Exhaust cam-train damage. Why?

[MrZig]

Why do I deserve this? Ugh. I hate this bike now.

Look what both my exhaust cams look like:



This is how both my intakes look like:



Why are my exhaust cams so screwed up? There's a ridge on the lobe that is quite feelable by finger, and they've dug a valley in the rockers.

The only thing I can think that would do this is bad valve clearance, but theyre both OK from how Haynes says to do it. What would cause this?

[Steve]

I'll take a wild stab at this and ask you "are you using the correct Haynes manual?"

If memory serves me correctly, the '78 GS400 was a four-valve engine (two valves for each of the two cylinders) and the '82 GSX400 was an eight-valve engine (four valves for each of the two cylinders). They have different clearances. The valve clearance specs for the earlier two valve per cylinder engine are .03-.08mm, but the specs for the later four valve per cylinder engines are .09-.13mm. If you happen to have the valves at the tighter specs, it is conceivable that the lobes have just been running too tight for too long and have not allowed the normal oil film to protect them. This would result in the wear that you are seeing. Looks to me like you need new camshafts. Those appear to be beyond rescuing.

.

[MrZig]

I'll take a wild stab at this and ask you "are you using the correct Haynes manual?"

If memory serves me correctly, the '78 GS400 was a four-valve engine (two valves for each of the two cylinders) and the '82 GSX400 was an eight-valve engine (four valves for each of the two cylinders). They have different clearances. The valve clearance specs for the earlier two valve per cylinder engine are .03-.08mm, but the specs for the later four valve per cylinder engines are .09-.13mm. If you happen to have the valves at the tighter specs, it is conceivable that the lobes have just been running too tight for too long and have not allowed the normal oil film to protect them. This would result in the wear that you are seeing. Looks to me like you need new camshafts. Those appear to be beyond rescuing.

.

I'm using the Haynes for the GSX400, so the correct one and the correct specs, yup.

I don't think the clearances were THAT out of wack, and 700 km ago the cams didn't look anything like this. I did adjust the valves, but I'm wondering if I did them wrong? I aligned the "T" timing mark up and made sure the notches on the camshafts were pointed paralell to the gasket surface, and yet opposite of eachother, and adjusted the left exhaust valves. Thing is, when this is all set up perfectly, I noticed that the right exhaust lobe is putting pressure on the rocker arm. When I turn the engine over 180 degrees to do the right exhaust lobe, neither exhaust lobes are putting pressure on any rockers.

If I keep it in that position (no pressure on any rockers) and check the left's specs again, they seem too tight. Problem?

[posplayr]

I'm guessing those exhaust tappets are like those on the 16V GS750E (80-81), The have a divide between the left and right exhaust tappets. There will be a little carbon buildup on the cam lobes, but the deep gouge on tappet is factory casting.

Why they did this I would not know. The GS1100E's have full pads on both intake and exhaust like your intakes.

[posplayr]

see some pics here

http://www.thegsresources.com/_forum/showpost.php?p=1081217&postcount=1

[gearhead13]

Ya, what he says. They dont look too bad to me, I would be more worried about the reddish sediment. How aften do you change your oil?
If thats the base circle showing on the cams, then your clearance is too tight, the cam should not touch the follower on the base circle.

[76FJ55]

It looks to mee like the exhaust cam is o the lobe so I don't think the lack of gap is necessarily a concern in that picture. It does look to me as though this engine either sat for an extended time or sat with the valve cover off as it appears to have surface rust showing up on the valve spring caps, on the cams and on the lifters. I don't know that it is cause for concern at this point though. the exhaus rocker are came from Suzuki with the center line groove so I don't think you should wory about it. Re chech your valve clearance between the adjusting bolt and the top of the valve stem and re-adjust iff necessary and close it up.

[posplayr]

It looks to mee like the exhaust cam is o the lobe so I don't think the lack of gap is necessarily a concern in that picture. It does look to me as though this engine either sat for an extended time or sat with the valve cover off as it appears to have surface rust showing up on the valve spring caps, on the cams and on the lifters. I don't know that it is cause for concern at this point though. the exhaus rocker are came from Suzuki with the center line groove so I don't think you should wory about it. Re chech your valve clearance between the adjusting bolt and the top of the valve stem and re-adjust iff necessary and close it up.

Rust tends to generally turns out very bright in a dark photo so I think most of that is just oil residue and carbon build up the motor actually looks pretty clean ; agree set valves with cold engine; insure you properly enguage the cam gear and go.

[MrZig]

Okay it actually looks like everything is perfect in there. Whew, thanks for helping out guys, that's a piece of mind.

I think it had sat for awhile, as its a used engine I bought from a wrecker. Changed the oil as soon as I got it. Valve clearances are perfect set to the book. The 0.08mm fits in every one of them.

Time to run it!

[posplayr]

Okay it actually looks like everything is perfect in there. Whew, thanks for helping out guys, that's a piece of mind.

I think it had sat for awhile, as its a used engine I bought from a wrecker. Changed the oil as soon as I got it. Valve clearances are perfect set to the book. The 0.08mm fits in every one of them.

Time to run it!

If you bought it at a wrecker, I would drop the pan and clean the screen change oil and filter. Looks for any metal bits.

[MrZig]

If you bought it at a wrecker, I would drop the pan and clean the screen change oil and filter. Looks for any metal bits.

Already did. There was some dirt in the pan, and some small flakes but nothing to be concerned about. Cleaned the oil pump screen as well and it was clear.

The oil filter was also clean. I'm guessing the small flakes I saw in the pan were normal wear/from break-in. I don't know if the pan was ever off before.

It was NOTHING like this: