Hey folks, hoping someone can help or has run into similar issues.

My daughter has a 2008 CBR125R (Canada) with only about 4,000kms on it. When it works, it works great. But after riding for awhile (20-30 minutes) it develops an issue where it won't exceed 6 or 7k RPM (I need to take it back out to get the exact RPM).

When it's happening it feels very ignition timing or electrical related, there are no hesitations or misfires, it just WON'T go above that RPM. If you pull over and wait 5 mins it will resume normal operations for a few mins and then it will come back. Next ride the first 20-30mins are fine and then repeat. Occurs in all gears so at low speed you can mitigate it by not trying to pass that RPM range, but if you're riding along above that RPM when it happens it hard drops that RPM suddenly which can be quite jarring.

It seems like something spark plug, ignition coil, R/R or stator related, but I don't know if this issue is commonly known and I'm trying to avoid taking it to Honda at least initially for them to "poke around" when I can do the initial poking.

I'm going to replace the plug and clean the injector and see if that resolves it, but it feels like something is overheating and misbehaving as it only manifests after a bit and then goes away after cooldown.

Anyone having experienced similar and can provide some feedback is greatly appreciated, thanks!

 

Cracked things open on the weekend.

The airbox was spotless, the injector is very hard to get at to remove so I left it for now but one find was that the previous owner used a CR6E plug instead of a CR8E.

Looking at the plug it looked ok against a standard "read your plug" chart although maybe a little bit of extra carbon, you can't really tell unless you put a fresh plug in and ride it and then check it.

But a CR6E is hotter than an CR8E by 2 steps, and with the high RPMS of the little 125 I'm hoping that was the issue and it needed a colder plug. She rode it the other day for 40 minutes without any issues after the new plug, but one time in a row certainly isn't definitive.

I also checked the breather hose for the gas tank and it seemed to be clear but I blew it out with compressed air anyway and there was definitely flow into the tank.

So we'll ride it for a bit an see if it comes back!

 

Good find, well done and fingers crossed.