Dinged up Piston help

[Tombstones81]

Well, seems when the exhaust valve broke, the bottom of it came loose too and dinged up the middle of the piston.

Not sure what to do.
Smooth it out and see if it runs good or just replace both pistons.

Also, around the bottom of the valves on the edges got dinged up a little bit too.





looks worse in the pic, pretty much only the inside got dinged up. (i wiped the area up a lil bit before taking a pic)
(wish I had the $ for that cylinder head that was on ebay for $20 bid like a week ago ><...)


(edit)
and just to be on the safe side.
I'm currently bidding on a used cylinder section of the motor and matching pistons from the same bike for pretty cheap if nobody else bids.
missed out on the cylinder head tho from the same bike 

[mitch79]

I see two options. Do it properly with new pistons, rings, head, rebore and hone.
For that money you could probably pick up a good running used engine.

Or just replace the valve and see how it goes. If it eventually dies you haven't spent much on it anyway.

[Kijona]

I agree. Just replace the valve and ride it until it blows up. That's the cheapest way and will probably get you a few more years with any luck. After that, you could buy a good running used motor. I see them on eBay for a few hundred bucks all the time.

Another option would be see if you can find a non-running GS and see if the motor is in good enough shape to use the parts off it.

[Tombstones81]

thanks.

and I would of been golden if I wasnt broke when the bidding ended on a cheap cylinder head...
Going to contact the ebay seller right now and make 100% sure if it sold or not.
as im bidding on the the cylinder and pistons from the same motor now

if i had all 3 pieces from the same motor, im pretty certain I wouldnt have any worries.

here is the seller if any of our parts whores did buy it off him (the cylinder head) and didnt necessarily NEED it.
http://myworld.ebay.com/starsandstripesllc/

think if I win the auctions for the cylinders and matching pistons, that a head from a different motor would be good to bolt on and go???

[Kijona]

thanks.

and I would of been golden if I wasnt broke when the bidding ended on a cheap cylinder head...
Going to contact the ebay seller right now and make 100% sure if it sold or not.
as im bidding on the the cylinder and pistons from the same motor now

if i had all 3 pieces from the same motor, im pretty certain I wouldnt have any worries.

here is the seller if any of our parts whores did buy it off him (the cylinder head) and didnt necessarily NEED it.
http://myworld.ebay.com/starsandstripesllc/

think if I win the auctions for the cylinders and matching pistons, that a head from a different motor would be good to bolt on and go???

Personally, I'd at least replace the piston rings. You can try without...but just to be safe I'd follow the break-in procedures just to see if it'll take.

Worst thing that will happen is low compression (rings too small for the new head), or you'll burn some oil after it re-breaks in.

[Funderb]

oh! check the valve guide too, make sure it isnt messed up too bad.
Sorry this happened to you!

The piston might be okay, unless the impact marks deform the whole crown, look on the interior side and see if any marks bulge through it. it will probably fail if that happens, otherwise, you'll just have a funky burn, but you aren't racing, i think, so you wont even notice.

[Kijona]

Tombstone, where are you in the US? Or the US at all?

[Tombstones81]

North east Pennsylvania

(edit)
tnx and haha u got more ppl near u then me.
only know One person in this entire area with a GS500 and not even sure if hes registered on here yet.

and this whole mess is my own dumb fault for cranking the engine multiple times.
I THOUGHT the problem was electrical....

so once again, I learn a lesson... The Hard Way! as always hahaha

[Kijona]

North east Pennsylvania

WHY IS EVERYONE SO FAR AWAY!? I'm down here in Atlanta, GA. I was gonna offer to help you with it.

[BaltimoreGS]

Have you added up the cost of all the parts and gaskets yet?  Sometimes a good used engine is cheaper than fixing your current one.  Do you ever make it to the Bedford, PA area?  There is a junk engine on my porch you can rob the pistons off of.  Since you already bought a valve you might as well rebuild what you have and hope it works.  Are there any scrapes in your cylinde walls that you can catch your finger nail in?  If not, you should be able to reuse what you have.  A light honing may be in order if the cross hatching is worn.  Is the seller guaranteeing the parts?  I got burned buying a used cylinder jug that had a vertical gouge in one of the cylinders that made it unusable with out over boring.

-Jessie

[Kijona]

North east Pennsylvania

(edit)
tnx and haha u got more ppl near u then me.
only know One person in this entire area with a GS500 and not even sure if hes registered on here yet.

and this whole mess is my own dumb fault for cranking the engine multiple times.
I THOUGHT the problem was electrical....

so once again, I learn a lesson... The Hard Way! as always hahaha

Who!? Nobody's responded to my post about people in ATL yet.

[Tombstones81]

Have you added up the cost of all the parts and gaskets yet?  Sometimes a good used engine is cheaper than fixing your current one.  Do you ever make it to the Bedford, PA area?  There is a junk engine on my porch you can rob the pistons off of.  Since you already bought a valve you might as well rebuild what you have and hope it works.  Are there any scrapes in your cylinde walls that you can catch your finger nail in?  If not, you should be able to reuse what you have.  A light honing may be in order if the cross hatching is worn.  Is the seller guaranteeing the parts?  I got burned buying a used cylinder jug that had a vertical gouge in one of the cylinders that made it unusable with out over boring.

-Jessie

wont be passing thru that area until spring or summer when I "now hopefully" ride my bike to my brothers in Pitt.
otherwise a bit far as im up right next to Scranton in the north east.

and the cylinder walls on mine look fine, checked em out earlier when I was taking more pics.
nothing stood out but I didnt sit there rubbing every nook and cranny yet.
yeah it can go with or without a light honing, can still see the marks but didnt take a ton of time seeing if it was smooth completely.

well, i already have a new valve bucket and the new exhaust valve is otw.

current bids on the cylinders and pistons (from the same motor)  will be about $50 total if nobody else bids (hope nobody does since I actually Need the parts vs someone lookin just to get something cheap)

and gasket set is like what $50?

Honing brush or whatever its called is like $20 if I dont have the local machine shop take 5 mins to do it for me.

and then about $75 shipped for 2 sets of new Piston rings.

am I missing anything?

[twinrat]

81 you could use that head and piston if you can get your valve to seat.Make sure there are no sharp edges on piston and head that could glow and cause hot spots ,and check for cracks in piston to .Have raced with heads and pistons in similar condition and even pistons that have been welded up  after holeing a piston .

[adidasguy]

Not to hijack the thread, ok, hijack.....
Are all jugs and pistons compatible (other than the emissions hole on the front between the exhaust pipes)? (and other than black .vs. silver)
Have engine on parts bike with compression of 90. Though of just getting jugs and pistons from a newer low mileage bike then fixing the ones on the 89 parts bike later. That way I'd have a running engine pretty quick.

Might help 81 if he needs a replacement piston - will any year be OK?

[Tombstones81]

not fluent with all the terms but by Jugs do u mean the whole cylinder assembly? the middle portion of the engine.

not sure whats compatible between older and newer parts.
which is why im trying to get a cylinder assembly and pistons from the same engine (a 90 to my 94)

[BaltimoreGS]

not fluent with all the terms but by Jugs do u mean the whole cylinder assembly? the middle portion of the engine.

not sure whats compatible between older and newer parts.
which is why im trying to get a cylinder assembly and pistons from the same engine (a 90 to my 94)

Jug is a dirt biker term for the middle part of the engine where the pistons go.  To fix ver4's bike we took the top end off his '92 and used the bottom end of a '96 I had that got water in one of the cylinders.  As far as I know, '89-00 engine parts are interchangeable (though color varies).  Check to see if different years use the same part number if you want to be safe. 

I have 2 sets of GS jugs at work that are good examples of ones that are not good to use as is, I'll snap some pics if I remember my camera.

-Jessie

[The Buddha]

No a dinged up piston will be a hot spot, and will cause detonation. I dont think you can smooth it and run it either, cast aluminum has a lot of problems, its got a memory, its got uneven strengths and could have stress cracks.
New or used undamaged pistons is the only way to go.
Cool.
Buddha.

[Dizzledan]

I've got a junk engine that had good compression before being torn down.
Pistons-good (dirty)
Jug- Good
Head- Bent valves (from cranking w/ incorrect timing like you) but gasket surfaces and guides are good

The pistons I haven't taken out yet, but considering you and Adidas are looking for some I may just go do that.
Tomb- let me know what parts you need
Adidas- you too

[sledge]

Stick with the devil you know 

This is gonna cost you time and money so you may as well do it right......Go for a 0.5mm rebore with oversize slugs and rings....Tolerances will be factory spec and you WONT have any unbalanced or mismatched parts shaking or wearing the rest of the engine to a premature death....

win...win...win 

I got one done 3-4 yrs ago....cost then was £100, thats about $150.....your call.

[adidasguy]

I've got that parts bike with poor compression. Parting it out except for the engine and carbs. Compression was 90 according to seller and 140-150 with oil in the cylinders. (Mileage is unknown.)

It is an 89 so I'd rather drop on new jugs and pistons then fix up the take-off's later as spares.
Haven't opened up the engine yet.
I do have 2 good heads and a gasket set.

So get busy and tear  that thing apart!