DT125R ARCHIVE

AndyA · DTR Member

Advice on Jetting?

Gixergav · DTR Senior Member

Use the standard 240 jet and the needle should be 4th clip from top.It sounds as though the powervalve is not operating correctly so the engine cannot rev higher.
Open the valve manually and see if this sorts it.

SimsonS51E · Guru

MedX has same model ??

http://www.activeboard.com/forum.spark?forumID=66365&p=3&topicID=23688862

The sites info on de-restricting your year shows no reference to the PV,

So i had assumed PV was working properly [giving grunty bottom & letting rev' freely?] up to the Reed Switch max speed then the restrictions came in via the Cdi - ??

Seems odd giving a bike a low rev ceiling After they have already restricted by speed ??

It does sound like the PV is not opening properly to let engine rev though !

Questions .... ?

How would a too small jet size let a bike rev' or not rev ? Would it not just lean up the mixture at high revs through lack of fuel [creating too much power heat ??]

How do the different reeds Richen the mixture ?? I can't work out how they increase petroil only .. or cut down the air content of the mixture ?

?

Gixergav · DTR Senior Member

Although the bike may not be restricted by the powervalve from the factory who knows what other cretin has been tinkering with it and caused more harm than good.The valve may have been set wrong and given that it dies off at 7500 rpm sounds exactly the same symptoms as an early unrestricted dt with the valve closed.
A small jet will restrict engine revs by not allowing enough fuel to rev higher.It will only rev as high as the fuel content will allow.Too big a jet will cause the mixture to become too rich with too much fuel causing it to bog as there isn't enough air to burn with it.
Different reeds don't richen the mixture.All they do is open/close quickly allowing incoming fuel mixture into the cylinder.They stay shut on the firing cycle to prevent blowback of gases into the carb.Kinda like an intake valve on a 4 stroke.The more flexible the better as they can open further and quicker giving crisper throttle response

AndyA · DTR Member

Thanks for your replys guys, that was my next step having a look at the power valve although I have steered away from that up until now as I don't want to bugger some thing up but it looks like I will have to.
Thanks again.

ash ace mechanic · DTR Newbie

hi i had same prob on my 2003 dtr i removed standered down pipe and put a big one on it and now it goes to 10000rpm and wow!!! these worked for my bike but it gets hot and is melting the spark plug so id recomend getting one with a higher heat rating and it should go fine, ash

Gixergav · DTR Senior Member

Big one pipes are ****e
Use derestricted standard or dep

ash ace mechanic · DTR Newbie

i tried dep it i didnt really like it as much as the big one especially as police have started noticing performance pipes and big one looks like standerd

SimsonS51E · Guru

Poliss..

Gixergav · DTR Senior Member

RE: Advice on Jetting?

SimsonS51E · Guru

Gixergav wrote:

Not against the law to run a performance pipe?

Yea .....

But F*ck Em' Anyhow !

born2race · DTR Senior Member

if it still not working try standard reeds because ive heard there racing ones not good in dts

Mugen Seiki · Guru

Gixergav wrote:

Not against the law to run a performance pipe?

On L plates yes mate disbelief

Gixergav · DTR Senior Member

No.You can run any performance pipe you like on L plates and whatever engine tuning takes your fancy.Its your responsibility to make sure it doesn't affect the power output and takes it over the legal limit wink

dtrcruzer · DTR Senior Member

personaly i have never herd of any one getting done for a performance pipe or anything like that on a 125 or L plates in my life