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Tips: Change Valve Spring to increase rpm and speed

xyience87

New Member
smx owner here,.. i already installed rextoradjustable rcdi and mtrt valve spring in my mc.., result 2nd gear 60kph 3rd gear 80-85kph 4th gear 110-115kph limiter krrrt sound... no problem w/ 5th gear ts 130-140kph.. my cra cguro rcdi ko., pg on ko ng susi d tumitigil ung fan, nung bago ung rcdi ko ok nmn ung fan nya..
 

jiGGer

Super Veteran
smx or classic, better change to a stiffer valvespring bro to do away from valve float problems..RCDI dont have rpm limiter anymore..stock vs wont match with it..you cant maximize your RCDI potential..it would turn out useless and worst, might cause trouble on your engine head..
 

xyience87

New Member
my smx reach 130 w/ rcdi and open pipe 14/42 sprocket combi.. when i change my stock v. spring w/ mtrt v. spring, nothing change w/ the limiter problem. u can still hear the krrrrrt sound when i reach 80 w/ my 3rd gear...
 

Barurot

Super Veteran
my smx reach 130 w/ rcdi and open pipe 14/42 sprocket combi.. when i change my stock v. spring w/ mtrt v. spring, nothing change w/ the limiter problem. u can still hear the krrrrrt sound when i reach 80 w/ my 3rd gear...
thanks for the experience. im planning to buy brt hyperband and 42T sprocket. our stock is 14/38 right?
 

jiGGer

Super Veteran
my smx reach 130 w/ rcdi and open pipe 14/42 sprocket combi.. when i change my stock v. spring w/ mtrt v. spring, nothing change w/ the limiter problem. u can still hear the krrrrrt sound when i reach 80 w/ my 3rd gear...
base on experiences of our veterans here @ t135, i must say that its not the limiter anymore thats causing the sound bro..RCDIs do not have limiters anymore..just pm our masters..or better yet, explore and read posts..i believe you'd be answered
 

pepe_135

New Member
make sure your MTRT spring is stiffer than your stock. it doesn't mean you've changed "STOCK" vspring to "RACING" vspring will get rid of valve floating. it all boils down to spring rate and spring rate is 100% based on the spring material.
 

kojack

Super Veteran
Hey guys, if i were to replace the stock valve spring with the vixion/fz150i valve springs or any other type of any aftermarket valves spring, the valve clearance for an all stock mc is still at 0.10mm intake and 0.16mm exhaust... is this right?:confused: thanks in advanced...
Vixion/FZ150i Valvespring max rpm = 12,500rpm
 

docgabby

Super Veteran
Hey guys, if i were to replace the stock valve spring with the vixion/fz150i valve springs or any other type of any aftermarket valves spring, the valve clearance for an all stock mc is still at 0.10mm intake and 0.16mm exhaust... is this right?:confused: thanks in advanced...
Vixion/FZ150i Valvespring max rpm = 12,500rpm
yes....
 

bhek_21

Super Veteran
my smx reach 130 w/ rcdi and open pipe 14/42 sprocket combi.. when i change my stock v. spring w/ mtrt v. spring, nothing change w/ the limiter problem. u can still hear the krrrrrt sound when i reach 80 w/ my 3rd gear...
base on experiences of our veterans here @ t135, i must say that its not the limiter anymore thats causing the sound bro..RCDIs do not have limiters anymore..just pm our masters..or better yet, explore and read posts..i believe you'd be answered
Racing CDI still have limiter.. but the difference is that the racing cdi's have a longer limit compared from a stock CDI, thus, giving your bike additional edge.. the problem of @xyience87 is the combination of his sprocket.. 14/42 is very consuming on RPM, but it will give you good kick in acceleration though.. try to use 14/40 or 15/42, you will feel the difference.. IMHO :D
 

boytiempoh

Member
my smx reach 130 w/ rcdi and open pipe 14/42 sprocket combi.. when i change my stock v. spring w/ mtrt v. spring, nothing change w/ the limiter problem. u can still hear the krrrrrt sound when i reach 80 w/ my 3rd gear...
if it is not the cdi.
i think what you've experience is valve float.
I compared the sound of valve float and the limiter in the cdi.
and valve float does the krrrt sound not the cdi limiter
 

agustin arcilla

New Member
Hi guys

today i just had a new valvespring installed.
im planning to install it myself but since i dont have the necessary
tools like valvespring compressor, they i decided to install it through
a yamaha service center.


why did i decided to change valve spring?
based from my experience, our stock t135 valve spring can only
run upto 10,000rpm. beyond that it will have a valve float.
if you have a stock cdi, you wont reach 10,000rpm because
the stock cdi limits its rpm to 9200 only.

but if you have aftermarket cdi like mine i use rextor.
the cdi doesnt have limiter, its your engine thats now the limiter :)
in this particularly the valve spring.

valve spring will float or they simple call this valve float.
its a status where your valve spring will bounce like a basketball
and cannot do its function properly due to too much rpm.
the stock valve spring just "cannot" take more than 10,000rpm!

beyond 10,000rpm you will hear the famous "krrrrrt" sound in your engine.
it simply says, lower down your throttle or shift to next higher gear.

btw, if you want to see valve float video

so to get rid of that valve float (bouncing ball effect).
you need a stiffer spring designed for our bike.

ive got a TK racing valve spring (yamaha asean cup specs)
You can use any other aftermarket valve spring designed for our bike too
but havent tried others. anyway any aftermarket valvespring will definitely
increase rpm range.
how much is the tk valve spring
 

Jiou de Leon

Veteran
Hey doc, what else did you change when u use highspeed valve spring? My friend sold me his highspeed vspring because it's noisy, and i've read feedbacks that highspeed vpsring kinda you know. hehehe. some users experience their valve tip to b "pudpud".

Thanks doc, :help:
 

ace123

New Member
Hey doc, what else did you change when u use highspeed valve spring? My friend sold me his highspeed vspring because it's noisy, and i've read feedbacks that highspeed vpsring kinda you know. hehehe. some users experience their valve tip to b "pudpud".

Thanks doc, :help:
hispeed v.spring is very stifffffff ^^ pare it with non-magnetic valves ^^
 
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