cbr125 forum

Hi guys,

First post although have read many articles on the forum before. I am having a couple issues with my cbr125r rw7, It's a 2008 fuel injected model.

Problem number one. For a few weeks/months now it has been stalling at idle and cutting out when I give it too much gas too quickly. I thought this might just he because it was cold weather and normally wet at first but the past few days it's been 23 degrees Celsius (74f for anybody outside of the UK) and still having the issue. I'm going to put in a new spark plug change my oil etc this weekend and see if that helps but I only did that 3000 miles ago so not too sure on whether it will. Any ideas if that fails?

Problem number 2. Yesterday I was at my parents (around 30 miles away) and I thought I'd top up my coolant. I noticed that the radiator cap was oily and the seal had torn. I topped it up and put it back on and when I started the bike it spewed out everywhere, I figured I'd attempt to ride it home and take it easy to make sure it didn't overheat. Eventually made it home but noticed that when I got there there was white smoke coming out of the exhaust when I turned it off. I've bought a new radiator cap since and am planning on flushing the coolant this weekend. I am a bit worried that I've done something serious, I've looked online and have seen that oil in the coolant could indicate a bad head gasket... any other reasons why that I could check first?

Cheers guys, any response is greatly appreciated

Edit*: Forgot to mention that my bike has 24k miles on it and has not had the valves checked, i have a feeler gauge and will be doing that at some point soon. I am planning on doing a teardown of the bike cleaning bits up and making sure things are all where they are supposed to be. Also the bike was without an MOT for 2 years between 2016 and when i bought it in 2018 (so possibly sat for 2 years with fuel and oil in it). The bloke told me that he used to run it monthly up and down his road but im not sure if i believe him... The reason it had no MOT was because he got bored of biking and just stopped. The last couple times that ive filled up ive been putting in REDEX which supposedly cleans out injectors and that has kind of helped but only really short term.

For your first issue, it looks like you need to change your fuel pump. For the second issue, did you check the coolant level while the engine was hot ? It makes a huge difference for the coolant level.

Cheers man, I will check my fuel pumps flow rate soon and hopefully it's not that because they look pretty pricey... the engine was hot when I topped it up.

Update: did a compression test the other day was getting 130psi the owners manual says 195 but that seems high. Gonna do my head gasket, piston rings and check clearances on the valves.

I checked my fuel pump and that was fine, hopefully this fixes things, if not I'll start checking all the fuel lines/injectors for crap...

Update: It was the Head Gasket. I replaced Head Gasket, Rings and adjusted the valves. Runs great now and has a little more torque maybe? I guess the idle issue was due to the compression being lost.

For anybody thinking of doing this, i have fairly limited knowledge of mechanical stuff. It took me probably 16 hrs in total and cost 30 quid, so definitely worth a go if you have similar issues