order a tach plug from Cycle X and put an electronic tach on my bike?  I don't really want to pull the engine to fix this since my '74 engine doesn't have a drive gear you can remove with the valve cover on the engine.  I suppose I could use this as a good excuse to rebuild the factory engine for my bike, but I doubt I can get approval from my wife for that right now.

[Old Scrambler]

The gear-drive inside of the valve cover is STEEL. I have never seen a stripped one. Some of the cables are known to have stripped gear problems because they are not properly mounted....i.e. when the oil seal leaked the old one was not removed and a new one was crammed into the valve cover.

[smccloud]

The gear-drive inside of the valve cover is STEEL. I have never seen a stripped one. Some of the cables are known to have stripped gear problems because they are not properly mounted....i.e. when the oil seal leaked the old one was not removed and a new one was crammed into the valve cover.

I did replace the seal a while ago, although I pulled the old one out before putting the new one in.  Still leaked on me though   Could the small neoprene washer I put below the cable have cause the cable/end of the drive gear to break?

[madmtnmotors]

Did you pull the tach cable out of its sheath? It will only come out from one direction (from the connector that mates to the valve cover I believe). Pull the inner cable and check for breakage. Sounds like broken tach cable. The tach usually starts bouncing as the neglected cable starts to dry out and the cable starts catching at the dry spots from the excessive friction until the cable succumbs to the added friction and breaks.

[smccloud]

Did you pull the tach cable out of its sheath? It will only come out from one direction (from the connector that mates to the valve cover I believe). Pull the inner cable and check for breakage. Sounds like broken tach cable. The tach usually starts bouncing as the neglected cable starts to dry out and the cable starts catching at the dry spots from the excessive friction until the cable succumbs to the added friction and breaks.

I have yet, have to find my 8mm wrench or buy a new one. I did check the new cable for lube when I put it on at the beginning of the summer and it was fine (as was my old one?). I'm just confused since I thought it was the cable, wasn't and now it's doing this.

Sent from my Galaxy Nexus using Tapatalk 2

[madmtnmotors]

Ahhhhh.... I was not aware that we were dealing with a new cable. If you have a spare, or can borrow a tach, maybe hook up a different tach to veryify that the problem is not the tach itself, especially before pulling the motor just to get to the tach drive. 

[scottly]

Could the small neoprene washer I put below the cable have cause the cable/end of the drive gear to break?

It might prevent the cable from seating fully, stripping the end?

[smccloud]

Ahhhhh.... I was not aware that we were dealing with a new cable. If you have a spare, or can borrow a tach, maybe hook up a different tach to veryify that the problem is not the tach itself, especially before pulling the motor just to get to the tach drive. 

I still have the old cable, so I can test that.  However the problem happened with two tachs.  The original one and the one from my '74 parts bike

Could the small neoprene washer I put below the cable have cause the cable/end of the drive gear to break?

It might prevent the cable from seating fully, stripping the end?

I will find out tonight once I pull the cable from the cylinder head (replaced the factory retention screw with a small bolt hence the need for the 8mm wrench).