Scooterotica

OK, recently checked out a few posts on here and LCGB, all relating to tuned bikes using SX200 gearing.

I've got a Challenger 240 (originally worked by Bob Monkhouse and Martin Cook), in the 80's.

Recently needed honing out and new piston (got Kawi 750 Wiseco piston and fettled by Martin at Chiselspeed.

Have now run in and its almost running sweet.

2nd and 3rd gears are really awesome.

1st gear won't rev out fully. 4th gear cannot be used in anger unless downhill or zero wind.

so its currently running Mikuni TMX 35, with reed valve porting, and JL4 exhaust.

I'm just wondering if the JL4 might be too revvy for this setup, and from everyone else's comments on other posts, a JL3 or Taffspeed might be better and get me to be able to use 4th more.

Finally, 1st gear, do you think thats an exhaust or carb issue ?

I have some other gearboxes I could swap in, but for moment would like to try and get SX200 working acceptible, as I beleive was originally built with the SX200 gearing

Thoughts ??

a more torquey exhaust would help but the final ratio of the sx is a little tall for tuned revy motors, its a 4.8 and i reckon you wanna be around 5 or even 5.2 if its peaky.
so if ya wanna keep your sx box in it a 48t crownwheel would do it
better to change the box tho and get 3rd closer to 4th.
ie a pacemaker with 17/47 sprockets, or if ya got one put in an li150 box.

as for 1st its probably a bit rich on yer jetting

the taffy pipe will limit the revs available
I have a mugello 225 with
179 exh
153 inl
124 tran port timings
with jetting set slightly rich this will only rev to 7000 ish on sx200 gearing mind you pulls like a train all the way up .depending on your timings and what you want,you may be better off with something else .I haven't tried a jl3 but am considering a devtour myself in search of another 500 or so rpm

Paul

I had the same sort of problems with my race rapido 225 on sx 200 gearing, swapped to li150 box and it is sweet now.