dt 125 re carb inlet boost bottle missing
-
Hi all I've come across a very nice dt re it's been stood a while and is almost brand new the problem I have is when I had a good look round it seems to have been messed with i am aware of the boost bottle that should be on the inlet and this bike does not have one it's plugged
I've not run the bike so I can't tell if it's an issue yet but does anyone know why this may have been removed and is it a problem the bikes don't only a few hundred miles from new any help would be great Tia -
Just found it weird it was gone the bike is brand new almost having only done a couple 100 miles
-
@reecesloane-2017 I removed mine and subsequently had a loss in performance. My top speed dropped by 10mph. So I put it back on and everything was back to normal.
-
For some reason a guy made a thread on how to "de-restrict" the Dt125rs
Some were correct but made 3 mistakes-
Remove the boost bottle on airbox to carb hose and bung it.
-
Blank off y.e.i.s. On inlet manifold.
-
Cut off the airflow guide on the inlet manifold. (the part that sits inside the reed block.
This has misinformed many people, so many previous owners of your DTs have been messed about with.
-
-
I'll go ahead and check it out before I buy it with the bike being so new I expected it to be in messed with
-
I have a boost bottle on myn and I was thinking of taking it off but iam thinking yamaha put it there for a reason. Why is this I can't find any plausible information relating to this subject
-
@Carl-Kennedy Yamaha have a profound knowledge on resonance and sustain thanks to their background in music. The YEIS system is a boost bottle designed to dump air at a certain rpm where resonance is created. This helps create extra torque and more linear powerband.
Thats how I understand it, there’s probably someone more knowledgeable than me who could explain it.
-
It’s not a restriction, keep it.
Like stevie, I don’t know how it works enough to explain it, but it’s there to smooth out flat spots at certain rpm’s. I think of it (& the other one on the airbox side) as ‘harmonising’ any peaks or drops in the pressure wave of air passing back and forwards through the carb…
It’s definitely there for a reason
… -
The cylinder sucks in air at intervals, leading to a pulsation in the inlet airflow. That bottle is a buffer that smooths out the pulsations.
The piston goes up, sucking in air through the carburetor which is (and should be) the main restriction in the intake. This causes a low pressure on the engine side of the carburetor, including that bottle.
When the piston goes down and closes the intake port, there would be a rather sudden pulse where air rush in through the carburetor and meets a dead end. Pressure rises, gas stops throughout the manifold, including the carburetor. Then when the port opens and the piston sucks in gas again, it would have to accelerate the gas mass from zero.
With the bottle, the volume of that closed-off manifold is artificially increased, so it takes longer for the gas to fill the cavity and come to a stop. Hence it keeps moving, supposedly until the port opens again and the piston suck in gas again.
The effect should be that there is a more constant flow of air through the carburetor, which likely improves the atomization or decrease condensation or whatever.
4-stroke engines usually tune the intake manifold runner lengths such that the air pulsations should cause the "pillar of gas" that comes at the intake valve at high speed should "ram" through it when it opens. While the mass of the air is small and it is very elastic, the velocities are substantial so it counts. I wager this is sort of the same thing.
In 4-stroke engines it is also not uncommon that the intake runner lengths vary with engine speed. I know my car has a valve that opens and shorten the length above some rpms. My Honda Fireblade also had something like it in the airbox.
