EPP Posted March 30, 2009 Share Posted March 30, 2009 Hi all, I've been riding my xj600 for a while now, despite a tapping/light knocking noise that's impossible to locate! It isn't there when the engine is cold, but get louder as the engine warms up and can be felt through the bike. It doesn't get worse under load (back brake applied and slipping the clutch), which makes me think it isn't a connecting rod or main bearing. In fact, it might even improve under load (or the noise is just damped somehow). I've been using the 'screwdriver as a stethoscope' method (I think the neighbours are wondering what on earth I'm doing) and listening to various areas. Seems to be strongest around the exhaust valve area of the RH cylinder, but rather confusingly also seems to be quite strong around the top of the alternator cover. I've checked the valve clearances, which are spot on. What other parts of the valve assembly might lead to this kind of noise? I'm particularly interested in the fact it's only noisy when the engine's hot. The bike was stolen and ragged abut a local park before being recovered, so I reckon the engine has been over revved a bit... Cheers, Ewan Link to comment Share on other sites More sharing options...
tzr92 Posted March 30, 2009 Share Posted March 30, 2009 Hi all, I've been riding my xj600 for a while now, despite a tapping/light knocking noise that's impossible to locate! It isn't there when the engine is cold, but get louder as the engine warms up and can be felt through the bike. It doesn't get worse under load (back brake applied and slipping the clutch), which makes me think it isn't a connecting rod or main bearing. In fact, it might even improve under load (or the noise is just damped somehow). I've been using the 'screwdriver as a stethoscope' method (I think the neighbours are wondering what on earth I'm doing) and listening to various areas. Seems to be strongest around the exhaust valve area of the RH cylinder, but rather confusingly also seems to be quite strong around the top of the alternator cover. I've checked the valve clearances, which are spot on. What other parts of the valve assembly might lead to this kind of noise? I'm particularly interested in the fact it's only noisy when the engine's hot. The bike was stolen and ragged abut a local park before being recovered, so I reckon the engine has been over revved a bit... Cheers, Ewan It could be worn cams and rockers and cam journals. Which can be caused by not enough oil or poor quality oil. Have you checked for oil leaks or a lot of smoke coming out of your exhaust. I dont know your bike well but check that there are no oil lines blocked and the oil pump is working. If it is worn cams then expect to have a large bill as you will probably have to change the cam chain and cam followers. How old is your bike? Good luck anyway Link to comment Share on other sites More sharing options...
EPP Posted March 30, 2009 Author Share Posted March 30, 2009 It could be worn cams and rockers and cam journals. Which can be caused by not enough oil or poor quality oil. Have you checked for oil leaks or a lot of smoke coming out of your exhaust. I dont know your bike well but check that there are no oil lines blocked and the oil pump is working. If it is worn cams then expect to have a large bill as you will probably have to change the cam chain and cam followers. How old is your bike? Good luck anyway It's a 1990 model. Doesn't leak any oil that I can see, and the exhaust is clean. I've not been able to check the oil pressure, but it seeps out of the little bolt that you unscrew at the top of the cylinder to check oil is circulating up to the cylinder head. How would I check the oil lines? That's always been a mystery to me. I've had a look at the cams and there's no sign of wear (although I haven't checked with a micrometer), plus the clearances are fine. I'm wondering if it could be worn springs, or some other part of the valve train... If it's something I can fix myself then I'll probably do it. If it's going to cost a lot then I'll scrap the bike and get a new one Ewan Link to comment Share on other sites More sharing options...
fosdyke Posted March 30, 2009 Share Posted March 30, 2009 It's a 1990 model. Doesn't leak any oil that I can see, and the exhaust is clean. I've not been able to check the oil pressure, but it seeps out of the little bolt that you unscrew at the top of the cylinder to check oil is circulating up to the cylinder head. How would I check the oil lines? That's always been a mystery to me. I've had a look at the cams and there's no sign of wear (although I haven't checked with a micrometer), plus the clearances are fine. I'm wondering if it could be worn springs, or some other part of the valve train... If it's something I can fix myself then I'll probably do it. If it's going to cost a lot then I'll scrap the bike and get a new one Ewan Just a possibility here .......... check the final drive bearing you can do this by taking off the cover to give access to the front sprocket - check for play. Happened to my mates Divvy = new engine as the bearing is part of the drive shaft and costs about £180! Don't want to worry you - but is was just that you said it vibrated through the bike - which is what it did on my mates bike - and a failure is not only expensive but potentially lethal - imagine your back wheel locking up at 70mph as the bearing melts!!! Hope it's not that serious though. Link to comment Share on other sites More sharing options...
EPP Posted March 30, 2009 Author Share Posted March 30, 2009 Just a possibility here .......... check the final drive bearing you can do this by taking off the cover to give access to the front sprocket - check for play. Happened to my mates Divvy = new engine as the bearing is part of the drive shaft and costs about £180! Don't want to worry you - but is was just that you said it vibrated through the bike - which is what it did on my mates bike - and a failure is not only expensive but potentially lethal - imagine your back wheel locking up at 70mph as the bearing melts!!! Hope it's not that serious though. Thanks for letting me know about that. I'll certainly check it out! But I don't think it explains the current noise, as it occurs with the bike stationary, and is in time with the revs. Ewan Link to comment Share on other sites More sharing options...
JimR Posted March 31, 2009 Share Posted March 31, 2009 Hi all, I've been riding my xj600 for a while now, despite a tapping/light knocking noise that's impossible to locate! It isn't there when the engine is cold, but get louder as the engine warms up and can be felt through the bike. It doesn't get worse under load (back brake applied and slipping the clutch), which makes me think it isn't a connecting rod or main bearing. In fact, it might even improve under load (or the noise is just damped somehow). I've been using the 'screwdriver as a stethoscope' method (I think the neighbours are wondering what on earth I'm doing) and listening to various areas. Seems to be strongest around the exhaust valve area of the RH cylinder, but rather confusingly also seems to be quite strong around the top of the alternator cover. I've checked the valve clearances, which are spot on. What other parts of the valve assembly might lead to this kind of noise? I'm particularly interested in the fact it's only noisy when the engine's hot. The bike was stolen and ragged abut a local park before being recovered, so I reckon the engine has been over revved a bit... Cheers, Ewan I know it sounds silly but check the carb balance & mix strengh the noise you here from the alternator area is the hyvo chain flapping about and the knock from the top end is the cams moving slightly from the in balance of the carbs Regards Jim Link to comment Share on other sites More sharing options...
EPP Posted March 31, 2009 Author Share Posted March 31, 2009 I know it sounds silly but check the carb balance & mix strengh the noise you here from the alternator area is the hyvo chain flapping about and the knock from the top end is the cams moving slightly from the in balance of the carbs Regards Jim The hyvo chain is the cam chain - that right? I did adjust the tension a while back, which reduced a rattle I was getting. It was after I did this that I became aware of the knocking once the engine was warm. How do poorly balanced carbs lead to the cams moving, and what are they knocking against? The carbs have been dismantled and cleaned, but I didn't have the tools to balance them. When you say mix strength, is this the idle mix strength that's adjusted via the pilot screws? cheers Link to comment Share on other sites More sharing options...
JimR Posted March 31, 2009 Share Posted March 31, 2009 The hyvo chain is the cam chain - that right? I did adjust the tension a while back, which reduced a rattle I was getting. It was after I did this that I became aware of the knocking once the engine was warm. How do poorly balanced carbs lead to the cams moving, and what are they knocking against? The carbs have been dismantled and cleaned, but I didn't have the tools to balance them. When you say mix strength, is this the idle mix strength that's adjusted via the pilot screws? cheers Hi Ewan, The hyvo chain is the chain that links the crankshaft to the gearbox, When the motor was new (XJ550), this noise was prevalent and was cured using the above methods .... Get some vacuum guages, a small fuel tank to supply fuel while the main tank is off and a good screw driver (from memory the XJ600 didn't have YICS, XJ550 did for sure, but if it has you will need a YICS shutoff tool also). I do have all of these tools so it could be done. Method Valve Clearences Done Cam Chain Tension Done Start the motor and allow it to warm and run off choke Adjust the balance of the carbs cyl 1~2 then cyl 3~4 and lastly cyl 2~3 so the guages all read the same At this point most of the knocks will have disappeard, with fine tuning of the mixture screws (they will not be all the same) you should end up with a knock free engine Regards Jim Link to comment Share on other sites More sharing options...
EPP Posted April 1, 2009 Author Share Posted April 1, 2009 Hi Ewan, The hyvo chain is the chain that links the crankshaft to the gearbox, When the motor was new (XJ550), this noise was prevalent and was cured using the above methods .... Get some vacuum guages, a small fuel tank to supply fuel while the main tank is off and a good screw driver (from memory the XJ600 didn't have YICS, XJ550 did for sure, but if it has you will need a YICS shutoff tool also). I do have all of these tools so it could be done. Method Valve Clearences Done Cam Chain Tension Done Start the motor and allow it to warm and run off choke Adjust the balance of the carbs cyl 1~2 then cyl 3~4 and lastly cyl 2~3 so the guages all read the same At this point most of the knocks will have disappeard, with fine tuning of the mixture screws (they will not be all the same) you should end up with a knock free engine Regards Jim Cheers Jim, I'm going to have a go at balancing them and see if that cures things. Should the choke be on or off when the actual balancing is done? I'll be sure to post my results! Ewan Link to comment Share on other sites More sharing options...
yoda Posted April 1, 2009 Share Posted April 1, 2009 Cheers Jim, I'm going to have a go at balancing them and see if that cures things. Should the choke be on or off when the actual balancing is done? I'll be sure to post my results! Ewan Choke off, warm engine. If the knock will not go away and appears to be at the top of the engine, it is probably little end knock. Link to comment Share on other sites More sharing options...
EPP Posted April 1, 2009 Author Share Posted April 1, 2009 Choke off, warm engine. If the knock will not go away and appears to be at the top of the engine, it is probably little end knock. Yeah, I was wondering if it might be conrod knock. I've just been reading that one way of diagnosing this is to remove the plug cap from each cylinder in turn while the engine is running. The absence of combustion means the piston isn't forced down, so any free play doesn't cause as much (or any) knock. As long as it's mainly one cylinder contributing to the sound, this should isolate it. I'll be giving that a try once I get to work tomorrow morning and the engine's warm. Cheers, Ewan Link to comment Share on other sites More sharing options...
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