Thank you for your reply!

It seems every time I am troubleshooting a problem, especially if it is on my own gear, if you can find either the most expensive or most difficult thing it could be, that will be the problem. So, I will take your advice and try that because it is probably the most difficult to fix and because the other part is not available. Thank you for the part number.

First question, could that be the problem and not show any leaks? Obviously with 2 stroke there is no oil in the crank case but it does pass through and when the exhaust was leaking at the head it did have some oil leaking out so just wondering.

Second question, to replace those seals don't I have to take apart the whole engine to get to them, right? Are there other seals I'll need to put it back together? I know there is no "seal" per say between the two half cases but maybe others. I'm sure I can figure it out but thought I'd ask in case you had a list. Sounds like you've done this before . . .

Thanks again for your reply. I'll get back to you all when I finish and let you know how it went for the purpose of closing out this discussion and hopefully helping others in the future.

Cheers!

BTW it used to rev by itself but now it only does that when the chock is on past warm up. With the chock off it seems to only do that when rev'ed and not under load. It is not the throttle sticking I know! For a long time that was questionable but I have gone to extreme lengths now to assure that is no longer the issue. Just wanted to address that concern. Thanks

Thank you for your reply. Yeah I've checked it over and over and I'm convinced at this point the carb is not the issue at this point. You are correct though, my understanding is anything that makes it run lean can/will cause an over-speed issue. Mainly why I've been chasing potential leaks in the fuel/exhaust systems. I think I've covered all possible sources for leaks except the main seals and that is why I started thinking it was on the ignition side. Since the governor is not available I guess I'll break down and do the main seals and see what happen?

Thanks everyone for your input! If you come up with anything else or a source for the governor please add it to this string. I will keep checking back and post an update when I complete the main seals.

Cheers!

Not many things that can cause 'Wide Open Throttle' & really needs input from the rider in some way. Cable pull etc. Caught in the steering stop & squashed the outer so when opened--it stays open. Slide in the carb half a turn out--would end up about 3/4 throttle but would be like it from start up.
If the governor/advancer is faulty in its movement, you could somehow modify it so it's set on full advance & forget it. Electric start might kick back but you know first try & with a good battery it might be ok. Otherwise just kick start it. timing on advance it just at the normal 1.8mm or 72thou btdc, same as magneto models so nothing to worry about.

Thank you for your reply.

Yeah that is exactly what I thought but I have verified it's not the throttle. I'll check the barrel but I would expect slack in the throttle cable if that was the case. I'll check it again. Seems the general consensus is there must be something wrong with the throttle input. I am going to try and set the advance wide open as that was done before and it seemed to work the best. The electric start/charging system is working correctly. So, I'll keep at it and see what I can find.

Thanks again

If you do really want to replace the governor, I do have that '74 DT-125 engine sitting a tuperware and can tear into it some time next week, though like MarkT said, it's not the source of your problem and he knows his way around these bikes much better than I do.

Greetings,

Great post! After figuring out how to pull the coil I checked and sure enough the crank seal on the timing side was seriously shot! I replaced it and the broken holder and presto; it works great! Now it has a little wiggle on the crank shaft bearings so I'm supposing there not good either. I don't see how any amount play on the crank bearings can be acceptable, but yeah thank you very much for the advice!

Hello,

He sure does! If you see my previous post I explained how it turned out. Question I posted in a round about way, is there any amount of acceptable play at the crank. Now that it's running the governor screw king lose. So, how do you know when the armature in on tight enough, since the armature was taken off for the first time and is the only change since the governor screw started coming lose, OR is it working lose because there is too much play on the crank bearings?

What condition is the engine you have in? If for sale at the right price I might buy it off of you for extra parts, especially if I have to tear mine down to the crank. LMK thank you!

That's a good question that I don't have the answer to. Someone bought a wrecked frame '74 dt125 for the gas tank. I bought the engine from him for $50 because I needed clutch and kickstart parts for a '73 ct3. Swapped those over and threw the engine in a Tupperware. I'll have the head off it late next week and can access better then.

I have a Dt125a that is my first restoration and I seem to recall mention somewhere that 125s tended to wear that bearing out because of the weight of the armature. I can’t personally vouch for that as all of my bearings were shot and I replaced them all. I would buy into the idea that any extra play on those two crank bearings will result in failed seals. Taking these engines down to every last part and building back up is doable by almost anyone here. A manual or three, correct tools, proper parts, and a lot of patience are all anyone needs to pull off the deed. Good luck!