Advice fitting WISECO´s 78mm Piston! :cheers:

Started by Filipe_500, July 12, 2006, 09:30:05 PM

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Filipe_500

Hi guys!


As I said on the other topic i´ve posted, i´m rebuilding my engine.  I just brought a pair of new wiseco 78mm pistons and I notice the sleeve will be too thin if i just bore it to 78mm... I´m thinking about re-sleeve it with a 82mm- 83mm sleeve and bore it to 78mm...

Also, i would like some advise on other stuff that i might have problem with...  like balancing, etc... i dunno...

What kind of sleeve material you guys recommend?

My head is 0.7mm milled!!


ps: í´m planning to use it with a 38mm GSXR carb, (pic below), and a yoshimura exaust...

Thx a lot!

Filipe


Pics:








Lukewarm Wilson

You'll have to ask the racers about that one :dunno_white: :thumb: :cheers:
Experience enables you to recognise a mistake when you make it again

CirclesCenter

#2
Wow.

Fillipe, I'd love to help but you've gone outside of what I know.

I'll start reading and come back with some answers.

In the meantime.

BUMP.

BUMP until a mod shows up.

Oh wait, some easy ones.

Yes you'll have to rebalance, after all your engine has been through I think a balance is in order anyways.

Sleeve material.... I did some searching and it seems to be cast iron. Academic papers talk of Aluminum 390 alloy, but I'm thinking that it is just that, Academic.
Ah Chrome Molybendium steel seems to be the enthusiast's choice. I think that's what you want.
A big thing you'll want to think about with sleeving is heat transfer. I don't know if sleeving impedes that. Need to look into that.

You need to find two things.
1. A good Machinist. Let him work out what the sleeve's thickness should be.
2. A different mechanic. I can't say I would trust yours anymore.

To move those pistons I don't know if I would trust a brand new stock crank. Go aftermarket if possible.

You might want to run an oil cooler, it will help keep your bike happy with the extra power you are undoubtedly planning.


The more power you make, the more heat, with the new pistons, crank (rods too if you can afford them!), and sleeves you can make an incredible ammount of power. The only thing you'll have to fight with will be heat.
Rich, RIP.

Mandres

The best person to ask would be Dgyver.  I know he has some experience with oversized pistons / more aggressive cams / higher compression ratios.  Maybe try running a search on his name and see what comes up.

-M

Filipe_500

thx mates! I will see if Dgyver comes along and sort my problem!


:)


Can´t wait until I install them and kick some b6´s ass!

sledge

Circles???
Looks like its my turn to chastise you!!!
A question for you. You advise in this thread an aftermarket crank on the grounds you wouldnt trust it with what are essentially oversize pistions. Yet back in Rangerbrowns Turbo thread you agree with me in saying the crank is not the sturdiest but go on to state the crank has in fact been been proven in a NA race bike USING oversize pistons, and the pistons failed before the crank!!!!!......Dont believe me??? have a look back. Am I missing something? Have you overlooked something?  or is it just you not knowing what you are talking about???  :laugh: :laugh: :laugh: Fillipe? stick with cast iron my friend, there are no real advantages in using other materials for your application. Consult a good and I mean GOOD engine rebuild/reconditiong firm

sledge

#6
Fillipe?
Can I offer some more advice, try posting your questions in  an additional forum in addition to this one (link below). Whilst there are some very knowledgable and experienced individuals in this forum It pays to get second opinions from individuals in other forums.
http://www.eng-tips.com/threadminder.cfm?pid=668

dgyver

#7
Stock sleeves will work. The sleeves are tapered outside of the cylinder making it look too thin. The largest you can bore to is 79mm but the lower skirt get very thin and can crack if run too lean. I have one as proof. I have had one bored to 79mm (with a .002" piston/cylinder clearance) and it ran great but I had to sell the bike. One motor I have has 78mm pistons in it now.

Neither of these engines were rebalanced. The vibration was basically the same as stock. But then I only really run them above 8K.

Always used stock cranks, never had a problem.

Valve float will kill the engine before most everything else that would fail mechanically.
Common sense in not very common.

LimaXray

Quote from: sledge on July 14, 2006, 02:07:41 AM
Circles???
Looks like its my turn to chastise you!!!
A question for you. You advise in this thread an aftermarket crank on the grounds you wouldnt trust it with what are essentially oversize pistions. Yet back in Rangerbrowns Turbo thread you agree with me in saying the crank is not the sturdiest but go on to state the crank has in fact been been proven in a NA race bike USING oversize pistons, and the pistons failed before the crank!!!!!......Dont believe me??? have a look back. Am I missing something? Have you overlooked something?  or is it just you not knowing what you are talking about???  :laugh: :laugh: :laugh: Fillipe? stick with cast iron my friend, there are no real advantages in using other materials for your application. Consult a good and I mean GOOD engine rebuild/reconditiong firm

The guy with the GS with the 8-valve head had problems with breaking cranks IIRC.  The crank does seem to be the weak link here, but having said that, I doubt the stock crank will be a problem in this application. 
'05 GS500 : RU-2970 Lunchbox : V&H Exhaust : 20/65/145 : 15T : LED Dash : Sonic Springs : Braided Front Brake Line : E conversion with Buell Dual Headlight : SW-Motech Engine Gaurds ...

Filipe_500

Quote from: dgyver on July 14, 2006, 04:12:33 AM
Stock sleeves will work. The sleeves are tapered outside of the cylinder making it look too thin. The largest you can bore to is 79mm but the lower skirt get very thin and can crack if run too lean. I have one as proof. I have had one bored to 79mm (with a .002" piston/cylinder clearance) and it ran great but I had to sell the bike. One motor I have has 78mm pistons in it now.

Neither of these engines were rebalanced. The vibration was basically the same as stock. But then I only really run them above 8K.

Always used stock cranks, never had a problem.

Valve float will kill the engine before most everything else that would fail mechanically.


Thx!

Just a thing, what´s the reability of this sleeve, because i measured that and notice that if i bore to 78mm, the botton of the sleeve will measure only 1mm !!

The machine shop needs to pay some stuff to me cuz of the damages on my engine.... they said they would fit a iron sleeve (82mm) and bore it to 78mm for free to me, what u think? would it be better than stock?

thx a lot mate!


Filipe

dgyver

The bored stock sleeve's reliablity is relative to how lean and hot the motor gets. The 78mm motor used to be raced and the sleeves show no sign of damage.

If they are willing to put bigger sleeves in for free, then go for it. You will need to grind a little clearance in the cases though.
Common sense in not very common.

CirclesCenter

Fillipe.

Dude, go for the sleeves.

You have a long list of broken crap already, I say go the rockstar route with the bigger sleeves, and forget your worries. (And then build your bike more hardcore than any GS ever.)

Just replace and reblanace and re-hone everything. I know that seems drastic, but think about it, that engine would be damn near invincible. And able to handle any ammount of boost/compressio/torque/horsepower basically ANYTHING you throw at it. Just give it oil and gas and it will rip the rear tire to shreds.

Anyways man, your bike, your choice. But I remember you saying something about wanting the most tricked GS ever. Going the extra mile here would assure that.

Like my Buddy said, "Just get what you want the first time around. In the end it saves you a lot of time, pain and general bullshit, cause life is short." Except he cursed a lot more, cause he's like that.
Rich, RIP.

FearedGS500

i have a Q? ... if its seleved . then you would not be able to bore it right ? i just ask beacuse when i raced motocross i went threw another topend so i desided to go bigger and when i took it in they started todo it then told me they could not do it beacuse it was sleveed ........

ducati_nolan

ballancing your engine is always a good idea, especially for sustained high RPM, but you don't NEED to unless the piston is a different weight from stock. If you weigh the stock piston and the new one is the same weight, you can just run it as is without ballancing for street use, as the GS can take plenty of flogging. If they are more than a gram or so different than the stock pistons, you will NEED to ballance. I't would be a good idea to sleve the cylinders, if you don't, the biggest risk would be cracking from shock cooling.

dgyver

Quote from: FearedGS500 on July 15, 2006, 08:28:48 AM
i have a Q? ... if its seleved . then you would not be able to bore it right ? i just ask beacuse when i raced motocross i went threw another topend so i desided to go bigger and when i took it in they started todo it then told me they could not do it beacuse it was sleveed ........

It all depends on how thick the sleeve is if it can be bored. Suzuki (used to) sell over sized pistons (+0.5 & 1mm) for the GS. So the sleeves woould have to be bored. The GS sleeves are pretty thick, 5mm max over-bore. Also, you were problably racing a 2-stoke...different motors.
Common sense in not very common.

onefastgs500

gs crankshafts break with big pistons ask me how i know this .you should have tha crank radius cut it will have to be undercut but this will allow flex where the counterweight meets the bearing journal surface.tha factory does not do this on the gs 500 because it is a bargain basement machine they do radiuscut the bigger machines cranks.rebalancing the rotating mass is a totally different thing ,to start you need to know at what rpm you want it to run smooth at and then start adding(by welding)material on the cranks counterweight on the appropiate side and grinding material off where not needed,this requires knowledge of applied engineering and even falicon did not want to do this for me ,you will make the most horsepower gains with extensive headwork than just large pistons but together you gain loads
90 red 628cc 67hp racebike  90 fj1200streetbike
                              lee adams

Lukewarm Wilson

Quote from: FearedGS500 on July 15, 2006, 08:28:48 AM
i have a Q? ... if its seleved . then you would not be able to bore it right ? i just ask beacuse when i raced motocross i went threw another topend so i desided to go bigger and when i took it in they started todo it then told me they could not do it beacuse it was sleveed ........

May have something to do with coating on the sleeve walls like nikasel or what ever that coating is called alot of 2stroke MX bikes had that on there cylinder walls. :thumb: :cheers:
Experience enables you to recognise a mistake when you make it again

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