DT125R ARCHIVE

karl_skyline · DTR Respected Member

dtr 125 2002 wont fully rev

medxb183 · DTR Senior Member

what i did on my 2003 model was
gutted the standard exhaust and fitted a big one rear box
took the white oblong connector from under speedo and taped it up with duck tape
removed snorkel from airbox
modified inlet manifold as on de-restricting page
mine will rev to the red line and speedo will go off the clck
try the reed switch removal first and see if it will redline then

karl_skyline · DTR Respected Member

yer i'l try that but doesnt the speedo thing just stop u going over 60? i just use for offroading at the moment and ive only ever been to 60mph in a feild but ill try it anyway.

Seiki · Admin

if its just a field bike you can run it on the basic engine electrics and do away with all the other stuff it sounds like something is limiting the spark

rip out the stuff you dont need if your keeping it for the fields and i recon this may help the less stuff on the bike the less there is to go wrong

karl_skyline · DTR Respected Member

nar i dont want to do that its still got the speedo rev counter and the sockets for the lights etc and i was thinking about putting on the road

Gixergav · DTR Senior Member

karl_skyline wrote:

sometimes it would not rev past 7-8000 but disconnecting and reconnecting the battery sorted it and it would rev fully again but thats not working now

You have answered your own question.Does it have the servo still attached? Sounds like you have an intermittent electrical fault which is not supplying power to the servo all of the time

karl_skyline · DTR Respected Member

yes the servo is attached and appears to work fine turns clockwise when reved low then anti clockwise when the revs increase further thats right isnt it? could the missing exhuast side powervalve cover effect anything? as i think the fumes are leaking from there now would realy like to sort this out and any help is much appreiated i may just pin the valve open but i'm not sure how to do this or whether its best to have the servo working it

-- Edited by karl_skyline on Friday 13th of March 2009 10:07:24 PM

Gixergav · DTR Senior Member

When looking from the left side of the barrel the valve should move clockwise at high revs to move into the open position.It then moves anti clockwise at low revs to shut it again.
Get the side cover replaced too as leaks will only rob power
My guide to pinning the valve open: http://www.activeboard.com/forum.spark?forumID=66365&p=3&topicID=25126106

karl_skyline · DTR Respected Member

hi mate mine doesnt do that mine goes clockwise at low revs and anti clockwise at higher revs it moves to the line up hole? is that wrong? i can get to 60 with it in a feild i dont think i could if it was closing? and where can i buy the powervalve cover?

Cheers

Gixergav · DTR Senior Member

A dtr with a closed valve will hit 60-65mph.Looks as though the valve is operating incorrectly.
Valve cover can be bought from yamaha or have a search on ebay

karl_skyline · DTR Respected Member

mine works like this one http://www.youtube.com/watch?v=vPGTb0yg1UA&feature=related

Gixergav · DTR Senior Member

Its turning the valve the wrong way.
Look at this clip and you can see that the valve is upside down
http://www.youtube.com/watch?v=vPGTb0yg1UA&feature=related

karl_skyline · DTR Respected Member

what do you mean mate so the valve on that video is not working correctly? as thats how mine works?

so the valve is not open when its lined up with the hole?

Thanks for the help

-- Edited by karl_skyline on Saturday 14th of March 2009 03:16:08 PM

Gixergav · DTR Senior Member

The valve on that video is fitted upside down so is not opening the valve correctly therefore not making maximum bhp
The rounded part of the valve should be at the top and the flat bottom should be at the bottom

Gixergav · DTR Senior Member

Sorry bud i put the wrong vid up.Try this one http://www.youtube.com/watch?v=UsWwQssiK-w&feature=related

karl_skyline · DTR Respected Member

but all of the powervalves ive seen go that way the plastic part with the cables on flat part with the hole at the top and round bit at the bottom?

thanks

Gixergav · DTR Senior Member

No i mean the actual valve not the pulley is upside down on the vid.
The valve may well have been set like this by the factory to cap power at 12bhp

karl_skyline · DTR Respected Member

but how do you tell if its upside down?
heres a few pics of mine

Theres the exhuast side power valve cover that is missing but ive just orderd one up.

Thanks

-- Edited by karl_skyline on Saturday 14th of March 2009 06:22:41 PM

Gixergav · DTR Senior Member

Only way to know for sure is to take the front exhaust off and have a look up the exhaust port

karl_skyline · DTR Respected Member

ok thanks mate do u think i should pin it open or let the servo work it? also is the valve suposed to be fully open when both holes on the plastic wheel and engine line up?

Gixergav · DTR Senior Member

Only open the valve whilst looking/feeling up the exhaust port.Otherwise the valve can hit the piston if turned incorrectly
Servo? It depends on your riding style but i have always manually opened the valve on dtr's and ditched the servo.If you need low down grunt then keep the servo.Take some time out and check the valve position and set the ypvs to operate correctly.It helps enormously by looking up the port to get it spot on

karl_skyline · DTR Respected Member

ok i unplugged the servo when the pully was lined up with the hole like where it goes if u turn the key on and off i'm pretty sure the valve was open as they was no power low down in the revs then when it got to 7000 there was but because it wont fully rev still it wasnt very good at all it sounded better when being revved with it open! would a leak where the expanny chamber connects to the silencer cause much problems?

Gixergav · DTR Senior Member

The valve may still not be in the right position.If its not fully open it will cause the power to die off and not rev right through.Only align the powervalve whilst looking up the exhaust port.Its not worth guessing otherwise.
If this doesn't solve it then maybe the problem lies elsewhere
Have you changed the spark plug recently?
Give the carb a good clean out and blow compressed air through all the jets
Check the position of the clip on the needle
Air filter clean?

A bit of a leak on the silencer joint is not a massive problem and would not lose a lot of power but it would be best to sort it

karl_skyline · DTR Respected Member

new sparkplug a few months ago not realy been used that much air filter is clean cleaned the carb out when i first got the bike less than a year ago also it used to red line with the powervalve the same way it is now with the servo working it would the missing exhuast side power valve cap make it lose power as i seen smoke come out of it when started from cold also on a odd time it does red line but most of time stops at around 7-8000

another question smile

does the dep silencer fit onto the standard expanny chamber no problem as i havent got the rubber pipe thing but ive been told it doesnt need it?

Thanks for the reply

-- Edited by karl_skyline on Wednesday 18th of March 2009 01:46:57 AM

Gixergav · DTR Senior Member

The missing cap will make it lose power but not to the extent of your problem.It definitley needs doing though
The dep can does fit onto the standard front pipe but you will always need the sealing rubber on a 2 stroke cos it will leak oil otherwise.There quite cheap to get too
If your quite certain it isn't the powervalve causing the problem then its either fuel or electrical related
It maybe the carb has sucked dirt through and is partially blocking the main jet
Check all contacts in the loom particularly cdi,flywheel,coil,ignition wires

karl_skyline · DTR Respected Member

thanks for the reply after i pinned the valve open and had a ride for abit still would not rev fully then plugged the servo back in it was reving to the red line for abit then it stopped again very strange you think maybe could have something to do with the servo connection plug? then again when the valve was pinned open it wouldnt rev fully

Gixergav · DTR Senior Member

Sounds like something electrical is going wrong.I'd check all the connections from the motor,servo,cdi,ignition.
Sounds like the spark is being limited by the servo somehow.Check for any wires earthing out on the frame

karl_skyline · DTR Respected Member

will do is it not possible for the cdi to restrict like that or do they never do that i used to think that unplugging the battery was reseting the cdi of errors or something but i dont think there that smart on the dtrs lol so if i buy a dep silencer ill need the original rubber connector pipe?

Cheers

Gixergav · DTR Senior Member

Yes ideally you will need the sealing rubber for the pipe.
A wire that is shorting out can cause all kinds of hassles.Wires can crack/fray and cause max grief too

karl_skyline · DTR Respected Member

ok i had a fiddle with the cdi wires etc looks like they run quite close to the top of the engine it started reving to the red line but when the bike got realy hot like the temp needle on the rev counter was in the middle is that right? it started to not rev fully again any ideas? also is it possible to fit an older cdi to the new wiring harness if u join the wires and dont use the plugs? and does the cdi on the oil tank restrict it very much?

cheers