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Author Topic: Tach suddenly died...pegged at zero  (Read 894 times)

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Offline BlackMax

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Tach suddenly died...pegged at zero
« on: January 29, 2014, 12:59:32 PM »
Options?  Probably pretty common.  Replace whole deal or....??   It has always worked perfectly, but just pegged to zero the other day.  Won't move.  This is a '78 CB750 "super sport". 

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1978 CB750SS, 4-1 Yoshi, Pods, 3-angle valve job, ported chambers, ported intake, 41a cam

Offline flybox1

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Re: Tach suddenly died...pegged at zero
« Reply #1 on: January 29, 2014, 01:09:58 PM »
cable snapped?
unscrew the end from the tach and see if its spinning when the engine is running.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline bjbuchanan

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Re: Tach suddenly died...pegged at zero
« Reply #2 on: January 29, 2014, 01:14:02 PM »
Like flybox said, probably snapped. Was the tach "bouncy" before this or made any whurring noises, usually a good hint the cable was shot.
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The dirty girl-1976 cb750k, Ebay 836, Tracy bodykit
Round top carbs w/ 38 pilots, middle needle position, airscrew 7/8ths out, 122 main jet
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Offline BlackMax

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Re: Tach suddenly died...pegged at zero
« Reply #3 on: January 29, 2014, 01:36:02 PM »
thanks.  I'll unsrew the cable at the tach to see if it's spinning. No, it wasn't bouncing at ALL.  Smooth like a modern electronic to be honest.   That's why I was kind of surprised.  Hope it's just a cable.  That's easy.  Actually, it's all easy...just not nec as cheap.
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1978 CB750SS, 4-1 Yoshi, Pods, 3-angle valve job, ported chambers, ported intake, 41a cam

Offline BlackMax

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Re: Tach suddenly died...pegged at zero
« Reply #4 on: January 31, 2014, 02:43:40 PM »
Yea, the cable is snapped. It came out in two pieces.   

Best source to replace? 
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1978 CB750SS, 4-1 Yoshi, Pods, 3-angle valve job, ported chambers, ported intake, 41a cam

Offline flybox1

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Re: Tach suddenly died...pegged at zero
« Reply #5 on: January 31, 2014, 02:49:34 PM »
you'll want to bookmark pages like this to find part numbers, and then just search the web...
http://www.cmsnl.com/honda-cb750f-750-super-sport-1977-usa_model491/partslist/

and find the deals like this...
http://www.partzilla.com/parts/detail/honda/HP-37260-KB7-010.html
« Last Edit: January 31, 2014, 02:51:59 PM by flybox1 »
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Don R

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Re: Tach suddenly died...pegged at zero
« Reply #6 on: January 31, 2014, 03:31:40 PM »
 Check the tach before installing the new cable. I had a tach that was stuck. It broke the new cable too. Insert the broken end and spin it with your fingers.
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