Slow DT125R

[DirtBar]

Hi guys, I got this 1998 DT125R a couple of weeks ago https://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&?ViewItem&item=2483889178
As you can see it has had a bit of engine work, the reason i am posting is because it'll only do about 55 - 60 mph, when i brought it the guy said some wires were disconected down the left hand side behind the fairing so i located and reconected them but this seems to have done nothing. i have also talken both the front and back exhust off to look for "half moon washers" but it seems they have already been removed, AND i have taken the speedo out to look for a rumored "reed switch cable" which aparently limits speeds over 60 but i could not find it.
if anyone has any suggestions on where to go next (apart form spending £200 on a dep pipe) i would be very appreciative, thanks

[carvell]

Diet.
____________________
Yamaha TDM 850

[AzA]

You could give it to me because you like giving away bikes.

Please
____________________
Currently riding a 2000 RS125, ( I have a bike at last )
https://www.bikepics.com/members/bcfaza/
Ride Safe

[Spiral]

After reading about it on e-bay and the information about the engine rebuild i would say get it checked out again!

unless it is just knackered
____________________
****NORTHERN IRELAND NEWSFLASH!!**** According to a recent survey, 94% of loyalists said the best sex they ever had was in the shower; the other 6% haven't been to jail yet.***

[DirtBar]

I only weigh 11 stone

[Dr Nick]

DEP Pipe , is needed i think, thats all my mates did to his, and played with the powervalve so it opened fully.

Definitely go for the DEP pipe, makes a nice crisp sound too.
____________________
is that it

[stinkwheel]

The way to make a DT125 go fast is to get a powervalve control box and servo for it. But you can't get them.

The powervalve is there but does not move. Opening it fully is common but moves all the power to the top-end so you have to rag the arse off it to get anywhere, I found them better with the powervalve closed (my brother used to have virtually the same model).

With the amount of work done on the engine for such a new bike, you have to wonder what everything else is like? Has it been serviced since the rebuild...if it has done a few hundred miles since then it should be. Might be worth checking out the state of the air filter and reed valves at the same time, and the throttle needle position.

A simple good going over may show up something simple, for example a worn and rusty chain can rob 5mph.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[DirtBar]

i would love to check the air filter and such, but i am completly new to bikes and have no idea how to do anything ! .... dam

[stinkwheel]

[stinkwheel]

Oh yeah, oil your throttle cable, that always used to be good for another 5mph out of my old 125
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[DirtBar]

lol really, i will try that tomorrow.
i was messing with the wiring because i found what seemed to be a fool proof guide
basically it said that under the speedo casing there would be one set of wires for the bulb and another for the restriction, all it said to do was pull it out and set it to one side, but nothing was there !

[stinkwheel]

I know that some of the older DT125s (air cooled ones) definatley had a rev-limiter on the 'black box', you used to cut a wire and release a lot more power. The restriction on the newer ones is more down to the absence of the electrical parts that automatically open and close the powervavle in the exhaust port. I don't think they ever imported ones with these parts fitted so you can't get them.

Seriously though, I wouldn't go messing about with the wiring unless you know and understand exactly what the wire you are cutting does. I have owned too many bikes where someone inexperienced has 'messed' with the wiring, it causes annoying and hard to track down faults, often intermittant.

Oh, and I didn't have my brain in gear with my previous bit of advice. I meant to say to oil the SPEEDO cable , but oiling the throttle cable does no harm.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Frost]

Connecting up the powervalve wont do anything if the exaust is still restricted in some way or is plate/washer thingys have been put into the carbs.
A tweeked black box is more likely what is needed. the DT doesnt have the power of the 125 sportsbikes, and certainly doesnt have their aerodynamics. i would expect a restricted DT to perform how yours does and a derestricted one to be 10mph faster. if top end speed really bugs you that much then try dropping 4-5 teeth on the rear sprocket, this will improve top speed by around 15mph, but will make the lower gears taller.

[M1ke]

Derestricted DT125's can actually go 90MPH.

[DirtBar]

indeed they can :p
they can accually go a bit faster than that if u get a dep and stuff, but they dont last very long

https://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2485107828&ssPageName=STRK:MEWA:IT

I am hoping that will slove my problem, i will share all info on here if i decide to buy

[Smoto Bob]

mine went 84 ish with full knobbly on the back and that was scary fast for teh amount of wobbling it would do

Its not that difficult to de-restric but not realy wort it if you dont do it properly and that involes getting a proper non-restriced cdi for the later models. You can jam teh powervalve open, get a dep ,.. ect but it still wont be as fun or as ridable as the bike was with the original exhaust trust me on this one.

i have a fresco big one exhaust that would probly fit yours in the shed mine was 1995?? and its for more peeky bhp but its stupid when it goes on pipe lol
____________________
F'it DO WHAT EVER MAKES YOU HAPPY!!!!! Even if it screws over everyone else :p
Titz wrote: "..and my 3rd accident was when this police car....."

[DirtBar]

how can it be less fun with a louder and faster exhaust ! i dont understand...

so whats the price on the fresco

[stinkwheel]

[Smoto Bob]

i will have a gander see what dad gave away when he sold my dt125r, GRGR i think i have got a nackerd original as well.

The best set up i had was with the original exhaust and the valve jammed open. This gave quite a lot of low power because of the washers in the pipe chamber but still have a little kick at 7k
____________________
F'it DO WHAT EVER MAKES YOU HAPPY!!!!! Even if it screws over everyone else :p
Titz wrote: "..and my 3rd accident was when this police car....."

[DirtBar]

ah i see,
i will have a go at jamming the valve open when i buy that book from ebay, hopfully it should tell me how
i did have a poke in the original exhaust to try and find washers, but nothing was there, unless its really deep inside

[Smoto Bob]

the "washers" on the first part of teh exhasut are realy noticable as you will be abot the feel and see with you fingue thata huge lip has been welded in, hard to exsplain.

Have a gnader on the left hand side of your engine, theres a covers, with 1 allen screw in holding a plate on OR it has 2 allen screws and 2 adjustable cables coming out the top, thats the powervalve under that. Take exhaust off you will see it, its teh thing making teh hole coming out the the barrel smaller.


Have a gander on where ever the nsr guide its the same thing will give you a clue about what going on.
____________________
F'it DO WHAT EVER MAKES YOU HAPPY!!!!! Even if it screws over everyone else :p
Titz wrote: "..and my 3rd accident was when this police car....."

[DirtBar]

do you mean this? https://www.nsr125.com/derestrict.htm