hi i got my cen ct4-s a few months ago no probs but now it wont shift in to second gear! is there a reason for this and what is the best set up for it...to fly. can anyone help me please? i just wont this beast to fly. could you email me back


thanks dan.

Did your car come with red spur gears or yellow and green ones? If red check the lip where the shift finger engages. That might be worn out.

yes i see what you mean and are the green and yellow gears better?and what would be the best set up for the gear ratio in basic terms like how meany turns on the 1.5mm screw?

yea the green and yellow gears are better.

they screw to alloy housings for better strength and alignment, the red ones seem to wobble about a lot more than these.

also the 2nd gear hub has an alloy pin that the clutch hits when it engages instead of the plastic lump in the red 2nd gear.

ive just put my rally back together, otherwise i would send a pic. well worth gettin the green n yellow set if u r havin lots of probs with the reds. not very cheap tho, and they dont stop u havin to take the whole back end to bits to replace them....

I asked the same question about the set screw for 2nd gear, and was told the stock setting on the MT was 4 turns out from fully screwed in. This setting might get u started - its always much easier to set when its changing at the wrong point rather than not changing at all. ur correct setting is probably slighty less turns out than this than this, but i could be wrong. Dont unscrew it much further than 4 turns out as it will get too loose and go walkabout at very hi speed!! All this is presuming u r running the silver spring and not the black one...?

hope that helps

thanks for that so what diffrance would it make if i change how many teeth i have on the gears and how many teeth should i go up?

i believe that the ct4s comes with these ratios as standard: Spurs 42/38 teeth, Pinions 15/20 teeth - 1st gear/2nd gear respectively. Second gear is the tallest (highest speed) ratio there is for the cen.
There are quite a few combinations that u could use tho. have a search on the net for the ratios available, just remember to be sure they will mesh ok. if u have a diffence of 4 teeth between the spurs, u will need a diff of 4 teeth between the pinions if u see what i mean. (usually - as u can see by the standard ratios is a little u can get away with - 20t - 15t = 5t diff, make sure u are spot on with this or at least very close indeed, and u should be ok)

smaller pinion and/or larger spur = shorter gears
larger pinion and/or smaller spur = longer gears

so ur only options are to go with shorter ratios (better acceleration) or to make the gearing of 1st gear closer to 2nd. I found that 14/18t pinions on 42/38t spurs was a good compromise between speed and acceleration on my rally, although i have now fitted 16t/20t with the same spurs, cos my .18 is still spinnin the wheels too much!!

www.cenracing.com has most ratios available, get the part numbers and run a search on those.

just a small point - when setting your gear mesh, check it at 90, 180, 270 and 360 degrees on the gears as they are not always perfectly circular im afraid.