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GS500 - Cam lobe on exhaust cam damaged

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Ohmigosh, Apr 28, 2010.

  1. Hey guys

    I know computers but mechanical things have me at a loss. Can someone interpret this for me please?

    I had my bike's 1000k service done today and the fellows doing the service discovered a problem when checking the valve clearance. The note says...

    It is covered under warranty and they have ordered the parts that are needed and it won't cost me anything besides a bit of time to take the bike in and pick it up a later.

    I can ask them questions next time I go in but I want to understand the basics of the problem and what is buggered.

    Thanks and Fun Ha!


     
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  3. In general, your cam sits in the top of the cylinder head, and is rotated by a chain that is connected to the crank in the bottom of your engine. The crank is the bit that rotates, due to the pistons moving up and down.

    As the cam rotates, it has lumps (lobes) on it, that push against the valves in your cylinder head. The valves move in and out allowing fuel and air in to the engine, and exhaust gases out.

    These lobes have a hardened surface on them that is designed to protect them from wear through the use of oil as a lubricant. If something is rubbing on it, or it does not receive the oil like it is supposed to, it can generate more heat than it is supposed to do, and the hard coating can be worn and chipped away. Eventually you can end up with bits of it floating around in your engine, and if it wears to the point of getting down to the softer cam material, it can be quite damaging, and the valves that it is supposed to operate can stop working.

    The camshafts are the rotating parts right at the top with the lump on one side.

    4-Stroke-Engine.
     
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  4. Thanks VTRAffair. So the damaged one in my engine in the exhaust cam lob which is on the top left in your animated pic?

    What are the "shims" that are mentioned? I know that a shim is a small thin (metal?) thing that gets inserted into gaps but I can't connect it in my mind to the engine and cams. :-s

    Fun Ha!
     
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  5. The shims are used to ensure that the fitment between the cam lobe and the follower on the back of the valve is accurate.

    The shim sits between the valve stem and the bucket shaped follower (green in the animation) that is in contact with the cam lobe itself.

    If the gap is too small, or non-existant then the hard finish on the moving parts will be ground off.
     
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  6. Cheers Miraz

    I think I need to see it so I'll ask the service guys to keep the rubbish bits to show me what was going on.

    Fun Ha!
     
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  7. This might make it a bit clearer....

    The big things are the followers, the little buttons are shims that fit inside the follower, on the back of the valve stem.

    [​IMG]
     
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  8. Pictures good!!! [​IMG]
     
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  9. Does the GS500 have shims? I'm a little suprised by that. I would have thought it would be screw and locknut.

    Make sure you keep an eye on it as the warranty progresses. It may be there is inadequate lube in the top end or you may get a cam with similar case hardening, so it could happen again. You don't want to be mucking around with reground or new cams outside of warranty, because bike cams are stupidly dear.
     
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  10. hotcams time. dont laugh, megacycle make em for gs 500 race bikes
     
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  11. Yes GSs have shims, but they sit on top of the buckets rather than under them, so the cam lobe bears directly on the shim.
    I've got an '06 GS that has excessive wear on all the cams and I'm going to replace the camshafts soon.
     
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  12. Update: Suzuki rejected the warranty claim indicating that the problem did not need any rectification.

    Hills MC have noted in writing to Suzuki that they will have another look at the cams when the 6000 kilometre service rolls around and if further wear is noted then they will be following the claim up again with Suzuki.

    They have reasurred me that there should not be any problems over the next 5000 kilometre and I hope that is indeed the case.

    Fun Ha!
     
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  13. Did they tell you how much it had worn (had to shim)?
     
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  14. They did say that the problem would not be an issue for (probably) another 15,000-20,000 kilometres. From that I would assume the wearing was not that great.

    The verbal description of the problem to me when the service guys discovered it was was that the shims were not correctly in place and so the wearing occurred when the bike was started up the first time in the factory, which also settled them into the correct place.

    Fun Ha!
     
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  15. Something tells me you don't have a problem at all...

    I'm not suprised.
     
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  16. Yup

    I am happy the service guys took the time to go through the process though. Makes me feel very comfortable with them servicing teh bike in the future.

    Fun Ha!
     
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  17. Yes, good to see honest mechanics around and they should be commended for this.

    Quite a few years ago Suzuki GSXR750's had an issue with hard chrome coming off the cams, but Suzuki refused to do anything about it. I used to send the cams away for re-chroming which worked quite well. I still have a box full of re-chromed cams in my garage. It normally turns out to be the exhaust cams wearing first because they obviously run much hotter than the inlet, but the wear wasn't really excessive, and the old GSXR's had followers with adjustable screws and lock nuts. Suzuki also recommended setting valve clearances to max spec, obviously to increase lubrication between shim and cam or follower, but it also gave good increase in power as valves were snapped open quicker. Valve clearances usually decrease between services, not increase; with such high revving engines, the valves embed themselves deeper into the head therefore closing up the clearance, so it's a lesson to all motorcyclists to check valve clearances at specified intervals. Personally, I would prefer slightly noisier valves than quiet ones, just to be on the safe side.... and it goes without saying, use a good quality oil, there are many, but my preference is Belray....

    Sass
     
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  18. Unpaid shout-out:

    Hills Motorcycles

    (y)
     
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  19. I must say that I'm somewhat atonished by this mechanical issue; I had a 1961 Anglia damage the cam lobe, but that was British metalurgy and dodgy servicing!!!
     
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  20. Ahhh - Yes ye olde "use the skin off last night's custard" trick. :D
     
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