Great explanation MarkT!!  motobatt has 140 cca  yuasa has 74 cca both batteries that fit AT2

Then the Motobatt would be my choice... keeping in mind that Motobatt might not crank any faster if starter can't draw more power than the 74 CCA of the Yuasa.

My guess is there will be a difference.

Now that's a great way to describe it in #20 MarkT. I like that.

Interesting discussion on the different aspects of batteries in view of the Yamaha dynamo start bikes (AT-DT 125s).


UPDATE:

SO... the OEM hot wire to the starter relay turned out to be EIGHT ga (according to the O'Reily guy). There was no such automotive wire in all of Poteau (and I went to 5-6 locations).

Upon discovering there's no such wire in my town, I purchased a small roll of 10 ga, and once home I purchased a NOS AT/DT ground/earth wire off eBay. I then set about to fabricate a ground using 10 ga for the interim. That I did.

With the new battery installed, and the hot wire hooked up, at key-off there's no little spark when touching the ground to the frame. With key-on, there's a little low grade spark (normal) when touching the frame, but holding the ground to the frame with my bare thumb resulted in zero warmth of any type. Primitive technique, perhaps, but if a dead short existed, it would have heated up immediately and my bare thumb would have felt it immediately.

That so, I then reinstalled all the things I had to remove, and it sits ready to come off the lift for an attempted kick start. I ran out of time yesterday, and it was too stinkin' cold (wind chills in the 20s... which is cold for us around these parts), so waiting for the mid-forties this afternoon before I attempt to kick start it.

I am strongly suspecting the tiny 14 ga ground/earth wire that was barely touching at the terminal, combined with my repeated use of the start dynamo, simply overloaded the puny ground wire and bad connection, and melted/smoldering insulation on the 14 ga ground wire was the result.

I'm hoping the start up this afternoon goes without issues and the bike is good to go. Upon the arrival of the OEM ground wire, I will pull my temp wire and install it.

That's all for now.

Andre

Not sure what was original but doesn't matter in my book...

Bad juju IMHO to run less capacity ground wire than the power wire. You could go with something larger than 8 gauge for ground or run multiple ground wires. 6 gauge is usually available.

Agree: A small 14 ga ground wire w/loose terminal connection were items I should have caught and didn't. I'm kicking myself for that. Never entered my mind that the ground wire was replaced at some point previous to my ownership. Also, with the ground terminal being hard to see/check, I didn't catch the looseness either. Shame on me.

However, I seriously doubt the OEM positive leed is 8 ga. That was the O'Reily counter guy's best guess. Upon obtaining 10 ga, it appears to me that the OEM positive leed and the 10 ga are the same size. (Going by the copper wire size and not the insulating size.)

Regardless, for now I will be using the kick start and not be using the e-start.

The bike will get the OEM NOS ground wire shortly after I receive it. Going forward from that point... I still plan on always kick starting when cold, and use the e start sparingly once warm until if/when the time arrives my legs/etc says no on kick starting.

Andre

Good battery & wiring it should button start when cold no problem--just saying. Choke open & throttle closed when cold.

RT325:

Hope you're right. The e-start is THE reason I purchased this bike as my vintage tiddler Geezer Scoot as I age. (I also have my XT225 for non-vintage tiddler times.)

Andre

2/17/23 UPDATE:

Finally got to 45 degrees out in the sun. Un-stacked the bikes and got the DT125 off the lift. Fuel on, key on, no lights on, kick: Started immediately. Rode it around the yard long enough to freeze my fingers off (these nubs are harder to work with. Miss my fingers already) and all seems well.

Looks as if I dodged a bullet.

IF I was half the riding man I used to be, I would suit up and start the shakedown runs. However, I'm not, so once it warms up a bit more (in a few days), I will begin riding it around town until I'm satisfied it's good to go. (That is, ride it around town WHEN Wild Child the wife is home so she can rescue my arse if needed!)

Assuming it successfully does about 100 combined miles around town, I may not take it on an all-dayer out in the mountains until I meet up with a long time vintage bike friend and we ride the "T-Town Tiddler Spring Ride" in April. That way, I have a support truck following along with the group in case it DOES have an intermittent electrical issue!

However, I may become convinced I found/fixed the issue, and if so... to the mountains I shall go.

In the meantime, it's going to be stacked alongside the bikes that are available for riding, and now my '72 DKW GS125 goes onto the lift for a look over/maintenance prior to my 2-day "Vinduro Tiddler Dual Sport '23" ride I'll be hosting in a few weeks.

How do I get myself into these "work on bikes all riding season long" deals??? (Hint: I need to quit buying bikes during ride season!!)

All fer now.

Andre

SHAKEDOWN RUN #1...

Yesterday afternoon was the first time away from the house aboard the DT125 since my ill-fated trip a few days ago. (Was riding it around town and had some issues that resulted in hollering at Wild Child the wife to throw the loading ramp in the back of Deer Slayer the pickup truck and come rescue me.)

After finding the 14 ga ground cable/strap being the culprit (heated during an e-start session and smoldered the rubber insulation off it, blowing a fuse in the process), I purchased a NOS OEM ground strap off eBay.

However, I didn't want to wait another week or so, thus I went to town and got some 10 ga automotive wire and fabricated my own.

Anyway, I had decided that I would use l would use the kick start until the OEM part arrived. So, I did. Use the kicks starter that is. For the cold start, after turning on the fuel and pulling out the choke, it started with a half-azzed kick.

Getting underway, it runs great. Feels/sounds like I would suspect a new one would. Crisp throttle response, returns to idle quickly when the clutch is pulled in for a stop, or even when the clutch is pulled in going 30 MPH down the road. I'm also pleased that there's smoke present at all times. (Once warm and at idle, you have to look closely, but there's smoke, so it's getting oil.)

I rode it around the neighborhood a bit over 20 miles. Zero issues.

In fact, I deviated from my decision to only use the kick start until after I had the OEM ground wire in hand and installed. Instead of waiting, I happened to think that IF there is some other underlying issue than my diagnosis, I want to find it ASAP to minimize lost time. That so, after the first stop, I slid the lights on/off switch to the off position, and hit the button. It was running instantly. Seems that 11ah Motobatt battery really gives the start dynamo an assist.

From that point on, I used the starter after a stop w/engine off. Like I said, I decided that IF there's an issue, I want to find it out ASAP. However, I strongly suspect I've found/fixed the issue with a new, more powerful, battery and a 10 ga negative ground strap.

In fact, this ride was so encouraging, that I'm going to cautiously, declare that it's a "Definite Maybe" that all is in good order and it's ready to go to the mountains.

However, I don't foresee a possible mountain ride on it for a while, so in the meantime, I'll continue to putt around the neighborhood, and once I tag it this upcoming week, I'll ride it around town until I can take it to the mountains.

All fer now!

Andre