Piston compatibility

[sulacet]

Hey guys. I did a search, but didn't see anything outright, so forgive me if this has been asked before.

My 79 GS425 broke down Monday, and was leaking oil from the exhaust. I finally got around to yanking the engine apart today, and was greeted by this:

So, my question: Are any other pistons compatible with my bike? I'm finding some 550 and 750 ones, but no 425 ones. The main one I'm looking at is here.http://www.ebay.com/itm/Suzuki-New-Piston-GS550-1977-1980-12111-47000-/281095821495?pt=Motorcycles_Parts_Accessories&fits=Year%3A1979%7CModel%3AGS550%7CMake%3ASuzuki&hash=item41729dd8b7&vxp=mtr

Thanks in advance for the help.

 

[rapidray]

OUCH!! The GS 450 piston is just an over bore for you. Ray.

 

[sulacet]

That's fair enough. Are there any compatible ones, or am I just sorta screwed until someone sells a 425 piston on Ebay?

Edit: I just found these, but I really don't trust ebay listings, so I'd like to be sure that these would actually fit my bike. http://www.ebay.com/itm/SUZUKI-GS-750-79-FIT-OTHER-YEARS-PISTONS-/120987037128?pt=Motorcycles_Parts_Accessories&fits=Model%3AGS425%7CMake%3ASuzuki&hash=item1c2b63adc8&vxp=mtr

 

[Agemax]

That's fair enough. Are there any compatible ones, or am I just sorta screwed until someone sells a 425 piston on Ebay?

i think what Ray meant was you can use 450 pistons in your motor, the liners would just need to be bored out to suit the bigger pistons

 

[sulacet]

Alright, cool. Sorry for the confusion, this is just my first time working on an anything engine. (You can see the Clymer manual in the background.)

Thanks so much for the help guys.

New question:

Is a shorter stroke (4.4 mm) going to impact the performance at all?

 

[Guest]

Yes. What little torque you have now would drop even more. Why the question?

 

[Guest]

Stock is 67mm bore , 66mm stroke

Your boring it up to 71mm if you use gs450 pistons so that means you need to take 4mm out of the liner to fit these pistons.

Now the only problem is: was the 425 a 16mm wrist pin or 18mm?

Well unfortunately its 16mm so you can't use the 71mm gs450 pistons.

Your first choice is: gs850 pistons @ 69mm. That's only a 1 mm increase on each side. Its barely an overbore so you should be fine.

Actually its only the second stock overbore.

Read this thread:
http://www.thegsresources.com/_forum/showthread.php?t=178368

Talk to droyce for what to do.