Big Bore RS

[Damon]

Hi all,

Just a quick update, After blowing a hole in the crankcase big enough to fit you fist through on the 750, I am back to riding my mean, green, lawnmower machine.

It's coming to that time where a top end rebuild is in order. I have done a few of these before so I think I might bite the bullet and go for a big bore kit. I just have a question regarding carbs. Can I use the standard Carb the RS125 comes with or do I have to run a 34mm carb.

Thanks in advance and I hope everyone is well.

Damon

[Coxyzxr]

[temeluchus]

I dont think youd HAVE to use the bigger carb. Depending how much bigger you go it may restrict it a little but it will work. Almost certainly need some jetting tho.

[Kickstart]

Hi

You could probably either carb. The 34mm carb might well help, but the big bore kits are unlikely to give massively more power (although often a better spread of power) and should still be within reason for the 28mm carb.

Not sure for road use I would bother with a big bore kit on a 125. But then riding a 125 is a choice and I like the silly way of producing power.

All the best

Keith
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[bmwsport]

yea i wouldnt bother going for big bore kits, from what ive read they dont seem to be that much better, i'd have a look at a 34mm carb, v force reed block, forged piston, vhm head, decent exhaust if you dont have one already, should be plenty enough.

[Damon]

ok thanks all, I'll just go for a standard barrell and piston i think.

And coxyzxr, I was riding down the A217 and accellerating hard from each set of traffic lights. I accellerated from one set of lights and heard a small bang. The bike started sounding like it had no exhaust once it got about 5 - 6k revs. I slowed down and turned her round. It was all going well until I hit a red light just at the start of the mad mile. This is where I went wrong. I should have crawled home to live another day, but no, I decided to pin the throttle and cane it. I got to about 1**mph and it just let go. A rather loud bang followed by a smokescreen and a full pair of boxershorts. I dont think I should be aloud out of the house sometimes...

[Coxyzxr]

[bladerunner]

I've just rebuilt an rs125 with a polini big bore after the crank went south on the std 125 motor. the 125 top end was spotless rather lucky seeing as the big end went at a steady 70 on the duel carrageway. I must say the 154 kit with a 28mm carb does not have the top end zing after 10.5K compared to the 125 but the mid range is LOADS better. almost like riding a proper bike and it does wheelie a lot better with the torque. But for the money.....£380 just for the big bore....is it really worth it?

if I was back on a 125 then yes it's loads more fun in general day to day use as you have a choice of gears to be in but on std gearing it still has the same top end as the 125. Thats running a tyga pipe with std needle and now running a 132 main jet. the needle jet in the BB instructions was just too rich (x17) and it does vibrate a fair bit more as well
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[Damon]