Wiseco (//www.wiseco.com) makes 78mm (3.071") pistons for the 83-84 Kawasaki GPZ1100 (1262cc). These are normal stock items and they do have some pistons on the shelf right now. I called to confirm this. They are $109.13 for 1 piston, ring set, wrist pin and circlips.
GPZ bore kit number: K1262 (this complete kit is not required)
Piston: 4304M07800 (4304PS is stamped on the top of a actual piston)
Rings: 3071XG
Wrist pin: S555 (18mm) $13.95 each
Circlips: CW18
Page 15 in their catalog has all this info listed:
http://wiseco.com/PDFcatalogs/ps04-kawa.pdf
I can confirm this works since I have a 541 motor sitting at my house with these 78mm pistons already installed.
Got any numbers on this? Did you do anything besides the obvious bore? I'd like to do something like this when I blow up my original motor...but it wont' die. 30K of abuse and it still puts 45 hp to the wheel with no hiccups.
The 541 I have came from JamesG when I bought all of his stuff. It split a shim and put a hole in the head at a cam gallery. Not sure of all that has been done to the top end of the 541. No numbers as of yet. Eventually I will take my 555 and the 541 to a dyno for a run.
Would a 547 or 555 be considered 'streetable'?
I'm considering buying an engine to putz around rebuilding...
You will hear both sides of this....but I do not see any major reasons why it would not be streetable.
it should last just as long as a 487
Do you use stock rods? Deck the head?
Quote from: octaneGot any numbers on this? Did you do anything besides the obvious bore? I'd like to do something like this when I blow up my original motor...but it wont' die. 30K of abuse and it still puts 45 hp to the wheel with no hiccups.
Yea mine too ... 47K and it wont die inspite of the constant kicking of it... and now I think its burning oil and making horsepower ... :lol: but see oil is 74 cents a quart ... gas is 2.10 a gallon ~55 cents a quart ... so I am not losing that much $$$ ... besides I get 250-300 miles for each quart ...
Cool.
Srinath.
hahah beat y'all ! ! ! mines died at 6000 miles=P.. anyways, I am hella interested in this conversion.. hmmm....
what exactly is needed to do a swap out?? any help??
The minimum to install the larger pistons is to have the cylinder bored to match the pistons. It cost me $130 to have a stock cylinder bored.
There will be plenty of valve and head clearance. Even with a high lift cams and a milled head there will be enough clearance. Only until you add a milled cylinder top with the previous mods will there be any issues. Then the pistons may hit the spark plugs. But grinding a little off of the pistons will take care of that problem.
Stock rods are retained.
You can get a reuseable copper head gasket from Cometic. They are about $30. I took a stock head gasket and enlarged the holes with a drum sander, no problems.
A high flow exhaust and air filter are a good idea.
You will probably need to run 92 octane with these high compression pistons.
How much do you mill the head? Coupla inches?
So bottom line question is, about how much would I be spending miniimum to get this baby put in??
I do not have have any hard numbers on how much can be milled off a head yet. When I take another head to get milled I will have the one I have measured. This head was milled when I bought it. By looking at it, the whole step on the bottom of the head has been removed which guessing is about 1mm.
Milled Head (http://img.photobucket.com/albums/v64/dgyver/GS500/GSmilledhead01.jpg)
Stock Head (http://img.photobucket.com/albums/v64/dgyver/GS500/GSstockhead01.jpg)
Note that as you mill the head, the cams may need to adjusted.
As for the cost just add it up:
Pistons: $109.13 x 2 = $218.26
Cylinder milling: $65/cylinder x 2 = $130 (cost will vary by shop and the more they remove the more it costs, this is what it cost me)
Base Gasket: $10
Head Gasket: $30
Total: $388.26
Ok, I'm doing this today. I need to know how much to mill the head though. I also would love to know how/where to adjust the cams to. Did you just do the advance mod in the racing section?
I have no idea on how to mill off the head. I use Megacycle cams that are set at the factory. I use either a V&H advancer or a modified one from Bob Broussard.
NOTE: I edited my above posts to the correct displacement of 541 instead of 547
I was reading this thread and was inclear about the amount of work needed modify the GS us to a 541 CC. All you need to do is bore the cylinder and put in the new pistons?
That and I'm having the heads milled and ported for a lil extra gogo. In time I'll do new cams and I already ordered the new cam springs. There's never 'this is all there is to it?' You always get carried away when you start doing stuff like this.
Quote from: Whatever6060I was reading this thread and was inclear about the amount of work needed modify the GS us to a 541 CC. All you need to do is bore the cylinder and put in the new pistons?
Yep.
Wouldn't there be a need to increase the amount of air and fuel to compensate for the new increased size chamber? Or would the size of the new chamber consequently pull more air and gas in?
yes you will probably have to rejet...big deal :roll:
compression should go up...probably...
just remember....when you modify it....stuff will break
Quote from: Whatever6060Wouldn't there be a need to increase the amount of air and fuel to compensate for the new increased size chamber? Or would the size of the new chamber consequently pull more air and gas in?
If you mill that heads a good bit, then the chamber won't be that much bigger. On that thought, won't you NEED to mill the heads to keep the compression the same?
The compression will increase with these pistons without milling the head. These have a high dome that really fills the head cavity. I tried running a milled cylinder and milled head and the piston was hitting the spark plug. Even wiith that setup and high lift cams, there was still plenty of valve/piston clearance.
Yep, a rejet is needed. But not like most would think. Larger carbs will help as well as flatslide carbs. They are better than CV carbs.
hold on here, so what your saying is that for under $400 I can make the gs's 487cc motor into a 541cc motor with nothing more than milling out the cylenders and bolting on the new pistons? come on, theres got to be more to it than that... sounds far to easy
Yes it is that simple.
It may cost less (or maybe more) depending on what the machine shop charges to bore the cylinders, there is a lot of meat to remove. Good thing the GS only has 2 cylinders. I felt like I may have paid too much but then I spent several hours talking to Ed about motor building. It was well worth the cost for the info I gained.
did you notice a big power difference when you put the bigger pistons in? alot more power? less power? the same?
Quote from: budget speed demondid you notice a big power difference when you put the bigger pistons in? alot more power? less power? the same?
More low end torque. Bigger displacement and greater compression will increase power.
so what kind of a CR are we talking about?
I have never calculated it, but I guess it would be over 10:1 and probably close to 11:1. Stock is 9:1. You need to run premium gas.
Is any one actually running one of these on the street?
Sounds like a straight forward mod/rebuild.
Bike, money, parts, machine shop, inclination.
Or am I missing something?
I do not know of anyone running anything larger than 75's on the street.
A $400 mod is not something that many people are willing to do on their entry level bike if they are planning on upgrading. As for racers and track junkies, that cost is nothing in the quest of more power.
As for your second question, it was answered 5 posts back.
Second question?? That's a statement, I saw the original post. It was kinda my own personal inventory. Inclination and money I have, parts and a good machine shop I'd have to look for. However, I must admit I confuse even myself.
I agree your not likely to see someone spend $400.00 on an entry level street bike when they are considering upgrading. But then you don't expect them to put a turbo on it either. :)
I guess if you go into it knowing you aren't going to recoupe your initial investment you'd be OK. Like owning a boat or plane.
Nothing to stop you from doing the engine mod, running on the street and then going to the track if you wish I guess.
I appreciate all the info you've set out for us. It's one of the things that makes this message board worth visiting. :thumb:
(I just had to use those emoticons)
Thanks
Ok fair enough.
Yeah, doubtful that you would recoup all of the cost but it would definitly help with resale. I would look into if I was having to do a rebuild, it is not that much more than going with factory oversize pistons.
When I sold my bike with the 555 (http://img.photobucket.com/albums/v64/dgyver/GS500/91GS500R01.jpg), he drove from MN to pick it up. I bought the bike as a cheap track toy and ended up spending a lot of time and a fair amount of money on it, which I did recover in the sale.
I need to rebuild mine :) it only has 90 pounds.... Was it 10-11:1 with or without milling the head to? Also, the stock pistons are 74mm, right? are the stock liners thick enough to be honned 4mm?
My guess of 10-11:1 is with a stock head. Most sportbikes are around 12:1.
74mm is the stock piston size. The stock liners can be bored up to 5mm over for 79mm pistons. Do not bother looking for any 79's... they have not been made since '92. I found 2 of them and built one motor, acquired another and looking for just one more......
Quote from: dgyver on January 07, 2005, 06:31:21 AM
You can get a reuseable copper head gasket from Cometic. They are about $30. I took a stock head gasket and enlarged the holes with a drum sander, no problems.
Does anyone have info on which gasket to buy from Cometic? I see they sell one for a GS850. Or are you talking about taking a 4-cyl gasket and cutting it down?
Thanks.
Could something like these be used?
http://www.usa2strokers.com/forum/forum_posts.asp?TID=28757&PN=1
Quote from: dgyver on September 16, 2005, 03:13:45 PM
The compression will increase with these pistons without milling the head. These have a high dome that really fills the head cavity. I tried running a milled cylinder and milled head and the piston was hitting the spark plug. Even wiith that setup and high lift cams, there was still plenty of valve/piston clearance.
Yep, a rejet is needed. But not like most would think. Larger carbs will help as well as flatslide carbs. They are better than CV carbs.
Hate to 'revive' an old thread....
So what did you do about the new pistons hitting the spark plugs? Could the top of the pistons be milled down or is that something that you just don't do? Also, did you end up getting new carbs or staying with stock (and if new ones, what'd ya get)?
You do not machine the top of a dome piston. The top is like an arch, and machining that is like removing 1 brick from the arch.
You set it to not hit or space the plug up or well ... deck it less, or extra base gasket or whetever.
Cool.
Buddha.
>:(
Warning!
Wiseco seems to have changed the profile of the dome on their piston number 4304M07800.
>:(
It doesn't fit under a GS500 head any more. I'm investigating to confirm the changes in the design, and I'm looking for solutions...
Meanwhile, I don't recommend anyone order this piston unless you can confirm it is stamped with '4304PS' on the top, like the ones that Dgyver has.
Any update on this? I'm hoping to get pistons this winter when I rebuild my motor.....
can any one confirm that these pistons will not fit the gs500?
I am extremely interested in buying a set although they went up in price but not if they don't fit
I believe the last I heard wiesco wasnt making these any more but someone found a replacement from another bike that could be used in place.
Quote from: Chanse on August 30, 2009, 04:58:04 AM
I believe the last I heard wiesco wasnt making these any more but someone found a replacement from another bike that could be used in place.
Not correct. Wiseco stopped making the 79mm pistons for V&H years ago (1992 maybe?), which were originally design for the GS450. These pistons are made for the FJ1200.
Apparently Wiseco had changed the dome profile by increasing it between the time I acquired a set and now. Note the previous post by 5thAve reguarding part numbers of the pistons he has that did not fit. Modifications to the piston dome (if there is enough material to be removed) or head clearance would be needed. A thicker head gasket may work, depending on the amount of interference.
Well after doing the research on the pistons and things like this yes I know its old and I myself have not posted in a while. The piston listed from the start of the post is for a GPZ1100 set up for 2 valve which is good. 78mm good. pin size 18mm good. 66.2 stroke. Bad um I know you can shift stroke like one or maybe 2 mm but the stock stroke for the little pup is 56.6mm and this is almost a 10mm or to put it in terms of inches about 3/8ths that is a lot. That means this piston had a stroke of 66.2mm in mind when created. Now if the pin location is shifted this would be or could be why it does not fit. We have to be a two valve piston face in the 78mm range bore with a stroke around 55-58mm. I haven't said it won't work but I wouldn't throw the dough out there for that to not work and at the current list prices of 155 per piston. I would find that maybe if there is enough people intrested in doing a bored over motor then we could get a group buy going but i can't see that with me right now as the econ. I bookmarked this one in hopes of getting around to it and doing this one myself figured I would let any of those out there know. As for why it worked for Dgyver I have no clue. Generally with manufacturing you never change a part number to a complete new profile.
Hey,
I was just looking through this tread and decided to check out Wiseco myself. Would the 1995 Yamaha GPZ 1100 Pistons work. I randomly looked at them and noticed they have a 58mm stroke as opposed to the 1983's 66.2 mm stroke. Going off what the previous poster said, would this make the difference?
Here is the 1983 Pistons:
http://www.wiseco.com/ProductDetail.aspx?ItemID=4304M07800&ModelID=175&ModelYear=1983&AppID=7880
Here is the 1995 Pistons:
http://www.wiseco.com/ProductDetail.aspx?ItemID=4578M07800&ModelID=175&ModelYear=1995&AppID=7648
The pins also have the same inner and outer diameter.
Jay
Stroke is determined by the crankshaft, not the pistons or the connecting rods. So, the difference in stroke won't matter. There is something that could be a concern; I recall reading in another thread that WISECO changed the shape of their 78mm pistons, increasing the size of the piston crown. From what I recall, there may be clearance issues with the stock GS500 heads. Some investigation would be valuable.
For my part, I'm racing the GS, and have no plans to go larger than 76mm.
FYI: http://gstwins.com/gsboard/index.php?topic=48095.0
Make sure you get the right 78mm pistons...
Also, WISECO part #4578M07800 is wrong for your engine. It's for a ewer GPZ engine, which is 4 valves per cylinder. You're going to need a pair of the older GPZ1100 pistons, for a ~1982 model year bike.
Ahhh ok, I was hoping it was not 4 valve. I was just going off what the previous poster said becasue it sounded like he was thinking that the pin on the pistons designed with a longer stroke may have been placed farther away from the top of the piston thus making the total length of the rod+piston a bit longer(but keeping the stroke the same) so therefore making it hit the head
Jay
I would think that that would also bump up the compression as well though and that would not make to much sense as they are meant to be replacement pistons I think.
Jay
Yes, if the distance between the pin and crown increase, compression will also increase. Pretty much all of the aftermarket pistons will bump up the compression ratio... Which really is fine, given how low the ratio is on the stock GS.
You may have to run premium after installing new pistons, but you'll get a bump in power just from the increased compression ratio.
Just say no they don't work.... 5thAve provide it. And going back and looking at the post again and seeing the pictures my suspect is they have made a drastic change as Wesico in there manufacturing process I did not catch it before but they did change the manufactured number.. though it may have the same part number 4304M07800 Its not the same Forging #'s ? which would indicate the major change. Yeah it still doesn't exclude the fact that they redesigned the piston. Kind of looks like to me they went to a full CNC billet as the forged one that Dgyver has looks less CNC milled where as the 5thAve could be fully processed on a CNC machine today. Though if someone really wanted to beat them up on it here is a nice http://www.wiseco.com/PDFs/DealerNewsArticle.pdf (http://www.wiseco.com/PDFs/DealerNewsArticle.pdf) read down and see how they dedicate each Forging for an application. That would kind of indicate that you should be able to order the old profile number according to there own Dealer News as of 2009.
I can see how my statement for the stroke of 66.2 could miss lead. But its more the pin height from crown of piston to the center of the piston pin that matters and the rod info I was referencing . Also the quench area is drastically wider examining the pictures from 5thAve vs Dgyvers pistons.
Yes its old and I still would like to see it happen.
Jay These are in no way meant for our bike. They are not meant to be replacement pistons for our motorcycles. So your statement about bumping compression would take place is a yes a massive bump. So massive they will smash into the Top head according to 5th Ave 5/32 but I Suspect more. To the statement of Burning1 make sure you get the right 78mm pistons would be correct too. I went through the whole catalog There is no out of the box design that works for our motors.
Again you can't install these piston unless you can verify they are the Dgyvers profile.
Just to keep this thread up to date, I still have the 4304M07800 pistons and I'm still talking back and forth with Wiseco to figure out why they are a different shape of dome than what others before me apparently received. As of right now, I recommend that these pistons are NOT a drop-in fit. Some machining of the piston dome and/or combustion chamber in the head will be required.
If / when I make any progress on this issue I'll post here. :embarassed:
Be sure to read this:
http://gstwins.com/gsboard/index.php?topic=48095
Some people are mentioning the 1985 FJ1100 pistons. Note that was a 4-valve per cylinder head design. Even though the pistons are the right diameter and wrist pin size (18mm), I doubt very much they would have proper clearance in our 2-valve per cylinder engine. I think the confusion comes because some of the racers on thegsresources.com have used FJ pistons in their EIGHT VALVE GS450 hybrid racebikes. (Yes there were both 2 and 4-valve per cylinder versions of the GS450).
5thAve: I started some initial grinding work on my GS500 head. I'll probably do enough work to fit the stock GS450 pistons. When I do the full race build, I'll probably have JE make me some custom pistons.
I'd love to see photos of your modified head.
Sent from my T-Mobile G2 using Tapatalk 2
Quote from: 5thAve on June 19, 2012, 09:41:16 AM
I'd love to see photos of your modified head.
Sent from my T-Mobile G2 using Tapatalk 2
I'll take some pictures when it's finished, before installing it on the bike.
Found out a few things from my test grindings...
If you're taking off just a small amount of material, a sanding roll works fine. Seems to produce smoother results than using a burr grinder.
Machinists blue die is pretty handy. Might be able to make a pretty accurate guide line by blueig the head, and marking by running a scribe around the bore of the block.
UPDATE!
Dgyver and I started on a 569cc engine for my bike.Here are some specs.
80mm Wiesco pistons and sleeves-We are unsure what bike they came from,but they test fit perfectly.
Copper head gasket
polished and ported head
Mega Cycle Cams with adjustable cam gears
36mm GSXR carbs-36mm Flat Slides are on hold until break in is accomplished.
Bottom end and case checked out so all new bearings and seals have been installed.We buttoned up the bottom end this evening.I did swap out a bad output shaft for a used one in good condition.
Go big or go home!
Quote from: dgyver on April 27, 2013, 07:24:15 PM
Go big or go home!
We are and unfortunately I had to.LOL
Awesome Ben!
You have to put pics are my attention can not be focused.. ... hint hint.. :confused:
Do you have a part number and a photo of those pistons? My project is still sitting in boxes in my basement driving me nuts. I'm going to have to reshape the combustion pocket in the head and maybe machine down the pistons too in order to make my setup fit. Else I'll just abandon my current pistons and seek out something new...like what you're trying maybe?
No part number. I bought them used.
The cylinder was bored to fit a larger sleeve. The upper case had to be cleared to accept the larger sleeve. I had the sleeves honed properly to fit the pistons. Using Wiseco XG rings.
Reprofile the pistons. That has to be done most of the time with these type of mods. I have yet to see a piston that does not have enough material.
The pistons we are using are 80mm(569cc). THEY ARE NOT IN THE PISTON LINE UP PICS.
74mm is stock size.
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/GSpistons01_zpsfb2cd4cc.jpg)
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/GSpistons02_zpsd906d989.jpg)
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/GSpistons03_zps1fda7624.jpg)
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/GSpistons04_zps3a697bcf.jpg)
This is the clearanced case for the bored and sleeved cylinder block.
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/80mmPistonsFit02_zps7b81af69.jpg)
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/80mmPistonsFit01_zps4240425f.jpg)
Here is the bored and sleeved cylinder block with the pistons set it.
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/1989%20GS500%20Build/80mmPistonsFit03_zpsc1e96345.jpg)
Jumping to 78mm, assuming all other things are the same (some are not) but for the sake of comparison lets assume they are.
Stock 74mm bore with
56.6mm stroke
The compression is 9.0:1
With a 78mm bore @541cc
It brings it up to 10:1
With 80mm bore @ 569 it goes up to 10.4:1
http://www.cbperformance.com/v/enginecalc.html (http://www.cbperformance.com/v/enginecalc.html) Feel free to mess around with the calculations to see what you get if you change things.
If those pistons are have a larger volume than stock (I'm guessing they do quite a bit) then the compression ratio goes up even more.
The stock cylinder has 4mm of wall thickness. Going to 78 leaves 2mm of wall left. After that you would need sleeves installed.
The GR 650 sleeves can be installed with some milling work. They start off at 77mm and have 4mm worth of material to go from there.
This is an example of GR 650 sleeves fitted to a GSX400 block with 78mm bore 1100 pistons.
(http://farm8.staticflickr.com/7041/6887656896_905ac32f41_z.jpg)
Biggest you can go with the GR sleeves is 597 @ 82mm and that leaves 2mm left of wall thickness.
What about any big bore kits for the 2 valve GS1100's ?
Where did you get those sleeves from ? How much flange was left on the top?
I bought them used.
I haven't cc'd everything but I think I will be at 11:1 CR when we are done.The copper head gasket is a little thicker than the GS unit so may bring that down a little.It will be a premium pump gas engine.MekanniX,what head gasket are you using and did you have to open the gasket up to fit the cylinder bore?
This is getting good! After rebuilding moped engines for a while- I have great respect for you all attempting this. I will be following in yer footsteps someday!!
I went with cometic fiber gasket. 0.043" @78mm
Quote from: MekaniX on April 29, 2013, 08:12:17 AM
I went with cometic fiber gasket. 0.043" @78mm
Thanks.