Need to verify my bike year and model so i can look for restrictions
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@erionmustafa
Yeah, I think some of the designations are E for Europe… -
My French import (96) fitted with 3 pin power valve and full power cdi (3NC-00) happily do off the clocks and pulls better than my mates uk bikes, and that’s even with the 3BN restricted cylinder head. I’m in the process of rebuilding it and got the dome 3MB head off @HOTSHOT-III so I’m interested to see how that goes
How many wires does your PV have?
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@erionmustafa im rebuilding it too rn my piston got fucked
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Well it happens to nearly everyone in time. At least you have the unrestricted version of the dtr125
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You have the 3 wire servo fitted to your power valve. Your bike is a full power model. There are no restrictions. Changing the exhaust may help unleash a few ponies, but your model was never intentionally restricted…
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@SpookDog i want to cut the exhaust and remove the restrictor will i need to get a bigger carb jet or not
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You will never need to make the mixture richer with a bigger jet!…
What makes you think that the exhaust is restricted? It’s a full power model, why would Yamaha go out of their way to restrict it? That said there are better ‘tuned’ exhausts out there…Someone else please chime in here?…
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@erionmustafa Don't gut the stock exhaust, you'll probably lose power by doing that. When the DTR came out in 1988, they based the styling on the '88 YZ250 and the DTR front pipe is roughly the same size as the YZ, which is a single-skin racing exhaust system. On the DTR this allowed them to fit into this space an appropriately sized expansion chamber for a 125cc road bike and enough noise suppression material for the bike to be quiet enough for the roads/trails. So in most cases the front pipe isn't restricted on the DTR, I've heard stories of some of them having a washer in the header pipe but this would be pretty obvious and you wouldn't have to cut open the pipe to get to it.
You'd be better off getting an aftermarket pipe and trying that. On my 3NC the Tecno front pipe/DEP silencer combo worked well and the Tecno pipe costs around £100 even though it's identical to the Athena pipe. It gives a good spread of power from 5k to around 9k and I think the DEP front pipe would allow it to rev out a bit more, a bit faster but maybe not as good off road. I didn't need to re-jet for the Tecno and DEP advised me I wouldn't need to for their pipe either. @SpookDog runs the Romeu Henriques pipe and is happy with it. Any of these options will be good depending on what you want the bike to do, and if you ever want to sell it it will be worth more with a decent (i.e uncut) stock pipe fitted so paint this heatproof black and store it.
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On my 2005 Yamaha DTRE, as well as the header restriction and a breather pipe back into the airbox, there was a huge honeycombe system inside the expansion chamber.
Regardless, the biggest resulting factor for me was the weight of the DEP compared to the stock pipe.
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Is the Tecno the “unrestricted pipe” that appears on eBay, for about £100? Doesn’t look too shabbily made (though not well finished/painted) It was going to be my first choice until I got put into touch with HR. I wasn’t willing to throw down the money for a DEP. I think that they’re overpriced, but that’s just my gut feeling. Not that they’re bad. Just flimsy with no longevity. I’d rather pay £350 once, not once every couple years
…Dtre’s seem to be one of the most horribly restricted iterations of the bike from what I’ve read!…
PS I think that Hotshot has a really sweet 3MB front pipe for sale. I would of bought it if I had enough disposable income
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@SpookDog The Tecno is the unrestricted pipe on ebay yes. It's well made, fits well and is pretty solid, only bad point is the clearcoat that bubbles off the header and is too tough to remove for painting everywhere else. If I bought another brand new one now I'd probably try paintstripper before fitting it, then just paint it heatproof black
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@SpookDog i tried my best to understand the derestricting guides but as you guys are saying it seems for me to be blessed with a unrestricted one
PS i didn't notice that the power valve was stuck half open and wasn't getting enough power so i reduced front sprocket to 14 and seemed to catch 80kmh i can't wait till i fix the cylinder and get a piston to test it i was surprised when i found out that i wasn't getting full power and with a 14tooth sprocket doing 80kmh its crazy -
@Calum previous owner put a fake akrapovic slip on that is for 4strokes can it make lose power or anything ??
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@erionmustafa Uhhmm absolutely. You want a proper two stroke exhaust to go with the expansion chamber.
In addition to head pipe length, divergent and convergent cone lengths, an expansion chamber has three more crucial dimensions. The length of the straight 'belly' between the divergent and the convergent cones, the length of the tailpiece 'stinger', or muffler, and the diameter of the belly section. The stinger acts as a pressure bleed, allowing pressure to escape from the pipe. Back pressure in the pipe, caused by a smaller-diameter or longer stinger section, helps the wave action of the pipe, and can increase the engine's performance.
