|
Author |
Message |
giggl3fac3 |
This post is not being displayed .
|
giggl3fac3 L Plate Warrior
Joined: 06 Sep 2018 Karma :
|
Posted: 21:14 - 06 Sep 2018 Post subject: CBF 125 bore kit??? |
|
|
I'm using a CBF 125 as a commuter to work. It's great on fuel but I want to be able to sit at 70 comfortably and not get stuck behind lorries .
Has anyone fitted a bore kit?
Is it worth it?
I have a full licence so I could get a bigger bike with high mpg but I cant find any that come close to my CBF. |
|
Back to top |
|
You must be logged in to rate posts |
|
|
MarJay |
This post is not being displayed .
|
MarJay But it's British!
Joined: 15 Sep 2003 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
FretGrinder |
This post is not being displayed .
|
FretGrinder World Chat Champion
Joined: 29 Jul 2010 Karma :
|
Posted: 21:34 - 06 Sep 2018 Post subject: |
|
|
Leave it alone. It's not worth it.
Get a full licence.
Get a bigger bike.
____________________ Yamaha MT-09
ಠ_ಠ |
|
Back to top |
|
You must be logged in to rate posts |
|
|
giggl3fac3 |
This post is not being displayed .
|
giggl3fac3 L Plate Warrior
Joined: 06 Sep 2018 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
giggl3fac3 |
This post is not being displayed .
|
giggl3fac3 L Plate Warrior
Joined: 06 Sep 2018 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike tl;dr
Joined: 01 Jun 2010 Karma :
|
Posted: 23:24 - 06 Sep 2018 Post subject: |
|
|
In long hand, engine power is Cylinder pressure, times Cylinder displacement times crank revs.
More cylinder capacity should then equate to more power, but only if you can maintain the same cylinder pressure. Here-in lies the niggle.
Power tends to increase with engine revs; up to peak torque engine revs, so does cylinder pressure. There the valve timing and port sizes etc reach an optimum to cram as much charge in the pot as possible, and make as much cylinder pressure as you can. Below peak torque revs, the optimum hasn't been reached and cylinder pressure will be below maximum, and so will power. Above peak torque revs, the cylinder pressure is starting to fall, as the ports cant keep up the rate of flow to fill the cylinder to capacity each cycle, but, more cycles at less pressure, make up the difference, and power tends to continue increasing up to peak power rpm, where the flow capacity starts to choke the cylinder filling, and cylinder pressure drope more than revs can make up.
With the same cam, valves, same valve lift... a bigger pot, will tend to drag peak torque down the rpm range a bit, as the ports flow the amount of charge they might up to thier capacity, so fill the larger cylinder earlier; but then, the ports start to choke the flow, and peak power will also be reached earlier, as the cylinder is short filled each cycle as revs increase; and you 'probably' wont get any more power from the bigger engine.. you might.... but not a lot; because the cylinder pressure has been falling for however many rpm up the range.
70mph?
To achieve that, well, you might get it with about 12bhp, but only in more ideal conditions. To achieve it more often and more reliably, you really need to have a surfiet, around maybe 20bhp... that would mean doubling the power of most humble soft-tuned 125's, and that is not an easy job, and would take an awful lot of tuning above and beyond merely boring the thing out; where even boring the thing to 250cc wouldn't do the job, as the competing factors of cylinder pressure and revs work against the one of cylinder displacement.
Could be done...... but..... I VERY much doubt you'd get that sort of power from a humble air-cooled four-stroke single.
Honda CB125Twin, with two pots and a pretty wild cam, and hemi heads, managed 17bhp, and not all that reliably. The Yamaha / Minarelli YZF-R125 motor, as stock makes A1 complient 15bhp.... tuning can get them up to around 17/18bhp or so, with varying degrees of UNreliability, and ading a big-bore kit 'may' as long as they dont sieze, get them scaring the 20bhp mark....
BUT, point is, you are still looking at achieving something that has 70, probably even 80+mph potential, you are not realistically looking at creating something capable of sustained 70mph 'cruising' with a bit of spare to get past artics and dodge audi-enemas.
MY answer is, stuff it, sit it out behind the artic.... at 55mph; the m-way is boring as feck anyway, relax, enjoy the fact that you are still making a batter average speed than trying to batt it out cross country, where roundabouts and traffic lights bring a 60mph road-speed down to more like 30 average, very quickly; enjoy the lack of SMIDSY stress, and if you are a bit brave.... being in the 'bubble' of an artic's slip stream, being sucked along in its wake, in a bubble of effectively still air on a whiff of throttle, pushing MPG up to moped MPG's!
Or, get a bigger bike... and even then.... I tend to avoid the M-Way cos of boring, but when I do use it, 55 in the truck-stack is still easy riding and more progress than trying to point to point cross country; saves fuel and stress, and an Audi-Enema.... and on a 100+ motorcycle, that is something the extra is inclined to beg you engage in... trying to play with the blitzen-bimmers in the middle and outer- lanes... and its a game you really just cant win... dey got a box round'em! They aint putting the same stake on the table when they call your bluff! so why even get in the game? Its just extra stress, extra fuel, and risk to life and licence you really dont need.
But your call... but a big bore kit really isn't much of a solution to very much, I'm afraid. ____________________ My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
Back to top |
|
You must be logged in to rate posts |
|
|
temeluchus |
This post is not being displayed .
|
temeluchus World Chat Champion
Joined: 01 Oct 2008 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Ste |
This post is not being displayed .
|
Ste Not Work Safe
Joined: 01 Sep 2002 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
pits |
This post is not being displayed .
|
pits World Chat Champion
Joined: 22 Apr 2008 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Wonko The Sane |
This post is not being displayed .
|
Wonko The Sane World Chat Champion
Joined: 20 Jan 2013 Karma :
|
Posted: 17:01 - 18 Sep 2018 Post subject: |
|
|
Teflon-Mike wrote: | In long hand, engine power is Cylinder pressure, times Cylinder displacement times crank revs.
More cylinder capacity should then equate to more power, but only if you can maintain the same cylinder pressure. Here-in lies the niggle.
Power tends to increase with engine revs; up to peak torque engine revs, so does cylinder pressure. There the valve timing and port sizes etc reach an optimum to cram as much charge in the pot as possible, and make as much cylinder pressure as you can. Below peak torque revs, the optimum hasn't been reached and cylinder pressure will be below maximum, and so will power. Above peak torque revs, the cylinder pressure is starting to fall, as the ports cant keep up the rate of flow to fill the cylinder to capacity each cycle, but, more cycles at less pressure, make up the difference, and power tends to continue increasing up to peak power rpm, where the flow capacity starts to choke the cylinder filling, and cylinder pressure drope more than revs can make up. |
I got about that far and thought "turbo" ____________________ Looking to pass your CBT / Bike tests in Bury Lancashire? try www.focusridertraining.co.uk Would recommend.
They're also on Facebook https://www.facebook.com/pages/Focus-Rider-Training/196832923734251 |
|
Back to top |
|
You must be logged in to rate posts |
|
|
Pigeon |
This post is not being displayed .
|
Pigeon World Chat Champion
Joined: 27 Sep 2012 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
stevo as b4 |
This post is not being displayed .
|
stevo as b4 World Chat Champion
Joined: 17 Jul 2003 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Triton Thrasher |
This post is not being displayed .
|
Triton Thrasher Could Be A Chat Bot
Joined: 16 Oct 2012 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Evil Hans |
This post is not being displayed .
|
Evil Hans World Chat Champion
Joined: 08 Nov 2015 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
stevo as b4 |
This post is not being displayed .
|
stevo as b4 World Chat Champion
Joined: 17 Jul 2003 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Ste |
This post is not being displayed .
|
Ste Not Work Safe
Joined: 01 Sep 2002 Karma :
|
Posted: 22:52 - 18 Sep 2018 Post subject: |
|
|
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
pits |
This post is not being displayed .
|
pits World Chat Champion
Joined: 22 Apr 2008 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Northern Monkey |
This post is not being displayed .
|
Northern Monkey World Chat Champion
Joined: 17 Nov 2013 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Evil Hans |
This post is not being displayed .
|
Evil Hans World Chat Champion
Joined: 08 Nov 2015 Karma :
|
|
Back to top |
|
You must be logged in to rate posts |
|
|
Old Thread Alert!
The last post was made 5 years, 218 days ago. Instead of replying here, would creating a new thread be more useful? |
|
|
|