Big Bore Pistons are they available?

[mfleck]

  Is anyone out there than knows a piston that will still fit the gs500 for a big bore? I am aware of the option of the more powerful bike but am extremely farmiliar with this ones engne now. Please searching on the forum has only yielded discontinued priduct results. I fear tha I shall have to turn to shoeing in a dr 650 engine with a 785 cc kit to suit my mod addiction.

[xunedeinx]

The gs500 is all ready pretty much punched out to the max reliability wise. Its been done, it may be fun, but your results may vary.

If you do it, post pics!

[weedahoe]

My second GS had a bad engine and I looked and hunted and searched all over and found nothing useful. In the end, I replaced the engine as whole

[yamahonkawazuki]

My second GS had a bad engine and I looked and hunted and searched all over and found nothing useful. In the end, I replaced the engine as whole

IIRC wiseco USED to make them. i dont recall the product number though. im sorry

[werase643]

pistons would have to be custom made... send email to elmerc@ariaspistons.com

there are a couple places still.... expect them to make 4 as a min. run..... sooooo find a friend to go halvsies with you


speed is just a question of money..... how fast do you want to go?

[Steve146]

I have an 07 and am looking to replace the pistons and cam with a slightly upgraded version.

I'm not finding much in the way of aftermarket HC pistons so I find that Arias pistons will custom make a set in any bore or compression ratio.  If we can get a group of 4 there is a price break.  I am looking for a size of 74.5 mm with a CR of about 10.25-1.  They need a sample piston and if possible a head.  With the price break the piston set including rings, pins and clips is around $150 each.  (you need 2)

Megacycle cam will build a 384-70 cam  .380" lift  261°duration (stock is .345" 243°) for $299 per set and $35 for springs on your cores.  Because of the higher CR we need to be sure the valve relief cutouts are adequate.

Is anyone else interested?

[xunedeinx]

Honestly, 350ish for cams, 150 for pistons, 150-500 for boring, decking and cleaning. add in cost of all the bearings, seals, etcetc you looking at 1k for a few extra hp.

I can buy a ninja 650 twin longblock for 800, wiring harness for 30, fuel pump for 50, and borrow a friend for his mount making abilities for the cost of beer.

Probably wind up around the same price, and end up with 150+ more cc's, more hp and tq, fuel injection, reliability, and WTF? factor.

Why not spend that money on track days, its more use learning how to ride fast than making your ride fast.

[wera90ex]

The gs500 is all ready pretty much punched out to the max reliability wise. Its been done, it may be fun, but your results may vary.

If you do it, post pics!

The most you can bore the stock sleeve is 78mm, that should leave about .060" of sleeve. Still, you want to be VERY careful with the bottom of the sleeve. Don't ask me how I know.
I have one motor that's out to 83mm but it's sleeved.

[Steve146]

Honestly, 350ish for cams, 150 for pistons, 150-500 for boring, decking and cleaning. add in cost of all the bearings, seals, etcetc you looking at 1k for a few extra hp.

I can buy a ninja 650 twin longblock for 800, wiring harness for 30, fuel pump for 50, and borrow a friend for his mount making abilities for the cost of beer.

Probably wind up around the same price, and end up with 150+ more cc's, more hp and tq, fuel injection, reliability, and WTF? factor.

Why not spend that money on track days, its more use learning how to ride fast than making your ride fast.

Of course you are correct.

A quick look at the other Projects/Builds shows us that there aren't any ongoing projects such as I am considering.  Also that fact there are no off the shelf pistons or cams available indicates that there is no call for this sort of thing.  There's probably a good reason for that.

This is  probably because the basic GS design is hopelessly outdated and there isn't much capability for additional power.  I should listen to the voice of reason and forget the whole thing and just ride.

However, I think I'll go ahead anyway and be back here to report my findings when it's done.

[xunedeinx]

Post pics!

[OrTahor]

On the main topic of this thread :
While wiseco have changed the design of their GPZ1100 pistons (as evident in other threads), MTC Engineering makes 78mm( 10.5:1 CR) for the 1981-1982 GPZ1100 which I have been told will fit. I havent tried myself mainly due to being poor atm but a set of 4 pistons with rings and pins is about 550 USD. As I understand the design on the 1981 GPZ pistons is different than the 1984 and up models, and those are the ones that will fit our trustworthy GS.

If anyone has info on these, it would be much appreciated.