Camshaft Top End Rattle

[TheCafeKid]

Def NOT cam walk... I hate to say it, and I know you just rebuilt that motor, but that sounds like a shelled conrod bearing to me... I have heard that jack-hammer sound out of more than a couple plain bearing GS motors now..

[tkent02]

This is not a plain bearing GS motor...
The noise goes away as RPM comes up?
Bad rods I have had got louder at higher RPM, although they were on car engines.
Did the cam caps stay bolted down correctly?
Someone had a similar noise on a 450 or something and it was one of the cam caps that had come loose.

[TheCafeKid]

This is not a plain bearing GS motor...
The noise goes away as RPM comes up?
Bad rods I have had got louder at higher RPM, although they were on car engines.
Did the cam caps stay bolted down correctly?
Someone had a similar noise on a 450 or something and it was one of the cam caps that had come loose.

It's a 650G or no?? Certainly sounds like slap. What in the hell could make sounds like that in the top end and not result in destruction? Sticking valve (s)? Broken springs? That sounds nasty. And like i said the only thing I've ever heard come out of a GS motor that sounds like that is a blown conrod bearing. But if it's not a plain bearing crank... Then I'm at a loss as much as anyone. Is it possible that the cam sprockets are taller and the chain is slapping the valve cover?

[Suzuki_Don]

Thanks guys for all the suggestions.

JOSH it is a roller crank, no shell bearings in this motor and all radial clearances were checked when the crank was out of the motor by a velocette specialist who regularly replaces roller bearings on cranks for customers.

From the suggestions made I now plan to check the following after removing the valve cover:

1. If any of the cam caps are loose. (Done & OK)
2. If there is any play in the cam bearings. (Can anyone give me instructions on which plastigage to buy and how to use it on the cam bearings). (OK I
think)
3. Check cam end float. (Done & OK)
4. Check valve shim clearances. (Done & OK)
5. Check if cam chain is slapping against valve cover. (Done & OK)
6. Check the number of links between arrows 2 and 3 on the cam sprockets (make sure cam timing is correct). (Done & OK)
7. Check if cam sprocket bolts are loose. (Done & OK)

Is there anything that I have forgotten? Is there anything else that I should check?

Thanks again fellas.

[BadBillyB]

Before taking parts off the motor, see if you can at least pinpoint the general area of the noise. I am a professional car mechanic and I use a very simple device to pinpoint noises. A 36" piece of steel brake line with a length of vacuum hose attached to one end. Stick the vacuum hose in your ear and bend the brake line into any shape needed to get to the source of the noise. The better you can narrow down where the noise is coming from, the better chances of finding it during disassembly....I listened to the video numerous times and cant quite put a finger on it. An old shop towel put in the exhaust pipe would have made it easier for me to focus on the noise.....Billy

[Suzuki_Don]

An old shop towel put in the exhaust pipe would have made it easier for me to focus on the noise.....Billy

Billy do you want to explain the shop towel in the exhaust principle please.

[TheCafeKid]

Billy do you want to explain the shop towel in the exhaust principle please.

It'll stuff up the exhaust noise so you can actually hear the motor spinning rather than all the clatter and noise coming through the pipes. It works quite well actually. Billy is right in that these noises bounce all around inside the cases. It makes it hard sometimes to pinpoint where it's coming from exactly. Using his suggestion, or a cheap mechs stethoscope or even a screwdriver (stick your ear to the handle, use the tip like a stethoscope) can aid in pinpointing where in the motor the racket is originating.

[blowerbike]

It'll stuff up the exhaust noise so you can actually hear the motor spinning rather than all the clatter and noise coming through the pipes. It works quite well actually. Billy is right in that these noises bounce all around inside the cases. It makes it hard sometimes to pinpoint where it's coming from exactly. Using his suggestion, or a cheap mechs stethoscope or even a screwdriver (stick your ear to the handle, use the tip like a stethoscope) can aid in pinpointing where in the motor the racket is originating.

hey!!
thats what i do but with an old towel..shop rags are handier though!

[TheCafeKid]

Just another thought... And I dunno so it's why I'm asking... Was there any difference in deck height on the Kat head than the G head? I didn't see... The only thing From a G in this motor are the cams?

Not too long ago someone was talking about using bits from a 700 motor (short stroke) in a 750 motor... Or vice versa. Seems to me that there would/could have been issues with that...depending on which way it went.. Conrods longer or shorter,etc. Smacking the head/valves... Dunno if that's how it worked or not... Just wondering if there are any sorts of possibilities of something like that?

[tkent02]

It's a 650G or no?? Certainly sounds like slap. What in the hell could make sounds like that in the top end and not result in destruction? Sticking valve (s)? Broken springs? That sounds nasty. And like i said the only thing I've ever heard come out of a GS motor that sounds like that is a blown conrod bearing. But if it's not a plain bearing crank... Then I'm at a loss as much as anyone. Is it possible that the cam sprockets are taller and the chain is slapping the valve cover?

It's a 650G top end on a 550E bottom, just like mine, only his is done and mine is still a pile of parts in the parts washer.

[Suzuki_Don]

Just another thought... And I dunno so it's why I'm asking... Was there any difference in deck height on the Kat head than the G head? I didn't see... The only thing From a G in this motor are the cams?

Not too long ago someone was talking about using bits from a 700 motor (short stroke) in a 750 motor... Or vice versa. Seems to me that there would/could have been issues with that...depending on which way it went.. Conrods longer or shorter,etc. Smacking the head/valves... Dunno if that's how it worked or not... Just wondering if there are any sorts of possibilities of something like that?

JOSH all the 650 cams are the same with the same Part#. Good thinking though. Keep them coming. I am wondering if this noise only appeared after I lost the tension on my cam chain tensioner when the knurled nut came loose and went for a walk down the road. Another reason why I want to have a look under the valve cover to check things out. make sure it hasn't jumped a tooth. Although it is pulling really strongly on the road and I think the performance would be OFF if it was a tooth out. Does it sound like a bent valve?

[blowerbike]

bent valve=dead/weak hole=lack of power.

[Suzuki_Don]

bent valve=dead/weak hole=lack of power.

Thanks BB. I should have thought about it a bit more before asking the question. An impromptu thing, you know, mouth in gear, brain having a rest; or fingers typing in my case. I've just added 2 more points to the list of things to check when the valve cover comes off; so now it is up to 7 things to check. Refer to page 2 of this thread.

[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.

[Suzuki_Don]

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.