need help rebuilding cr125 top end

[q2418130103p]

Hello all,

I recently decided to rebuild my top end on my 1991 cr125r. Its my first time rebuilding anything and im alittle stuck. I am now at the point where I am putting the negine back together and heres where my problems lie


1) I bought a wiesco piston that is pakaged as a replacement for the stock piston and labled 90-91 cr125. When I opened the new ring that came with it, it says that the piston ring will damage chrome plated cylinders, is mine chrome plated? If it is, why would wiesco package an imcomplatable piston rign?

2) the piston does not have the word IN written on it, it instead has an arrow, I installed the piston with the arrow pointing to the rear of the bike. this puts the notched out side of the piston facing the front of the bike, is this correct?

3) the gasket kit that I bought claims to be OEM direct replacement. The gaskest sizes are spot on, the head gasket is perfect, but the gasket for te cylinder feels almost like rubber coated cardboard.

4) the piston came with isntructions that say i need to file the butts of the ring. should i have to do this with a stock clyider? I installed the piston into the cylinder and it seems to fit percetly, the cylinder is currently back on, but its just sitting there, not bolted down yet.

5) the piston came with instructions that also said the cylinder MUST be honed to remove the glaze so the ring seals better. I didnt do this because this cylinder is bascily perfect. I took it to a service center and they advised not to bother doing anything to the cylinder.

i think thats it... can anyone offer me some help with some of these?

 

[IndyMX]

The arrow on the piston should point toward the exhaust port.

 

[klg10]

The arrow on the piston should point toward the exhaust port.

yes sir.

 

[76GMC1500]

According to your description, your piston is installed backwards.

The cylinder does not need to be honed.


You can't judge a gasket's sealing properties by the way it feels between your fingers. It is probably the correct material and will work fine.

You probably don't need to file fit your rings but the gaps should be checked before installing the piston. Insert the ring in the bore and then use the piston to square it to the bore. Use a feeler gauge to measure the gap. Loose is safe when it comes to ring gaps. It's ok if they're loose but if it's too tight, you could do serious damage to your engine.

Is Nikasil considered chrome plated?

 

[q2418130103p]

ok, so the piston is backwards, i assume i didnt damage anything by simply sliding the cylinder over it, its not like i started it or anything, right?


for the piston ring, i put it in the bore and slid it in with the old piston, i could just barely see through the gap. what should the gap be? i believe i remember seeing the gap as 0.004" per inch of bore, so something like 0.012", which im guessing i can just about see through. (long story short, i dont have a feeler gage, so is it important that im really accurate?)

wikipedia says "Nikasil is a trademarked electrodeposited oleophilic nickel matrix silicium carbide coating"... if that helps anyone....

 

[76GMC1500]

A feeler guage costs about $3 and is available at most automotive and hardware stores. Be precise

As for the Nikasil thing, I do think that ring is ok to run in a Nikasil cylinder even though it is not ok to run in chrome. Nikasil cylinders are sometimes, though incorrectly, reffered to chrome plated cylinders. I'll let someone else confirm that that ring is ok to run.

 

[mxdj666]

your cylinder is not crome so you'll be good to go, i think the only chrome cylinders where on the late 70s and early 80s kawasakis and they sucked, as for honing it , i would definitly run a ball hone through the cylinder, you want the new ring to break in properly

 

[q2418130103p]

turns out i have a feeler gauge, so i filed the butt gap to 0.008", and i turned the piston around.

but i guess i have to take the cylinder back off again to run a ball hone through it.

 

[q2418130103p]

ive got a couple other questions for you guys.

should i use a sealer on the cylinder gasket or the head gasket?

is it possible to get the cylinder on and not have the ring centered the ring pin?

 

[mxdj666]

i usually dont use any types of sealers on the gaskets when i do a top end job , just make sure all the surfaces are super clean . make sure the pin on the piston is lined up with the gaps in the ring ,and when your putting the piston in ,try to just put it straight in dont try to wiggle or twist the cylinder to get it in or you'll get the ring caught in a port and believe me it sucks .other then that it should go right together

 

[KX'er]

ive got a couple other questions for you guys.

should i use a sealer on the cylinder gasket or the head gasket?

is it possible to get the cylinder on and not have the ring centered the ring pin?

I've always used copper coat on the gaskets. The one time I didn't the head gasket leaked.

As for your other question, not sure. I would say no.

 

[q2418130103p]

great, thanx for allthe input guys.

ive got the cylinder on, the piston facing the correct direction, the piston ring hopefully centered on the ring pin and it looks perty with all that shiney metal now.

we'll see what happens on saturday when i clamp everything down and start it up :-D (maybe ill get a neighbor to start it in case something comes flying off...)

 

[76GMC1500]

You can use Copper coat or any paint containing a high amount of aluminum pigment such as metallic paints on the head gasket. Not other gasket requires sealant. Using sealant will make future disassembly a pain. Hylomar HPF can be used if you absolutely must use something, it mainly just holds the gaskets in place and wont harden.

 

[whenfoxforks-ruled]

I thought that ALL water cooled oem cylinders after 81 were plated.Putting a liner in was an option for rebuild. If you are filing ring gap then they are iron,for a iron cylinder. The only way you will need a gasket sealer is to compensate for a problem,not flat or clean.

 

[q2418130103p]

I thought that ALL water cooled oem cylinders after 81 were plated.Putting a liner in was an option for rebuild. If you are filing ring gap then they are iron,for a iron cylinder. The only way you will need a gasket sealer is to compensate for a problem,not flat or clean.

so are you saying i will have a problem with an iron ring?

 

[whenfoxforks-ruled]

With out a doubt,if that cylinder is plated and you put an iron ring in it,it will not be plated for long! You should be able to see a difference in the finish,it is a micro fine finish,not the 1/4 inch liner!

 

[q2418130103p]

wiesco says the ring will damage chrome plated specificly, do they consider naksil coated to be chrome coated?

 

[q2418130103p]

http://www.wiseco.com/PDFs/Catalogs/CB07/Comp-Rings.pdf

"All Wiseco rings can be used in cast iron, nickel ceramic platings (Nikasil), boron composite, and Electrofusion bores."

so im expecting to be ok... even though the ring is not from 2007, its form like 2004 but i imagine they are the same.

 

[whenfoxforks-ruled]

All Wiseco rings can be used in cast iron, nickel ceramic platings (Nikasil), boron composite, and Electrofusion bores.
CAUTION: Unless otherwise noted, Wiseco rings can NOT be used in chrome plated bores. Engine damage will occur.
*CSM & CDM rings are designed to be used in chrome bores. I do stand semi corrected.Good luck on id ing the material in your cylinder?

 

[pradami]

and when your putting the piston in ,try to just put it straight in dont try to wiggle or twist the cylinder to get it in or you'll get the ring caught in a port and believe me it sucks .other then that it should go right together

Yeah....did this the other day.....pain in the....butt!! :bang: had to order new rings ($50).....stupid mistake!!

 

[shifter48]

Let me say something here....The opening of the C clips that keep the piston pin in must be either at 12 O'clock or 6 O'clock or you might throw one and do damange to your cyclinder and crank. The reason is that the piston goes up and down very fast and if the opening is at 3 or 9 o'clock it can compress and come out causing lots of $ damage, at 12 or 6 oclock it will only compress to the sides of the walls keeping it in....very important

 

[q2418130103p]

Let me say something here....The opening of the C clips that keep the piston pin in must be either at 12 O'clock or 6 O'clock or you might throw one and do damange to your cyclinder and crank. The reason is that the piston goes up and down very fast and if the opening is at 3 or 9 o'clock it can compress and come out causing lots of $ damage, at 12 or 6 oclock it will only compress to the sides of the walls keeping it in....very important

great, thanx for the heads up! i paid attention to that section of the manual and did my best to rotate the openings in the clip away from the reomval notch and down towords 6 o'clock, but i will pull it back off and double check it.