YVPS.
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Hello I have got a Yamaha DTR 125, 1992 apparantly it says and It's in the garage at the moment getting a rebuild new speedo/thermo and whatnot and I do not have a YVPS servo or my powervalve open as it was turned off when I had gotten it and I am looking to buy a servo any ideas where I can get one for my model? I have been told by the garage that my bike could have different wiring and CDI to what my engine could be.
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I believe they didn't fit the servo before 97 unless it's a import I have a 94 and mine doesn't have a servo, your best bet is to open the power valve and pin it
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You could get a servo from the factory on pre 97 IF you presented Yamaha with a full bike license. Otherwise no they didn't come with one.
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@Calum learn something new every day
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@andrewj1680 How many people with a license bought a brand new dt125. Pretty sure they would have just bought something bigger.
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Thanks for the response I have seen loads on the internet for sale and I am wondering if I should buy it as my bike is restricted and no powervalve open and no servo and it's really slow at the moment and plus I have been told pinning the powervalve open will fuck your bike up quicker and I am getting a full engine rebuild done soon so I'll need to bed the engine in for around 500 miles, what do you guys recon?
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@Calum I know wouldn't be buying a dt125r if I had a full licence lol defeats the whole idea surely
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@Kieron12345 I've seen it where it's fried the piston All down the front with the power valve shut too where it can't get the exhaust gasses out quick enough apparently, It's 2 stroke it's gonna go through pistons no matter how you ride it so you may aswell get the most out of it
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@Calum mines a 1990 with a servo does have ks on the clocks tho
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@andrewj1680 that really doesn't seem very accurate to me...
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@Mightyman Frying pistons? Yeah that sounds about right to me.
Having the powervalve pinned open damages the engine as it puts undue stress on the bottom end.
You are talking about reducing its life by a fraction. As Andrew says, pistons are serviceable items on two smokes.
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@Mightyman I've seen it first hand mate it melts the front of the piston dead in line with the exhaust port, I personally pinned the power valve with the idea it's 2 stroke it's gonna want rebuilding from time to time
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@Calum I meant when @andrewj1680 said he has seen a piston fried because the power valve was shut not letting the exhaust gasses out quick enough. @andrewj1680 are you sure it wasn't just coming into contact with the power valve? As they do need shaving down if the cylinder has been rebored.
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@Mightyman
That's result of a piston hitting a power valve the cylinder melting shows the carbon buildup etc I know the difference -
When the servo is operated there is no risk of this happening.
With the servo pinned shut, yeah I could see why this would happen.
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I must be getting the wrong end of the stick here, but are you saying that from the factory, a restricted DT (ie servo not operating) has a chance of the front of the piston melting because of the exhaust gases not getting out of the cylinder fast enough...?
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@Mightyman The Powervalves from the factory were pinned open, not shut.
It styfuls the engine having the valve shut.
The exhaust is unable to scavenge effectively and reduce the NoX gaes, as a result the engine goes into detonation, which is an engine killer.
Now that's the theory, I don't know whether the DT is tuned enough to do this. But I don't doubt its possibility.
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@Calum even DTREs were pinned open from factory?! I thought they were restricted to conform to the 15bhp limit of younger riders? Surely pinned open they would have the full power at higher revs?
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@Mightyman Nah the DTRE's were given full YPVS servos.
Although you make a good point, the YPVS does shut off at 10'000 rpm as a restriction.
But the point here is the build up of NoX's gases. So whilst they did shut off, the normal person would be part throttle anyway. And if you were pinning it, well you would expect it to give up eventually and this might be why.
