Adding a Tachometer to 78' CB125s (didn't come with one from factory)

I'm trying to figure out if it's possible to add a tachometer to my 78' CB125s that never came with one from the factory in the US. 1974 US version of the bikes came with a tachometer and also, the 1978 CB125j (europe) & 1978 125jx (japan) came with it. I did manage to find the part, wondering what i need to do to add it on. is this even possible? do i need additional parts besides that tach? If anyone could speak some wisdom into this I'd appreciate it.

Where is the gear fitted on the ones that came factory with a tach? If it ran off the idler gear out of the right hand case you may be able to swap the case cover and gear from a US or EU unit. If it ran from the head it may be a bit more pricy to swap


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Thank you for the reply. I believe it came from the idler gear out of the right hand case. here is what I found in the shop manual. what next? still guessing it isn't a simple plug and play?

In that case, the tachometer gear is likely driven by the idler gear, which is that smaller gear with a nose between the oil pump gear and the clutch basket in the top photo. With a the tach run from that, the "nose" on that gear will have splines, which will mesh with a tachometer unit on the right hand case that your cable will come from.

You may be able to swap the gear and the case, provided they are compatible.



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An alternative approach is to fit an electronic tacho.

Yikes! this seems more complicated than I thought. Don't understand why they didn't add a tach in the first place, would be so helpful for making adjustments. is the electronic method much easier?

Yes, they generally just run off the spark plug lead/coil. Beware the cheap ones, they don't work well at all.

First, I'd check to see if the 125 had a tach option on another model. The 1978 400s could be bought with or without a tach, so the side cover came with a plug where the tach gear goes. It may be just a matter of buying the parts and swapping over.

deviant said:

First, I'd check to see if the 125 had a tach option on another model.

Click to expand...

1974 US version of the bikes came with a tachometer and also, the 1978 CB125j (europe) & 1978 125jx (japan)
I wish i could find some pictures of the other bikes to pinpoint what we need to do here.

according to Wikipedia:
.
.
1974 - Front drum brake changed to disk, tachometer was added.
1976 - Engine displacement increased from 122 to 124 cc (7.4 to 7.6 cu in), tachometer was eliminated.
.
.

found this

I've done this on my bike. It is a direct bolt on mod, you will need a right side cover, from an engine that came with a tach, and the oil pump assembly. It is just a matter of swapping the parts out. Be sure to replace the o-rings between the oil pump body and the engine case, and use a new case gasket. While your in the right side be sure to clean out the oil filter on the end of the crankshaft. If you have questions PM me.

This is good to know. I got home to inspect my bike and it looks like there is a place for that connector excpet it's been filled in :'( literally a circle outline with no opening. I'm guessing I can't really do anything about that unfortunately. (Cant just drill there ) I've found the side cover of a 74' but the problem is that they changed the engine displacement a little bit and form 76+ so the side cover looks completely different and placement of clutch cable is in a completely different location.

Only way out is to find that piece from Europe or Japan? that can easily cost an arm or leg. would a cover be compatible form a similar bike perhaps a 175cc or 200cc?

Please let me know.



just want to say thank you to all, this place is amazing to have people that are so knowledgeable!

this is my 78' cb125s http://www.ebay.com/itm/1978-HONDA-CB125-CB-125S-125-S-VINTAGE-ENGINE-CLUTCH-BASKET-SIDE-CASE-COVER-/381473927849?fits=Year%3A1978%7CModel%3ACB125S&hash=item58d19e32a9:g5sAAOSwbdpWUgpC&vxp=mtr

this is the 75' xl125 http://www.ebay.com/itm/1975-Honda-XL125-XL-125-Clutch-Cover-/252511859871?fits=Model%3AXL125&hash=item3acae1349f:g:0nsAAOSwgZ1Xvhnw&vxp=mtr

do these look interchangeable?

**UPDATE**

Hi Everyone.

After days of research I can confirm that the CB125S and XL125 share parts.

75' CB125S clutch cover wont work on 78' CB125S it is a different part altogether.

76'+ CB125J (europe, with tach) shares the same part as a 75' XL125 (USA, with tach)



78' CB125S USA Clutch Cover without tach:
COVER, R. CRANKCASE
11330-383-670

76' CB125J Europe Clutch Cover with tach (75' XL125 USA)
COVER, R. CRANKCASE
11330-383-000
http://www.bike-parts-honda.com/Catalog/Honda/0125_CB125J_Microfiches_Honda/parts_list_0125_CB125J/0023-view.html

**this product is superseded by 11330-383-010**
more info http://www.cmsnl.com/products/11330-383-010-cover_11330383000/
- its a bit hard to search for this.



Total for this mod will cost me around ~ $100.
Crankcase from XL: with tach gear on ebay ~$34
Tach assembly with cable $25 on craigslist
Oil pump form XL ~$16
Gasket ~$5
O rings ~$5
tach pinion ~$10



Hope this will be helpful to anyone trying to add a tach to a CB125, ill be holding this particular project since I need to get some essentials done on the bike. this is more of a wanted feature to be added on in the future. thank you to all for your help.