jsp Posted August 8, 2009 Report Share Posted August 8, 2009 My 300 rev 4 seems to have developed a slight rattle which i am informed by my riding mates, is the cam chain. is there any way to adjust it ? jsp Quote Link to comment Share on other sites More sharing options...
rlracer Posted August 8, 2009 Report Share Posted August 8, 2009 If it is your cam chain , on the right side of the motor ,on the back of the cylinder you will find a 10mm bolt, remove it and insert a small flat blade screw driver and push it in until light resistance is felt, reinstall bolt, done. Very easy to do. If that doesn't fix the sound it maybe time to run the valves. Now a rattle could be a broken tooth off the idler gear next to the kickstarter gear. Quote Link to comment Share on other sites More sharing options...
jsp Posted August 9, 2009 Author Report Share Posted August 9, 2009 when i remove the 10mm bolt is there a spring behind it ? and do use the screw to turn the screw or just push it in ? i think it is the cam chain as its a spradic rattle and not happening at the same time every stroke. but if not is there any other sympton to say its the idler gear jsp Quote Link to comment Share on other sites More sharing options...
rlracer Posted August 9, 2009 Report Share Posted August 9, 2009 Yes there is a small spring,,, Just use a small short screw driver i.e 1/8 x 3" there is NO screw inside just a plunger, you will be pushing again light pressure , you will hear it make a little click sound that is the plunger moving in the ratchet. If the bike has kick back or you wacked at the kickstart lever and then you hear a rattle there is a small chance you may have broke a tooth off. But first things first try what you think then move on. Feel free to P.M. me. If you can get your hands on the motor service manual it is very helpfull, Beta did a very good job of putting a lot of info in it. Quote Link to comment Share on other sites More sharing options...
nzralphy Posted August 9, 2009 Report Share Posted August 9, 2009 At low RPM some times the auto decompressor weight can rattle about - try increasing the idle speed to around 1200-1400 rpm Quote Link to comment Share on other sites More sharing options...
dgshannon Posted August 10, 2009 Report Share Posted August 10, 2009 "auto decompressor weight" Say what? Quote Link to comment Share on other sites More sharing options...
nzralphy Posted August 11, 2009 Report Share Posted August 11, 2009 The the 4T cam has a small weight that moves inward when revs are low/stopped. This weight holds open one exhaust valve to allow easy starting. Once running the weight is flung out of the way. AAAAAAnd explains why this won't be the noise explained.... sorry. Ralphy Quote Link to comment Share on other sites More sharing options...
dgshannon Posted August 11, 2009 Report Share Posted August 11, 2009 The the 4T cam has a small weight that moves inward when revs are low/stopped. This weight holds open one exhaust valve to allow easy starting. Once running the weight is flung out of the way. AAAAAAnd explains why this won't be the noise explained.... sorry.Ralphy I have serious doubts on that. Where did you come across this information? Quote Link to comment Share on other sites More sharing options...
nzralphy Posted August 11, 2009 Report Share Posted August 11, 2009 Err why the serious doubts??? strange! ..... i took appart my bike to replace a head gasget and there, on the cam, is the little weight system. It is also in the workshop manual. Quote Link to comment Share on other sites More sharing options...
stork955 Posted August 11, 2009 Report Share Posted August 11, 2009 Most modern 4 stroke singles have this system. Have a listen to a BMW F650, KLR, XR, CRF, DR, YZF, WR, RMZ, etc. In fact every modern Dirt bike I can think of... Most of them have a slight "rattle" at idle which is the weight not quite "swinging" out after decompression for starting. Very common. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
madmostin Posted March 21, 2016 Report Share Posted March 21, 2016 My bike yesterday seemed to develop the 'rattle' still ran fine. But I will investigate the cam chain and kickstart gear as the bike did kick back a good un Quote Link to comment Share on other sites More sharing options...
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