Scored Cam.....

[mpogue]

I decided to save money and do the whole pre-season maintenance myself. I've use a few of the great tips that I came across here, but from what I just found today, I need your help. I'm panicing.

When I was removing the valve cover, I found that one of the screws has a smaller thread. (pic 1 Sorry for being blurry) It looks like on a past tuneup, someone stripped the thread and decided to take a die to the screw to make the thread smaller and helicoil the camshaft holder. :? The thread isn't too great, actually it's rather pathetic. I'd like to fix it properly by changing the camshaft holder. Should I buy new or used? Can I just r&r a camshaft holder? What problems can I run into?

http://groups.msn.com/SuzukiGSGarage/mpogue.msnw?action=ShowPhoto&PhotoID=5025

As well, the valve cover gasket has this hard yellow stuff stuck to it. The manual says to put some 1207B Suzuki Bond on it to stick it to the valve cover and at the cam ends at assembly. Is silicon okay?

The really annoying thing I found was that the right two lobes on the front cam are scored. (pic 2) How bad is this? How much longer can I ride before I have to change the cam and valve rockers? I really don't have the money right now to fix it. From searching GS Resources, I found that a used cam seems the best way. I have noticed that Bike Bandit shows the cam as discontinued so new is out of the question. What are my options? Another set of cams maybe?

http://groups.msn.com/SuzukiGSGarage/mpogue.msnw?action=ShowPhoto&PhotoID=5023

Thanks in advance for any info on this. I figured I will need help from the group someday, but this is not what I was expecting

[Anonymous]

I'm assuming that the camshaft holder you are refering to is the the top half of the cam journal. Those are precision machined to the head. I'd fix it rather than get another. Get another screw (the right size - not that piece of tooled garbage) and put in a helicoil to fit. Why they cut that screw down is one of lifes great mysteries.

Used cams are the way to go, especially since you don't have mega bucks.

Can you feel the scoring with your fingernail? It's hard to tell how bad it is from a picture. Also, the worn part in the pic is on the cams base circle. Odd, since they should have a clearance at that point. What do the lobes look like? That's where cams usually wear.

[mpogue]

I'm assuming that the camshaft holder you are refering to is the the top half of the cam journal. Those are precision machined to the head. I'd fix it rather than get another. Get another screw (the right size - not that piece of tooled garbage) and put in a helicoil to fit. Why they cut that screw down is one of lifes great mysteries.

Used cams are the way to go, especially since you don't have mega bucks.

Can you feel the scoring with your fingernail? It's hard to tell how bad it is from a picture. Also, the worn part in the pic is on the cams base circle. Odd, since they should have a clearance at that point. What do the lobes look like? That's where cams usually wear.

If I was only able to get a good picture of the screw, you'd see how butchered it really is. Since I always took it to a mechanic for the tuneups and it's been to three different shops in its lifetime, I don't really know which to smack up side the head for the stupid fix.

If I get a used cam, will the existing camshaft holders be okay? From your first paragraph, the holder and journal are precision made to fit together. Will a used cam create any problem from wear?

Ya, I can feel it with my fingernail. It's what I would call pickup. (one piece of steel rubbing against another piece of steel. The harder piece ends up pickuping up deposits from the softer steel due to excessive friction) The lobes also have the scoring. The right lobe is worse than the left.

I was wondering, would lack of lubrication cause this? Should I be looking for a root cause? Where?

[Anonymous]

lobaphobia

remember that what is done to the cam is also done to the rocker surface that rides on the cam. If you get a different cam, also get a new or at least used rocker or you may just pass the score back and forth from old rocker to new cam and so forth like a disease. Ideally, get the rockers that ran on that particular cam and replace them in their correct positions.

[biker66]

3phase is right.

My guess is your followers have had it.
Remove the cam and check their surfaces. I believe you'll find very small, often square, pieces missing from their hard surface. In effect it's like flaking chrome, the edges cutting away on the cam lobes.

Change any worn follower and the exhaust cam and you're good to go.

If the valve cover screw does its job and keeps the cover in place it's not a problem, no need to fix.
I've done the same mod on a screw on my smaller bike as I didn't have a M7 Helicoil.

[mpogue]

I figured the two rockers were needing replacement. Not having to work on an engine at this level before makes me a little nervous.

The problem now will be trying to find a cam and rockers. Any searches I've done on the web have come up empty.

Looking at the job, is there any way to do it while the engine is in the bike or am I going to have to take it out?

[Anonymous]

If I was only able to get a good picture of the screw, you'd see how butchered it really is. Since I always took it to a mechanic for the tuneups and it's been to three different shops in its lifetime, I don't really know which to smack up side the head for the stupid fix.

If I get a used cam, will the existing camshaft holders be okay? From your first paragraph, the holder and journal are precision made to fit together. Will a used cam create any problem from wear?

That's why I do all my own work. You should also. Besides knowing it's done right, you will save lots and lots of money.

The bore for the camshaft is created with the cap in place, not separate. That is why I said they are precision fit. A used camshaft will work perfectly fine. As was ponted out, get some used rockers also. Better yet, get the ones that come with the used cam and even better yet, mated to the same cam lobes.

Ya, I can feel it with my fingernail. It's what I would call pickup. (one piece of steel rubbing against another piece of steel. The harder piece ends up pickuping up deposits from the softer steel due to excessive friction) The lobes also have the scoring. The right lobe is worse than the left.

I was wondering, would lack of lubrication cause this? Should I be looking for a root cause? Where?

If you can feel it the cams are going fast. They have a hardened surface. Once that wears away they are not long for this earth.

[Anonymous]

If the backside of the cam is scored, it is because the valve clearances were too tight.

You should be able to use a fine 600 grit with a little light oil and burnish the backside of the cam. Keep in mind that this part of the cam should not touch anyway as the cam turns - provided your clearance is proper.

What is more important is the peak and sides of the lobe. Are they smooth? Are they cracked or chipped (metal fatigue). Any bluing?

If you cam looks good on the lobe. Burnish the backside and run a synthetic oil. Mobil 1 works quite well. Why - because I tightened my valves too much and scored the backside of my cams. I cleaned up the back side with 400 - 600 grit then I used crocus cloth on the lobes very lightly. Then reset the clearances and ran synthetic. 1000 miles later I pulled the valve cover off - the cams were the smoothest you ever saw.

...BUT make sure the coating on your rockers is not worn through. It does protect the cam lobes and is needed regardless of the quality oil used. - Dieter

[mpogue]

If the backside of the cam is scored, it is because the valve clearances were too tight.

You should be able to use a fine 600 grit with a little light oil and burnish the backside of the cam. Keep in mind that this part of the cam should not touch anyway as the cam turns - provided your clearance is proper.

What is more important is the peak and sides of the lobe. Are they smooth? Are they cracked or chipped (metal fatigue). Any bluing?

If you cam looks good on the lobe. Burnish the backside and run a synthetic oil. Mobil 1 works quite well. Why - because I tightened my valves too much and scored the backside of my cams. I cleaned up the back side with 400 - 600 grit then I used crocus cloth on the lobes very lightly. Then reset the clearances and ran synthetic. 1000 miles later I pulled the valve cover off - the cams were the smoothest you ever saw.

...BUT make sure the coating on your rockers is not worn through. It does protect the cam lobes and is needed regardless of the quality oil used. - Dieter

Looking at the inner lobe, the scoring is around the peak and sides. I haven't tried to turn the engine over yet. I can't see the peak on the outside lobe, but it has more scoring than the inner. There is no bluing or chipping from what I can see. It's hard to tell if theres cracks.

This is kinda what I said earlier about it looking like pickup. If I'm able to remove it from the cam, then thats pickup. Now the problem is the rockers, I'd suspect them to be bad.

Tony, did you clean up the cam with it out of the enine or in?