DT125R ARCHIVE

Calum122 · Guru

Advice regarding a German import DTR

toffeeroffles · DTR Member

Hi all

I close friend of mine has recently picked up a DTR as his first bike. Unfortunately I was unaware of the restrictions placed on the German models, it would seem they are restricted via the CDi from what I have gathered from what I have read here so far.

The bike pulls very strong through the gears but loses alot of power in 6th gear (and the very top of 5th I think) and doesn't really want to go above 7500rpm/60mph unless you're going down hill with the wind behind etc. I have had 75mph out of it, approaching 80mph in these "ideal" circumstances. So am pretty sure everything else is set up correctly. I gather this is down to the CDi using a retarded spark mapping.

Its fitted with a Mph speedo which contains a reed switch but these wires have been cut back as there is nowhere in the loom for them to connect to. We have checked all the other things listed elsewhere on the forum.

I checked the CDi the other day, the numbers printed on it read 3NC - 00 5Y4 and has 10 wires( I think ) on it.

Does anyone know what CDi we could use to replace it? I saw mention of selling to German buyers of CDis the other day but dont recall seeing a model number mentioned.

Also, its down as first registered in 1996 we believe (still awaiting log book arrival) but has a 4 on the frame number and also a steering lock on the headstock which would lead me to believe its 97'

Any help with this would be very much appreciated. Even though hes a learner I feel that its quite important that the bike is capable of getting upto 70mph, at least breaking 60mph easily to stop muppet car drivers making stupid overtakes as they so often do to anyone with L plates.

I look forward to any input you guys might have. Thanks

MDK · DTR Legend

hi and welcome

I know not everyone understands this but some guys on here get all funky about it and will not respond unless you first take the time to post in the newbies section dt125r.activeboard.com/f556646/newbies/ it dont bother me but we see all the time some one pops in ask.s a qestion gets the answer and then never posts back with if it worked or if we help fix something .

now this is fine but I am sure you will know that many ppl search google for help topics only to find 1000 tipics that have the same problem and fix but no post about if it worked or not .. sure you get what I mean ?

some pics of the bike would be good so we can get a idea of what model it realy is we see bikes all the time that claim to be say a 1989 but in fact are more like a 2000 model .

so whats his total topend speed as it is now ? have you removed any restrictions already reed switch - exhaust - has it got the servo fitted or is it pinned ?

scrimsmustang · DTR Mechanic

German bikes from the 90,s with the cdi under the tank where restricted just the same as the UK bikes except some of the late ones 97/98 have an easily removed resistor wired in bolted to the oil tank but this will be long gone probably, they also had servos and ours did not but they just require the normal checks to see if they are set correctly. The 3NC is not a restricted cdi and the reed switch in the mph speedo is nothing to worry about its just a speedo from a newer bike thats been fitted to replace the old kph speedo. I would 75 to 80 mph aint bad for an old derestricted DT. Try fitting a front sprocket with one tooth less to see if it will pull a bit better in 6th gear.

toffeeroffles · DTR Member

Noworries, I understand completely. I'll go say a hi there in a sec. I'll also get some pics sorted and post them up. I also have some helmet cam footage to render and upload of the sluggish 6th gear and of it running down one of my favourite bits of road thats guaranteed to test any bikes topspeed. Its a very long downhill dual carriage way sheltered in a valley with high trees either side.

As it stands currently, you thrash 5th to 60-62ish mph, change to 6th and any uphill/headwind and the bike will steadily lose revs untill around 7500rpm then it will sit there cruising at around 55mph. Get on a nice downhill sheltered long road and it will very,very slowly pick up untill it hits the powerband, once it does hit the power it will stay in the band quite nicely though.

Some other details we've checked through. The CDi is under the tank but mounted on the side of the frame, right hand side, I understand some are narrower boxes mounted on the top spar of the frame. As mentioned, reads 3NC and has 10 wires.

The frame number starts with a 4BL.

Servo is fitted, fully functional and adjusted. Though I am still to check the position of the powervalve to make sure its not 180 degrees out, this would be highly apparent if this was the case, right? I understand the symptoms of this are having no topend power what so ever.

BigOne expansion chamber and silencer.

The carb has been cleaned and the jet checked, its a #240. The carb was very clean anyway and the needle is in perfect condition and set at the 4th groove from the top as standard

Plug cleaned and checked and replaced with an Iridium. Looks to be running a little oily and maybe a tiny tad on the rich side. The electrode arm has a nice brown to it and the heat range band looks to be in the perfect place, right on the curve of the leg.

No reed switch, UK speedo fitted but no wiring on the loom for one to connect.

Cleaned and lubed air filter, snorkel still on airbox

Ok, so the 3NC CDi is good? That would be cool as they can be pretty pricey on Ebay. It definitely feels and sounds like some retarded sparking though.

Many thanks

Reef · Guru

Defiantly get that video uploaded mush. not too sure on the other bits but..

The big one expansion chamber.... so many people have said how when using them top end is shocking... I'd recommend for best top end investing in a used standard dtr expansion chamber and gutting it (removing the 'restrictions' with a grinder and get it welded back up and use that)

Calum122 · Guru

+1 on what reefy said mate. That sounds like the culprit. Those big one expansion chambers are poo! Look it up on here. Top end problems. And you will see that a lot of them ste because they have just fitted a big one spanny.

That would be my first point of call. Get a gutted standard or a dep system.

Energized · DTR Legend

There's your answer, you have a bigone expansion chamber. Those exhausts give the DT no power in 6th gear which is why we say the bigone fitted to your DT is like taking away 6th gear. Get a new expansion chamber, DEP is your best bet or if you're on a budget then go for a standard gutted pipe.

Nathlaad · DTR Legend

ark at Ennles pipeing up

scrimsmustang · DTR Mechanic

I would try one tooth off on the front sprocket first they are cheap as chips and it wont hurt to try, sounds like them exhausts have a problem though with what people are saying.

Calum122 · Guru

First post i came across.

dt125r.activeboard.com/t38577027/big-one-exhaust/

toffeeroffles · DTR Member

Thanks for the input guys. It would seem BigOne ****ed up the measurements or rate of expansion in the chamber then. Shame, I thought it was good buying point for the bike. I've discussed it with the owner and we'll probably look into getting a stock one and gutting it. He wont be razzing it about quite as quick as I do for a while, so hes says but I dont think it'll take too long. It certainly gives a nice sound. Its been a while since I have ridden a little 2 stroke but I did think that the powerband was rather narrow, coming in rather high and not lasting long. The manifold connection is also a bit of a dodgy design imo but does the job I guess.

Its pretty tidy, was recently given an overhaul by the previous owner, paint and SM wheel conversion, top end rebuild. It has the standard of single pot caliper fitted on a bracket but we've just managed to source a YZF R125 twin pot for £25 which I'm hoping will fit straight on.

We've changed all the fluids and lubed everything up, Stiffened the rear shock and have a nice lot of 15w fork oil to go in.

Just before I recorded the vid we treated all the fluids to a dose of ZX1- Extralube. Not sure if any of you guys have used the stuff but I find it pretty amazing. 5% ratio to the gearbox oil, 2stroke oil, coolant and brake fluids. I think it actually helped the bike pull a bit more as you can see in the vid, at the beginning it really doesnt seem to want to pull but come the end of the vid after the treatment has bonded it does seem to want to pull a bit more through 6th. As well as reducing friction it can increase compression. Works really well in my CB500 too.

Its a bit of a long one.

Jace · DTR Respected Member

Ive just junked my big one for a dep,gone from strugling at 60 to hitting 75-80 and pulling in top gear not dying back!

scrimsmustang · DTR Mechanic

To tall gearing

toffeeroffles · DTR Member

Aye, I have that seller bookmarked. Looks like he has a wide range of parts. Definitely on the to do list.

Oh yeah heh I know its only an ickle 125 :) My only concern was as I mentioned, still pulling that little bit more to keep over 60 for safety's sake. I'm on the boat that thinks restricting learners to speeds lower than speed limits is a silly idea (ie 50cc bikes restricted to 30mph etc). I also will be riding with the bike on my CB500 and although getting him in the slipstream all the time would be fun, it might be a tad unpractical :)

We're looking on ebay right now at stock chambers, should be able to get the money back from selling the BigOne on hopefuly. Sounds very much like thats the culprit here.

Got a big chain and ground anchor ready and waiting and the alarm is in the process of being fitted. We went with a Cyclone universal after mailing the seller for advice on fitment. The bike is being stored at another mates factory, locked and alarmed warehouse with 24hour security, cant complain!

I'm pretty sure the gearing is stock, 57 on the rear cog. I'll have to take a closer look at the front. Going from the vid and where the revs where at 75mph and from what I've read here, I'm fairly sure its stock gearing.

Many thanks for all your responses guys. Much appreciated. I'll let you know how it goes from here. He might decide on living with it for a while as hes still yet to book up his CBT. I've been giving him some coaching hes been riding about on private roads a good few hours a week. Once hes passed and riding it around I think he'll want to swap it out.

kebabby · DTR Respected Member

+1 on Bigone. I have one and does exactly same thing, have to scream through 5th to get it right going into 6th or it just bogs down back to 60.