EPP

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

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

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

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

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

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've had a lot of luck with ebay for pre-divvy parts. If you need a few things, find someone breaking a whole bike and negotiate a discount for bulk buying! They're sometimes just glad to get rid of it. Ewan

There's a few noises... One is the usual xj600 clutch rattle. I fabricated a replacement pin to reduce the play of of the oil pump drive gear on the back of the clutch basket (which is apparently a common cause) whilst I had the clutch apart to replace the friction plates and clutch springs. Unfortunately this didn't fix it. There also seems to be a rattle from deeper within the transmission mechanism. If you pull the clutch lever in, the clutch rattle goes - it's not the thrust bearing (it's in good condition), I reckon it's the pull rod rattling in it's housing, which goes when under load (from pulling the clutch). If you engage 1st, apply the brakes and release the clutch to biting point to load the engine, all the rattles go very quiet. However, all this seems to independent of the regular knocking noise that appears to come from the crankcase when the engine's hot. The bike's actually with a mechanic now! I demonstrated the noises and stressed it was the knocking noise I was interested in, as I reckoned I knew what was happening in the clutch. He wasn't sure, and I agreed for him to spend an hour looking into it. Phoned today, and all he's done is pull the clutch open again and confirm what I already knew about the pull rod. A total waste of money... The shop said a strip down and rebuild would be the only way to work it out. I'll have a look into getting all the parts together, although i really don't have the time for this at the mo! Already got the workshop manual and have skim read through all the steps. Cheers

Hi all, I am considering the possiblity of an engine rebuild on my XJ600. There's a regular knocking noise coming from (I think) the crankcase that's audible at tickover and even more so using a screwdriver as a 'stethoscope' pressed to the engine. The engine seems to run absuolutely fine, but I'd rather get this sorted before it fails properly. Where can i buy all the bearings/gaskets/etc that I'll need, or should I be giving up on this bike? Cheers! Ewan

Repaired the clutch, refilled the engine with oil and got the bike running today. No rattle!! So it looks like it was the cam chain. Unfortunately, a short way into the test ride I noticed a regular knocking sound coming from the engine, in time with the revs. Could be felt through the bike and heard at tickover, but not audible at higher revs (may just be drowned out). The knocking wasn't there when I first started the bike, only when it had got pretty warm. Got the bike home, and when I listened to the engine it sounded like it was coming from the cylinders (I just put my ear near - have since read about using a screwdriver as a stethascope to help locate the noise more accurately. I'll try this tomorrow). No idea if just one, or more, cylinders involved. I also noticed the engine was hotter than usual, or seemed to be anyway. I had already topped the oil up after running it for a few minutes to fill the filter etc, but it needed another 300-500ml on returning from the test ride, and a vapour rose from the crankcase when the cap was removed - definitely seemed hot! Could this just be the result of low oil? How much below the recommended level would cause overheating? And would overheating lead to the knocking noise? Cheers all, Ewan

I may be barking up the wrong tree entirely, but could it be well-known xj600 clutch rattle caused by the oil drive gear at the back of the clutch cage? Ewan

Yeah, I lined up the marks (I've got the later model that required you to line the C up with the mark on the crankcase). The manual didn't say to loosen the bolt to release the tensioner first - that's the vital bit of info I was missing. I had a hunch it might be necessary, thanks for confirming! I wonder if that will have fixed the rattle. Need to replace some bits of the clutch and refill with oil before I find out...

Valve clearances - fine Cam chain tension - well, it seems pretty tight to me. Can't imagine it slapping around. I've been tinkering with the cam chain adjuster, but I can't see how it changes the tension. It seems to operate as a lock screw for the spring mechanism rather than something that adjusts the tension directly. Am I missing something? I've replaced the dowel pin on the oil drive gear at the back of the clutch. Very little play there now, so hopefully that'll cure the clutch rattle. But seeing as I've not found anything wrong, the rattle that seems to come from the valves will presumably still be there. Any suggestions much appreciated! Ewan

I'll have a go with the redex - can't do any harm... Matty, I think my engine needs a similar amount of attention to yours on startup. Have taken it for a ride and checked the plugs - no fouling, so looks like the engine is breathing properly now as well. However, have now identified a rattling noise from the engine that I'm not happy with (see my other post). One day, I'm going to find out if I actually enjoy riding a motorcycle rather than just taking them apart

I'm getting there with my bike... Exhaust - done Starting - sorted (overhauled carbs, replaced caps and plugs) Brakes - bedding in So, I took it for a ride the other night and noticed the engine was making a kind of buzzing noise, or high frequency rattle, at about 3-4000 revs (I was bedding in the brakes so didn't get much above that). I've since had a listen with the bike in the drive, and it sounds like it's coming from the cam chain or the valves. Seems okay at tickover and just above (where the clutch rattle comes into play - but that's another story). If the engine is revved, the noise kicks in and then recedes as the revs drop. I'm going to adjust the cam chain tension first, then check the valve clearances and valve spring, as suggested in the manual. Bearing in mind the bike was stolen and most likely ragged about the local park before being recovered, what other things might I be looking for? Cheers, Ewan