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Subject: 250 with Resonant rattle sound - Cam chain?
Posted by: Kristian, Sydney, Australia | Posted:
23/04/2010 |
Having gone over the electrics I have now got a new issue. A relatively loud resonating rattle that seems to come and go.
I can't seem to locate where it comes from as it is generally only heard while riding the bike. But it seems to amplify at certain revs as if there's some sort of natural frequency at play. It appears to come from the left side of the engine and quite often while downshifting before coming to a standstill. It seems to go away if I press the clutch so I'd say it's engine rather than gearbox.
Could it be that the cam chain has lost tension? |
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Replies To This Topic (Oldest First):
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| Posted by: Kristian, Sydney, Australia | 23/04/2010 |
I've done some reading and it seems likely that it is cam chain related. This could also explain the occasional powerlosses I experience if the valves slip out of sync slightly
From what I've been told the engine should now have about 37000 kms on it. Would it be likely that the chain is worn already?
I'm hoping for the tensioner and will have a look at that tomorrow. I understand they are hydraulic? I guess the oil lamp would come on if the oil pressure was too low to properly operate an otherwise functioning tensioner?
Ok, I'll hopefully know more tomorrow when I've looked at the tensioner! |
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| Posted by: Kristian, Sydney, Australia | 25/04/2010 |
Please disregard my hydraulic comments. It is obviously a spring operated tensioner!
I took it out and it seems to move freely enough (once I figured out I had to turn the screw at the spring to make it move in).
But I still can't quite work out exactly how this thing operates. It would seem that the only way the tension can be slackened is by turning that screw? I.e. the tensioner is only able to move in and maintain the tension as the chain lengthens and can never move back out? Or is there some thermal action in that spring, backing off the tension as the engine cools down? I've seen those manual tensioners designed to replace the automatic ones for high performance riding. Is it a good idea to fit one of these?
Assuming the chain tensioner is ok, could the rattle come from a worn outer bearing on the front sprocket shaft? I may have kept the drive chain a bit tight in my first months of owning the bike, potentially putting a bit of strain on that bearing....
Or could the rattle come from other internal components such as clutch basket, other bearings etc.? It only really comes when the engine starts to warm up....
But when it comes on it's so bad that I am concerned that I'm causing more damage by riding the bike.
Any tips on what it can be?
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| Posted by: Mike, Perth WA, Australia | 26/04/2010 |
G'day Kristian,
Unfortunately the silence of the web means that describing sounds for diagnostic purposes is a little difficult!
You are on the money, though, as to how the tensioner works. And they have a reputation for not working properly -- so it's wise to dismantle it and polish any parts (eg. the sliding rod) which may have become pitted or scored. Best solution of all is to get a manual tensioner from APE or some crew like that.
From what you say, I would incline away from thinking it's cam chain rattle, though. Perhaps it's the three bolts holding the starter clutch to the back of the alternator rotor? Pop off the left-hand side engine cover and see if anything's loose in there.
And yes, pull off the sprocket cover and see how things look in there. If you had a ruined output shaft bearing, I expect you would have oil leaking past the seal there too. I'd be more inclined to check if the sprocket nut was tight on the shaft.
It might also be an idea to drain your oil and see if you have any metal appearing in the oil.
All the best,
Mike. |
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| Posted by: Kristian, Sydney, Australia | 27/04/2010 |
Thanks Mike!
I thought I had gotten rid of the noise and changed the oil and filter on the weekend as it was due for a service. Stupidly I did not check for metal. The oil is now in a can with other waste oil.... I kept the used filter for a number reference - will see if I find any shawings there! But the oil looked really good in colour - still a dark nutty brown after 5000kms!
The bike went pretty well today, but the noise comes on again when the engine is fully warmed up (after 20-30 mins in traffic)! And particularly if I close the throttle and let it engine brake. Today I was not so convinced that it came from the left side...
I had the sprocket cover off and there was no sign of any oil leaks from the output shaft. There is a bit of backlash on this shaft, maybe 15 degrees? Does this sound normal? I might take that side cover off next weekend if I haven't figured it out by then! But I don't have gaskets - will it seal ok with that red stuff (RV-sealant?)?
I thought the cam chain tensioner seemed fine - certainly no stickyness! I used the screw to retract the rod again after installation. It goes back in again quite effortlessly.
I'll see if I can somehow record the noise while riding :) |
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| Posted by: fossie, mcr, United Kingdom | 27/04/2010 |
In your diagosis you mentioned 15 degree backlash , in all honesty 0 degrees is what was intended. Hence the bearing around the out put shaft.
Take the sproket off and check the side movement with chain off . There should be nil. Oil would not nessecarily get past this bearing even when goosed as it has a metal cover on both sides.
However the waterpump is also housed on the left side and would possibly sound worn as the water warms up. |
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| Posted by: Kristian, Sydney, Australia | 27/04/2010 |
What I call backlash is rotational (not sure if it's the correct term..). There is no sideways play.
Hmm, what's the life expectancy of the water pump? There is really no noise to speak of until the engine is thoroughly warm.
The bike performs really well at the moment. But that noise is a worry!
By the way Fossie, have you had any more of those air filter adaptors made up? I'm still interested! |
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| Posted by: johnr, preston, United Kingdom | 28/04/2010 |
| ok, lets get the basics done first. it has a rattle that goes away when you pull in the clutch? am i the only person here who reads that as clutch basket rattling? like the bigger kats do. before you start taking anything else to bits. are your carbs in perfect balance? cos out of balance carbs will cause a clutch basket to rattle its little head off if they are far enough out of synch. before searching for something as elusive as a random mechanical rattle, you need to make sure everything else is ok first |
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| Posted by: Kristian, Sydney, Australia | 29/04/2010 |
I can't really say that the noise goes away when I pull the clutch in. I tried it several times on the way home today and it doesn't even seem to affect the noise at all. But the comment about carb sync is an interesting one. I did synchronise them recently so they should be pretty good at idle. But then again, I don't hear the noise at idle, or when the bike stands still for that matter. However, the noise typically accompanies the down shifts before coming to a standstill at traffic lights (which leads me to think that it's gearbox or drivetrain related).
Back to the synchronising: I have fitted M2.5 washers at the needle jets to tweak these. I have noticed that it is technically possible for the washers to get stuck in the needle grooves, effectively moving the needle up half a notch if this happens. So if this has happened to one of the carbs than they would be out of sync but only when the slide is open. Will definitely check to make sure this is not the case. I assume the slides can stay open after the throttle is closed given high enough revs at engine braking? In support of this theory I have noticed an increase in fuel consumption that could coincide roughly with the emergence of the noise....
It would be great if the solution is this easy! But I somehow think there is more to it... Think I will have to pop that engine side cover soon! |
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| Posted by: rob, perth, Australia | 29/04/2010 |
| I dont know any thing about the 250's but I ounce had a 650 katana that when you geared down there was a rattle/vib that was the cam chain tensioner backing off , I used to be able to reach under carbs and touch the knurled nut and feel it moving when you touched it it stopped the noise , may be ths is you problem??. To rectify I set can chain tension as normal but the loosened the lock bolt and tightened it onto tensioner rod to lock it , It then wouldnt move in or out(locked) not how iy was intended but worked for me . good luck . Regards Rob |
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| Posted by: fossie, mcr, United Kingdom | 30/04/2010 |
I've haven'tforgotten you re filter adaptors , in fact I ordered them a couple of months ago.
He normally dosen't let me down, so I'll either get them sorted or try else where.
Sorry for delay. |
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| Posted by: johnr, preston, United Kingdom | 30/04/2010 |
| ahhh right, when you said "it seems to go away if i press the clutch" i thought that meant that it seemed to go away when you pressed the clutch!!!!!!!! |
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| Posted by: Kristian, Sydney, Australia | 02/05/2010 |
I did indeed say so :) I think what I meant was that if I pressed the clutch long enough for the engine to return to idle then it would go away.
Diagnostics running over such a long time get tricky as I'll most definitely forget things. I've probably done almost 500kms since the rattle started and it's gotten worse.
It is no longer a warm engine only phenomenon. When I left work on friday it was rattling from the first few metres of riding. But after 15-20kms the noise mysteriously went away and when I got home the engine was not making funny noises at all!
I think it must be the chain tensioner after all. It seemed fine when i inspected it, I was not able to push the rod in by putting weight on it. But maybe the vibrations in the engine are enough to make the mechanism slip a little, causing chain slack? Then I might stay at a set of traffic lights for a while, enough to let the tensioner tighten up the chain again. This time it might find better grip in the ratchet mechanism (That's how the tension is kept, isn't it? I assume it's not just that little spring holding the tension?) and work all the way home...?
They don't have a compatible tensioner listed at the APE dealer I found from google. I'll measure mine up and hopefully I can find something suitable on monday!
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| Posted by: Kristian, Sydney, Australia | 04/05/2010 |
Took some calculated risks today and loosened the tensioner by turning the screw with the engine running. It doesn't take much loosening before a rattle is heard (Much like pulling a chain over a metal edge I suppose). I'm pretty sure it's the rattle I hear when riding. I've been in touch with Serco (Australian agent for APE) and had them measure up the tensioners. It seems that the Hayabusa tensioner will fit the Katana. I will order one tomorrow for $105 plus shipping (How can they be so much more expensive than in the US!! http://store.valueweb.com/servlet/starrace/Detail?no=773).
Hopefully I'm right in my diagnosis... And hopefully the Hayabusa tensioner will fit! Anyone know if it definitely does? Hopefully it's not the chain itself that is shot. The noise is now heard in the following situations:
Accelerating in a certain lower rev range, provided throttle is applied only lightly
Roughly in the same range when throttle is let off carefully
If throttle is closed completely and engine braking (at most revs).
It does occasionally come up when downshifting into 2nd and 1st just before coming to a stop, even if the clutch is pressed in. I attribute this to the clutch design (there is obviously always some friction between the clutch plates).
What is actually causing this noise? Is the chain banging against some engine part in a way that is likely to chip off metal particles? Could it be that those plastic chain guides are worn beyond serviceable?
Guess I'll have to wait for that hopefully compatible tensioner and see! |
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| Posted by: Kristian, Sydney, Australia | 10/05/2010 |
Ok....
The APE ST1300GX tensioner fits the 250 Katana. Handy to know but unfortunately it didn't cure my rattle....
I set it with the engine running at a position juuust tight enough to make it go quiet at idle. I found that this corresponds to a bit tighter than the APE suggested approach, which is:
Tighten by hand until resistance is felt (while turning engine over with a spanner to make sure any slack is taken up). Then back out 1/4 of a turn.
When starting the bike after the APE approach there was a pretty loud rattle. But with the engine running I was able to hand tighten it until the rattle went away. I assume the stock tensioner would need to be this tight or it would also rattle with that on!
Well, apart from now having a flash looking blue anodized tensioner I guess nothing has changed... The rattle is mainly found in the area 4-5000RPM. So it's not normally heard at speed. Mainly when taking off and when coming to a stop.
Hmmm...
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| Posted by: Kristian, Sydney, Australia | 12/05/2010 |
My vague diagnostics must be getting annoying by now but guess what!
Going home from work on monday the bike was starting to feel better. Going into work again on tuesday it felt better still! More smooth and consistent and a bit more grunt I think. And wasn't that rattle getting a bit less obvious? Before leaving work yesterday I decided to tighten the tensioner a wee bit more (bit less than from edge up to flat up on the bolt, about 25 degrees). Pulling on to the road there was only a very slight rattle before shifting into 2nd. And that was about the last rattle I heard - no rattle at all this morning!
So it really was the cam chain! Strange how it took a bit of time to adjust to the new tensioner.... But I'm concerned that I've now set it too tight and that I really need to replace the cam chain to properly fix the problem. There is no "whirring" sound as far as I can tell but I'm wondering if it didn't have a tad more grunt before I made the final adjustment.. Bit early to conclude but at least I've nailed the noise!
Will keep investigating that tension! |
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| Posted by: Kristian, Sydney, Australia | 12/05/2010 |
New blog post:
Just checked the tension again with the engine running. My new setting as described in the last post is less than 1/4 turn beyond the point where audible rattling at idle stops. I was able to turn the screw a further 1/2 turn past my setting by hand with the engine running and I don't have particularly strong fingers!
Does this sound loose enough to avoid engine damage??? Does it sound about right in terms of tightness? Am about to take the bike on my longest trip yet, about 400kms each way. Don't want the engine breaking down on me half way.... |
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| Posted by: David, Guildford, United Kingdom | 12/05/2010 |
Hello Kristian.
I am afraid I don't have anything useful to help you in your diagnosis, but I would like to thank you, and other contributors, for giving such a good account and follow up to your problems. My bike produces a similar sound and I have been following this thread with interest.
David. |
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| Posted by: rob, perth, Australia | 15/05/2010 |
| If you over tighten the cam chain you will here a whinning noise when operated long before you gave enough tension to damage your timing chain |
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