HiDo you have any experience with modifying the right side exhaust of a 1976 DT 125?I have an idea to grind it in weld and open it up.I assume there will be baffles inside.If I remove the baffles and leave just the wrapper will the engine performance increase?Do you know what the exhaust looks like inside?I'm attaching a photo.Thank you Daniel

I think you're about to show us what's in there. She'll ring ding through the walls but probably go better so long as the tail muffler is clean--proper clean burnt out.
Your exhaust body i think will have various plates spot welded so might need to find those & drill them so as to be able to part it fully along the seam.
Alternatively just burn it out clean in the bonfire over night.
Sounds very interesting.
Welcome if you're new!!.

Thank you I'm new.
I left the original exhaust in its original condition.
I bought another piece for experimentation.
I know it's going to be tricky, but it's going to come apart.
I'm curious what's inside.I'll post pictures here when I take it apart.
They're typing through a translator.
I'm from Europe, Czech Republic.Thank you, Daniel.

Good man. It's great to experiment if you have other parts incase it all goes wroing haha.
Look forward to the pics.
The exhaust might resonate through the walls once the insides have been cleared out.
We had instructions from yamaha back in about 1973 to drill a hole each side & insert a small steel rod across & weld it in. To stop the exhaust walls sounding like a tin can,
Actualy that might've been when the spot welds were not done well in one year farm model AG100 & rattled at the baffle plate welds.
Think we had to clamp them tight then weld the rod ends both sides.
If it 'ring dings' through the walls you could wrap the entire chamber with that wide car exhaust wrap. I often wondered how that would work--should work.

I understand.
I don't mind the higher exhaust volume.
I want it to have a high volume.
Theoretically, if the baffles are removed, can the power be increased?
I have a friend who modifies 2T's for racing .
I want to try to modify the inner chamber if I can and it's necessary.
Were these exhausts tuned with the engine like modern motorcycles?
I would prefer to get the AT3 exhaust with the outlet to the side it is the nicest.
Will the AT3 exhaust fit the 1G0?
Thank you Daniel

As RT325 suggests, clean the carbon out, by putting the exhaust on a bonfire. If you can find a back box intended for an MX bike, that can be modified to fit, the exhaust will then work quite well. Not a good idea to take out the insides, as other than making the bike a lot louder, its not going to do a great deal. There is a Clymer manual that shows porting alterations for 125/175.

I was thinking your exhaust goes through the frame but expanding the pic i see the heat shield & looks much like a CT3 [AT1-AT2--AT3--CT etc] so goes along the side. Quite possible an earlier model exhaust will fit then. Can't say for sure, but if yours bolts up to the cylinder you'll need to do something either a slip in flange like an AT/CT exhaust or change the end to bolt up like yours.
I've forgotten why you want to do that. Is it just to try something different with exhaust.

Probably not strictly relevant to what you plan to do but here's a link to a page running my AT1 with a 175 top end now. Exhaust [like what you're asking] is gutted inside by memory. You can see the cross cut from about 40 years ago. Can barely remember doing it. Can see it near the end of the video.
yamaha-enduros.com/index.php/forums/1968...-chinese-carb-on-175.

Thank you for your advice and consultation.I'll try burning the exhaust first.I understand it's irrelevant.I only repair motorcycles made in the Czech Republic and they run better when the exhaust is gutted, so to speak.I have no experience with Japanese machines. My machine has been with us since December.Still getting familiar and looking for options and possible improvements.I respect that it is a historical machine so it should be treated as such.I don't expect to race it...Thank you Daniel

Gutting is a lot of work....  I've done it, not on your exact model though.  Was a waste of time in my case, just made it louder.  All that was inside was a perforated metal liner with a thin layer of fiberglass mat underneath to insulate the walls of the pipe. 

You might look through the "sleeper pipe" threads here...  some members installed a baffle cone inside original pipe to emulate the exit cone of  true expansion chambers.  They did this by trial and error for each model and their efforts resulted in noticeable improvements. 

Good luck and looking forward to seeing what you find inside and to hear about the results of your experiments!