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Want a 541cc motor w/ 78mm pistons?

Started by dgyver, January 06, 2005, 09:50:58 AM

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dgyver

Wiseco 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.
Common sense in not very common.

octane

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.

dgyver

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.
Common sense in not very common.

gobstopper

Would a 547 or 555 be considered 'streetable'?

I'm considering buying an engine to putz around rebuilding...
QuoteApathy is the best thing that ever happened to me.

dgyver

You will hear both sides of this....but I do not see any major reasons why it would not be streetable.
Common sense in not very common.

GRU

it should last just as long as a 487

Dom

Do you use stock rods? Deck the head?

The Buddha

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.
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I run a business based on other people's junk.
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TeBo

hahah beat y'all ! ! !  mines died at 6000 miles=P.. anyways, I am hella interested in this conversion.. hmmm....

TeBo

what exactly is needed to do a swap out??  any help??

dgyver

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.
Common sense in not very common.

Dom

How much do you mill the head?  Coupla inches?

TeBo

So bottom line question is, about how much would I be spending miniimum to get this baby put in??

dgyver

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

Stock Head

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
Common sense in not very common.

fat_sac

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?

dgyver

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
Common sense in not very common.

Whatever6060

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?

fat_sac

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.

dgyver

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.
Common sense in not very common.

Whatever6060

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?

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