Yasuni C21 Jetting problem helpp!!

hi been working on my bike all day ive just got a c21 pipe did have a zx running on a 85 jet, so bought 95 100 & 105 for the c21 put it on and it has nooo power at all any idea jet what to use?? cratch: cratch:

oh and ive got a stage 6 racing barrel cheers

will more than likely need lighter rollers as well as upjetting, possibly stiffer clutch springs or the tension increasing if youve got an adjustable clutch...

The C16 is the better pipe on an unported stage 6 racing, yes the C21 develops more top end power but the c16 beats it everywhere else

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cheers il try that tomorrow, i wanted to get the c16 but got given the c21 for free so werent going to argue with that lol, what jetting would u recommend? 95 100 or 105?? cheers sam

what carb are you using ?

dellorto phbg 21mm

CherryAerox said:

dellorto phbg 21mm

open filter ?

malossi foam

selling or trying to swap the c21 for a c16 now do u reckon anyone will??

CherryAerox said:

selling or trying to swap the c21 for a c16 now do u reckon anyone will??

as youve got the C21 already, you may as well try and get it running properly...

will be a case of dropping your roller weight and possibly fitting stiffer clutch springs to compensate for the big loss in torque lower down the power curve

so u reckon its only that?? earlyer we put a zx pipe on with 85 jet and it run like normal but as soon as we put the c21 on and up jetting it hardly moves has no power at all??

A C21 is a totally different animal to a ZX, get the clutch set up to pull away with higher revs and drop the roller weight

Everything happens much higher up the rev band on a C21, you need to adjust your transmission to suit :good:

once you get it set up properly, the 1st time you feel the full effect of the pipe you will have a smile on your face...

As Capri dave said, the C16 has decent bottom & topend.. The C21 has vertially no bottom end performance, ALL the power comes in a certain Rpm range and on a C21 that Rpm range is freaking high! So your engine will not perform unless its running in the correct Rpm range (also known as a powerband).

So you want light rollers, stiff clutch springs, so the engine will have to rev into that powerband and your'll fly off, you want to be hitting atleast 10,000-12,000rpm to get the bike moving.

The C21 is pretty much useless on the roads, its full throttle or no throttle with this pipe, theres no mid or bottom performance at all meaning you cannot cruise at 30 or 40mph, you have to blip the throttle and keep that engine revving high.

And as said by dave, C21 wont run brilliant anyway on an un-ported kit.
Get a spanking new kit, S6 racing, polini evo or Malossi MHR, then send it off to minor or shiney red and have them port it to suit your setup.

My aerox with polini corsa, std carb, std airbox, crank e.t.c with a giannelli extra on has a 78 jet in i put my yasuni on and it runs really rich so im guessing i will need to downjet? and i will need lighter rollers and stiffer clutch springs.

04rox said:

My aerox with polini corsa, standard carb, standard airbox, crank e.t.c with a giannelli extra on has a 78 jet in i put my yasuni on and it runs really rich so i'm guessing i will need to downjet? and i will need lighter rollers and stiffer clutch springs.

what yasuni is it ? and what makes you think its running rich ?

Yasuni R and i know its running rich because of the sparkplug i put my giannelli extra back on n took it for a quick spin probs wont make no difference but il check the spark plug later on.

Hi i have an yamaha aerox with similar problems Setup:
Mhr rep 70
Crank
21 delloroto carb (92 jet open stage 6 air filter)
Yasuni c21
polini 9 speed variator 3 gram rollers
Clutch and blue springs

I dont seem to be getting no where with it it. when its cold the first time i open it up it will really kicks in and gets into high revs then it like theres a powerloss and just boggs once it gets to like 25 mph and doesnt seem to want to get back into high revs and get in the next gear any help please??????????

A C21 is totally the wrong pipe for a mhr rep. Please start a new topic instead of taking over someone elses.