Why is my Honda CBR125R losing power?

Published: 13 July 2011

Q. I have a 2005 Honda CBR125R and often have a problem with it when opening the throttle on a uphill stretch of road. It happened a few times before, so I removed and totally cleaned the carb and needles andhoped it would help.

What it does is that if I have turned onto a stretch of uphill road (doesn't even have to be too steep), and open the throttle a fair amount, it suddenly loses all power for a second and then cuts back in (sometimes it helps knocking it down a gear).
Cbrgaz, MCN forums
 
A. It sounds like the mixture is leaning out too much, with not enough fuel or too much air. Those bikes do get air leaks between the carb and the air filter box, so you need to check that.

Get the bike warmed up and running on tickover, then get a can of EasyStart and spray a little around the carb intake rubber and air filter junction in turn - don't use too much or you could get more flames than you bargained for. If the revs rise that'll tell you that EasyStart is being sucked in there when it should be airtight.

If you have no air leaks, and you can't seem to cure the problem and the carb is set up properly on the mixture, then order a #45 pilot or slow running jet from your main dealer and fit it, thatshould sort the problem. Your standard jet is a #38.

Get yours at MCNshop.com