DT125R ARCHIVE

polsta · DTR Senior Member

Power Valve Exact Guide and Position ??

Gixergav · DTR Senior Member

Diconnect the servo and open the powervalve to its open position.This will allow you to see if your bike is still being held back by other retrictions.You will feel the difference if you get it right.When your happy that its running good you can reconnect the ypvs.Make sure the powervalve is closed wih ignition on but bike not running.It should start to move to fully open at around 5500-6000rpm.I dont bother with the servo.I can run my bike quite comfortable below 5000rpm with the powervalve fixed open.

polsta · DTR Senior Member

hello mate thanks for the replies

im having a mare , i tried to take the exhaust off,and both the little bolts on the rubber bit that holds the exhaust up, are cross threaded and wont un-do , so i cant get the exhaust of at the moment , any ideas on that ?

can the power valve actualy be pulled out and cleaned ? and see what position its in without having to put the finger in the manifold/slid back in in the right position do you reckon ?

i might just have a quick gamble on the power valve being in the right position and dissconect the servo for a test ride anyway just to see

had a quick go with the snorkel removed today,and it made it a bit spluttery and wouldnt rev so high in 3rd and 4th n seemed to keep judder/spluttering at the top end of the gear ?, it seemed to make it crap, although sounded deep and nice, so ive put it back on

, just 1 more thing...any idea what that 6 block connector thing is the bloke mentions above in that post and do i need to do that ??

thanks mate, appriciate the help

Gixergav · DTR Senior Member

The 6 wire connector block is the servo connector.Unplug it if you dont want the ypvs to work.The powervalve can be taken out of the side of the barrel but i wouldn't trust taking a gamble as to its position.If you get it wrong you will smash the front crown of the piston.Take your time and do it right.Try drilling the bolts out of the exhaust bracket.You can use a nut and bolt to replace them.Removing the snorkel will not make it go quicker.In fact it will make it run lean.It flows plenty enough air as stock

polsta · DTR Senior Member

thanks mate !

how do i slide the power valve out then ? i justw ant to check its not coked up and give it a clean

ive tried pulling the end with pliars but it wont budge, and as it is its just sliding round 360 degrees so without having access to the manifold port i have no idea what way it is

also i just wanted to ask....when putting the bolt back in for the servo plastic thing that the wires go in,you have to tighten it and it moves the power valve ? so how do you do it all back up properly and still keeping the power valve in the fully open position ?

sorry for all the questions, i just want to be sure about it all

nice one !

Gixergav · DTR Senior Member

The powervale has an allen key bolt in it which seperates the two halves.One side comes out of the left, one side comes out of the right.There are two locating pins in the middle of the powervalve, dont lose them.When tightening the bolt on the plastic bit you will see a hole cast into the side of the barrel.By moving the plastic bit into different places you will eventually find that the cast hole lines up with a hole on the plastic bit and the valve will be open.I use a drill bit thats a tight fit and fix it into these holes.This will then lock the powervalve in place.

polsta · DTR Senior Member

nice one mate cheers !

i was just having a look in the haynes manual and ima little confused...can the power valve be slide out then easy ? it says somehting about the taking the head off and barrel out ?

if not, any chance of a detailed guide how to get it out and take a look ? as in the mnual it says it should be de coked at intervals , i have no idea when it was last done

inside the bit around the end of the power valve , there are 2 alan keys there to undo, is it them ?

i dont want to mess with that unless im certian how to do it

appriciate your help mate cheers

Gixergav · DTR Senior Member

Your going to need to remove your exhaust.Unbolt the caps on the left and right sides of the barrel.You will see the powervalve and one allen key bolt.This bolt joins the powervalve together because it comes in two pieces.Undo this bolt and one half comes out of the left and the other half comes out of the right.There are two locating pins in the middle of the powervalve.Dont lose these.Reassembly is the exact opposite.Its pretty basic and if you have a manual you'll be fine.Don't guess that the valve will be in the right position when you install it.When you tighten up your valve you will need to check that it sits right at the exhaust port.The last check you should make before you put your pipe back on is that your valve is sitting flush.

polsta · DTR Senior Member

hello mate

right after a mission ive managed to get the duff bolt out and the exhaust is now off !

ive just had a twirl of it while looking/feeling up the manifold, and it seems ok and clean, so i might give taking it out a miss at the moment , or would you recomend i do ?

its still confusing lol

so when i line it up, i have ignition on or off ?

, so just to get this clear....to have the valve in the fully open position, is where at the top kinda bit it feels smooth on the finger ??

so to peg it open, i put something in the 2 holes to stop it moving and keep it flush ? and dont conect the servo ? and put the exhaust back on, is that correct ??

then to have it open but working on the servo, i make sure its flush, then just do it all back up ? or should it be closed when i do it up, so it moves and starts to open at 8k ?

il hang fire touching it till you reply !!

thanks mate

polsta · DTR Senior Member

or if pos , give me an exact run down of each way, pegged open no servo, then with servo ?

ie 1- make sure its flush
2. do this
3 do that

etc , then same again for with servo

lol sorry for being a pain, and i appriciate the help , hopefully wel sort it so its boosting tonight !

polsta · DTR Senior Member

also mate i just wondered, if i have it pegged open, is there any need to disconect the servo from the cdi ? does that make any difference at all to anything ?

Gixergav · DTR Senior Member

When the valve is open you will feel the exhaust port at its largest point.The valve kinda blends in to the port if you know what i mean.If your looking at the powervalve from the left hand side of your bike the powervalve moves clockwise to open and anti clockwise to close.Make sure the valve is smooth up to the bore and that you dont go too far that the piston will touch it.Peg the valve in place by locking the plastic part so it cant move.Tighten the plastic part down and recheck the valve hasn't moved.Disconnect the servo cables but not the wiring just yet.Put the pipe on and try it.If it runs the same disconnect the servo wiring from the loom.That will tell you if the bike is still restricted elsewhere cos the bike should do at least 70mph in that state.If you want to use the servo then the valve should be closed with ignition on but engine not running and then the valve should move to fully open at around 5000-5500 rpm.

Powervalve fixed open= No servo attached.

polsta · DTR Senior Member

thanks mate

i pegged it open all ok,and just got in from a test ride, not much bottom end power but she hits 8000 and woooosh she kicks in and takes off and bought a smile to my face

)) !!! much quicker than it did before when i had the servo connected when i thought id turned it round the right way

only thing was it started to miss fire or/and splutter a bit or something,at about 9.5-10 rather than revving all the way like it has been before , ????? any idea whats causing that ??? ,not sure if its not enough fuel getting through ? or possibly the spark plug ? i have a high performance irridum one here, im just waiting for the bike to cool down and im gonna give that a try n see if that makes any difference

still i got to 55mph like that in 4th with the last 2 gears left !! , so i presume she could be sorted once i get this spluttering sorted , then il give it a try with the servo on tomorrow and play some more

polsta · DTR Senior Member

just thought....thats not hitting the piston is it ? how would i know ? i dont quite get what you mean by making sure its not hitting the pistion ? i had it all flush inside the top so its all smooth and you can see right through to the barrel or whatver

polsta · DTR Senior Member

just tried the irridium plug and its still the same , it gets to 9.5k and splutter/judders ?

aaaaaaaaaaaaRRGGGGGGGGGGHHHHHHHHHHH LOL

Gixergav · DTR Senior Member

If you turn the powervalve too far the valve can 'enter' the cylinder.You haven't hit your piston cos your bikes running.You'd know if you hit it.The valve must be flush with the cylinder wall.Best way to check is turn the engine over by hand on the kickstart before you run the engine.What exhaust have you got.If its standard it must be derestricted, and get a free flowing can like a dep or similar.Have you modified anything else.Everything else should be standard.

polsta · DTR Senior Member

ok cool

right ive got a full big one system ? that wouldnt cause the splutter/juddering tho would it ?

before i got the big one, my engine wouldnt rev past 8k, when i put the big one on it sorted that and let it rev all the way and gave the power

i still have the standard exhaust here, im not sure if its restricted or not ? ,

nothing else has been modified , there was no spluttering before , so i presume thats down to something other than the exaust ? its all fine, then when it hits 8k it takes off, but then starts to splutter/judder at 9.5 and wont freely rev to 10-11-12 like it did before

also ive taken the reed switch out the speedo a couple of weeks ago, but that didnt seem to make any difference to the bike when i did

any idea whats causing the judder then mate ?

Gixergav · DTR Senior Member

Full Big one is the worst exhaust for a dtr.I know it may be hard to swallow but seriously ditch it.It will do no favours.Use a dep or better, derestrict your standard pipe.It will need cutting on the expansion chamber to get the resrictor out and then welded back up again.Or fit a pre '96 pipe.Your powerband will come in lower, at around 5000 rpm instead of 8000rpm.Big one's give no bottom end power.I can run my dtr on a standard pipe comfortable below 5000rpm with plenty of torque and thats with the valve open.You will get a much bigger kick from the powerband too

polsta · DTR Senior Member

i weighed up getting a dep, but at £250 odd and more than double what i paid for the big one, i decided it just wasnt worth it and i dont have cash to burn, or i would of !!

where exacltly do i cut the standard pipe open and what with ? ,im upf or giving that a go and a mates got a welder ! , if that works better than the big one front pipe il keep that with the big one silencer

ive been happy with the big one tho and was better than the standard set up, and let the engine rev freely ,the bottom end power has been ok with the big one , its the top end ive been trying to sort to get it past 60 ! ,read on here and elsewhere plenty of ppl have had big one front pipes and rear deps

, any idea on what the splutter/juddering is then i had earlier and how i fix it ?? i really wanna gte that sorted out in the morning

Gixergav · DTR Senior Member

Powervalve open+ Big one front pipe= no bottom end.Been there and tried it. http://www.dtr125.net/tuningf.htm. Use the link on what to do to the standard exhaust.I have never got a dtr to respond right to a big one pipe, and i've never got one to seal at the exahust flange either! At a guess i'd say its the big one making it splutter at this stage.Derestrict the standard pipe if you can

polsta · DTR Senior Member

i cant see mate on that link ? thats just a link on where to buy deps and big ones etc ??

il give it a go on my standard pipe as its just sitting there and got nothing to loose , just need to know exactyl where and how much to cut and what to take out !

polsta · DTR Senior Member

if you click the de restricting bit on the main site,then click 00-03 bikes , it shows an exhaust cut in half , but mines a 1998 ??

would my exaust have that bit ?

is that the only restrictor in a standard front pipe ??

syks · DTR Respected Member

Mate the spluttering may indicate that you need to up the main jet,spluttering or high temp readings usually is a inication that it needs a bigger jet especialy if you have a bigone pipe and opened the valve,i personly would also ditch the bigone,if you look at the main page you can get a full nikkon exhaust system for around £175(i think) which will be loads better or even save up n get a dep.I have a full dep system on my 94 dtr,my bike hits 80mph and i havnt needed to upjet it,im not sure if the powervalve has been pegged open but i personly havnt touched it and it will red line in EVERY gear.

polsta · DTR Senior Member

when it did it my 1st thought was its not getting enough fuel through to get the power it wants to give, by how it was i think it will fly when i sort it

im gonna leave it exactly how it is and try the standard front pipe tomorrow and see how thta goes, if it doesnt fly il look in to cutting it open and seeing if its got the washer bit in

im not gonna buy another exhaust for it either way as another £175-250 for a max extra 20mph isnt worth it and ive got other things i need to be spending money on !

where do i buy a new jet from and how much are they ? how do i go about it ?

cheers !

syks · DTR Respected Member

I suppose it is a waste of time for you to spend out again on another exhaust and good idea mate,change the exhaust back around and try it then,im not sure but i dont think it will splutter with the standered on,if it dosnt then i would say it is probably the jet that needs uping to make it run right with the big one.Let us know how you get on.

polsta · DTR Senior Member

will do mate, im just about to change it round now and have a test ride n see what the powers like

im not sure if my standard exhaust has been de restricted or not, the bit has been taken out the manifold end if it had one, but i have no idea about the inside, its been re painted not long before i bought the bike, so cant tell if its been cut open or not , spose the power will tell me ?

is a new main jet something i can buy cheap in any bike shop or what ? , as if thats whats causing the splutter with the big one, if that was sorted it would have superb power

right il post back soon as ive been out

also today i want to try the power valve with the servo working , to see if that splutters

so do i put it so its not flush and fully blocked to start with with ignition on but engine not running ?

syks · DTR Respected Member

Sorry mate im not 100% on the powervalve(im still learning myself),gixergav seems to know what hes on about though and yes you should be able to order a main jet from any bike shop/garage.

polsta · DTR Senior Member

hello mate, just seen your whiteboard message, in near portsmouth !! so around an hour away, id defo be up for a ride ! , do you know any/many off road or green lane places around ? , theres not a lot of legal places round this way, although some cracking country lanes and a few gravel track kinda places

ive just got the bike out, just about to go for a quick blast to see if the spluttering goes , just on the offchance like as you know what bikes can be like !!

also...ive just had a look at my standard pipe, and the weld seam around the widest point doesnt look too proffesional/clean, so i think it might of already been cut open and welded back with a bit of luck !

polsta · DTR Senior Member

GIXERGAV = LEGEND !!!!

Well f**k me,

put the standard pipe on and started her up, she sounded nice, bit deeper and not as loud and hollowy sounding as the big one if you know what i mean, and off i went

1st round the corner of my road ,a nice longer power band from 5/6 all the way to about 10-10.5 (hmmmm whats this then i thought) , then a little ,but not a great deal or as much splutter as the big one

then turned in to a road thats up a fairly steepish hill/incline, before id never get more than 40 up it, i was just going past 50 when i ran out of road, in 4th i think

hmmmmmm interesting !!!

then about a mile up a slow twisty lane, loving the power band in 2nd and 3rd

then got stuck behind an old biddy in a car going up an even steeper hill !! grrrrrrr come on bitch , the bike wanted to go....

then a bit more booting in 2nd and 3rd on a few turns in to my top end long straight and lets see what shes got .....

gradual inclined on the way up, id never go past 45 before on the way up 55+ loving it and then kept some back, i was flying up there with a big smile !!!

turned round on the end and now lets see what shes got ..

she boosted, 50,55, 60 now lets see if shes restricted.... 63 -previous best)....65,(smiles) 70 (yeeeehaaa) 75 (smiles and laughter ) ,slight spluttering and ran out of road !! :))))))))))))))))))))))) LOVING IT, fastest ive ever been on it ,

then some testing on the way home..

shes a f**king beast !! it absoloutly flys and power all the way , before i thought it quick up to 40, 40-50 not bad , 50-60 slow but got there and needed a lot of road

now she flys past 40 and gets to 60 like i cant belive

im absoloutly amazed and chuffed to bits !!!

gav i applaud you , youve sorted me right out !!

polsta · DTR Senior Member

now what do i do ???

the standard front pipe cant be restricted ???? surely not worth cutting it open and seeing ? or is it ???

do i leave it like that ? or do i put the power valve back on the servo ??

i gotta take the exhaust off anyway quick as i neede to get the rubber 2 bolt bit off the big one pipe and put that on now !

what difference will putting the servo on make now from that ? coz it was sublime !!!

i think i still defo need a slightly bigger jet, more fuel will eliminate that stutter and give more power, shel do 80 for sure i should imagine ??

what size jet will i have now and what should i get ??? !