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Re: Getting the most out of a 125

Posted: Fri Oct 13, 2017 7:09 am
by davebike
Odd
I run a tuned (better cam valve springs and inigtion ) 90 (85cc) engine with an ACF70 four speed gearbox and I touched 60 on the flat !
But I got a rev counter and spent some time setting up the gearing to be spot on !

DW

Re: Getting the most out of a 125

Posted: Fri Oct 13, 2017 6:10 pm
by ChesterC90
I've heard of modding your standard c90 engine, taking it up to 110 using a 70 head? But I've mot done enough research to understand how it works.
Getting on a bit does slow the old noggin. So I come here? For advise and inspiration!

Re: Getting the most out of a 125

Posted: Fri Oct 13, 2017 6:17 pm
by Diesel Dave
Try going for a run at full speed but your only allowed to breathe through a straw.

You will take off like a scalded bat but be unable to reach anything like top speed.

Your carb is waaaay too small for a 125 unless you want a trials bike with loads of torque and bottom end but no rev's

ATC carb and BBR manifold would allow the motor to breathe much better.

Re: Getting the most out of a 125

Posted: Sat Oct 14, 2017 7:54 pm
by ChesterC90
Update:

Fitted a mikuni 28 carb, which I know is probably too big, but 1st signs are good. Bike starts and runs, but Boggs when either the main jet or needle come into play.
Going to 1st try needle on top and middle, then get into main jets. I'm thinking the pilot I ok, as it runs well when ridden 1/4 throttle.

And the sound.. Well it's like a my neighbours Harley, very loud with some great tick over notes.

I'm hopefull this carb when set up right will do the trick, remains to e seen if it can go over 50, but fingers crossed.

Thanks for the input by other members.

Re: Getting the most out of a 125

Posted: Sun Oct 15, 2017 8:22 am
by Diesel Dave
Main jet size first - everything else follows.....

Re: Getting the most out of a 125

Posted: Sun Oct 15, 2017 5:48 pm
by ChesterC90
Have you a link on flea bay where you got your atc 1 Dave?
Cheers

Re: Getting the most out of a 125

Posted: Mon Oct 16, 2017 11:01 am
by Diesel Dave

Re: Getting the most out of a 125

Posted: Mon Oct 23, 2017 11:54 pm
by gtd65
Strange, my Rider's Super Cub goes a lot faster than that and it's totally standard.

I've had (an indicated ) >100km/h on the speedo.

Nips along very happily at 85~90 km/h on the flat too.