KX 500 Flat on Mid and top end

[lsampson]

Wiseco is Forged Correct?

The center valve moves  just a little, maybe 1/32th up and down if that. It is the slop where the center valve pins move within the drum valve channels.

I did preload the kips arm, I pushed the rod all the way in, then tightened the arm against the full closed position, which basically happened anyways since the nut forces the rod closed during tightening.

[lsampson]

something just dawned on me, do you think the piston is the wrong size? I ordered a std size from chaparral, and my cylinder has never been bored out, but isn't there various bore sizes? Chaparral OEM says its a "size B" piston..

[Motorrad]

something just dawned on me, do you think the piston is the wrong size? I ordered a std size from chaparral, and my cylinder has never been bored out, but isn't there various bore sizes? Chaparral OEM says its a "size B" piston..

This is the reason why usmc 500 didnt ride his K5 for 3 years.

the guy he bought it from put in a fresh piston. and NEVER bothered to check the piston wall clearance.


well. I did once I got the motor.

more info on that subject can be found in usmc500's build thread   

needless to say.. Im shocked it never seized...

[lsampson]

This is the reason why usmc 500 didnt ride his K5 for 3 years.

the guy he bought it from put in a fresh piston. and NEVER bothered to check the piston wall clearance.

soo... I should probably tear it down and check piston clearance...?  If the wiseco rings were within new spec, shouldn't the piston be within new spec? The wiseco was an 86mm piston, which I believe is standard.  I was looking at the OEM pistons when I mentioned a size B piston..

[lsampson]

The heck with it. I just ordered new gaskets, new exhaust valves (both drum and center), new guides,  guide orings, exhaust o rings and gasket, and will tear it back down. I will check the piston clearance this time. Should the wiseco piston have the same piston-cylinder clearance as the OEM, or is there a spec out there?

[cbrfrenzie]

Typically Wiseco states their PTW clearance on the box the piston comes in.  Usually these specs are different than OEM, to account for the different thermal expansion rates of the two materials (cast vs forged).

[lsampson]

So..... I Figured Som Stuff Out Tonight. The Piston That came Out Of The Bike Has A "C" stamped On The Crown, And Fits Tighter Than The Wiseco. I Do Not Have Ash Inside Micrometer So I Couldn't Measure The Bore, But The Old Oem Piston Measures 85.94Mm And The New Wiseco Measures 85.84Mm. The WIseco piston-Cylinder Clearance Is .127 Mm, And Spec Is .100Mm. So I Have A Larger Bore. I Have Not Seen An Oem Piston sold In A "C", Where Are They Available?

[lsampson]

"C" Stands For Cast...Doesn't It...

[motopunk]

http://www.wiseco.com/ProductSearch.aspx

measure your cylinder and look good in this list, which piston you need . your old size is 85,94, than is your needed size 85,95 in cast!

if you replace a cast-piston by a forged piston you have to know, that forged pistons need more clearance, caused of the different material character. a long time ago i found out that cast pistons with the same mark on the top, are a little bit bigger than forged pistons.
     
forged                                            cast
    -                    =                             A
    A                    =                             B
    B                    =                             C
    C                    =                             D ...

feel free to contact wiseco for the right piston size and your problem with the rattling in the motor will be gone forever. than it will sound like a swiss rolex... you heared motorads bike in the video,

the C -size cast piston, you found in your motor you can get at all kawasaki-dealers . the stock pistons and con rods, that kawasaki build in all kx-modells are made by prox in japan, but without the prox-logo in the inside.

[lsampson]

I think what I need is a SLIGHT OEM oversized piston... I'm borrowing an inside micrometer today, so I should be able to get it measured up tonight.

All I can find is 0.50 mm over sizes in Wiseco for over-bored engines (like the link you included), and all I can find in OEM is 1 size, part number 13001A (13001A: PISTON-ENGINE,B) but NO C pistons...

 

[lsampson]

I'm going to start a new post..

[motopunk]

you can also use wössner,  prox or vertex pistons ...  you should take contact to one of the sellers. not all, that they offering is to find on theyre websites...

you could also give a call to an kawasaki dealer.. for an oem c piston... 

[lsampson]

I contacted my dealer, and they can only get the same B piston. Same part number.

[Motorrad]

I wasnt done typing.   read it again

[Motorrad]

if you take that measurement.  and assume you didnt factor in the measurement for the stock piston wall clearance.      you should be pretty darn close. to spec..  off memory.     Ill have to go look up what wiseco wants again. but I recall it being .004"  (I dont work in metric.  youll have to deal with it.)

so.  math time.

85.94mm - 85.84mm = .1mm   conv to in  is .0039".......      
lets assume your stock setup had a .0015" clearance.

so    


plus the .0015" (theoretical)


.0054"














But this is a HORRIBLE way to check piston wall clearnace.  and very inaccurate. as lots of assumptions.   and you know what happens when you assume..................


even checking the piston wall with a feeler gauge is more accurate than the way your trying to do it.