I have a 2007 DT125RE. Ive done most of the mods mentioned in this thread.
I have the power valve set in the fully open position when the ignition is turned on. Not tried to pin it fully open and would be interesting to know if it makes a difference if it is pinned in the fully open position.
Fitted a full DEP pipe and blocked off the catalytic convertor pipe from the Airbox.( I used the nozzle from a standard silicone sealant tube. Wedged it into the hole in the Airbox and put the rubber pipe back on over it)
Blocked off the snorkel that fits into the Airbox. (I used a blank rubber washer and wedged it into the bottle and the refitted the bottle)
I think there are a few people who get confused which bottle that needs blocking off. Its not the one that fits on top of the carb inlet manifold. That one is a boost bottle.
This is the one.
Cut off the rubber restrictor on the carb inlet manifold and chamfered the hole in the rubber.
Like this.
Changed the stock Carb 210 sized jet to a 240. (Ive checked my plug and the 240 jet is bang on. I wouldn't recommend going any higher) The Bike already has great throttle response and runs cooler)
I removed the rev limter by earthing the Green/Black wire that goes into the speedo.
I am trying to get hold of the inlet rubber Airbox manifold from a DT230 lanza.
Like this one.
I did look into fitting some racing reeds. I liked the idea of the dual Boyesen type. I emailed them and this was their reply:- We list Boyesen Power Reeds, part # 666, to fit the ’88-’93 Yamaha DT125/R. Attached is a picture of reed # 666, and the dimensions are: length = 48.1mm and width = 49.1mm. Unfortunately, we do not list reeds to fit the newer Yamaha DT125re.
Anyone know if these will still fit?
The difference in performance is massive to what it was when i got the Bike. It was extremely slow at first and the rev limiter was an awful restriction on these Bikes. The Bike was being held back so much. It was like the Bike was telling you to change gear at 5000rpm.
The most noticeable mods was definately the DEP Pipe and removing the rev limiter.The DEP is definately worth shelling out the coin. Removing the rev limiter costs nothing.
I decided not to cut open my standard exhaust cos i will probably need to fit it back on along with the hotcat catalytic convertor for MOT purposes.
As for the rest of the mods that ive done. I would say each one on their own doesn't really make a huge noticeable difference but when you combine them all together there is a big difference.
The only thing that i'm not too happy about is that the power band is quite high. Easy enough to hit the PB in first and second but you have to thrash it through all the gears to keep the Bike in the PB. Maybe i will try a slightly smaller front sprocket.