Posted February 6, 200421 yr Just bought a dt125r 1998 s reg and want to know if you can tweak the powervalve and/or change the exhuast to fully release its power Many thanks in advance J
February 6, 200421 yr Just guessing here Jon but the restriction is usually in the exhaust via a sort of washer and in the carbs where you'll need bigger jets.
February 6, 200421 yr Admin Yep get a new exhaust, have a bike gear thingy so you can manually open the powervalve, (or fix tzr elecrric one), add some carbon reeds and bigger jets and away you go :shock:
February 6, 200421 yr have a bike gear thingy Read Alexasigno's post Jon, Sounds like he really knows his onions!!!
February 6, 200421 yr Author wicked stuff... ill be ordering a full DEP system next week and also will i need to change the jets?? :)J
February 6, 200421 yr that sounds ok for a full system. when you have the exhaust off look up the exhaust port and you'll see the power valve. turn it through about 180 degrees till the valve is flush with the top of the port. this will give full power. don't worry much about 'performance reeds' they're not worth it in my opinion. i've tried a few out. you'll need to upjet the mains for the exhaust. usually about two sizes for an exhaust and more for an airfilter. hope this helps. any more info needed then just ask mate :wink:
February 7, 200421 yr right buddy follow these simple steps and your biike will be a beast change the exhaust dep is chrome and looks the beezkbeez although dtr125s pre 1999 wasnt restricted through the exhaust so ur front pipe should be alright the deps have a good performance enhancer then get the carb rejetted to a 240 they are 210 when standard then a set of boyussen racing reeds and obviously open the power valve and all dtrs from 91 til 98 were derestricted through i think it was the cdi the black box in the rubber mount under the fuel tank change that for one off a pre 91 and ul be sorted the pre 91 although looks different still works with all the stator coils and so on obviously mine being a g reg i dont need to upgarde my cdi unit let us know how u get on oh yes and for some better sound and very slight improvement on accelleration get a k&n filter
February 7, 200421 yr john what colour is your bike and did u buy it from bristol my mate just sold a black s reg to a guy in cirencester for £1200 i think the one he sold had the old style power valve on it because the servo packed on the electric one
February 7, 200421 yr Author Its blue and white. i bought it from a old kiddy in cirencester :!: . 1 previous owner and i know the previous owner hes my mums best friends dad. Your close on the price £1100 down from £1200.... not bad really.. that covered the cost for sum new tires. :wink: p.s the bike has only done 10K and the engine is as smooth as a babys arse and i know the bike hasnt been ramped!
February 7, 200421 yr Admin Yeah forgot about that mozzy, your right my dtr was 91on a h, and had the old cdi unit, as the newer ones dont rev as high, i think that was the difference :roll:
February 7, 200421 yr Admin Well if your good with electronics this site tells you how to modify the cdi http://translate.google.com/translate?hl=e...DUTF-8%26sa%3DG CLick on the tuning on the left and Schaltplan CDI on the top, for the instructions. They also show you how to unrestrict etc.. GOod site, but the site has been translated via google so is quite funny but all seems pretty simple to follow 8)
February 7, 200421 yr Author Just been out for a ride... great weather for it! the bike maxes out at 65MPH, 8000RPM she will cruise happily at 55-58MPH. if i change the exhuast i think i will only reach 70-72MPH coz of the gearing and it redlines at 10500 also it will only rev to 8000RPM is this normal??? Thanks :)J
February 7, 200421 yr Moderator You'll might pick up that extra 2.5k on the clock after a new pipe & jetting is in place :wink:
February 7, 200421 yr Admin Thats the cdi which is restricting the rpm, the old ones can go to around 12k, check the link and it has a wiring diagram of how to change it, or get an older cdi.
February 7, 200421 yr just give mine a thrashing today alex i got that dep front pipe for £135 in the end from ard racing components in walsall i have details if anyone needs em it is a very noticable difference to my old fresco{big one} i pulled away same as i usually would and the power valve seems to come in alot sooner and it was on the back wheel i was crapping myself but tried to control cause there was loads of people around it seems to have sacrificed a little bit of top end for a lot more bottom end which is fine for me a.r.d racing sell the complete dep system for £175 + p+p which is bloody reasonable
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