Wiseco 120 BB = race gas ?

Does anyone know if you run the 120 bb piston in a XR 100 - do you need to run race gas? Can you get away with running pump gas? If not - is there another brand that I could use that I don't need to run race gas? Just don't really want to have to deal with dif. gasses with all the bikes! Wiseco seems to be the cheepest way to go - this is for my son's bike.

Thanks dp :naughty:

You can run pump gas if you don't machine anything off the cylinder deck height.

I would use premium pump gas (93-94 octane) if you do need to machine the barrel or head use 2 base gaskets to lower the compresion.

Thanks :naughty:

Is there a reason I may need to have the head or barrel shaved?

Any idea if the bike will be as dependible as stock?

Will it run hot or hotter due to the thinner sleve? Not sure how much room there is for shaving the sleeve down - or how much "meat" is left after milling the sleeve?

Thanks Dan :naughty:

have a 1985 xr 100 with wiseco 120 kit, re-sleeved,cam, and heavy duty valve springs, it rips with super unleaded

have a 1985 xr 100 with wiseco 120 kit, re-sleeved,cam, and heavy duty valve springs, it rips with super unleaded


Do I need to resleeve the cylinder or can you just boar it out?

What cam are you useing?

Why the heavy valve springs? Floating at high revs?

Does your bike run hot at all ?

Did you have to change the jetting - if so what did you go to?

Thanks for the help!! :naughty:


i do believe you need to resleeve, if you go with the 120 kit, stock sleeve is to thin wont work, i got a cam through engines only near my home in san jose area, there web site is xr100.com, cam came from a company in san rafeal,ca. my weight 230lbs and cam and bore you will need to go with heavy duty valve springs, i did have problem with exhaust valve hitting top of piston before and after new cam and springs, filed piston down some but valve still hits piston. i have been riding it like that for a long time and just dont care anymore, engine just ticks real loud but no problems. bike runs normal temp maybe a little hotter i am not sure, as far as the carb goes i run a late 70s elsinore cr125 carb. it has the same openings as the 200atx or atc or whatever it is that everybody else is using, also run header wrap, uni pod filter, homemade power now, and white bros r4 pipe, hope this helps

It does help.....thanks!! :naughty:

It sounds like a fun bike - I love riding my kids 100s - my son is 9 and weighs 90 lbs so I will prob. just go with the 120 kit. I live just up the Hy from you in San Carlos - who did the resleeveing for you - did you send it out?

Thanks dp

I think it might be easyier buying the L.A. Sleeve 120cc kit from denniskirk.com I was looking and the kit comes with a brand new cylinder already pre bored with the cylindere it from the way they describe it.

Yes, you have to re-sleeve. Most machine shops can do it. Run two base gaskets. The problem of running race or not, mainly has to to with running at peak performance or not and most importantly pre-ignition wrecks havoc on you piston, which can lead to granading the motor. The machine shop can probably take a little off the top of the piston too. As far as reliabilty goes, as long as you change the oil all the time, it will last for a long time. For a cam, you probably should get a mild cam, larger cams require grinding you rocker arms and exhaust valve guide. Combine this with a 1984-85 atc 200x carb and the motor will go pretty good.

Are you saying that I should run a dif. cam with the BB kit? If so why?

And are you saying if I do get a cam - to get a mild one so I don't have to grind the rocker arms?


I talked to DK and that is a misprint - does not come with the cylinder - just the sleeve.

Stupid ? - where do you buy the sleeve?


that sucks. they all come with the sleeve

Or a kitaco kit.


Are you saying that I should run a dif. cam with the BB kit? If so why?

And are you saying if I do get a cam - to get a mild one so I don't have to grind the rocker arms?

Stupid ? - where do you buy the sleeve?


Wiseco or LA sleve have them

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