DT125 '89 De-restriction

[ZaphodBeeble]

Hey guys, I'm going to be having a go at de-restricting my new monstah today. Gonna strip the exhaust off and check for washers or something and I'll probably take the carb off too. (I might aswell, I can clean it too.)

Just need to know a few things:

What do I do to the exhaust valve to give more power? Seeing as it's a 1989 model I don't think it has a servo but a standard one. Could I buy the servo for it and fit it? I would need the electronics too wouldn't I?

By the way I have a DEP exhaust so the back pipe won't be restricted.

Cheers for the help ('cause I know you will ).
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[priller]

I've got a magazine article somewhere with something about derestricting a DT. I'll see if I can find it tonight and scan it. From what I can remember you need to adjust the powervalve with an allen key, not 100% sure though. Keith should now though.

[ZaphodBeeble]

OK cheers prilly-boy. I'll be doing the exhaust anyway, but I'll do the valve when I know what to do.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[Kickstart]

Hi

Is it a DT125LC or a DT125R? The first one did not have a power valve.

From very vague memory there was a washer in the front of the exhaust. For the power valve you need to rotate it to the open position and then clamp it like that (think there is a small pin to hold it in the closed / restricted position). If you take the exhaust off you should be able to look up the exhaust port to check the valve position.

A kit used to be available. Doubt you can still get it, and it was not cheap. It probably consisted of a control unit, servo motor, cables and a few brackets. There was also a crude kit available for the TZR so that you could open and close the power valve using a lever on the handlebars.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Smoto Bob]

in the exhaust port ie where the pipe screws into the engin you can feel up there and there is a valve that reduces the size of the hole.

If you look on t he left hand side of the engin( from sitting on it) there is a cover, thats either a blanking plate that holds this valve still OR has 2 clutch type cables going into it ( thats if you have a servo)

if you havent got these cables then rotate the valve untill the exhaust port is FULLY open, but then you wont have any power a the bottom.

If you do have restrictors in the exhaust then if i was you i would leave them and still jamb open the power valve this way its a bit nippy, 100 miles per tank 74mph ish and doesnt have to constantly kept at red lineing to go any where


have fun m8, myns dead atm see jmbing open not good but fun HHAHAHHAAHAHAH
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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....."

[Smoto Bob]

[ZaphodBeeble]

Well I stripped it down. There's no restrictor in the exhaust (that I can see) and I fiddled with the valve thingy but didn't notice much of a difference. Doesn't seem very peaky at all. One thing I noticed was on the inlet manifold, there was a weird plastic thing attached to the top of it. Looks like it allows the mixture to expand into it for some reason. Any idea what it is or what it does? (I took it off and blocked up the hole to see if it made any difference, I don't think it did).

Cheers guys...
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[Smoto Bob]

[stevo as b4]

Early DT125R's dont AFAIK have any exhaust pipe restrictions, as neither did the TZR125. There is no servo to operate the YPVS valve, nor is there the pulley housing and brackets etc. As keith says there was and probably still can be brought, the kit to convert to a fully working PV, but its gonna be more than a few quid. The CDI's were the same, but there was a control unit for the servo motor that plugged into the wiring loom or CDI conncetions, so you might find one form a 2000> DT at a breakers. You need all the bits though, as its all missing on the old DT's. The valve can be turned around and re-pegged in the high rev position, so that you lose all bottom end and midrange, and you will go from f*ck all to a sudden rush of power from 6.5k. There was no inlet restrictors or jetting changes onthe older DTR's. The DT125LC did have a restricted exhaust pipe, but no YPVS until the very last mk3 versions which there are hardly any of around now. My mate had a TZR with the all or nothing de-restriction method, and he happily rode it for a year like that. At least you havnt got the hassle of a new DT125R as you would really be pulling your hair out trying to de-restrict it.

[ZaphodBeeble]

Cheers for the info guys. Should I put that inlet manifold expansion thingy back on do you think? It seems to make the bike idle slower so it has obviously had an effect, but no real change in power. I'll try adjusting the valve again tomorrow by taking the exhaust off and checking inside the port.

Another thing, the swing arm/spring bush is worn on it, does anyone have or know where I can get a new one? Apparently it's a solid piece of metal in the bottom part of the spring where the swing arm bracket meets it.

Cheers.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[ZaphodBeeble]

BUMP. Sorry for the bump but I need to know where/if I can get the suspension bush. Cheers.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[priller]

You could try here.

[ZaphodBeeble]

It's OK. I phoned a few places and found that Bob Wilding in Merthyr can get me it by Monday (Along with all the other bits that I need at a good price).
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.