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

[crazypj]

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

The 26mm Mik. you describe,is that flange bolt-on or round throat ?

You can use either but would have to find the matching manifold ior get adapter
I used flange mount off left side of Suzuki GT250, there were a load of cheap ones around at the time (right side didn't have enrichener passages drilled)
You can get 'aftermarket Mikuni' from China with flange mount. IIRC, you have to file mounting holes into a slot with 1/4" round file and swap pilot and main jets for smaller ones

 

[grcamna5]

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

PJ,
I found a nice oem Honda round 'carb. insulator' Manifold w/ 'atomizer plate' from a 1976-79' model CB125S that's still in great cond. so if I find a round throat carb. that's good for this app. I'll give that a try.

 

[xb33bsa]

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

get an sl350 carb 24mm , the 350 hondas are prety much exactly the same engine as the little singles

 

[grcamna5]

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

get an sl350 carb 24mm , the 350 hondas are prety much exactly the same engine as the little singles

26mm would be better

 

[xb33bsa]

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

you can open up the 24 to a 25 with a rat tail file

 

[grcamna5]

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

you can open up the 24 to a 25 with a rat tail file

OUCH ! open up the carb. w/ a 'rat tail' file ? :
I would prefer to get a carb. that already has it's precision shaped inner throat/venturi open to 26mm;I wouldn't know the correct way to file a carb. throat and would rather not do that.

 

[grcamna5]

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

bump, Still looking to see if anyone here has installed a bigger sleeve and early CB750 61mm piston. I think a big bore CB550 piston could be similar

 

[xb33bsa]

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

OUCH ! open up the carb. w/ a 'rat tail' file ? :
I would prefer to get a carb. that already has it's precision shaped inner throat/venturi open to 26mm;I wouldn't know the correct way to file a carb. throat and would rather not do that.

i did it for the pair on my sl350 worked great,takes a lot of skill and knowhow tho

 

[Tune-A-Fish]

use a brake cyinder hone and the shop fox Oscillating Drill Press man!

Or buy a 26mm carby.

 

[xb33bsa]

use a brake cyinder hone and the shop fox Oscillating Drill Press man!

Or buy a 26mm carby.

HA WELL THE OVAL kehins take some fine rat tail work it aint a round hole thru there
the thing is the sock oval bore keihins are a far superior carb than a vm minkuni

 

[grcamna5]

I got a stock 87' XR200R carb. off ebay for it and hope it'll be good.

 

[crazypj]

XR200 carb should be even easier to make work.
Oval bore Kei-Hin are real easy to modify, 'pear shape' the top so you get higher airflow at max rpm (Honda did it years ago)
Using anything inside bore usually doesn't work properly as you need to offset bore or slide doesn't seat (I saw some 'clever' stuff back in the 70's ;D )

 

[Tune-A-Fish]

HA WELL THE OVAL kehins take some fine rat tail work it aint a round hole thru there
the thing is the sock oval bore keihins are a far superior carb than a vm minkuni

Oh come on just wrap some emery around a soft sponge it will conform to the shape just fine.

 

[crazypj]

Just for polishing after filing..
As long as you mark where the skide is at full throttle plus give at least 1/2mm support either side, it works fine going 'pear shaped' ;D

 

[xb33bsa]

yeah for the sl cobbs i got these jinormis rat tails course bastards about 16" long and 5/8" dia. 8)

 

[grcamna5]

xb,
Tell me about that avatar 8) Did you meet her broken down on a trail when you were out riding ? ;D tough to imagine her going out for a ride w/o a helmet...

 

[crazypj]

It was posted in 'Uncle Ernie's Inspirational Pics' awhile ago (maybe a year or two?)

 

[Tune-A-Fish]

xb,
Tell me about that avatar 8) Did you meet her broken down on a trail when you were out riding ? ;D tough to imagine her going out for a ride w/o a helmet...

I did, last nigh and the night before :-\

 

[grcamna5]

I did, last nigh and the night before :-\

Was it that bad?

 

[xb33bsa]

back in the day,on another planet i knew a redhead that played state college soccer 1rst string and she had back dimples just like that