rs125 engined cr

[gainsboro]

i am building a bike for beach racing using a 1994 rs125 road race engine in a 2000 cr125 chassis
please tell me ,
do i want a "long front section " to thefirst part of the exhaust pipe,either using a spacer or particular make of pipe?

will vforce reeds help as they do on the cr engine ?
do i want a reed spacer ?
obviously im trying to get some low/midrange improvements
it will be an experiance if nothing else ?
any help will be gratefully received
thanks

 

[David Trustrum]

do i want a reed spacer ?

No you want a CR engine. An RS will make a miserable bike in the sand.

Oh please tell me you are not running the RS gearbox!! First gear is insane & close ratio means you have to gear it up to get any speed out of it.

Oh yeah, don’t grind the step out of the exhaust port.

 

[gainsboro]

which year rs engine did you try ?
this is a 94,with later conrod enabling use of 2001 pistons
d shaped 39mm carb,rs ignition
std gearbox ratios,6 speed
will be using 49 to 52 teeth as opposed to the rs,s 30 teeth
we already have bikes with cr engines,launch control,quickshift etc
we also have a room full of trophys stamped 1st !

 

[Pekka Hänninen]

CR-125's with RS-125 top end were very popular ice racing bikes here in Finland couple of years ago. Maybe you could find someone with more info at http://www.iceroadracing.com/ or http://www.teamlaine.com/

 

[David Trustrum]

RSs are brilliant bikes, but the power characteristics & the gearbox are suited to high speed on hard pack surfaces (tarmac) where you don’t have to slow down for the corners. Unless your beach racing differs from what I remember here I think your launch speed out of loamy corners will be somewhat depressing.

My first racestart on an RS had me releasing the last mm of clutch at about 50mph only to have the bike bog & I just remember saying “You’re joking there can’t be MORE!?!” Obviously yours will be geared down (from ~ 1.8:1 to 3:1) but I remain sceptical.

Prove me wrong & have a good time.

But a smaller carb (that has a change of fitting into the airbox) will help down low, skim the base of the barrel to lower the exhaust & a decent pipe to suit the conditions.

 

[gainsboro]

track is long oval,from the start gate to first corner the bikes are flat out in 5th,using 49t
as long as we can gear it right,you can clutch it out the corners,something you cant do on tarmac !