Bike overheated and now engine problems

[The Buddha]

If a valve, then a replacement top end from any year GS500 would fit. Not hard to replace a top end. Just be careful you separate the head from the jugs so you don't pull the jugs up and off of the pistons (pain to get the pistons back in).

A replacement top can be $100-$200. An hour or three to put it on. You do not have to remove the engine to do it.

No harm in removing the head to check it out. I'd do that before paying someone more than the cost of a replacement engine to repair it.

Adidasguy for the win....didn't even think about a head swap. That'll work perfectly.

Probably not.
A valve that has broke off and dropped in the cyl when the bike was running will have done lots of piston and rod bearing damage.
You wont know what damage till you yank that head off. Of course there is no reason a valve will break off without the bike running ... but if that was the case ... head swap all the way ... 
Cool.
Buddha.

[bombsquad83]

I don't think that it's gaurenteed to have done in the bottom end. I would take the head and jugs off and inspect everything. Test the piston rods and crank for unwanted play or physical damage.

[The Buddha]

You cant quite tell that rod and play business ...
However if you take off the head and find damage to the piston form the valve - your bottom end is dead.
If you find no damage to the piston - its pristine - just like the other one - the bottom end is fine

There is a huge grey area in the middle - it has damage but not so bad ... You will then have to figure out what you want to do.

Cool.
Buddha.

[nutmunk]

I would try a compression check on the cylinder...if a valve is just bent or burnt, it should still have some compression? As opposed to if it has broken off entirely where there will be no compression at all?

Watched the video...she doesn't sound like she's running on one only, so i'm guessing the valve is just damaged, not broken.

Correct me if i'm wrong here guys...

[bombsquad83]

I would try a compression check on the cylinder...if a valve is just bent or burnt, it should still have some compression? As opposed to if it has broken off entirely where there will be no compression at all?

Watched the video...she doesn't sound like she's running on one only, so i'm guessing the valve is just damaged, not broken.

Correct me if i'm wrong here guys...

Maybe, but it doesn't really matter at this point.  He already needs to take the head completely off and inspect it anyway.

[The Buddha]

I would try a compression check on the cylinder...if a valve is just bent or burnt, it should still have some compression? As opposed to if it has broken off entirely where there will be no compression at all?

Watched the video...she doesn't sound like she's running on one only, so i'm guessing the valve is just damaged, not broken.

Correct me if i'm wrong here guys...

Maybe, but it doesn't really matter at this point.  He already needs to take the head completely off and inspect it anyway.

If a valve bent will not run on that cyl.
If its broken, it will make a banging sound like you're hitting the piston with a hammer ... which you are.
If neither ... you may still ahve issues, but it aint one of those.
Cool.
Buddha.

[AlexT]

Thank for the conversation everyone, you have all given me hope. Also, shout out to Adidas for offering his insight.

After reading what everyone had to say, here are my plans for this weekend:

- Pull the spark plugs and try to do a visual inspection to see if there's a broken valve in the cylinder or any broken metal bits (Thanks for the concern, Buddha). I pray that there aren't. If there are, I can skip the next two bullets.

- Hold my breath and take the bike out for one final trip to get a second opinion from another recommended shop. See what he quotes.

- If I can afford it, I'll have the shop do the work.

- If not, I'll purchase this head: http://www.ebay.com/itm/2001-Gs500-Engine-Cylinder-Head-GS-500-GS500E-/221244839309?pt=Motorcycles_Parts_Accessories&hash=item338338558d&vxp=mtr and attempt to replace the head on my own. I found a pretty straightforward guide here: http://beergarage.com/GSHeadOff.aspx and BaltimoreGS has some pretty great videos that goes through head removal as well. I'll also have to purchase a Clymer manual off this site and some necessary tools.

Any guides that you can link me to or general bits of advice to give me would be greatly appreciated. I'll be around to give an update by this weekend!

[AlexT]

Update:

Pulled the spark plugs and took a peek inside. Shined a light in there and there didn't seem to be any metal bits of a valve laying in the cylinder but on the right side of my bike, I can actually see the edge of the exhaust valve. On the left side, I can't see the exhaust valve and on neither side can I see the intake valve. This makes me more confident that a valve just lost its seating when I overheated the bike.

Took it to two shops this weekend. The first ended up not actually being a repair shop but dealt more with vintage restorations. I asked anyways and he said that he could do it for me (kinda pricey) provided that I order and bring in a new head but at that point, I might as well get my hands dirty and do the project myself. I left my bike overnight at another shop and the owner told me that he didn't think I have a burnt/broken exhaust valve, saying that the head gasket should go first when an engine overheats and even if my valve burned, it should be quieter and not be making a rattling noise (). He wanted me to leave my bike there again for a few days and charge me $75 to diagnose to problem by checking for spark and doing a compression test. I graciously declined and took my bike back.

Now, I plan to tackle the problem on my own, having done a lot more research on my own. My next steps will be to take off the cylinder head tomorrow and gauge the damage. Depending on what I find, I may decide to move forward and buy a replacement head for the bike or sell it if there is damage the the lower end as well. Updates soon!

[bombsquad83]

You can probably see the valve just because that's where it is in the cycle.  The intakes are both closed and one exhaust valve is being pushed open by the cam.  Can't really tell anything from this, other than you don't have a valve completely broken off into the cylinder.

[AlexT]

Good point, I didn't realize that. I guess I'll just have to wait till the damn thing comes off to see whats wrong.

Here's a problem I ran into as I started today. The inside allen bolts on the exhaust heads are super rusty and rounded off as I tried to take them out... Anyone have any tips on getting it out? Vice grips don't quite fit but perhaps the pair I have is just too big.



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[bombsquad83]

Sometimes you can hammer in a similar size torx bit or slightly larger English size.  Vice grips would be good if you can reach it.

EDIT:  before you take the head off, did you ever do a compression test?

[AlexT]

I tried a torx bit but that rounded off as well. It's impossible to grab the bolts with anything other than the tip of the claws held vertically and there's not enough strength gripping the bolt in that case.

I never did a compression test, my reasoning being that once I got the head off, I could visually tell what the problems are. I could put the carbs and tank back on and buy a compression tester kit though. What are the benefits of doing that?

[bombsquad83]

Don't need the carbs for a compression test.  It will at least tell you if valves or rings are a problem to begin with.

[fetor56]

Good point, I didn't realize that. I guess I'll just have to wait till the damn thing comes off to see whats wrong.

Here's a problem I ran into as I started today. The inside allen bolts on the exhaust heads are super rusty and rounded off as I tried to take them out... Anyone have any tips on getting it out? Vice grips don't quite fit but perhaps the pair I have is just too big.

Get a Dremel or hacksaw blade & cut a slot in the top of the bolt.....use an impact driver with straight tip to remove bolt.
Save yourself huge headaches if u do this properly(removing front wheel/fork brace/guard)

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[The Buddha]

I drilled out that one, took the forks off and crouched in there with the bike strung up from the rafters of my friends shop. PITA.
You may be able to get an allen head socket inserted in there and welded as well as you can with the cyls wrapped with a wet towel ... so they dont burn ... cos you gonna be using a mig or stick welder ... and see if you can get it off that way. Easier than drilling IMHO.
Cool.
Buddha.

[Watevaman]

 Be careful with those bolts. If you break them you have to take the head off. Ask me how I know.

When you do get them out, I recommend putting studs back in their place (M8 x 1.25 I believe), so all you have are nuts on the ends.

[fetor56]

Part of the problem why these allen bolts get stripped is cos ppl use Imperial keys instead of Metric....their similar physically but NOT exact.

[nutmunk]

Alternative : for worn hex nuts I use easy-outs.  Bigger sizes fit nicely into the heads.

[Joolstacho]

Alex,  why not give it a try yourself. We all started out clueless, scared of making a stuff-up, but now many of us can do a complete engine reco. it's just about DOING it, that's how you learn... you'll find it really satisfying, and you'll save a load of dollars. There's an amazing amount of help and support on forums like this. Go fer it!

-J

Whoops, I mouthed off before reading the 2nd page of the thread... Anyway the point still stands, just want to encourage people to DIY. Motorbike mechanics are just like you and me, the only difference is that they've learnt about it and done it.

[nutmunk]

Part of the problem why these allen bolts get stripped is cos ppl use Imperial keys instead of Metric....their similar physically but NOT exact.

Or poor quality tools...had many a mate cry after taking a poor quality set of soft sockets or hex keys to their baby and end up stuffing up bolts. Their's a reason why name-brand tools cost a little extra.