Some Input As to Restoring a GS500E

[kevink]

I am definitely kind of confused now when trying to piece together what I'm looking at with the PO's story. Was the sound he was hearing little bits of rocks getting turned around in the cylinder, and the death of his engine just a culmination of him not putting any oil in the bike the whole time he owned it? Apparently, when he tried firing it up after pulling to the freeway, it did run, but he turned it off because of some bad sound, and thereafter let it sit. But the bearing, despite looking obviously fried, still moves around okay, so if those bits of rocks were still in the cylinder after the fact, I don't understand why the sound would be any worse to warrant him not wanting to keep using it. I R relaly konfused.

[Trwhouse]

Hi again,
There were no "rocks" in this engine.
The gouges, as I said, were made by metal fragments that were grenaded into the metal on the piston crown and the cylinder head.
It was metal, broken pieces of metal from the engine bearing failure most likely, that did this.
Yours,
Trwhouse

[noiseguy]

  Yeesh. That type of piston / head damage is dirt common in 2-stroke bikes that grenade a piston.

What I'm not understanding is how bearing fragments could get into the combustion chamber, which on a 4-stroke is technically sealed from the bottom end. I think it's more likely those bits are parts of the piston that chipped off from a soft seize due to overheating.

That said, as long as the valve seats are OK (which is questionable) the rest of that stuff should clean up on the head.

It sounds like this is a learning experience for you on bike engines. More power to you; I've torn down my share of these too. I think a new engine would be the way to go on this economically, though.

[The Buddha]

OK wait ... a bad rod bearing will let the piston float ... a piston moving upward is actually getting shoved up by the other piston moving down, when the crank reaches TDC, its the bearing's job to get the rod to stop and start moving down. With a eaten up bearing, you can contact the piston into the head.

However ... I dunno for sure ... and what was the gasket doing ... OK it may have been the thing that made those metallic marks ...

I would rate teh pistons as dead, the head as a very likely dead, you deck it 5 thou and if the marks disappear, that is OK, beyond that you cant deck it without well ... you can but it starts to bump up compression and cam chain fit.

Anyway your head-piston contact can be due to rod bearing failure. Though both of mine were not that way.

Cool.
Buddha.

[noiseguy]

That scarring is on the edge of the combustion chamber. Unless the head is warped, I'd do a careful clean and polish of the scored area with emery cloth / file / knife / deburr tool / whatever, staying out of the gasket area, rather than decking the head down.

Just get the impacted chunks of piston out and flatten it up; pockmarks won't have a marked impact on performance. It will take a while by hand, but if time's not an issue then have at. Polish the rest of the combustion chamber while your at it.

The caveat is the valve seats; if the seats look like the rest of the head edge then the head's probably toast, unless you can grind a new seat.

....

You know, I'm looking back over the pics. I'm not convinced that the head / piston damage is related to the failure. There should be chunks of piston missing and I'm not seeing it. It looks like something (rock / screw / metal) fell into the intake, got chewed a bit and spit out. I think those pistons are probably salvagable with a clean up as above if the bearing surface isn't out of spec. It well may be.

Heck, the bore's far from perfect but I've seen worse in running engines.

I realize I'm not exactly advocating the highest quality rebuild, but I'd be tempted to clean and reuse some of those bits.

[The Buddha]

The size and bore of the GS head almost requires a deck even if its perfectly running and was opened up for no reason.
The decking is to promote gasket seal wihtout having to over torqued. Its just making it perfectly flat ... you're confusing it with milling the head. That is for performance, decking is for mating wiht gasket.

The piston IMHO will develop hot spots if its not nice and smooth, will make it detonate. I dunno if it can be polished, but I'd get new cos 20 bucks over the cost of rings is a full on wiseco set.

Cool.
Buddha.

[noiseguy]

Not sure if Kevin is even working on this anymore... 

OK, I looked around. A set of Suzuki OEM rings is $30 / piston. O/S OEM pistons with rings are around $75-100 / pc.

I can't find a Wiseco piston that will fit the GS500, much less one for $50 (or $20 over the set of rings.) Most Wiseco pistons seem to run more like $120 / pc for other bikes. And I haven't found another aftermarket one.

What am I missing?

[kevink]

Hah! I don't get intimidated  that quick! lol, Actually yeah, I was demoralized for a bit, but this is going to be my friends bike as much as mine so I've been conferring with him about what to do.  Plus, I have finals coming up next week too so I've been buried under a mountain of textbooks.

Well, today I dropped by a local motoshop with the parts to have a mechanic give me his impressions. He gave me a pretty quick and conclusive prognosis: needs to get rebored, new pistons, piston rings, bearings, and should check the valve seats. Basically..everything you guys have been talking about! I've just been trying to skimp it, but I don't think I can ignore dishing out the money anymore. I don't particularly want a smoker after a thousand miles either.

I've worked up the math:

Rebore: $80(ea.)x2 = $160
Check Valve Seats = $80
Piston Rings$31x2 = $62
Pistons $56(ea.)x2 = $112
Piston Pins & assorted = $40

Total ~= $450

That's on top of the crankshaft and rods which I already bought which were $12 and $25, and a gasket kit, which I'm hoping to get from ebay for $50. That's also assuming there's nothing wrong with the valves.

So....you all must be wondering what I'm planning on doing .  Well, I'll be looking for a used engine first, starting with craigslist and ebay, just as you folks suggested. I'll spend a little time with that, and if it happens I can't find one for a reasonable price below the $450, then I guess I'll buy the parts and build it up. In the end it'll still be cheaper than what you can find a decent GS500 around here for.

Btw Buddha, you mentioned some sort of Wiseco 550cc kit? Do you have a link for that? I tried browsing their website and scouring google but to no avail found any indication of existence of such a kit.

[noiseguy]

What's the $80 for checking the valve seats entail? You can remove the valves yourself and check this pretty easily.

Just my 2 cents: I can't see your bore and assess it by pics, but it doesn't look that bad. If you can get the bottom end to be solid, I'd do this:

Measure bores for tolerance and flex hone the bores to establish a new cross-hatch: $30 for the tool
New rings, pins if needed, $60-100
Inspect, clean up, balance and polish pistons: Free
Remove valves, inspect seats, clean valves and hand-lap seats if needed.
Clean up head, deck head if needed, new gaskets ($)

Throw it back together.

Worst case, let's say it runs but uses a bit of oil or smokes. Ride it a bit and see if you want to keep the bike, then fix it next winter if it really bothers you; the top end is a lot easier to get to. If things are in tolerance and not cracked, it shouldn't fail catastrophically, which is my main concern on engines for bikes.

Speaking of which, what's up with that clutch basket? Do they all look like that? It looks like a time bomb to me.

[The Buddha]

Wiseco 550 ... what ... I've never ... dgyver maybe ?

I am doing upper end on an xs650. Its got a drop in kit to take it to 750 ... rephase to a 277 degree crank and bingo.
Anyway, not me with the 550.
Cool.
Buddha.

[Trwhouse]

Yo Kevin,
Did you see this 2006 engine on ebay starting at $300?
12 hours to go, in NY state.
http://cgi.ebay.com/ebaymotors/05-SUZUKI-GS500-MOTORCYCLE-ENGINE_W0QQcmdZViewItemQQhashZitem4cec468988QQitemZ330381560200QQptZMotorcyclesQ5fPartsQ5fAccessories

[kml.krk]

it went for $300. someone got a great deal!!