james.warrenfillbrook Posted November 19, 2014 Share Posted November 19, 2014 Hi there, I've got a ybr custom 125cc, love the bike just don't like the speed. I'm looking to get a big bore kit fitted, now are they easy to fit?? Do they make much difference??? Thanks in advance Link to comment Share on other sites More sharing options...
blackhat250 Posted November 19, 2014 Share Posted November 19, 2014 Hi james , its 4 stroke , so its more complicated than a 2stroke , I.M.O. I would save the cash for your test, then upgrade, 300-600cc Link to comment Share on other sites More sharing options...
Noise Posted November 20, 2014 Share Posted November 20, 2014 Setting it up to TDC, if its a OHC (dobt it is) then you need to keep the cam it the correct possion, then take off the head, then remove the barrel, take out the gudion pin locking ring, then remove the gudion pin from the piston, fit new piston and rings (the correct way) fit new bigger gudion pin, fit new barrel without damaging the piston rings, re-fit head and cams etc. Turn engine over by hand to make sure your not hitting the head with the piston. if all is ok then fire it up. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted November 22, 2014 Moderator Share Posted November 22, 2014 Setting it up to TDC, if its a OHC (dobt it is) then you need to keep the cam it the correct possion, then take off the head, then remove the barrel, take out the gudion pin locking ring, then remove the gudion pin from the piston, fit new piston and rings (the correct way) fit new bigger gudion pin, fit new barrel without damaging the piston rings, re-fit head and cams etc. Turn engine over by hand to make sure your not hitting the head with the piston. if all is ok then fire it up. what about the other bits? like a rebore(if there's enough meat to bore), carb rejet (poss a new carb needed) 1 Link to comment Share on other sites More sharing options...
Noise Posted November 23, 2014 Share Posted November 23, 2014 Yer thought id let someone else complicate things a bit further Link to comment Share on other sites More sharing options...
clarke Posted November 23, 2014 Share Posted November 23, 2014 If you've not done your test you probably can't ride it legally with a big bore kit... If you have done your test, buy a bigger cc bike, much easier, more reliable and the insurance companies won't rape you for modding the engine. Link to comment Share on other sites More sharing options...
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