Camshaft Top End Rattle

[hampshirehog]

There should be an arrow on the top of the lower tensioner and the arrow should point in the direction of travel of the cam chain.

I'm with you on not following Tom's suggestion of running it without the cover on. I've done it and then spent the next week cleaning up.

[Nessism]

The taller cover is most likely related to the larger cam sprockets. I still say mark the scuff marks and go run the engine with the 550 cover to see if the contact is still occurring.

Don, in the photo of the lower tensioner the exhaust cam sprocket looks as if it's touching it. If not it's blo*dy close. Some of those tensioners are a good tight fit and some aren't so tight. Maybe the cam chain is pulling it over and it's getting knocked back by the exhaust sprocket. Worth checking you've got the arrow pointing the right way.

Wally, I checked the clearance on the cam sprockets and the lower rubber tensioner on the head and there is plenty of clearance. It is the picture being a bit deceptive. And the tensioner part is a really tight fit in the head.

Tonight I measured the depth of the 550 cam cover where the cam chain had been rubbing the aluminium away. I also have a later model 650 cam cover which I took measurements on as well. This later cam cover will not bolt onto my head as two of the bolt holes do not line up, but everything else on the cam cover is the same as the 550 cover.

I measured the depth with a vernier gauge from the surface of the cam cover where it meets the head to the portion inside the cover where the chain had been rubbing.



The 550 cam cover measured at about 45mm.



The 650 cam cover measured at about 49mm.

So it looks like there is about 4mm difference between the two cam covers. I know the 650G cams have 34 tooth sprockets compared to the 550 sprockets with 30 teeth, but I still think there is something to be gained by milling some material from the inside of the 550 cam cover to give extra clearance.

As a trial I intend to fit the 650 cam cover and gasket and see if the noise is still apparent with that setup. If the noise is still there then I have to look elsewhere. If it goes away I will be well on the way to fixing the problem.

The cam cover may leak a bit of oil out of the front left while I am riding the bike to warm it up, but I will have to live with that.

Oil will go everywhere, but if it makes the noise when the cover isn't there, you will know a few things the noise isn't caused by.

Tom do you have a spare rain coat or spray jacket I could borrow.
Thanks.

It's not supposed to rub on those guides all the time, they are there if/when the chain slaps around.

Thanks Ed. That is good to know.

[tkent02]

I was not game to run the motor with no cam cover in place, thought I would get covered in oil.

Oil will go everywhere, but if it makes the noise when the cover isn't there, you will know a few things the noise isn't caused by.

[Nessism]

It's not supposed to rub on those guides all the time, they are there if/when the chain slaps around.

Don, in the photo of the lower tensioner the exhaust cam sprocket looks as if it's touching it. If not it's blo*dy close. Some of those tensioners are a good tight fit and some aren't so tight. Maybe the cam chain is pulling it over and it's getting knocked back by the exhaust sprocket. Worth checking you've got the arrow pointing the right way.

Thanks wally, I will check that. Where is the arrow that you speak of.

Here is a better picture Wally. And I agree it does look close, I will have to check that when I get home from work. Well spotted.



Thanks

[hampshirehog]

Don, in the photo of the lower tensioner the exhaust cam sprocket looks as if it's touching it. If not it's blo*dy close. Some of those tensioners are a good tight fit and some aren't so tight. Maybe the cam chain is pulling it over and it's getting knocked back by the exhaust sprocket. Worth checking you've got the arrow pointing the right way.

Thanks guys for the replies. I have checked the cam timing and it seems to be spot on. The 650G motor has 34 tooth cam sprocket and the E model has 30 tooth cam sprocket. I am using 30 tooth cam sprockets. There must be more space under the 650 cam cover to fit the larger sprocket for the G application. I can't imagine they would have two different cam covers for the 650 engines.

A good idea to run the engine with two gaskets to see if the noise goes away, through supplying more clearance in there. Thanks Tom. I will also try some permanent marker on the section that is scored to see if it wears away as per Ed's suggestion. Thanks Ed.

I did fit a new camchain when I rebuilt the motor. There is no joining link, it is a one piece endless chain.

I ran out of time last night to check the shim clearances. Maybe tonight if I can sneak out of the house for 15 minutes.

Any suggestions about the fact that the cam chain does not run directly on the rubber thingo in the head between the two cam sprockets.

I was not game to run the motor with no cam cover in place, thought I would get covered in oil.

[tkent02]

A few random thoughts...

So this is a 550 cover, does the 650 cover have more space under it?

The sound is a Clank, Clank, Clank, rythmic sound, so the chain would have to have one spot going around hitting something? Bad link? Bent side plate? Master link peened too tight? If all the links were the same, they would all make noise, more like a constant chain rubbing swoosh noise as each link hits the same, instead of a clank? Your noise sounds like a bigger piece of metal than a chain link.

Is the sound once per rev or is it slower, like once every time the chain does a full lap around the sprockets? We have had a few bikes lately that made a click, click every time a spot on the chain went past the cam sprockets, we have not found why this happens. Did you use a new chain on this engine?

Does it make the sound if you run it without the valve cover installed?

If you slow the idle way down, what happens to the noise?

Could you, for test purposes only, run the engine with two or three valve cover gaskets to raise the cover up? You would have to leave the tach drive out, but it might tell you something.

Definitely check the valve clearances, cam timing and compression.

[Nessism]

Don,
Those marks on the cam cover could have occurred when the chain was loose, you might have to use some marking color on them and put the engine back together to find out if that contact is still occurring.

Might be a good ideal to check the valve clearances next, and check compression too so make sure there isn't a bent valve from the tensioner escapade.

I Think I Have Found the Problem

I think you are right Ian, the noise is constant and I think it is the cam chain rubbing against the cam cover. I used the screwdriver technique to isolate the noise before I took the video and in one of the early posts I said the noise was worse on the exhaust cam side of the top end than the inlet side. And the noise was right on the top end near the cams and sprockets and not lower down near the combustion chamber.

Anyway I removed the cam cover and found the cam chain appears to be running in contact with the inner section of the cam cover, more so on the exhaust side than the inlet side.

See pictures below.







This picture of the cam chain shows it not actually running on the lower rubber tensioner on the top of the head. Is this normal and does the corresponding rubber tensioner in the cam cover push the chain down onto the lower one in practice. JOSH did mention in an earlier post that the cam sprockets may be a bit higher than the original 550 sprockets. This looks like it could be the case.



So how do I fix the problem. Can I machine the chain tunnel out by 0.020" or so to give the clearance needed? I cannot go for a thicker gasket as that will alter the depth of mesh the tacho drive requires into the camshaft skew gear. Do I need to look around for a 650 cam cover. The one on the bike at present is off a 550 model. I was hoping to not advertise that it has a 650 top end on it. The 650 has different end caps on it.

Any suggestions guys.

I also checked the camshaft end float tonight and found that the exhaust cam has a clearance of 0.013" and the intake cam has a clearance of 0.016". Though I do not think this is the problem.

Another thing that I do not understand is how the motor was quite at idle when cold and yet develops this noise once it is thoroughly warmed up. Is the aluminium cam cover expanding towards the sprocket as it heats up and is the sprocket expanding towards the cam cover in the same way. Any other explanations.

Any suggestions greatfully taken on board. Maybe I have got it wrong, if so don't be shy. Does this condition I have found tally with the noise in the video.

[49er]

Hey Don, I had been only browsing lately and missed your post.

I have listened to your video clip, but can't quite put my finger on the cause of that sound. It certainly sounds different to the typical cam walk knock. Yours is very constant, suggesting that it's a part making contact with the cam cover, very loose shims, or even valves touching.

I had a look at that possibility on my spare 850 head. Both valves need to be around 3+ mm off their seats to make contact, so probably not the cause. I was thinking that you may have jumped a tooth on the exhaust cam when the tensioner failed. This would retard the exhaust opening but increase the overlap period. The valves would likely contact the piston crown before making contact with each other though.

Do as DD has suggested. Use a stethoscope to track down the exact area that the sound is coming from. I do the same, by using a large screw driver handle against my ear while contacting the tip against the engine. Either way will work well.

Good luck.