DT125R FORUM

Hi, thanks again for the detailed reply and for all the information. I had already heard about the larger snorkel from the DT200/DT230, but I’ve seen that they are very difficult to find. Designing one in CAD could be possible, but I don’t have any experience with CAD programs and I also don’t have access to a 3D printer. Regarding the carbon reeds, I had heard about them before but I’m not sure which ones would be a good option at a reasonable price. I’ve also read that some people install a VForce4 reed block for the Yamaha Blaster on the DT125 with small modifications. However, it’s quite expensive. I did find a cheap copy on AliExpress, but I’m worried that the lower quality materials could damage the engine or even perform worse than the original reed block. The air filter was replaced a few months ago with a TwinAir filter, and the exhaust was also cleaned a few months ago. If I eventually decide to modify those spigots in the inlet port, do you know where I could find a good guide or tutorial to follow?

Cheers @beng1968 . I must admit, I bought 2 more Athena kits sometime after this post was made and can't concur with the opinions here. The casting was spot on and it was very good value for money. Considering it comes with everything you'd need to bolt it onto your engine, I'd say it's good value. I will agree it's not YZ rip roaring performance from stock, and considering the extent of tuning on my DTR, it's still nothing compared to a stock Aprilia RS 125. However, it's not without its merits. The extra CCs give a nice broader range of power, which as I've gotten older I've come to appreciate more (I'm no longer 75kgs wet ). I did take my cylinder to Mick Abbey for further porting and there is still more porting work that I need to do on my setup. It should be a decent bit of kit, when setup properly. The first experience I had was when I loaned my brothers 2001 DTR back in 2010, he'd fitted the Athena kit amongst various other mods, and that went very well. At the time, I went all in on a ported 3MB00P cylinder from the TZR Belgarda and that setup definitely served me well. I haven't been on my DTR for several years now and I am eager to fire it up again to rejudge my opinion.

Hello @chalcosoma, Apologise I didn't get around to replying last night. You can get away with running some pretty aggressive tyres on the stock rims, my friend once went very savage on his DTR (to the point spokes to breaking left right and center ). Sadly, I am not that clued up on tyres and availability in the States in general, but I certainly would have thought this wouldn't be a hard problem to solve. It would be interesting to hear what other people have run in the past as I know quite a few members had TDRs.

@Kristóf said in POS mode on switch: So does this mean that with the main switch to ON and the lights switch to POS it should light up the auxiliary light even with the engine off? No, lights switch to POS with the main switch to ON only illuminates the auxiliary light/tail light with the engine running because with the switches in these positions, the auxiliary and tail light receive an AC feed from the stator via the yellow/red wire. @Kristóf said in POS mode on switch: I'm asking this because my auxiliary light works when the main switch is to PARK but it doesn't work with the lights switch to POS Yes, this is because with the main switch in the PARK position, the auxiliary and tail lights receive a DC feed directly from the battery via the red wire (which connects to blue/red at the main switch in PARK). It took me a long time to fully understand this so glad I'm able to explain it properly!

After some research I did manage to find the sizes, and some more detailed photos so now I can actually buy some. I do think that it's rather a stopper or something than an adjustment tho obviously it changes the needle height, either way I'm sure they're important. Thank you all for the help!

Oh that's really cool! Well it looks well loved for, it's an appreciating classic that's for sure. I don't know of anyone who's done that conversion. The common one from back in the day were the Polysport conversions, but they're more enduro so not designed for peak brightness

Yes, the air leak will definitely not be helped by not plugging up the oil inlet on the manfild, albeit a tiny leak. Yes the '88 DTR ran the TMS26 carb not the TM28 carb found on all other years. That said, I am not aware of any other changes. So finding a suitable inlet manifold (probably can still be had new) and the airboot shouldn't be hard. But finding a genuine Mikuni 28mm is trickier. A split in the carb boot is not ideal, but it won't be the source of your problem. I'd just smear some silicone onto it and allow that to harden. Crank seals are common causes for air leaks, as well as the gasket on the inlet manifolds (once you sort the oil connector out). Spray some WD40 around the general vicinity and if the revs drop back to normal then you've found your culprit .

@Rat80y The drain bolt stretching is a common thing on the DTR, IMO it's a design feature as if you overtighten it it usually snaps. Whilst being a right PITA to get the clutch cover off and wind out the broken part, it does mean the thread in the crankcase is saved (new crankcases = much more difficult/expensive than taking off an engine cover) so I hope you've ordered genuine from Fowlers (get a load of copper washers as well for future gearbox oil changes). Tightening torque is 15Nm so it's also well worth getting yourself a 1/4" drive torque wrench like this one: https://planetx.co.uk/products/jobsworth-pro-torque-wrench-set-1 There is some truth in both your AI source and what your friend said. In the days of the 12bhp learner restriction, DTRs with the powervalve pinned shut would struggle to rev beyond 6k rpm but properly set up/derestricted/full power it should rev to around 10k.

Glad to have give it a once over Bent oil sump bolt

I use the Athena pipe with the 170 cylinder, it works quite well, and most of the power is in the midrange, even if I can get it to rev higher with modified ignition curve, the torque is in the midrange. I have seen Mick Abbey writing somewhere that the stinger ID needs to be at least 22mm (or was it 23) with the 170 kit, so that is a bit tight at least with the Athena pipe. The black paint seems to hold up quite well on the Athena-branded version.

I recommend Zeeltronic too.

@hotshot-iii @aragian Gawd! I made the mistake of buying a chinese "racing" coil and that caused me so much grief. A fresh DTR rebuild and I was plagued with running issues which I couldn't get my head around. Wasn't until my brother bought his RD 350 and he took it in for a Dyno where the chap refused to run the bike due to the coil and suddenly it hit me!

I found out that the shorter rear axle collar(part numper 90387-202U8) is the same on the Wr200 and Dt. If anyone has that longer collar(part numper 90387-206X8), could you measure its length? And if anyone has a wr200 rear axle, could you measure its length? The rear axle part numbers of the Wr and Dt are almost the same WR axle part numper 3XP-25381-00 DT axle part numper 3BN-25381-00

Yes your DT will be autolube. If it wasn't... you'd have known by now. You'll need to keep an on eye on the two stroke level and refill it as it gets depleted.

@Calum Is that undeslung exhaust a custom job? I'm building a DT LC 'X' (supermoto-inspired) and want to run a underslung exhaust on it. I'm thinking a underslung DTR exhaust could fit pretty well, some minor mods will probably be needed though. I have a modified DTR Athena 170 cylinder with cylinder reed, and a Zeeltronic for that engine.

Hi Mohamed, That is a cool looking bike you have there. I am not too familiar with the newer models as it's not something we get over here and I don't know what performance upgrades are available in your region. Definitely like to see more of what you do to the bike though! Welcome to the forum.

Hello there, As far as I was aware the Yamaha DT was discontinued in 2007 instead Yamaha makes rhe WR series. That looks like a cool looking bike though, would love to know more about it. I take it you're in the Asian market, hence why this is still available. I didn't know that the bike was still being produced there. I'd almost argue the bike's styling is closer to the 80's LC model vs the earlier 70's model, with the bike using an aircooled design over the liquid cooled variant. Sorry I can't be much more help than that, still cool bike though!

Could be a lot of things.. but everything is probably not as it should be if it's not starting.. What I can think of: -Leaky crank seals -Damaged/leaking reed/intake -Carb issue -Ignition angle off (flywheel key?) Is the spark plug wet? Is there a good suction pulse from the carb when kicking it? With some experience you can feel it if you cover the carb with your hand on full throttle while kicking/cranking the engine. It should not blow, only suck, and the pulse should be 'strong enough'. Old fuel can make it hard to start too.

@hotshot-iii That's a very cool video and local to me too! A crated Banshee, wow what a museum piece. I had no affiliation with the Banshee prior to this build, but what a machine and what an era for motorcycling. All lost to time now and kids these days won't know the joys of machines like that.