Topic: cl125 piston kit

[nk140]

Will this piston kit work for the 73 CL125S? 
http://www.ebay.com/itm/Honda-CB125-Cylinder-Bore-56-5mm-CB-CL-SL-XL-124CM3-/180659817775?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item2a102a0d2f

The shape of the piston looks to be from a 75+ cb125.  The 73-74 CL125 had a flatter top to the piston like this.

http://www.ebay.com/itm/HONDA-GENUINE-OEM-NOS-CB125-SL125-PISTON-KIT-06134-330-000-75-OVER-CB-CL-/310946670373?pt=Motorcycles_Parts_Accessories&hash=item4865dda725&vxp=mtr

I need to either buy a top end kit for my CL125 or buy piston/rings and have the cylinder bored.  What do you guys think?

[grcamna2]

What shape does your piston have on the top? do you have it apart yet ? I think you need to ask the sellers for an exact description of the one you'll be purchasing before choosing one of them.

[nk140]

What shape does your piston have on the top? do you have it apart yet ? I think you need to ask the sellers for an exact description of the one you'll be purchasing before choosing one of them.

I have my motor torn down.  Mine has the flat top like the second ebay listing except for a small chunk missing hence needing a new piston and bore possibly.  I notice that after 74 the piston shape changed when the displacement of the 125's went from 122cc to 124cc.  All the kits that are being sold on ebay are for the later piston shape/124cc.  If I bore the 122cc cylinder to .5mm over that will equal a 124cc.  I am just concerned about the shape of the piston with relation to the early head design.

[nk140]

I guess I could go this route but that throwing more $$ into a bike that I am giving to my brother is not desirable. I think this will eliminate my piston shape issue.

http://www.ebay.com/itm/171248479818?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

[grcamna2]

nk,
I think if you look for a piston & rings for an SL/CL125 you'll be good to go.I'm fairly certain that the newer 124cc motor comes w/ a 2-piece cyl. head and that has a slightly bigger intake valve;I'd keep the same piston that it has stock..the flat top.
I just hate Chinese stuff,if it was me I'd get a hold of an NOS piston and rings from the dealer,it'll last a LOT longer than that China Honda clone piston,etc.

[nk140]

nk,
I think if you look for a piston & rings for an SL/CL125 you'll be good to go.I'm fairly certain that the newer 124cc motor comes w/ a 2-piece cyl. head and that has a slightly bigger intake valve;I'd keep the same piston that it has stock..the flat top.
I just hate Chinese stuff,if it was me I'd get a hold of an NOS piston and rings from the dealer,it'll last a LOT longer than that China Honda clone piston,etc.

I was thinking the same with the NOS stuff.  I found a .75 overbore kit for fairly cheap.    I just need to get an answer from the seller if it comes with rings or not. Cylinder definitely needs a bore to fix the scoring that the small chunck of piston caused. Thanks for your advice.

[grcamna2]

nk,
You can find parts w/ the Honda dealer computer parts locator thing they have.

I'm looking for an 81-82' CB125S...kind of like a 'barn find' somewhere not far from me & if you ever hear of one or know of one that's complete but abandoned please let me know. 

[nk140]

nk,
You can find parts w/ the Honda dealer computer parts locator thing they have.

I'm looking for an 81-82' CB125S...kind of like a 'barn find' somewhere not far from me & if you ever hear of one or know of one that's complete but abandoned please let me know. 

I ended up buying the NOS Honda brand .75mm overbore piston.  Just need to get it in so the machinist can have both before starting the bore.

I will keep my eyes open for ya.

[grcamna2]

nk,
You can find parts w/ the Honda dealer computer parts locator thing they have.

I'm looking for an 81-82' CB125S...kind of like a 'barn find' somewhere not far from me & if you ever hear of one or know of one that's complete but abandoned please let me know. 

I ended up buying the NOS Honda brand .75mm overbore piston.  Just need to get it in so the machinist can have both before starting the bore.

I will keep my eyes open for ya.

nk,
I'm glad you purchased the Honda OEM piston,it's tougher & it'll last;did you get any OEM rings yet? I know of a few places who might have'em if you haven't.
When you bring the piston to the machinist make sure you tell him to make the clearance 'tight'(by that I mean,if he's an 'Auto' machine shop,he'll think the stock Honda clearances are too 'tight' by his automotive 'experiences'...)and I mean probably between .001-.0015 in. I hope you have a good Honda Service Manual to prove to him the 'tightness' of the Factory Honda clearances.
I'm really just saying:tell the guy to 'go by the HONDA book'... 
I've had auto machine shops set a few of my cylinder-piston side clearance up from .002-.003 in. and it was too loose and I had piston slap in a 1000 miles !
You just need to break it in right and then No Worries 

[nk140]

nk,
You can find parts w/ the Honda dealer computer parts locator thing they have.

I'm looking for an 81-82' CB125S...kind of like a 'barn find' somewhere not far from me & if you ever hear of one or know of one that's complete but abandoned please let me know. 

I ended up buying the NOS Honda brand .75mm overbore piston.  Just need to get it in so the machinist can have both before starting the bore.

I will keep my eyes open for ya.

nk,
I'm glad you purchased the Honda OEM piston,it's tougher & it'll last;did you get any OEM rings yet? I know of a few places who might have'em if you haven't.
When you bring the piston to the machinist make sure you tell him to make the clearance 'tight'(by that I mean,if he's an 'Auto' machine shop,he'll think the stock Honda clearances are too 'tight' by his automotive 'experiences'...)and I mean probably between .001-.0015 in. I hope you have a good Honda Service Manual to prove to him the 'tightness' of the Factory Honda clearances.
I'm really just saying:tell the guy to 'go by the HONDA book'... 
I've had auto machine shops set a few of my cylinder-piston side clearance up from .002-.003 in. and it was too loose and I had piston slap in a 1000 miles !
You just need to break it in right and then No Worries 

Thanks for the advice.  I downloaded a manual to show the tolerances.  I will definitely push for tight tolerances.  I got the kit with the Honda .75mm rings as well.  What is the correct way to break it in?  When I break an engine in, I just ride it like I would ride normally then change the oil early.

[grcamna2]

Nick,
Different people have different ways,lot's of conflicting views on Break-in   
 I like to do similar what you mentioned.I start it up w/ the first few miles and run it decently,make sure to give the RPM's what you normally have,go a bit easy the first ride;down shift a lot.I like to run it hard enough to break the rings in properly.I think it's good to put your hand on the left crankcase cover to judge how hot it's getting... The engine should be shut off when hot and allowed to cool off completely;do that over and over.The thing I think is important is the first 50 miles,the first ride go easy but the 2nd & 3rd one give it more gas and work it progressively more.I like to downshift and rev it towards 6-7(on the way to 8K) on your CB125 (if you have a tach.)and then let off to let the rpms drop.
I think the key is drive it as you normally would but vary the rpm's and let it cool off fully once it's heated up before you go again;don't baby it too much,don't climb hills in a high gear!,keep down shifting and up the rpm's to correctly 'seat' those new rings.I'd ask the machine shop to finish hone w/ #400 grit stones.
That little 125 likes RPM's so break it in the way you enjoy riding;the powerband runs nice from 6500-9500 rpms and that's the 'sweet spot' w/ your bike so get it used to 'powering up' to that regularly. I've owned many CB100/125's and that's what I've done and they worked out best that way.