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View Full Version : 81 250r 72mm over?


Deathrocket
08-03-2010, 10:38 PM
Hi folks!
its been a while.. still trying to catch up from being unemployed for almost a year.. but anywhoo I'm finally going to bring my 250r's cylender to the machinist next month and i was wondering whats the safest overbore you would run on this? theres a pretty good grove in the cylinder from the wrist pin circlip letting go and i may have to go to 72mm bore to clean it up. will there be any issues with going this far over? I am only going to bore it out enough to clean it up so I may go smaller then that.. what do y'all think? thanks folks.
84honda200s
08-03-2010, 11:44 PM
i wouldnt go more then 3mm over the stock bore but thats just my 2 cents lol
KASEY
08-04-2010, 12:15 AM
hell stock bore is 70mm so going to 72 is no big deal,, if that cleans it up GO!!!!
Yamaha_Rules69
08-04-2010, 09:18 PM
72 mm is maximum overbore - if the time ever came that it needed rebuilt, you would either have to have a sleeve installed, or replace the jug. A lot of people think that if they bore it to the max, they will gain a lot of power - not true! If you want more power, you need a big bore kit, or pipe, intake, carb, and head and porting mods to achieve what you really want. You are doing the right thing by just getting it bored to get it cleaned up, and not just wasting the cylinder sleeve. Show it to the machinist, and he should be able to tell you how much it will needto be bored. Good luck!
Tecate 50
08-04-2010, 09:20 PM
72 mm is maximum overbore - if the time ever came that it needed rebuilt, you would either have to have a sleeve installed, or replace the jug. A lot of people think that if they bore it to the max, they will gain a lot of power - not true! If you want more power, you need a big bore kit, or pipe, intake, carb, and head and porting mods to achieve what you really want. You are doing the right thing by just getting it bored to get it cleaned up, and not just wasting the cylinder sleeve. Show it to the machinist, and he should be able to tell you how much it will needto be bored. Good luck!

I agree...
Deathrocket
08-06-2010, 10:09 PM
Well WOOT!! took my cylinder to the machine shop today for a 2nd opinion and I measured the bore wrong its roughly at 70mm woohoo! machinist thinks .75 mm will clear it up.. so I will still have a few rebuilds left yay!! while its apart I am going to have the head milled .010 and maybe a stroker kit.. if one exists.. we shall see...