Need to verify my bike year and model so i can look for restrictions
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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. -
My bike would barely do 55mph when I tried a 14 tooth front sprocket, I use a 17 tooth front sprocket now and it’s absolutely perfect gearing for me…
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Oh hell yeah, 17 is road cruise stuff, but it really suits the 22 horses I think are going on with my bike…
It’s whatever suits you. If you need some 15 or 16 front sprockets let me know, you can have them (unused) I might even have a 13 kicking around somewhere, unless my memory has finally failed me! Just pay the postage
…I’ve got a ‘hardly used’ 55 rear as well, just to confuse the mix
. …Regarding the tailpipe/silencer, as long as the inner diameter of the baffle isn’t smaller than the ‘stinger’ end of the expansion chamber-front end, I wouldn’t of thought it would make any difference to performance. But! I am no expert by any means. Also I don’t mind being proven wrong
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@SpookDog its for 4strokes or road bikes im not sure my cousin welded it somehow but the silencer itself is wider where it connects and wider on the inside to it has the db killer removed and all the packing burnt on pourpuse it makes hella noise you can hear it from far away like if its a 250 or smth
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Yeah, I’d change it…
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Where do you live?…
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Just some product info: I got an Athena exhaust resonator for my bike when I derestricted it, kept the stock silencer.
The Athena gave the bike all the power it was supposed to have and then some - they write something like +3 hp on the site, which would put mine at 26 hp, and I believe it.
The sound became more peppy - not much louder, but with a harsher metallic zing to it. Could be because I used the old washer, I just got a new one I intend to put there instead.
However, the fit of the pipe was terrible. The exhaust port screwed on well, the first bracket was 5 mm too far front, the rear bracket a whole 10 mm, so I had to pull like mad and get rid of the screw insert that otherwise should be in the rubber buffer thingy in the bracket.
Then the rear end that goes into the rubber sleeve was another 10 mm too long on top of that. It basically got pressed into the front end of the silencer with the sleeve as some sort of band-aid around it.
I managed to get it in place with a bit of violence, and I just got a file and a hacksaw to correct it this weekend.
I am also not overly impressed with the paint job. It looks okay but seems a bit thin. I'm thinking of putting on an extra layer, but I am not sure what type of paint to use.
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I'll be amazed if it's 26hp. These bikes are seriously not geared up towards those types of numbers. I doubt even my 170 is making that much power. I am looking to get some dyno time very soon so I can say for sure what it makes. But it doesn't hold a candle to my RS or my Cagiva which is probably closer to 26.
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I can certainly be off by a good margin, I'm going by seat-of-pants feel here, comparing to 30 year old experiences. But are you speaking of crank hp or drive wheel hp?
I had a supposedly 22 hp (crank) DT125LC which I actually suspect was more like 19, because specs differ between sources. It was not as peppy as this.
Then I had a 23 hp DT125R 1990, it was clearly stronger than the first one, hard to tell the difference to this one (I am also 20 kg heavier now).
Then I had a TT350 - about the same weight and gearing, but 32 hp. It was wheelie friendly.
While the old DTR gave peak power at 7500 and lost breath at 8500 this one just improves to 9500 where it quits rather abruptly.
So assuming that it manages roughly the same torque up there as the old DTR, it could be 9000/7500 = 20% stronger, minus error of margin and wear, so I don't think 26 hp is unrealistic.
