Author Topic: KX 80 Rebuild/rebirth (Read 8281 times)

Stusmoke · « **Reply #15 on:** July 14, 2013, 08:16:47 AM »

Quote from: adzski on July 14, 2013, 01:54:06 PM

need help pikcing a piston.

went to local shop and got the jug and old piston measured.

he mentioned it may have orignally been 48.48 would have worn 48.50mm.

so i found this
http://www.ebay.com.au/itm/Wiseco-48-50-MM-Pro-Lite-Piston-fits-Kawasaki-KX-80-88-00-644M04850-/350832166942?pt=Motorcycles_Parts_Accessories&hash=item51af3a081e

How big was your cylinder? Remember that a cylinder that is 48.50 mm won't take a piston that is also exactly 48.5 mm. Judging by the .au part of the link i guess you're in Aus? If so, I would point you in the direction of: http://www.motocrossparts.co.nz/
Good stuff, good prices, good people. Those guys sell wossner pistons and the one I've put in my CR is ripper. Holds up well to my abuse and its good enough for Dungey, Roczen and Marv (I think Wossner supports the KTM factory teams anyway). If you're wondering about piston sizes, give them a bell and they're happy to help you out. And you get to giggle if you have lots of sevens in your credit card and ask them to read it back

adzski · « **Reply #16 on:** July 15, 2013, 01:06:24 AM »

well it would have to be 48.50

and the guy said the barrel was worn, so it would be bigger than 48.50?
im going to take it to another shop and get it measured again to be 100%

Stusmoke · « **Reply #17 on:** July 15, 2013, 04:16:10 AM »

Quote from: adzski on July 15, 2013, 08:06:24 AM

well it would have to be 48.50

and the guy said the barrel was worn, so it would be bigger than 48.50?
im going to take it to another shop and get it measured again to be 100%

Did the shop measure your cylinders bore? What was it?

adzski · « **Reply #18 on:** July 15, 2013, 07:57:00 AM »

got it measured again and another shop said to run a 48.5 piston.

yeh they both measured it and its larger than 48.5, id say it would be around 49 or slightly over cant exactly remember what he said but i made sure that it was over 48.5 anf there was enough room for ring gap.

that should be coming either tomorrow or the following day, so all i need now is the stator.

Stusmoke · « **Reply #19 on:** July 15, 2013, 08:34:31 AM »

..... If you run a 48.5 mil piston in a 49mm or more bore, expect disaster. You should have roughly 4/100ths (.04) mil clearance between bore and cylinder, not half a millimetre.

adzski · « **Reply #20 on:** July 15, 2013, 01:35:58 PM »

i may have mis-understood him, ill query it when i talk to him next.

so to clarify the bore size should be 48.9? or?

Stusmoke · « **Reply #21 on:** July 15, 2013, 10:44:07 PM »

I'm not sure what the bore or piston size should be, I'm just saying that you can see half a mil with the naked eye. If theres half a mil piston clearance, the piston will most likely catch on the exhaust port. Disaster.

http://wossneronline.com/forged_pistons/index.php?main_page=product_info&cPath=50_64_97&products_id=833

Theres all the piston sizes available for your bike. If you have to you can order directly off them, or visit http://www.motocrossparts.co.nz/ ring them up and see if they can't get you one.

I would get an accurate reading of how big your cylinder bore is. Actually I would go one step further and buy a Cbore gauge and do it myself to be certain. Then you can order in an appropriately sized piston.

adzski · « **Reply #22 on:** July 16, 2013, 10:11:02 AM »

i think i may have mis-understood him as both shops recommended the same size, so id say i mis-understood. i have already ordered it, and should have it tomorrow.
should be ok he has advised me with my bike and serviced it before and always done a good job.

adzski · « **Reply #23 on:** July 17, 2013, 10:27:32 AM »

Update.

so ive been a busy boy.

got the piston and gaskets today, everything fit perfect as the shop said it would, so now the top end is together and the motor is bolted into the frame, connected all the hoses to radiator, re-attached clutch cable, and just a bunch of little things.

all thats left to do is
.bleed the rear brakes
.put new stator on (picking up tomorrow)
.get radiator fluid, and new plug.

then start it

will takes pics tomorrow, took some today but will upload tomorrow.

Stusmoke · « **Reply #24 on:** July 17, 2013, 10:43:53 AM »

How tight was the piston fit? And the ring(s)

adzski · « **Reply #25 on:** July 17, 2013, 12:39:26 PM »

it was pretty tight my mechanic told me to put the piston in from the top and watch it slid down slowly and if it drops its to small and it slid down slowly, but felt the same as when i did my 250s piston, and as for the ring its only running one ring instead of two like the 2014 kx85.

Stusmoke · « **Reply #26 on:** July 17, 2013, 09:31:03 PM »

Quote from: adzski on July 17, 2013, 07:39:26 PM

it was pretty tight my mechanic told me to put the piston in from the top and watch it slid down slowly and if it drops its to small and it slid down slowly, but felt the same as when i did my 250s piston, and as for the ring its only running one ring instead of two like the 2014 kx85.

Sounds like everything is good there, that is a good little trick aswell. Make SURE You put the piston in the right way! Single ring pistons are good, but you need to change rings a little more often.

adzski · « **Reply #27 on:** July 19, 2013, 12:48:14 AM »

so as of yesterday the bike is now down, did 3 heat cycles and one little ride, will post pics later today.

adzski · « **Reply #28 on:** July 20, 2013, 04:04:50 AM »

Having a problem with the kx85s powerband.
It kinda comes on late, and only really felt it in 1st and 2nd.
I'm thinking a pv problem or maybe the carb needs adjusting.
I'm gonna get another plug and see if that helps.

Stusmoke · « **Reply #29 on:** July 20, 2013, 04:24:23 AM »

Lol an 85cc two stroke motocross bike redefines "late" in the powerband. they scream, and screaming is all they do. But its possible there is a problem, check it over I guess

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Author Topic: KX 80 Rebuild/rebirth (Read 8281 times)