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Gearbox issue possibly?? Honda cbr125r 2012


Jbradford517
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Hi all, hope you're all well.


im having a crazy problem and wondering if anyone could help?


Basically im aware of the known dreaded gearbox in these and people seem to have issues,


I'm also aware of the 1st to second clunk and the 1 to natural rather then 2nd but there not my issue :(


My issue isn't when the bikes stopped but when I'm riding.


When I'm riding it's all fine hunky dory no problems but then suddenly I'll be coming down from high revs in like 5th? Maybe 4th and when I'm coming to slow down all normal, correct down shifting etc.


it's rare and has only happened three time to many to me now but it's when I'm down shifting from high rev and in like 4th or 5th gear going down 1 gear I'll suddenly get no drive itl so to speak free roll like my clutch is in still and not engaged in gear, I'm not sure if it's going from 5th to 4th or 4th to 3rd but it happens so quickly and sometimes due to the free role it can be dangerous.


Now I know about the gears sometimes being a bit iffy in general, and you sometimes need to release the clutch a little to engage but this isn't that.


The only way best I can describe it is (this is two occasions) i was on a very slight down hill and I mean slight, slowing down all as usual gearing etc ,

then it just happened, there was nothing no drive engine still revving etc, i had to then tap it down a gear and release clutch again and it was then fine for a few days then today, same exact place roughly same sort of speed, only this time (this being the third time) I lost all drive and I could hear a very quiet like tapping , tinging noise maybe a quiet clunky?


this all happened quick and I was in a line of traffic slowing Down, I quickly pulled the clutch in almost instant still slightly hearing this noise i then tapped it down all the way so i didnt try the down tap 1 gear as I couldn't it was to late as the freely roll effect made the bike pick up some speed due to the free rolling. I'm puzzled.


I did a oil changed the other day usual oil, castrol power 1 10w 40 4T.


No signs of oil leaks or chain being to slack or to tight, recently had a chain and sprocket set a couple months ago max.


It's a 2012 plate cbr125r, no known engine faults current or to this date apart from this which has all happened over the space of a week?


Can anyone shed any light please??


Thank you

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It's like it doesn't select a gear at all possibly?? Its hard to explain, the third time was today and this is the only time iv heard the noise.


The first time I don't really remember how that happened but I do remember that day I had to go up a small drop curb about 25mph to avoid a collision as a dickhead was on coming on the wrong side of the road. I don't know if it's just a coincidence but like I say the same day the first time happened was that and the day I changed the oil as these were both on the same day

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As Snod says, false neutral. Sounds like engine apart for you, my boy (or girl). IIRC, you can get at some of the selector mechanism (pawls etc.) by removing the RH side cover. If you're unlucky, its a split-the-cases job. There are CBR 125 afficianados on here who will be able to give more detailed information. Good luck.

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Normally, in a gearbox, you have 3 parallel shafts that carry a number of gears.There is the input shaft which is powered by the engine, an output shaft which is connected to the gearbox sprocket and a layshaft that sits in the middle. As you operate the gearbox, the gears slide up and down each shaft and engage and disengage with each other to give you the different gear ratios. The movement of these gears is controlled by a selector drum that has grooves in it. In those grooves sit the ends of selector forks so as you operate the gear pedal, the drum clicks round and this rotation moves the selector forks up and down the drum. The other end of the selector fork sits in a groove on the gear pinions and this moves the gears sliding them up and down their shafts. Obviously, if the selector forks are bent or are nor seated in the selector drum properly, the gears do not slide into their intended positions, do not mesh correctly and this is where false neutrals come from. BUT it could be down to the pawl mechanism that rotates the drum, which is easier to get at. Is the clutch cable adjusted correctly? Always check the easy stuff first.

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Well it tops everything off really. My bike got stolen around 3 weeks or so ago, luckily got it back but had to sort the ignition and steering lock luckily no other damage. Finally done that and now this. Clutch feels exactly the same however I'll give it a little tweak and hopefully that helps failing that I'm guessing a trip to the garage as that's a bit of a big job for me. Thank you for your help! Jack

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Well it tops everything off really. My bike got stolen around 3 weeks or so ago, luckily got it back but had to sort the ignition and steering lock luckily no other damage. Finally done that and now this. Clutch feels exactly the same however I'll give it a little tweak and hopefully that helps failing that I'm guessing a trip to the garage as that's a bit of a big job for me. Thank you for your help! Jack

 

"Luckily no other damage" Errr , apart from the gearbox being viciously stomped up and down acompanied by horrible crunching noises . Unfortunately the catchy slogan "Ride it like you stole it " also applies to the scum who actually steal bikes . Sorry to paint a gloomy picture but there's a possibility that the teeth and dogs ( locating pins ) have had a proper battering which might explain why it is momentarily slipping out of gear.

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Well it tops everything off really. My bike got stolen around 3 weeks or so ago, luckily got it back but had to sort the ignition and steering lock luckily no other damage. Finally done that and now this. Clutch feels exactly the same however I'll give it a little tweak and hopefully that helps failing that I'm guessing a trip to the garage as that's a bit of a big job for me. Thank you for your help! Jack

 

"Luckily no other damage" Errr , apart from the gearbox being viciously stomped up and down acompanied by horrible crunching noises . Unfortunately the catchy slogan "Ride it like you stole it " also applies to the scum who actually steal bikes . Sorry to paint a gloomy picture but there's a possibility that the teeth and dogs ( locating pins ) have had a proper battering which might explain why it is momentarily slipping out of gear.

 

I thought that but they didnt even have it for 24 hours and they only did 12 miles so I'm hoping that isn't the case. Took a hell of a lot of help off social media and a few mates but we got it back.


Was fine up until the curb that day and that was a ride out from hull to squires cafe then back after about a hour or so (changed oil that day before the journey) was fine all the way there and back until about 25 minutes before the end

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Is there any other things that you guys can think of for me to try?


Might as well try everything first to eliminate it all.


Thinking a engine change would be my easiest option?

Probably cheapest? That's if everything else fails.


Local garages near me are charging £50-£70 a hour.


Not sure which route is best to go down.

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If the gear linkage is bent, that can play havoc with these bikes. How does it look?


I've known 3 of these little CBR's and I thought the gearbox was clunky but that's quite a typical Honda thing I've found.


If the selector drum is buggered, I don't think it's that big a job on this bike. Beyond basic ability, but something someone fairly competent could do with a Haynes manual and a good set of tools. I think I even have the Haynes manual lying around for this bike somewhere, I'm in the garage tonight so I'll look.

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Is the chain out of adjustment? Too tight can make gear changes play up.


Personally I think doing a full engine swap is a massive overkill :shock:

 

has the chain be readjustment since new sprockets etc ....

as you say it started to happen after a longish ride ...check simple things first .

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