hi i seached through every post just to see if this was a common problem to no avail.

right i have a 1999 cbr600 fx or f4 i have had it about 5 months everthing has been fine until last week when going to overtake a car in 4th gear it starts to accelarate for a second then revs with no accelaration for a sec or two then i hear a mechanical clunk sound and starts to accelarate again.its very hard to explain but i thought it was my chain at first which was loose but i have adjusted that and its still doing it only in 4th gear.

i dont know nothing about engines(only how to wreck them!)but do you think it could be a gear selector or gear cog worn or anything else?i know its impossible to tell over the internet but any ideas before i get ripped off by a garage?

to me what it sounds like is the gear selector is not holding the 4th gear cog in place and its able to move so its engaging at a slow speed and moving at a decent speed (but i dont know how a gearbox works)i have drained the oil to see if i could see any metallic fragments but it seems clean?

cheers for any input[sm=boohoo.gif]

 

does this happen all the time? sounds like what you hit is a false neutral. when shifting, you gots to do so with authority...like BAM...not just 'shift' but BAM...

 

[sm=funnypostabove.gif] You were probably going to do this anyway but I think it is a good idea to have the mechanic test ride your bike to see what he thinks, then see if you can fix it yourself. It cost me about 20$ to have him test ride it for 5-10 mins.

 

does this happen all the time? sounds like what you hit is a false neutral. when shifting, you gots to do so with authority...like BAM...not just 'shift' but BAM...

no its deffo in gear but it only does it in 4th

You were probably going to do this anyway but I think it is a good idea to have the mechanic test ride your bike to see what he thinks, then see if you can fix it yourself. It cost me about 20$ to have him test ride it for 5-10 mins.

yes i am but i'd just like to have an idea so he thinks i know what iam talking about

 

How high where the revs when this happened? You haven't hit the rev limiter have you?

 

If it was the rev limiter it would not have revved higher, it would have sounded like all holy hell breaking loose on two cylinders. I would have said that your clutches are worn out, but since it's only in 4th gear, I would guess that the teeth, or "dogs" as some manuals and many people call them, that engage the gears to each other have a tendency to round off if you aren't shifting fully into gear. Over time they will actually slip out from each other under heavy loads. Many folks overcome this by "undercutting" the gear dogs. This means they disassemble the transmission and cut each individual gear dogs with a special bit that cuts a reverse angle into them so that when they meet, they actually grip.

 

does that mean i cant buy new cogs or gear dogs or would they cost more than say a salvage gearbox or engine?

i,m coming round to thinking if the gearbox need taking apart to find whats up with it(which it probaly does)it might be quicker and cheaper to buy a salvage engine and brake mine.

i will take it to a mechanic to get some opinions just as sone as the rain stops in sunny england

 

How long have you had this bike?

Have you ever hit a false neutral before?

When you go for 4th gear right now what happens?

I've hit one false neutral on the f4 and it was because I didn't give it a good hard shift. I heard the clunking - grabbed the clutch and gave it a hard notch upwards... that fixed it

99% it's buttery smooth and just loading the clutch, preloading the shifter and click right in...

 

i have had the bike about 5 months

i have hit into neutral before

and when i go into 4th now if iam say doing 30mph it will run but pull the throttle it skips in and out of gear i have just took it to a mechanic and he reckons its the shift fork broken or bent he said hes done a couple looks like i have been to aggressive with the gears but the only way to tell is to strip the engine[:@]

 

hi, i have a 1999 900rr and sometimes if i dont shift hard, i get the same effect your talking about. i dont think its anything to do with your gears as much as it is with your shifting, i have the same problem sometimes. i am currently trying to find ways to fix this myself and if i find anything out ill make sure to post it. untill then, safe riding.