CBR 125 Performance Issues
 

Hi there,

Recently came into ownership of a 2004 CBR 125 and I'm having performance problems with it.

Lucky if I can get 45mph out of it going uphill, even on relatively gentle inclines. On the flat, I can barely get to 60mph.

Just wondering if anyone can offer any advice or info on what to look for?

I'm an older fella fairly tall and 12st so that's probably a factor, but reading the DSA website it says 125's should be capable of at least 100km/h or 62mph which mine seems barely able to do added to this the training bike that I did my CBT on seemed to hit 60 without much effort.

I've checked chain tension, the wheels are rolling free and there's no play on them. I've just put a new standard Honda exhaust on it.

I'm a little concerned about the gearbox because under high revving, say 10krpm I've changed up a gear to find the clutch instantly slips the engine red lines then I have to dip the clutch again and change down to get her back to normal. Only happens occassionally though but seems to occur in only high gears, 4th of 5th. It could be my fault, but I've also experienced the bike slip into neutral a coupe of times.

I understand these bikes have regulators, how do these work and where are they?

So if anyone can offer any input it would be much appreciated.

Thank you,

Jim

Replace the sparkplug and check the valves.

Make sure the airfilter is clean or buy a new one.

Check to make sure the carb is clean and not gunked up from sitting in storage or something.

Make sure the throttle cable is not binding up somewhere.

These are pretty basic things, no offence meant if you know all about them already, just trying to help or rule out stuff in case you are unfamiliar:)

They have never had a regulator as far as a horsepower/speed restriction goes, as far as I know. (With only 12-13 horespower, they don't need one) :lol:

The gear shift thing. A very high % of them do it. My 2007 EFI model did it. It's a swept under the Honda rug thing that afflicts almost exclusively the 5th to 6th gear change, but has also been known to occur very rarely in a few other gears. Has nothing to do with the clutch, no slipping is involved, it's just that the gear does not fully engage and pops back down to the previous one, resulting in the ziiiiiiing of high rpm:icon_hyper:

The going to "random" neutral bit is much less as far as a constant thing, mine isn't particularly worse or different from any other bike I've owned as far as either the no-man's land of a missed shift, or the dreaded 1st to 2nd middle of the intersection embarrassment, of flubbing a shift:icon_teeth:

If your bike has passed it's break-in, anything over a few thousand klicks, I would recommend going to the best fully synthetic motorcycle oil you can get your hands on. Car stuff is ok as long as it does not contain any friction modifiers, AKA "Energy Conserving" symbols or text!!!

Personally, I use Motul 300V, and it made a huge improvement in the feel of the transmission, much more positive feeling, and better, crisper shifts. I have not experienced any 5th to 6th gear drop outs or false neutrals since using this oil.

Your bike should easily be able to do 120 kph or more, depending on gearing. A lot of us put on a 14 tooth front sprocket (versus stock 15 tooth) to be able to raise the revs in 6th gear, and remain in a better area of the powerband.


Basically stay in 5th until you are minimum of 11,000 rpm before even thinking of going to 6th. Otherwise it's usually a slow down from dropping out of the "sweet spot", and you are too low rpm for 6th gear to be as effective.

I have no idea what 12 stone is, but I'm approaching 240lbs with gear on. There are a lot of guys who are 210-220 before gear, and over 6' that can cruise comfortably @ 110 kph without overly tucking down.

What's the mileage on your bike? Do you know of it's history? Has it been well maintained? As you know they have no oil filter, so you must be vigilant in oil changes, and make *sure* the the oil screen inside the clutch cover is spotless. This is an every 12,000 km maintenance item.

For the cost of 1 litre of oil, a clutch cover gasket, an oil drain plug crush washer, a small coolant bolt crush washer, 2 and a bit litres of coolant, and 1/2 hour of your time, I would do this immediately unless otherwise confident it's ok.

You can clean and reuse the oil screen, or buy a new one (they cost about a couple pounds I'd say, based on the cost here-aprox. $3.00- 4.00 dollars CDN or so.)

Hope this was of some help.

basiclly a damn good service using decent liquids and replacements. that will get her going good. i did the same, and still in the prosess of upgrading my CBR125. new chain and sprocket on the way, arrow exhaust and K&N replacement air filter are currently being saved up for. alost a new set of jets.