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Gear changing ranges on a Kawasaki GPX250R?

Discussion in 'New Riders and Riding Tips' at netrider.net.au started by pengo, Jan 3, 2011.

  1. Hey

    Just need some fine tuning on my gear change I think to get smooth gear changes, as at the moment I'm unsure if I'm changing into gear in the correct ranges. I do listen to the bike and think I'm changing at the right rev range, but I am unsure based on the sound the gearbox and clutch makes when the gear engages. Sometimess when I change gears it makes a "clunk" noise when the gearbox/clutch engages into gear and other times its quite silent. When it connects into gear silently it puts me off and I think I'm not in gear but then it obviously is as otherwise it would be in a false neutral I've encountered sometimes.

    Basically I just want to know for this bike, what sort of rev ranges should I be changing into the next gear up at? I find its power range is around 10k but it sounds really busy and loud when I'm sitting around there. Tho if I gear up and drop the revs to around 6-8k its a lot quieter and "calm" tho acceleration is lacking there.

    If anyone can provide some tips or advice that would be great. If it helps this bike maxes out at 15 and redline is from 13-15k.

    Might have another run on the bike this afternoon and experiment on some of the gear changes, and see where it makes the clunk sound when it kicks into gear and when its a lot quieter when it changes. I do think I'm changing gear way to high in the revs and the clunk sound isn't right but if I listen to the engine, it sounds like I should be reving a bit more before the change. So the sound the engine makes and then changing gear and what the gearbox makes is confusing (ie the clunk sound at the higher revs but engine sounds fine, vs no gear change "sound" but lower revs and engine sounds like its got more to give before changing).



    Well I hope I'm not too confusing :p
     
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  2. My ex did a billion kms on a ZZR250 (slight exageration) and the changes were best between 6k and 8k but it was happy to lug around town doing 4k so it all depends on how quickly you want to accellerate. They'll sit between 8 & 10k all day (if in good nick) but thats a bit high to be running through the gear box. A slack chain will make changes funny too so make sure thats adjusted right and chuck some fresh engine oil in it too so you have a baseline to work from.

    They're bullet proof if maintained.
     
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  3. When to shift depends on whether you're trying to accelerate as fast as possible, or ride as economically as possible (both in terms of engine wear and fuel consumption). For acceleration simply shift up whenever the engine hits peak power which is around 11,000rpm (revving to the redline achieves nothing).

    For economy you should shift up as early as is possible without the engine struggling in the higher gear. On the GPX the gap between 1st and 2nd is quite wide for some reason so whereas some 250s shift into 2nd easily at 20kph I've found the GPX really needs to be doing 30-40 which drops the engine to a happy 7k or so in 2nd, any lower than this and the engine tends to struggle. 3rd gear is usually good around 50-60kph, 4th gear for 70-80. The remaining three gears are only spaced apart by 1000rpm which in my opinion makes at least one of them redundant, but you can basically juggle between 4th, 5th and 6th out on the highway depending on the steepness of the road, headwinds, need to overtake etc.

    Finally, don't forget that bike gearboxes are meant to be shifted often, so focus less on what gear you're in and more on what rpm the engine is sitting on (either by feel or with the tacho). The GPX engine is happiest in the 6k-11k range so change gears whenever necessary to keep it there.
     
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  4. Thanks Jd thats exactly what I needed to know!

    What about the clunking or not clunking noise when I do gear changes? Is the clunking noise a sign I'm changing gears too high in the revs? I get this picture in my mind, the gearbox cogs are flying free really fast and then in snaps into gear really hard due to so high a rev, thus the noise. Where other times when its quieter, the cogs aren't spinning as fast or hard and so it is able to meet up the teeth of the cogs better. And so isn't so violent on the gearbox.

    Hope that makes sense.

    Also as far as 1st to 2nd I'm finding, when I change into 2nd the bike tends to lurch forward initally. Is this coz I've reved it a bit too much? I'll keep your advice in mind when I go out later to see if the change is smoother.
     
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  5. You referring to revving it before changing gears, or between changing gears with the clutch lever pulled in?

    As for the clunking that could be due to the chain being too loose, or could be due to not releasing the clutch lever smoothly enough. In either case the severity of the "clunk" would vary depending on the engine revs.
     
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  6. I'll accelerate, back off the throttle, grab the clutch lever fully, kick into gear, release the clutch and it tends to jerk forward. It really only does this from 1st to 2nd, I encounter this if I fail to get into 2nd right away. For example I'm stopped, then turning left or right and don't get into 2nd before turning. So the bike is revving pretty hard in first while I'm turning and then once I straighten up I change into 2nd and it lurches into 2nd.

    Should I be snapping the clutch or slowly releasing it when gearing up? I slowly release it when gearing down and found this to be excellent and does not result in the rear wheel locking up. Others say they "snap" the clutch but they are riding different bikes. When I say snap, its pretty much grab/release quickly - not slowly letting it out like when gearing down.

    Also the other night I found I had a weird habit of resting my hand on the clutch lever and the lever seems too tight/sensitive, that only a small amount of pressure on it the bike would slip out out of gear into a false neutral. I think I've made the lever come in too close to the handle bar, so thats its affecting how sensitive it is. Might have to let it out a bit more.
     
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  7. Sounds like you just need a bit more experience on the bike, and with gear changes in general. Don't worry, this is normal - everyone has to elarn sometime. Are you familiar with your clutch adjustment? It should have around 10mm of free play at the end of the lever before it starts taking up cable tension.

    If you are resting your hand on the clutch you need to remedy this but otherwise its just a learning process. 'Snapping' the clutch is generally as you are going up a gear and is done to get into the next egar as quickly as possible, thus letting you accelerate as quickly as possible. Slowly letting it out on downshifts is better for the reasons you have stated (ie not locking up) but even this can be done quickly given enough time and experience.

    Cheers - boingk
     
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  8. Yeah I need to remedy the hand on the clutch, at least I've identified it so now I can make a concerted effort to stop it.

    I only recently passed my Qride, but I think I've come a long way since then considering I've never riden a motorbike before then.

    Also been told u can "blip" the throttle and gear down without the use of the clutch too, but I'm not willing to do that use - fearful of locking up the wheel. I purposely locked the wheel up one time when practicing some stuff, just to see what its like. Didn't stack it or what not coz I was expecting it and only did it at a slow speed (as far as "slow" at 30-40 is).
     
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  9. How quick you can release the lever depends on what revs you're at - ie how much work the clutch needs to do to match the engine speed with the speed of the rear wheel. Given the large gap between 1st and 2nd on the GPX you need to be a little slower in releasing the clutch than with the higher gears.

    The point at which the clutch lever "bites" is easily changed with the threaded adjuster at the end of the lever. The recommended amount of free play is given in the owners manual, personally I just ignore this and set it to what feels right to me. You do need to be careful though in deviating from the recommended setting that you're not preventing the clutch from operating properly.
     
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  10. Thanks again guys you have been very helpful and its greatly appreciated.

    I found my experiences agree with what u say about 1st and 2nd and letting out the clutch. Might try slower release for 1st and 2nd. I've found snapping the clutch for other gears when gearing up not much of a problem at all.
     
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  11. Alright just got back from a few hours riding around the roads and then spent another hour in an industrial park, running a circuit to shift thru gears, slowdown, speedup, cornering etc...


    The clunk sound now seems to be really limited to 1st to 2nd, with it being more a "chookdonk" sound. My gear changes up to the other gears seems alot smoother now, with it either making a "clicking" sound into gear or actually no sound at all. Should I be worried that it is not making a sound when engaging into gear? Or does this mean I've hit the best spot for the gear change and the "clicking" sound mean I'm slightly outside of the "cherry" spot? I found the best way to change from 1st to 2nd was around 20-30, up near 40 it seemed too rev the bike out way to much and if I click into 2nd thats when it made the loudest "chook-donk" sound and bike also would try and leap out from under neath me the most.

    Started to get pretty good ripping around the industrial estate on one of the sweeping corners, nearly got my knee down lol. Scared me a bit when I scraped the ground with my toes, tho that just means I need to move my feet back further on the pegs.

    Thanks for your helpful advie guys, I just need to get 1st to 2nd sorted. It seems the most troublesome when I'm going up a hill, or coming out of a corner. After experimenting, I've found it best if I simply kick into 2nd as soon as possible from first thats best. Tho if I fail to get into 2nd in time before turning, i tend to really rev the guts out of the bike, and due to such a loud bike I get a bit "put off" and when I gear change I hesitate and its not as smooth so when the bike kicks into 2nd gear, it makes the "chookdonk" sound and lunges forward (nearly out from under neath me if it was an anymore powerful bike)... I adjusted the clutch lever and its much better now, I also tried to cause the gear to slip like it did prior by just resting my hand on the lever and it doesn't do it. So looks like I've got a good setup now on the bike. Just need to perfect 1st to 2nd.

    Also I found for all the other gears if I gear change just before 9k this seems to be best and does the smoothest change. With the bike not making much of a noise when changing gear.

    If someone can address my question about the loudness of the gear change (ie getting the "click" sound or not when i go into the next gear) if thats an indication of a "good" change or not, that would be much appreciated :)

    Thanks
     
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  12. The noises you're describing sound perfectly normal to me.

    As for the lunging on second gear it's possible that you might be leaning backwards slightly when you're shifting which is shifting weight off the front wheel and unsettling the bike. As your speed increases you tend to instinctively lean forward to counter the wind which would be why it's not a problem with higher gears.
     
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  13. Interesting, something I didn't think about. Will keep that in mind.
     
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  14. Thanks, my gpx maxes out at 15k, but most of that still applies as the manual also mentions not to downshift above 5k.
     
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  15. i don't ride a gpx, but my earlier experiences with the "clunk" you are having sound the same

    i would get a solid clunk every time engaging first gear, and then into second. didn't matter the revs.

    it was remedied by taking it back to the dealer, getting them to check and tighten the chain (which they did for free, it's only a 5 minute job for them).

    rode away with no more clunk!

    just remember to keep your chain lubed once adjusted and you'll be good.
     
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  16. Gear changes are much smoother now that I know what revs I should be in for the respective gears. Doesn't jerk or clunk as much anymore after the gear change.
     
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  17. i hope it is ok to add my question on this thread.

    my problem is not about shifting the gear from high to low. say i am on the third gear, i hold breaks in and slow down to,say 20kph, then at same time, change gear to second, then release slowly the clutch. however slowly i do, the bike always responds like it/we are pulled back by sth. the rev i noticed at that time is usually about 2k rpm. cos i am a learner and only practice in the residential zone, i have never rode beyond 55kph. dont really know where the problem is from...
     
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  18. I've been trying to work it out and I just can't. Pulled back by what?
     
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  19. Yeah im not sure either djay...

    Are you sure you are going third to second and not second to first? Engine braking in 2nd at 20kph hardly does a thing :) but even from 20ish kph and dropping to first can easily give you a big jerk forward like the bike wants to pitch you over the handlebars... That said, 2k rpm is barely over idle on an engine that redlines at 14-15k, and regardless of gear it shouldnt be so violent. If you are in a higher gear it might hop and shudder some as the engine struggles to keep running though!

    If it still seems to be pulling back some, dont be afraid to give the engine some revs as you release the clutch, which will smooth out the gear change. Once you get a feel for it, itll be nice and easy and smooth... and FAST! ;).
     
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