DT125R ARCHIVE

Calum122 · Guru

RE: Germans opinion on Athena exhaust :)

AndyYam · Guru

They restricted them mainly for the UK market whereby a 125cc bike is learner legal at 17 if it only puts out 12 or 14 bhp or something. The Cat in the exhaust was for the emissions and that restricted the bike as a by product. I would be suprised if the powervalve could affect the emissions though as it's still burning the same amount of fuel and the same amount is going out into the cat.

I know they powervalve was often pinned open as a restriction but never understood how that works as the max bhp is at something like 9.5rpm far past where the powervalve has any affect.

retarding the revs at 7krpm would as it might allow the bike to rev higher than 7 but be putting out less bhp as the PV would be closed and effectivly making the port smaller, similar to the exhust restrictions.

The other one was that they put the PV in 180 degress so that it just sat there and blocked the port and has the same result as above.

Calum122 · Guru

But if restrictin the YPVS stops the bike from revving freely then you therefore reduce imissions.

Plus uk road learning legal is up to 33bhp. No need to restrict the bikes performance n order to meet that requirement since the DTR has never matched that spec. Plus the restriction I'm thinking of came in in 2004 so therefore not related to 'Reducing performance'.

AndyYam · Guru

UK learner legal at 17 on 125cc machine and a CBT is about 12-14bhp. once you pass your test on a 125 you can ride up to 33bhp any size bike for 2 years, followed by any bike.

Retarding the revs doesnt stop it. It slows it down. meaning it will continue to rise but not as fast. You'll still have the same emmisions coming from the pipe just it wont get to the higher revs as fast and the mixure that is exploded wont be a potent and will be getting blocked by the pv, like the exhaust restriction and so the piston is pushed down less hard which in turn doesnt spin the crank as fast and so on and so on until you get to the rear wheel power. It was always the CAT that reduced emmisions. It's a Catalycic conveter.

NorDt · Guru

Well, Saying that yamaha made the powervalve work for maximum power isnt something i can say is false, But i wouldnt think they would really,

If they did, Why didnt they make the exhaust ports bigger or the inlet ports bigger ?, Well because of reliability and comfort. The DT isnt a Hard core enduro bike like a KTM exc 125 for example, Yamaha didnt push this engine to the limits, instead they made a reliable engine with alot of power from the bottom, Compared to alot of other 2 stroke 125cc i think the dt has alot of power from the bottom atleast,

And i felt that after adjusting my powervalve to open 100 % a bit earlier, My bike would wheelie easier and accelerate a bit better. Thats why i dont think yamaha made the powervalve to work for maximum acceleration and power. Because when you do this you loose a bit of low rpm power. But i never needed that tiny bit of low rpm power.

With the powervalve set like yamaha ment it to, My bike wouldnt wheelie easily in 2nd, But after i made it open a bit earlier, It would wheelie easily in 2nd, And with low fuel i could wheelie it in 3rd too. With just the throttle.

Calum122 · Guru

You're not on about the pipe going from the exhuast to the air box are you. According to yamah that's their yamaha's air intake system (YAIS) designed to increase performance. Pah bs in my opinion. Mate my old dtr would piss all
over the re. The R reved higher and there wasn't that feel of power cut off. My bike doesn't rev past 10K. So therefore no more emission test at 12k. At maximum capacity. By reducing maximum capacity you in turn reduce emmisions.

NorDt · Guru

Nah im just saying you get a noticably faster bike by making the powervalve open a bit earlier.

zander · DTR Senior Member

Weird that you didn't notice a difference when earthening the wire though, for me it was a huge difference

AndyYam · Guru

NorDt wrote:
Well, Saying that yamaha made the powervalve work for maximum power isnt something i can say is false, But i wouldnt think they would really,

If they did, Why didnt they make the exhaust ports bigger or the inlet ports bigger ?, Well because of reliability and comfort. The DT isnt a Hard core enduro bike like a KTM exc 125 for example, Yamaha didnt push this engine to the limits, instead they made a reliable engine with alot of power from the bottom, Compared to alot of other 2 stroke 125cc i think the dt has alot of power from the bottom atleast,

And i felt that after adjusting my powervalve to open 100 % a bit earlier, My bike would wheelie easier and accelerate a bit better. Thats why i dont think yamaha made the powervalve to work for maximum acceleration and power. Because when you do this you loose a bit of low rpm power. But i never needed that tiny bit of low rpm power.

With the powervalve set like yamaha ment it to, My bike wouldnt wheelie easily in 2nd, But after i made it open a bit earlier, It would wheelie easily in 2nd, And with low fuel i could wheelie it in 3rd too. With just the throttle.

Yeah as you say they would sacrifice some power for reliabiliy, after all this is a road going bike, not a racing machine tht will be re built after every race. However I still don't understand what you mean by setting the valve to open earlier. The servo controls how fast the valve turns based on the info given from the revs via the CDI or power valve control unit. I don't see how you can alter this.

The only thing i can see that you mean is turning the valves starting position so that it starts more open and therefore when the bike is at 3krp the valve is already slightly more open and then by 6 the valve would be a bit far past fully open and begining to block off the exhaust port at the exhaust end of the port. At 6krpm (fully open) it is matching the port perfectly and giving optimum power. You may ( if what you say is correct and yamaha have not set it to give optimum power) be getting more between 3 and say 5 but by the time it gets to 6 you'll be restritcing the flow again.

What do you mean by "powervalve to open 100% a bit earlier"?

AndyYam · Guru

Calum122 wrote:
You're not on about the pipe going from the exhuast to the air box are you. According to yamah that's their yamaha's air intake system (YAIS) designed to increase performance. Pah bs in my opinion. Mate my old dtr would piss all
over the re. The R reved higher and there wasn't that feel of power cut off. My bike doesn't rev past 10K. So therefore no more emission test at 12k. At maximum capacity. By reducing maximum capacity you in turn reduce emmisions.

The pipe going from the exhaust to the airbox sounds like part of the CAT which is only on RE models from 04 onwards. Thats about emissions and I beleive it recycles the gases coming out of the exhaust so that less emissions come out the pipe.

I think what you're thinking of is the YEIS (Yamaha Energy Induction System) which is the plastic bottle that fits into the top of the rubber inlet just before the reedblock and between the engine and carb. It's job is to hold a chunk of mixture in the bottle so that when the engine sucks it can deliver it. It is something to do with double dip or something and it basically is a fix to a common issue that causes flat spots in the rev range.

Think of it like a reserve tank of mixture that the engine will draw on when the carb misses a beat or something. This is my understanding of it anyway. It's quite complicated.

zander · DTR Senior Member

AndyJam, with "powervalve to open 100% a bit earlier" he means to make it open completely a bit earlier, if you now gets what he means...

Though I have now idea if it starts blocking off again, I'm sure it does if you adjust it to open too early, but it shouldn't matter if you just adjust it a little bit

found this in FunkeyMunkeyDavid's thread about "crankcase tuning"

As you can see it's not 180degrees, it's more like 150degrees, so you would have about 30 degrees free to adjust without loosing any power on topspeed

AndyYam · Guru

Yeah but as you can see in the photo, the valve is already closing the otherside. If you go any further past full open then you'll block the port and restrict the flow?

AndyYam · Guru

That will never be flush at both ends which is strange, im sure they should be.

zander · DTR Senior Member

you mean when it sticks out (down) a little bit?

Calum122 · Guru

You should look at Aprilia's rave system. Much better design. Just a blade that is controlled by a solenoide that lifts at a certain rpm until opn fully. Easy as that.

AndyYam · Guru

Yeah I've heard of that. Although they say that the YPVS is still the most effective. KIPS is kawasakis and also uses a blade but isnt as effective im led to believe.

NorDt · Guru

Andyyam, Yeah thats exactly what i mean, I change the starting position. And this actually makes it close a bit at the other end. But still the end result is a faster bike.

Well i never proved that it actually gets faster. I never did a comparison with and without the starting position a bit more open with a bike that has the same exhaust as me.

The difference i noticed is that it wheelied easier and therefore i think its faster.

And Zander, after i put on the DTX front fork and all the wires on the front there, (between the light and everything around there ) It was restricted and made the bike ****ing slow, When i earthened the wire it was back to being like a rocket.

AndyYam · Guru

I'm only speculating but I'd bet money that it only feels faster by comparison. You might be going from 12 bhp to 15 bhp as you get to the powerband whereas with the valve operating properly it will be at 14.5bhp just before then 15bhp as you hit the start of the powerband.

zander · DTR Senior Member

That would just depend on how much you adjust it, andy... I just like the small extra kick cuz it makes it a bit easier to get the front wheel up in the air ... It aint much, but it's a small difference.
That's just how I personally like it. IF I were using the bike going to a work, driving in town, and no playing around with it, I'd probably go for the standard adjustment.

Also I still don't know if I wanna get a new exhaust really, cuz I'm afraid I wont get more power. I dont want to be spendig 200euros+ for another look and a better sound xD
sux that I just didnt get the gianelli at the first place hehehe

AndyYam · Guru

I would stick with a stock and just fully de restrict it. If the 3MB pipes fit, find a 2nd hand one of those.

Lol i feel like im doing circles here. I'm not disputing that it will feel different im saying it definitly will. I'm saying that you're gaining nothing power wise. just losing it slightly lower down.

zander · DTR Senior Member

lower down, you mean in the powerband?

Well I have fully derestricted stock exhaust...
I heard almost all other people with DEP do about 80mph and I do about the same with my stock exhaust...
Maybe I just gotta accept that it wont get any more horsepowers then XD

It sucks though that so few have tried the Athena.
One guy says its sucks and it's worse than DEP, Germans says its alot better than stock and DEP and got alot more torque etc.

But... it's just a 125 XD maybe I should get something like a 450 ktm SM when I get 18
When I first bought the bike I was like: OMG shiet that power...
Then about 2 months later I derestricted it, and I was like: Ohh yeah now I can wheelie in 1st without clutch, 2nd with clutch and 3rd with a great pull and clutch (before that I had to use clutch in 1st and clutch + great pull in 2nd)
Then I tried driving my friends moped and it's like: wtf is this ****, is it a freakin bicycle? well he had it derestricted so I was able to wheelie with it XD
Now It's starting to get: I WANT MORE POWAH!!!! xD

Anyways, yeah we kinda make circles here, Im just desperate cuz I want more info about the Athena exhaust hehe
maybe I should forget about it all and start styling it, it looks so stocky(apart from headlight and front fender.... gottoa remove the rubber**** on the forks (rip it away with a knife :D) and maaaybe get a new rear fender + backlight :P

AndyYam · Guru

I'd love to try an Athena. Don't know what it is but i like them and reckon they'll perform well. Trust the Germans! The money is the only thin for me. When a stock pipe can be bought for around 30-40 quid, spending 200 on a pipe that might weigh less and add a little power, I'd rather buy something else.

I ride the rd350 for power and speed and will be riding the Dt for the ride style and fun you can have on it. Can't wait to get the dt200 going! A mix between the 2!

zander · DTR Senior Member

:) Maybe I'll get an Athena exhaust next spring. It's soon winter and I wont be riding much then.
I'm also really curious about them but I dont want to be the one finding out they suck xD
Well according to the germans it should be great so I'll probably get one next spring unless I find a cheap 2nd hand in good condition before

AndyYam · Guru

Sweet, i'll look forward to hearing about it. Wish they sold just the downpipe though. Id stick with a Dep silencer and have athena on the front. We'll have to keep an eye out for someone whos got one and can swap between stock and athena

NorDt · Guru

The dt has about 20-25 hk with a DEP or Gianelli.

Dont think your getting that much just derestricted ;)

AndyYam · Guru

NorDt wrote:
The dt has about 20-25 hk with a DEP or Gianelli.

Dont think your getting that much just derestricted ;)

Don't think who's getting how much?

GADGET · Guru

Nobody said they were

zander · DTR Senior Member

You dont have to buy the complete exhaust, you can buy the xpanny and silencer seperate

http://www.athenaparts.com/eng/kits/view/7515/complete-exhaust-pipe

scroll down and you'll see "Exhaust pipe" and "Silencer", then click on "Exhaust pipe"

But I'd rather buy a 2nd hand anyways

NorDt · Guru

Andyjam, I was saying that derestricted + gianelli or dep, A dt has about 20-25 bhp.

I dont think you can get that much just derestricted with the standard exhaust.

GADGET · Guru

No he means derestricted pipe and derestricted bike/engine