What oem piston will be a good overbore for my 81' CB125S ?

Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

"I think pin is bigger diameter on XR/XL185 piston" good info for the OP to consider I can measure the piston pin bore no pin as I used it for some bracket extensions on an oil cooler already... save your junk man!
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

You need to tell my wife that, she's still trying to make me clean out everything ;D
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

I'm sure that the pin dia. is 15mm across all these small Honda singles all the way from CB125S up to XR/XL/ATC200's

The more I think about it I want to keep the XL200R engine for just a little later when I can swap the 6 speed trans. from a later XR200R into it and fully assemble everything.
I just like to have a good size big-bore in the CB125S stock engine for now and run that all over the place before I find someone to build me a custom 'CB' style low head pipe to hook up a high flow muffler for the XL200R engine. I had the head ported in the XL200R so I need to research who'll do the custom pipe work too.I want to use a bigger size i.d. headpipe like some of the builders of Aussie bucket racers recommended,somewhere around 36mm i.d.
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

If you come up with a routing design and how/where you want to mount the header, I could build a header out of one donor Ti take off from about any inline 4 stock pipe (about $100 eBay)... chop cut weld and Akrapovic makes an SBK system with megas that are perfect size and with a little mod to the baffle can be tuned in Tokyo mang :eek:

Just happens I have one of these on the hangar

IMG_8100.jpg
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

Tune-A-Fish said:
If you come up with a routing design and how/where you want to mount the header, I could build a header out of one donor Ti take off from about any inline 4 stock pipe (about $100 eBay)... chop cut weld and Akrapovic makes an SBK system with megas that are perfect size and with a little mod to the baffle can be tuned in Tokyo mang :eek:

Just happens I have one of these on the hangar

IMG_8100.jpg
Click to expand...

That's a Nice looking exh. piece 8) I already have the muffler that I want and now,it's just finishing up the XL200R engine job.. and installing it into the frame w/ custom top motor mount,wiring,etc...
I don't have the time to finish the 200 swap now but like that pipe !
That's why I'm going to do big bore on the CB125S engine because it's quicker.
I'm running a used std. piston w/ NOS rings right now and it's lame but gets me around.
How far away are you from the Pittsburgh,PA. area? I imagine I'd have to be close to you or the tube bender w/ the bike right there to fit the pipe.
There aren't many 'Japanese friendly' cycle places/suppliers around this area unfortunately.,or I haven't(and don't plan on)been living here long enough(1.5 yrs.)to locate them.
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

Six speed transmissionin XR is same as in XL125S.
Second gear is a bit weak but you can use a bench grinder to narrow CG125 gear to fit, it will still be wider than original (I know CG is 5 speed)
The best 'bang for buck' is fitting a 26mm Mikuni, I've put them on XL125~XL185 8)
Needs an aftermarket head pipe as original is a bit small ;)
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

I just make em up from sections like the mega in the pic, one 4 - 1 header provides a ton of bends and nice lengths of straight pipe to build a few single headers, as long as the spigot fits or is under sized I can sleeve it to fit. The exposed welds just look like a works pipe.

This is pipe art to me:
 

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Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

crazypj said:
Six speed transmissionin XR is same as in XL125S.
Second gear is a bit weak but you can use a bench grinder to narrow CG125 gear to fit, it will still be wider than original (I know CG is 5 speed)
The best 'bang for buck' is fitting a 26mm Mikuni, I've put them on XL125~XL185 8)
Needs an aftermarket head pipe as original is a bit small ;)
Click to expand...

I appreciate the knowledge on that.
PJ,I've got an 01' XR200R bottom end already that I will open up and get that 6 spd. into my 83' XL200R cases.., I'm hoping I can properly space it and may have to change a needle bearing or two inside the case.. & I may use the 01'(or may have to)kickstarter shaft and better gears that goes w/ it.I heard they improved the kickstart in either the 86'0r 87'- and they're stronger now. The 26mm Mik. you describe,is that flange bolt-on or round throat ?
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

Tune-A-Fish said:
I just make em up from sections like the mega in the pic, one 4 - 1 header provides a ton of bends and nice lengths of straight pipe to build a few single headers, as long as the spigot fits or is under sized I can sleeve it to fit. The exposed welds just look like a works pipe.

This is pipe art to me:
Click to expand...

That's a nice 'Works' looking pipe dude, Where you located ?
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

Tune-A-Fish said:
Memphis 8)
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Sounds good. I'd like to be closer as I said before because that pipe would look Great on the front of my bike 8) 8) ;D
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

grcamna5 said:
That's a nice 'Works' looking pipe dude, Where you located ?
Click to expand...

BUT that is a robotic welded motogp pipe
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

xb33bsa said:
BUT that is a robotic welded motogp pipe
Click to expand...

I won't need That pipe,just the right one for my application. I still think the welding is nice on it 8)
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

xb33bsa said:
BUT that is a robotic welded motogp pipe
Click to expand...

I doubt it's robo welded, but yes its a the pipe Repsol runs I'm not that handy but my welds are just as contaminated with neatoh colours my ZX10 - CB750 header will flow just fine :eek:
 

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Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

oh yeah that stuff is absolutely cnc/robatic
nice work to you as well :)
what are those pipes off a 1000 ? they sure look big hope yer not going for good hp
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

xb33bsa said:
oh yeah that stuff is absolutely cnc/robatic
nice work to you as well :)
what are those pipes off a 1000 ? they sure look big hope yer not going for good hp
Click to expand...

Yeah ZX10 2004 model, and i was thinking the same, but the ID is actually a mm smaller at the spigot, CB tubes are thick dick so run hotter not really sure what I will have, but I'm prepared to take more than a few cans to dyno and some longer/shorter final tubes. as for HP not gonna happen, I want some grunt and good power up to the limiter on tall gears for shorter burst fun in the canyons, probably not too safe at high speeds anyway so I'll kill it short. The thing lost a lot of poundage so it will be a decent stock bore CB 3/4 liter
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

Tun-A,
Those are tig welded SS ?
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

I hate to be that guy, but I knew better of the welds on that pipe so I verified "Akraprovich, and some others employ a staff of trained TIG welders and hand cut and weld the exhausts." [end quote]. now that IS for the race and proto stuff, not production stuff so yeah Siemens is at work in the Ak shop. Lets face it though... those pipes are not best case, a fluid formed or mandrel bent tube will always be the choice for the best flow rates.

I also don't and can't reach to pat myself on the back, however, i did enjoy (if I can call it that) time setting up robo welders, benders C-arm and Mandrel and end op machines at an exhaust factory and spent some winters welding at Kawasaki both on bike frames and stoopid shit and some cool stuff and and and strange enough... subway car parts. I learned to Jog without shoes a looong time ago.

I will say, I don't consider myself a "welder" those guys have certs and much time on the torch with big time rates and inspections... pipe fitters, boiler techs, med welders and nuke pipe fitters are "welders" I just like to hot glue with a lot mohr expensive glue gun than the Wife's melting iron :eek:
 
Re: What oem piston will be a good 'drop-in' overbore for my 81' CB125S ?

grcamna5 said:
Tun-A,
Those are tig welded SS ?
Click to expand...

That would be Atomic 22... er Titanium alloy.
 
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