DT125R ARCHIVE

The top speed restricter, You take the front fairing/cowl off and unclip two pins and unscrew the speedo cable then u should be able to take it off (Still attached by wires ofcourse). Theres a Little White rectangle plug and if you take that out its got like a glass fuse in it. Get some Duct tape and tap over the hole and then tape the white box as far away as possible and tape it to something so it doesnt rattle around and put the speedo back and thats the Speed restricter done.

Exhaust Restricter, Your ment to cut it in half along the weld so when you re-weld it, the exhaust isnt a mess and full of welds. Once you have cut it in half take the half moon shaped peices of metal out and take your exhaust to a welders or do it yourself if your skilled enough. I think you can also cut the silencer in half and take out the crap and put a straight pipe with lots of holes through with some packing and it should be louder and be roughly the same as a full race system (Dont take my word for the Silencer, Im not 100% sure you can do that).

Theres ment to be a washer or something similer on the header of the exhaust wich restrictes the gas flow to the exhaust basicly sufficating it making it slower, Mine didnt have one so im sure theres one there as standerd.

De-restricting a DT125R
'00-'03 models
F

The later model DTR's have got the following restrictions fitted:

Exhaust restrictors (Front Pipe).
Speedo restriction (limits the revs when bike hits 60MPH).
Inlet manifold restricted.

Removing Exhaust restrictors

Removing the restrictors on a bike from '99 onwards is a bit more involved than for older model bikes.
The exhaust needs cutting in half at the largest place along the welding seem.



A Dremel is required to cut the two pieces of metal out of the exhaust. It then needs carefully welding back together. Remember to paint the welding seem afterwards to stop it rusting.

Removing Speedo Restriction

The speed is restricted by means of a reed switch which is mounted in the rear of the speedo. It tells the CDI when the bike reaches 60mph and stops the revs from increasing.
To remove the speedo restriction take off the headlamp cowl and pull out the spring clips holding the speedo in. Then unscrew the speedo cable and lift up the clock. You will see two things in the bottom of the clock casing. One is round and is the light bulb for the clock, the other is white and oblong. This is the reed switch and you carefully prise it out and tuck it to one side out of the clock. I suggest you put it in a bag and tuck it as far away as possible. Do not cut or disconnect it.

Modify Inlet Manifold

First you need to remove the carburettor (refer to Haynes Manual). To remove the inlet manifold, unscrew the 4 x 10MM bolts and gently remove the two-stroke oil feed pipe attached to the top of it. And either block the oil feed pipe with something small or just make sure it stays up in the air so no oil leaks out of it. You should now be able to remove the inlet manifold, although it may require a little help to un-stick the manifold gasket from the engine.

The square rubber piece attached to the inlet manifold (as shown in the photo) is designed to channel all the air/fuel mixture to the tip of the reed valve block, restricting the flow. To remove this square piece, get a stanley knife and first cut it off flat with the base. Next you need to carefully trim the flat surface so that you get a nice curved surface from the hole to the outside.



When i refitted mine, i used instant gasket paste to ensure a good seal on re-assembly.

Also: When re-assembling, block the hole in the large air bottle (the one that's got a screw holding it to the frame). This is another item that's been fitted to newer DTR's to mess with the air flow. Ideally it would be better to find an older model inlet pipe to replace the one (with the large hole in the left hand side) that's fitted between the airbox and the carburettor. To block the air bottle hole on mine i've used duct tape over the hole (on the bottle)(because duct tape is strong) and refitted the bottle hence blocking the hole. It seemed to have worked.
Make sure the bottle seals in the hole properly with the duct tape on it. I put a square of duct tape over the hole with a strip all the way round the edge to hold it in place.

And lastly on the inlet restrictions, remove the rubber snorkel off the top of the airbox under the seat. It'll help the air flow and you'll hear the induction sound.

Please note:

If you are planning to do a lot of muddy, wet greenlaning/offroading then it would probably be best to leave the rubber snorkel on as it would stop the airbox from sucking loads of crap into it.

rom sucking loads of crap into it.

i have done everything thats stated as in derestriction page bar the bottle thing, i have even done the inlet manifold,i have gutted stock exhaust,big one tail pipe,performance is very good,it will sit at 75 mph to 80mph on a wind free day...done over 3,000 miles since derestricting the bike (that was in january) without any probs,,,touch wood,,,i run the bike on castrol tts power 1 2t oil,smells great too,mind you at nearly £12 a bottle it should be a half decent 2t oil. I have to have a happy medium to the mileage i do,i dont constantly hammer the bike ,,hope this helps.

Hi Mate
From what i can gather and im no expert i would leave it at that.
Some say leave the air well alone others say do it but i personally dont think it will make a huge difference.

Let us know how you get on

Cheers Mark

lol yeah its expensive the 2t oil but i have used castrol in all my strokers,i find it good stuff to be honest,mpg wise,it all depends how much welly you give it,on average i would roughly estimate 110odd miles from full tank to going on to reserve. if my calculations are correct 60odd miles per gallon

Hi Mate
Thanks for the reply...................wish i was getting that kinda mpg im getting 30mpg about 50 out of a tank but thats not touching the reserve
Got it booked into a shop on monday coz its running like s***e so fingers crossed they can point me in the right direction about getting the mpg up
Ive been told its because ive got a huge main jet in so ive ordered a new one
Cheers Mark

so in the 2006 model dt's do they have the speedo restrictor or is this where you earth the cable because ive done this but i want more power lol

born2race wrote:

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so in the 2006 model dt's do they have the speedo restrictor or is this where you earth the cable because ive done this but i want more power lol

How much power do you want lol you got 2 bear in mind that they are only 125's and Dt's are really built for speed lol

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