Yup, spot on Mark, that's exactly what I would expect it to do! This is just bizarre

From what I understand the "auxiliary output" from most engines tends to drive the tacho (and the oil pump where present) and AFAIK only a few old bikes pick up a different way and require an angle drive. (BTW I've found an angle drive quite cheap, with luck I'll have it for the weekend just in case.)

Talking of the weekend, my apologies that I won't have time to post a video until then - unfortunately have to work for a living

Not one of my best days so apologies if I came off grumpy...

What I'd like to see is pictures of what the tach drive and gears look like when you pull the cover... even pictures of the outside before you pull the cover... Whether or not you see anything "wrong". Thanks

I think I can see where you're going with this: has someone in the past thrown in the wrong parts. Certainly Kawasaki tacho gears look like a mirror of Yamaha parts.

BTW it's no hardship taking off the engine cover: I was intending to do an oil pump delete and the blanking plate's turned up. As this will probably be a (very) occasional use bike it's going to be sitting around a while and I considered premix lounging about in a fuel tank is probably better than just petrol (and its rising Ethanol content these days.) That and I don't trust the oil pump much

Quick update: wrong parts.

The parts in my bike are mirrors of the "proper" parts (tacho drive and worm gear/cog) photos to follow...

As promised here's a video of the tacho cable going at quarter speed:


Here are the parts:




From all the pictures of parts I've seen those definitely aren't the right ones!

My choices now seem to be:

1. Get the tachometer rebuilt to go in reverse
2. Replace the tachometer with a reverse one... tricky to find one the same size?
3. Add an angle drive
4. Try and find the correct engine parts

If anyone has any more ideas I'm all ears

My browser or computer is acting up... I'm going to try to take pictures of the correct parts and post them. Which is exactly what I would do... get the correct parts as they are readily available.

Wasn't put together wrong... as you can see that's impossible.

Goes to show you that you just never know what someone has done... I can't imagine what those parts are from... also it's obvious that the tach could not have worked before engine was taken apart... I made the assumption that it did work because of the concern something was put together wrong. I have to try to remember to ask more of those types of questions instead of assuming.

I started looking into getting hold of the right parts. All sorted now although the plastic cog may take a few weeks to get to me!

From my browsing it seems I have the tacho parts for a DT125. I think I'm right in saying the DT100/DT125/DT175 were all sold as variations in Europe together. However, the DT125 being a 12V electric start is really a different beast to the other two. I could understand the mix-up - someone in the past thinking parts were interchangeable.

What I don't know is whether the 125 had a "reverse" tachometer or that the wildly different bottom end actually spins the cog the other way. I'm guessing the latter.

Curious, I got an entire 125 bottom end with this bike. I think it was the original restorer's intention to make an electric-start 175! If they had a mix of 125 & 175 parts on hand this would all start to make more sense Personally I can't see the point: yes, you get electric start and 12V electrics but then you start having to really get into the wiring loom, swapping bulbs and such. Of course there's the weight difference and the mismatched engine numbers...

"Back in the day" it might make sense, competitively, knowing you could quickly restart a stalled 175 but today? Hardly any effort to kick over especially if already warmed up.

p.s. fret ye not over your assumptions. You have been entirely helpful at all times

As far as the 125-175 upgrade - I have that exact upgrade on my 1970 (and my non-electric start 1980) 125. I believe the tach I have is original in the 1970 so I can't tell you if it is different. To do the swap you don't go into the case at all - everything from the cylinder base gasket and up is changed, but nothing in the case. In my case the 125 electrics were correct as it remained in the correct chassis. It now has a 12 volt CDI setup so no more electric start.

The 125 parts are not the reverse. I know this for a fact.

The electric start 125 is simply the "first generation" engine. Bottom end is virtually identical to the 69-73 AT1 (125) and 69-73 CT1 (175). The first generation 125 "kick start only" magneto model (sold in Europe but not in the US) and the 175 magneto model just had a few different parts (mainly left crank half and narrower side cover) than the 125 starter/generator models.

When the "second generation" redesign happened in 1974, the magneto models were changed to the newer "motocross" engine design. The starter/generator models kept the same basic "first generation" design which is why it looks different than your 1976-77 magneto model that is the "second generation".

When the "third generation" engine came with the monoshock models, the starter/generator was discontinued. The 125 and 175 bottom ends became pretty much identical.

All three generations are very close in design. Many parts interchange. I have built a first generation CT1 bottom end that has parts from all three generations... including a six speed transmission! No machine work on the early cases was needed... shaft spacing and the "basics" are the same for all three generations.

One note is that in about 1976, Yamaha had sort of a "transition" Enduro model... the twinshock was getting some of the improvements of the race bikes and had some changes to things like primary gear ratio..... so different size crank gear and clutch gear than the earlier models. Trans input shaft got smaller too... Those "upgrades" carried over to the "third generation" bikes.

The reason I mention this is because there are two sizes of tach drive gearsets depending on the primary gear ratio. I don't know if they changed the primary gear ratio on the Euro models in 1976 like they did with the US models... but if they did it's possible you could get new gears that don't fit unless you found new ones by part number for your model.

I checked the part numbers very carefully! And then I looked at photos of the parts... and then the parts diagram just to be sure

Anyhoo, what I have on order looks to be the exact mirror of what I have in at the moment. The reason I mention the 125 link is a few searches on eBay turned up these "mirror parts" (that I seem to have inherited) and every time the listing was for a DT125. eBay listings aren't the most reliable though!

Very interesting info though

On the 125/electric-start bottom end swap... nice to know it works! I'd only kept the spare bottom end in case the 175's one was junk but, as you can see from the photos, the internals look pretty mint. Certainly better than I'd expect I deserve

Fun fact I learned today: if you're having trouble kick starting your bike make sure you have the kicker on right and it has the full range of travel