kevhenson Posted May 17, 2009 Report Share Posted May 17, 2009 Hi all.. just brought a 06 which is really clean but has a fault... i know the gassers clutches all rattle and when you pull the lever it disappears... well on this one it doesnt... any ideas why??... it goes down by about half.... pull the lever and put it in gear and all is quiet and it pulls really well and all is quiet...... but... there just had to be one didnt there... if you come down a hill and back off the throttle with the clutch out there is only what i can describe as a loud noise that sounds just like the clutch but louder... put the power on at the bottom of the hill and all is quiet again... Help!!! does this one sound familiar to anyone or can someone point me in the right direction... and not to a dealers please thanks Quote Link to comment Share on other sites More sharing options...
markmaltby Posted May 22, 2009 Report Share Posted May 22, 2009 Could it be slack in the chain,i have just rebuilt my friends 2000 TXT and at sometime the chain has been so slack it has rubbed through the clutch slave cylinder housing and the only time i can see this happening is in the situation you describe i:e back wheel driving the engine. I hope this is of some use Mark Quote Link to comment Share on other sites More sharing options...
ian7 Posted May 22, 2009 Report Share Posted May 22, 2009 Hiya mate, I sort of have the same problem but am new to trials and bikes,my clutch noise on my 250 pro 2007 is doin my head in when its on tick over and then wack the clutch in,it goes,but the guy i got the bike from says you can get a bigger clutch resoivor and it should go do you or any one know if this is true if not what can i do to make it go or make it quiter? Quote Link to comment Share on other sites More sharing options...
kevhenson Posted May 23, 2009 Author Report Share Posted May 23, 2009 Could it be slack in the chain,i have just rebuilt my friends 2000 TXT and at sometime the chain has been so slack it has rubbed through the clutch slave cylinder housing and the only time i can see this happening is in the situation you describe i:e back wheel driving the engine.I hope this is of some use Mark Hi thanks mark... but sadly dont think its drive train noise.. its from within the engine... gonna have to pull it to bits once i get a flywheel puller Quote Link to comment Share on other sites More sharing options...
kevhenson Posted May 23, 2009 Author Report Share Posted May 23, 2009 (edited) Hiya mate,I sort of have the same problem but am new to trials and bikes,my clutch noise on my 250 pro 2007 is doin my head in when its on tick over and then wack the clutch in,it goes,but the guy i got the bike from says you can get a bigger clutch resoivor and it should go do you or any one know if this is true if not what can i do to make it go or make it quiter? Earplugs...lol.... but seriously they all sound like a bag of nails in neutral with the clutch out...so long as the noise goes when you pull the clutch in you really have nothing to worry about... even my 09 250 done it... just a gasser thing Edited May 23, 2009 by kevhenson Quote Link to comment Share on other sites More sharing options...
copemech Posted May 24, 2009 Report Share Posted May 24, 2009 I do not claim to be a gasser expert, yet I have listened to many of them and some just seem noisier than others even off new. My opinion on this may be off, yet I still think it may be mostly normal and in my mind I would still attribute it to primary gear rattle. Take up the slack by load an it is ok so all is well. Quote Link to comment Share on other sites More sharing options...
kevhenson Posted May 24, 2009 Author Report Share Posted May 24, 2009 I do not claim to be a gasser expert, yet I have listened to many of them and some just seem noisier than others even off new. My opinion on this may be off, yet I still think it may be mostly normal and in my mind I would still attribute it to primary gear rattle. Take up the slack by load an it is ok so all is well. Now im getting there... what causes the primary gear rattle? cos your right once everything is under load its fine... but once you back off the throttle on a descent it makes a right noise... similar to the clutch rattle but louder Quote Link to comment Share on other sites More sharing options...
copemech Posted May 26, 2009 Report Share Posted May 26, 2009 Now im getting there... what causes the primary gear rattle? cos your right once everything is under load its fine... but once you back off the throttle on a descent it makes a right noise... similar to the clutch rattle but louder Well, it would be due to excessive clearances and variences between the crankshaft drive gear and the clutch basket drive gear. I have no idea if this theory is totally correct, now exactly how one would fix it short of hopefully finding a better set? I am also unsure just how much research has been done on this issue? If I were going to inquire, I would seek out Factory Kev in the UK, as I cannot tell you more. Quote Link to comment Share on other sites More sharing options...
peterb Posted May 27, 2009 Report Share Posted May 27, 2009 Hi copemech, The clutch rattle on the Pro is due to the narrow, straight cut primary gears. Most motors have a wide primary gear and more so still, have a helical cut gear train which is generally very quiet. There is no fix for the gear rattle, just have to live with it. Bye, PeterB. Quote Link to comment Share on other sites More sharing options...
copemech Posted May 27, 2009 Report Share Posted May 27, 2009 Hi copemech,The clutch rattle on the Pro is due to the narrow, straight cut primary gears. Most motors have a wide primary gear and more so still, have a helical cut gear train which is generally very quiet. There is no fix for the gear rattle, just have to live with it. Bye, PeterB. Oh yes, Peter is very correct, and I have at some point examined these things up close. Contrary to popular belief, I usually try to steal a quick spin on a variety of new bikes every year. Yet in one instance I recall as example, one of the KS riders had a new 200 which I took about the venue. It was just horrid! Yet I have ridden others which seemed what I would consider quite acceptable by my poor set of averages and listening to other bikes. I am totally unsure other than the "what seems" given that some noise is just normal, if it can be reduced or not. No less, the bikes are good runners, so I don't knock them, as all seem to have their own quirks. Within all the brands there does seem to be some lack of response on various potential issues by the factories. Almost as though they do not understand, or do not want to? Quote Link to comment Share on other sites More sharing options...
jse Posted May 27, 2009 Report Share Posted May 27, 2009 Hi copemech,The clutch rattle on the Pro is due to the narrow, straight cut primary gears. Most motors have a wide primary gear and more so still, have a helical cut gear train which is generally very quiet. There is no fix for the gear rattle, just have to live with it. Bye, PeterB. I think Peter's got it. I'll try to do a quick-and-dirty, overslimplified technical answer as to gear design and function: There are basically two patterns in gear profiles, helical and straight-cut, and each has it's positive and negative points. Design Engineers will choose the pattern according to the gear's proposed use. Helical profile: nice and quiet (used a lot in various street bikes) as there is more than one tooth engaged with the corresponding gear it works with. If you look closely at engaged helical gears, you'll notice that in addition to the primary tooth contacting the corresponding gear tooth it works with, the teeth on either side of the primary tooth are partially contacting the teeth of the gears on either side of the corresponding gear tooth. The negative aspects of helical gears is that there is a lot of friction involved due, in part, to more surface area in contact. Another very big power robber is that the gear sets are always trying force each other apart sideways (they are like opposing screw drives, and exert a lot of side force) and the shaft bearings have to deal with a lot of pressure in two directions, up and down and left and right. Straight-cut profile: Good for transfering motion/energy with minumum power loss, but due to primarily one tooth at a time in contact (there is some secondary tooth contact) they can be noisey. As there is little side force, frictional losses are at a minumum and shaft bearings deal with mainly uni-directional pressures. The main reason the gears seem louder at idle (besides the exhaust audio pulses reduced) is that the crankshaft is not rotating at a constant rate. With the negative pressure on the crank pin (BTDC) caused by the piston compressing the fuel/air mixture, the crank is momentarially slowed down. With combustion pressure exerting positive force on the crank pin (ATDC), the crank is sped up. So you have the opposing pressures forcing the engaged teeth back and forth against each other, and at idle the pulses are farther apart (low RPM), which exacerbates the rattle. It's actually more complicated than my long-winded explanation (there are other minor factors to consider, but tooth design seems to be the major one from my experience), but I hope it made some sense. As Trials bikes are essentially full on competition motorcycles (and idling in neutral is a small part of their day), the design engineer's choice of putting up with a little rattle at idle to gain increased performance under competition conditions seems reasonable. The lightweight Pro engine, with it's lack of extra mass to absorb internal "noise" is more prone to the idle-rattle syndrome. When you pull in the clutch lever, frictional drag is introduced into the system, therefore the noise is lessened due to the damping effect on the contact/no-contact situation with the gear teeth. Jon, as usual, TMI..... Quote Link to comment Share on other sites More sharing options...
g14gav Posted May 27, 2009 Report Share Posted May 27, 2009 There is an engage idle kickstart sprocket in between the clutch basket and the kickstart half sprockit, if there is so much as a hairline scratch on this sprocket then they rattle and whine (noise your describing) like hell. 21 PI Quote Link to comment Share on other sites More sharing options...
copemech Posted May 28, 2009 Report Share Posted May 28, 2009 I think Peter's got it.I'll try to do a quick-and-dirty, overslimplified technical answer as to gear design and function: There are basically two patterns in gear profiles, helical and straight-cut, and each has it's positive and negative points. Design Engineers will choose the pattern according to the gear's proposed use. Helical profile: nice and quiet (used a lot in various street bikes) as there is more than one tooth engaged with the corresponding gear it works with. If you look closely at engaged helical gears, you'll notice that in addition to the primary tooth contacting the corresponding gear tooth it works with, the teeth on either side of the primary tooth are partially contacting the teeth of the gears on either side of the corresponding gear tooth. The negative aspects of helical gears is that there is a lot of friction involved due, in part, to more surface area in contact. Another very big power robber is that the gear sets are always trying force each other apart sideways (they are like opposing screw drives, and exert a lot of side force) and the shaft bearings have to deal with a lot of pressure in two directions, up and down and left and right. Straight-cut profile: Good for transfering motion/energy with minumum power loss, but due to primarily one tooth at a time in contact (there is some secondary tooth contact) they can be noisey. As there is little side force, frictional losses are at a minumum and shaft bearings deal with mainly uni-directional pressures. The main reason the gears seem louder at idle (besides the exhaust audio pulses reduced) is that the crankshaft is not rotating at a constant rate. With the negative pressure on the crank pin (BTDC) caused by the piston compressing the fuel/air mixture, the crank is momentarially slowed down. With combustion pressure exerting positive force on the crank pin (ATDC), the crank is sped up. So you have the opposing pressures forcing the engaged teeth back and forth against each other, and at idle the pulses are farther apart (low RPM), which exacerbates the rattle. It's actually more complicated than my long-winded explanation (there are other minor factors to consider, but tooth design seems to be the major one from my experience), but I hope it made some sense. As Trials bikes are essentially full on competition motorcycles (and idling in neutral is a small part of their day), the design engineer's choice of putting up with a little rattle at idle to gain increased performance under competition conditions seems reasonable. The lightweight Pro engine, with it's lack of extra mass to absorb internal "noise" is more prone to the idle-rattle syndrome. When you pull in the clutch lever, frictional drag is introduced into the system, therefore the noise is lessened due to the damping effect on the contact/no-contact situation with the gear teeth. Jon, as usual, TMI..... Jon, you are missing the point here I think. It just seems to me that some of these things just sound like a "Box 'o Rocks" as you ride them, and others do not! Oh, i agree with all that other crap(that I put much more basically) yet I cannot explain to anyone why there seems to be quite a bit of varience between some bikes? As with most anything, there seems to be a norm, and then both extremes. At what point does one consider the upper extreme abnormal? And what if anything can be done? In this instance, I do not have the answer and am not quite sure who does? Fact is, as we are not there, even quantifying this issue is difficult at best, yet we must rely upon the first hand info as given. And possibly he himself should get a better "feel" for the norm by riding other similar bikes? Quote Link to comment Share on other sites More sharing options...
kevhenson Posted May 29, 2009 Author Report Share Posted May 29, 2009 There is an engage idle kickstart sprocket in between the clutch basket and the kickstart half sprockit, if there is so much as a hairline scratch on this sprocket then they rattle and whine (noise your describing) like hell.21 PI Quote Link to comment Share on other sites More sharing options...
peterb Posted May 30, 2009 Report Share Posted May 30, 2009 Hi Jon, Thanks for the brief explanation, that's just what I was going to say! As for kevhenson's problem, it's not easy to define without listening. Usually, the kickstart idle gear creates a knocking noise when damaged (by a broken kickstart quadrant) but I don't know if these also produce a rumbling noise from being damaged, I don't think so - not sure. Clutch rumble from the primary gears does vary from bike to bike on the Pro's, I know the later bikes at least have supposed matched gear sets. Also, I found out from Mal in Oz that an awful gear whine noise that becomes apparrent when the bike is in gear and the clutch let out is attributed to slight damage on the primary gears - a new set is required to fix this. But this is a definate whine rather than a rumbling, the whine is in every gear and varies with engine speed, though not when in neutral. Ta ta, PeterB. Quote Link to comment Share on other sites More sharing options...
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