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Old 09-07-2010, 03:19 PM   #1 (permalink)
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Default Namura Replacement Piston and rings?? Your thoughts?

Ive posted on here several times about having issues with a smoking Z. It frustrated me to the point of selling but after taking a hiatus from working on it ive decided to go back to trying to fix her up.

Just a little background... I rebuilt my topend with wiseco valves, cut the seats, installed new valve seals, new DID timing chain, and all new gaskets. Well while i was in there, and a little uneducated i might add, i decided to rering the piston. Keep in mind its stock bore piston, cylinder, and the quad itsself is bone stock. So i used namura rings and installed them without honing or even cleaning the cylinder (i know, dumb) So i put it all back together and getting smoke on hard acceleration. I ran it for about 10 minutes and checked the dipstick and had nothing on it so i guess i am burning oil.

Ok so im back to square one. Im on a tight tight budget and im keeping this quad as stock as i can. All i want to do is get a nice reliable, NON smoking machine so heres what i found earlier and was wondering your guys opinoin on it?

Namura Piston and Rings

I found these on ebay today. ANd it seems like a great deal. I just wanna know what you guys think????

I guess then i was wondering, my cylinder looked good when i had it off. I dont know if its wore out or not, but with not visible wear on the cylinder, is it safe to assume its ok then just clean it up and i was gonna scotchbrite it cause again, im poor and dont want to take it to a machinist. BUT if you think its in my best interest to get it honed ill consider. How do you measure the cylinder to see if its in spec???

Also if someone could give me a run down on the absolute best method for installling a piston/rings, id appreciate it.
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Old 09-07-2010, 06:00 PM   #2 (permalink)
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I don't know if the stock piston works with namura rings. Also when you install a piston and rings and you are reusing the cylinder you should check and see if it still has the original cross hatch pattern from being honed at the factory. If you can still see the cross hatch you only need to clean the cylinder of all oil and glaze. You do this with a green scotchbrite pad and soapy water till the surface is not as mirrored or glazed as when you removed it. If you don't remove this glaze your new rings will not seal correctly and you will get blow by.
Honing nikasil should be left to a pro. If you go over .001 to .002 of an inch deep (I believe is the spec not 100% we farm out all our machine work from the shop)with the hone you could possibly ruin the coating.
Did you change the valve seals also? Anytime you remove the head you should change valve seals since you're in there. They might be good still but a 4 dollar part shouldn't hold you back and isnt worth not changing it out only to do the job again.
I think there are a few guys who had problems with Namura pistons on here in the past. I've always used JE pistons in all my bikes after the stock ones.
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Old 09-07-2010, 06:30 PM   #3 (permalink)
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excuse my ignorance but what does the cross hatching look like and how will i tell its there???

Its an 03 model. The piston and everything is still original and im the 3rd owner so im guess it would be wise to go ahead and replace the pistons AND rings as well? What compression piston do i need? 12:2:1 or 13:5:1?

And yes i JUST replaced the valve seals. It doesnt smoke on initial start up, its only when you get hard on the throttle that it does. Id replace the valve seals just to be safe but i dont have a valve spring compressor.
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Old 09-07-2010, 06:38 PM   #4 (permalink)
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what about this??

PRO-X SUZUKI LTZ400 Z400 LTZ TOP END PISTON KIT STD "B: eBay Motors (item 390200938028 end time Sep-22-10 21:14:49 PDT)
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Old 09-07-2010, 07:10 PM   #5 (permalink)
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The cross hatch is a pattern left in the cylinder from the honing process.
Looks like this
http://image.popularhotrodding.com/f...atch_angle.jpg
Its there to provide the proper lubrication of the rings and allow them a surface to mate to. With poor honing or a cylinder glaze the rings will not seal or break in correctly since the cylinder walls will not retain oil correctly without the pattern they allow it past the rings.
Go 12.5 that would be stock compression ratio or 11 something with the stock base gasket and if you use the drz gasket then you would have 12.5. The stock base gasket has three layers and the drz only has one layer. With the 13.5 you would have run race gas or a mixture of race gas and premium.
If you just replaced the valve seals I wouldn't worry about them.

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Old 09-07-2010, 10:40 PM   #6 (permalink)
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Also how did you put your rings on there? did you line them all up or did you space the gap in each ring out? I have a namura big bore piston in mine and flat tracking you dont come off your high rpm's very much and i've had mine in there for about 3 months no problems.
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Old 09-07-2010, 10:54 PM   #7 (permalink)
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Honestly man, just have it honed. It will cost like $25 max and they can check it before and after to make sure it is in spec. The most important thing is that you will KNOW its right instead of guessing.
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Old 09-07-2010, 11:24 PM   #8 (permalink)
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i am not a fan of Namura. i had a failure years ago... and wasnt happy. never had issues with prox, JE and wiseco
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Old 09-07-2010, 11:27 PM   #9 (permalink)
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Quote:
Originally Posted by CFM-Z440 View Post
Honestly man, just have it honed. It will cost like $25 max and they can check it before and after to make sure it is in spec. The most important thing is that you will KNOW its right instead of guessing.
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Old 09-08-2010, 12:02 AM   #10 (permalink)
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See this thread for a look at Namura.
Ebay big bore kit

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Old 09-08-2010, 12:57 AM   #11 (permalink)
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OK, Im probably gonna opt with the PROX kit, get some gaskets, then tear it all down, check the cylinder out and see, and if im questioning it at all, take it to a machinist, have it checked and honed.

You guys answered all my questions, THANKS A TON! CFM, i apologize for my redundancy, im hard headed... but i appreciate the patience!

Ill let you know how it goes
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