Posting for Benaddy92 Not really a mod - more of a removal. http://r125forum.com/threads/yzf-r125-air-valve-mod-simple-guide-with-pictures.32/ First of all I'm gonna say: This does not give you any extra performance...but it will make your bike sound better. I did it and several people (Including Adam on here) noticed straight away without me telling them. If you think your bike is faster it is just a placebo effect haha. Basically you just cut the two pipes and bung them up, then remove the valve. There are no ill-effects because I did this 6,000 miles ago and my bike still runs perfectly. If you really wanna sound good I'd get a scorp or akrapovic exhaust but they're not really cheap. This mod is free so have fun. Takes 10 minutes.
Interesting... Why does that small pipe run from the exhaust back up to the air filter box? Is it a modern day carb anti-freeze system?
It's a exhaust reusing pipe. It apparently lowers the amount of CO2 that exits the exhaust. The YBR had one, disconnecting it = More noise but less power (And reliability issues) http://www.yamahar125.com/threads/how-to-yzf-r125-air-valve-mod-to-increase-air-flow.69 As you can see on page 3, I tried it on Bee and it failed.. EDIT: For some reason, the first post of that thread has been removed?!
That sounds weird. I've never heard of problems on the YZF. Possibly because of the YZF being EFI and the YBR not? Actually - the way you described it made me think a little more...The valve is one-way, so by just blocking the exhaust end the gases were still going through the valve but then not being able to go back. I can't see that being a problem but I cut both ends of the pipe and bunged them up without any problems.
I had a check engine light come on when I went for a test ride. Benefits were really that I had a lot more exhaust noise and throttle response was increased. Downsides were that I had less power (I'd estimate about 6BHP, rather than Bee's current 8.5hp) and thus I used more fuel. Sorted everything out with a nice shiny new straight through exhaust system
