@Calum I've been using Flickr to post pics on here as you say, a bit long-winded but works well
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HOTSHOT III
@HOTSHOT III
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14mm rear master cylinder@gary76 Before going down that route I'd recondition your stock M/Cyl as well as the rear caliper and possibly upgrade the rear brake hose to an HEL. I'd hesitate doing any "upgrades" until you've got the stock setup as good as it can possibly be.
The Yambits rear master cylinder repair kit is good but I'd go genuine for the rear caliper pistons and seals as the quality of some of those eBay kits can be a bit patchy. I bought an eBay rear caliper rebuild kit once, cleaned the caliper completely including the seal grooves, put it together and bled it and there was a small dribble of brake fluid on the back of the pad on the piston side. Wiped it off and it came back several times, so I cleaned up the (old) genuine piston/seals and put them back in as I wanted to go for a ride that evening and it cured it, no issues for a couple of months whereupon I bought new genuine ones.
When doing the master cylinder, replace the O-ring and circlip where the plastic reservoir elbow fits with genuine and clean behind this as it gets scabby and blocks the tiny hole inside it. Take your time getting the plastic elbow out as it might be stuck in with more corrosion. New reservoir membrane (Yambits) is also a good shout. HEL rear main hose is a good fit but use the original banjo bolts as these have more threads than the HEL ones. The reservoir hoses on DTRs are now getting on for 30 years old so it's a good idea to change this but you can't just use any old length of rubber hose as the fluid seeps through it at a molecular level (looks like condensation when the rest of the bike is bone dry); Tygon 2375 is what road racers use for non-pressurised brake fluid connections:
There's nothing really wrong with the stock rear brake on the DTR but like a lot of things on bikes it's very sensitive to how it's maintained. A lot of people neglect the sliding pins which allow the caliper to float when the brake is applied and the rubbers/pins are well worth buying genuine and keeping well greased. Another thing that used to help me is, when going out for a ride with a freshly lubed chain, try and drag the rear brake fairly regularly for about the first 5 or so miles as chain lube goes everywhere including on the disc rotor face nearest the wheel. Doing this burns it off until the chain has flung off the excess and makes the brake noticeably better for the rest of the ride and it's also worth giving the rotor a wipe off with some brake cleaner when you're back home cleaning the bike and re-lubing the chain etc. with it on the workstand. Take out the pads and give them a blast off with brake cleaner regularly as well.
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Aprilia Rs 125 Bancaja@Calum Alitalia paintwork looks beautiful.
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Fitting gas tank@kubicz The Gillmoto sounds good if it's a like-for-like replacement besides being plastic. Beyond that I wouldn't start putting YZ bodywork on a DTR, I've seen it done and it looked ridiculous to be honest. A modern MX bike tank/seat has a much flatter profile and it just looked out of place. Lots of DTRs have been ruined over the years by people trying to turn them into YZs and you'll never do it, it's not meant for that and the two bikes are very different. The DTR styling is based on the 1988 YZ250 because that's when the DTR was released, just like the Suzuki TS125R looking like a 1989 RM125 with lights. They're in keeping with the era they're from and that makes them beautiful, which is why kids today are dragging DTRs twice their age out of barns and restoring them; thanks to the dumbing down of consumerism, nothing like the 125s of the late80s/early 90s exists any more.
If you're on a limited budget, try and make the stock setup as good as it can possibly be before you start modifying. Do you own a cable oiler and a grease gun? Running genuine clutch and throttle cables, or pattern ones which don't last five minutes? Done an Autolube recon with new seals etc.? Good quality chain and sprockets in good shape? Got a system for cleaning and re-oiling air filters in rotation? D you scrub your bike with degreaser and re-lube everything when cleaning it (see pic; this bike was used off-road regularly), or jet wash it and go for a beer? These are all better uses of your time and resources and will improve the bike a lot more than impressing your mates with a few fancy mods because YZ250.
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Fitting gas tank@kubicz DT200R 3ET alloy swingarm fits straight in as far as I can see, the bosses on this one I bought from Japan were the same size as the DT125R IIRC. It's basically what the DT125R should have had but Yamaha cheapened it with a (much heavier) replica steel swingarm as it was aimed at the youth market; the DT230 lanza also had a steel swingarm as it occupied a similar once-in-a-blue-moon-offroad-riding sector in the Yamaha range back in the day, whereas the DT200R was a slightly more enduro-ready machine (Kawasaki did the same with the KMX125 and a lot of KMX125 guys fit the KMX200 alloy arm).
The 3ET hub is different to the 125, and it runs 520 chain and sprockets; I didn't have any of these to try so I did a bench mock-up using 3ET swingarm, wheel spacers and brake caliper mount mated to a DT125R hub. A 3mm thick M20 washer between the swingarm and brake caliper mount appeared to line up the DT125R 428 sprockets as you can see (these are DT125RE crankcases and gearbox/output shaft). At the time I had no way of fitting this to a bike and trying it but in my view it gave me enough information that I would have been prepared to try it if I'd owned a roadworthy DT125R at the time.
This gets you an alloy swingarm which accepts the stock chain guide/slipper and retains wheel alignment (if the sprockets line up with the stock 125 hub, the wheels line up. Provided you've followed all the steps in the manual regarding setting the swingarm side clearance, the engine boss governs wheel alignment as much as the frame). You also get to carry on using the DT125R 28-1212 swingarm bearing kit and the OEM linkage bushes/seals.
https://huntersmotorcycles.co.uk/product/all-balls-racing-swing-arm-bearings-kit-set-28-1212-1117
I'd say the only drawback to doing this is, aluminium wears differently to steel and the rear of the linkage bearing housing on the 3ET swingarm is particularly prone to this becaue the rear shock mudflap rubs against it every time the suspension moves. Modern KTMs do this as well and some people glue or JB Weld a coin to the affected area. All that mud and chain lube makes for a pretty harsh environment for gluing two pieces of metal together, so onm my 250EXC I used one of those plastic tubes you get in the centre of a reel of sticky labels you buy in the Post Office (last 3 pics). It's a really nice plastic, tough yet flexible, you can cut it with scissors, open it out and use a hole punch to make the holes to zip tie it on. Anything like that will do the job.
There's a guy on DT200R Australia Facebook page called Peter MacDonald who's always rebuilding 200s and selling parts, see if you can get an alloy swingarm off him. Don't forget to ask him to include the DT200R rear wheel spacers and brake caliper mount as well (Oz is full of DT200Rs and shipping to the UK/Europe isn't as expensive as you might think):
https://www.facebook.com/groups/2895277973902854
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Project finally finished@gary76 That looks ace! Love the gold rims.
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DTX 125 2006 front fork damper rod holding tool@Mekoz To get the forks apart, a lot of bike shops buzz gun the bottom bolt out. It can help to get an assistant to compress the fork somehow while you do this so the spring pushes harder against the damper rod and makes it even less likely to rotate.
You would then at least have the forks apart which will make it a lot easier to examine the damper rod and see exactly what tool you need to make/buy to securely hold it when re-tightening the bottom bolt after replacing the seals etc.
Lidl impact wrench (just as good as DeWalt etc. from Screwfix) is around £60 plus battery/charger and will come in handy for removing other stuff on the bike like flywheel/primary drive gear/front sprocket nuts etc. (although I'd hesitate to use a buzz gun to re-tighten any of these).
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DTX 125 2006 front fork damper rod holding tool@Calum Thanks bud, yes I still have that tool I made somewhere. Been following this thread and it's puzzling there's no visible means of holding the damper rod like on DTR forks. Possibly someone on a WR125X forum or Facebook page might know?
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Thoughts on this billet head@YYHpilo It's a lovely piece of machining and I like the O-ring sealing but I'm not sure about omitting the thermostat. As well as regulating coolant temperature, the idea IIRC is to keep the coolant in the actual water jacket around the cylinder and head under higher pressure than the rest of the system to increase its boiling point. Even some competition bikes which don't run thermostats have restrictor plates at the outlet on top of the cylinder head to achieve this. The website says the DTR thermostat is prone to sticking; I've never had that happen on any DTR, including the one I owned for two years/30,000+ miles as a teenager. I did 3 or 4 top end rebuilds on that bike before selling it to a friend who did another few thousand miles before passing his test and getting a bigger bike, and neither of us ever touched the thermostat. I think this happens because people don't replace their coolant often enough or with the correct grade TBH. Or they just use water judging by the rust inside some of the secondhand barrels/heads I've bought in the past.
Also not sure why they'd supply stainless (not to be used in load-bearing applications) bolts for fixing the head to the cylinder; every time you take off the head (possibly to try a different squish shape according to track conditions etc. as the head is marketed as being "for tuners, not for people who don't know what they're doing") the threads in the cylinder will become a little more worn ultimately leading to failure. Incidentally the torque wrench setting for the cylinder/head studs is 13Nm whilst for the cylinder head nuts this is 22Nm (and 28Nm for the barrel nuts); the idea here is, the combination of long thread engagement, low (stud) torque value and being relatively undisturbed ensures long life for the threads in the cylinder and cases which are expensive. Surely supplying their own cylinder studs the correct length isn't beyond the wit of anyone capable of producing something as beautiful as that?
I have to say I don't go much on this guy; the upswept stainless expansion chamber appears to attach directly to the frame (which guarantees it will crack from vibration as the rubber vibration damper isn't present in the photos) and the Supermoto front caliper bracket looks a bit flimsy to me. Considering larger front disc rotor = increased braking forces, I'd want this to be at least as thick/beefy as the caliper mounting lugs on the fork slider. He's clearly good at machining and can in all probability use the two-stroke tuning equations to make an expansion chamber of the correct dimensions but beyond that, he seems to be of the rather dangerous mindset that no-one (including Yamaha) can tell him anything.
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Post derestriction jetting change on a 1998 Dtr de03@Dougster Even with a pinned powervalve the bike should pull smoothly right through the rev range, just with very little power until it comes on the pipe at 6-7000rpm.Actual backfiring could mean a CDI unit issue but this is quite rare; a lot of midrange running problems on the DTR are caused by a blocked emulsion tube in the carb.
If you've just bought the bike I'd do a full carb clean including the emulsion tube (the brass tube the main jet screws into). A lot of people (including bike shops) miss this and don't realise it comes out because you have to screw the main jet back in without the brass washer and tap it gently to remove it from the carb body. The space between this and the carb body gets blocked with moisture, dirt etc and blocks more and more holes in the tube until it just starts fourstroking and won't rev out one day as this controls the mid-throttle fuelling. Make sure the air supply to this is clear as well, it's the small brass tube on the right of the carb body just in front of the carb-to-airbox rubber. You should be able to blow through it, but only just.
You can also make future carb cleaning easier by bypassing the carb with the carb warmer hoses which come from the cooling system. These are only really needed to stop carb icing in countries with really cold winters but they serve another purpose which is to make the cooling system self-bleeding when refilling, so you don't get air gaps at the top of the cylinder head and unlike a lot of two-strokes you don't need bleed bolts in various places on the cooling system. Whilst you're getting the carb off, you can retain this feature by running a single hose directly from the banjo on the cylinder head to the one on the thermostat housing so you don't have to mess with the cooling system next time. Don't forget to check the coolant level in the radiator after doing this
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2002 Yamaha dt125r@mjmikey Koyo bearings are very good quality but did you order the correct ones for this application? I believe for crankshaft applications they need to have larger clearances to allow for heat expansion; PJME refer to this as "the correct R1 type" but I've also heard it referred to as C3/C4 clearance:
https://www.pjme.co.uk/acatalog/Yamaha-DT125LC-Crankshaft-Main-Bearing-RH-5698.html#SID=103
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Post derestriction jetting change on a 1998 Dtr de03@Dougster Most two-strokes are a bit boggy when cold and this is also when most engine damage occurs so warm it up carefully keeping the revs low for the first couple of miles.
If you mean the powervalve is pinned open, that is probably the source of your problem. Pinning the powervalve makes the DTR very difficult to ride as it robs it of low-end power without gaining any top-end.
As far as I'm aware the DE03 model ran the 5-wire servo; these are easier to find and cheaper than earlier 3-wire versions so if you don't have one on the bike ATM it might be easier than you think to sort this by having a look around eBay, Facebook DTR pages etc.
If the jets in the carb at the moment are what your manual says they should be, don't stray from this setup until you've got a servo fitted and working, it's a massive improvement to the DTR riding/ownership experience (particularly off-road) as you don't have to thrash the bike everywhere to make it do anything.
Look around eBay for a pulley/housing as well, these are the same as on most other YPVS-equipped Yamahas including the RD350YPVS, TZR/TDR250 and TZR125 (the "29L" on the inside of the pulley housing is the RD350YPVS model designation). Buy genuine powervalve cables from Fowlers (Yambits pattern ones are the wrong length) or make your own here, it's no more complicated than replacing gear cables on a mountain bike: https://dt125r.co.uk/post/28693
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New owner@daley1471 This stuff is ace, I ran it in my 1998 with no issues. Conforms to the Japanese industry standard for racing two-stroke oil, injector or premix (keep the oil pump) and exactly the same colour as Motorex Cross Power 2T which costs around 3 times as much:
You can save even more by getting a few mates together and chipping in for the 20L:
Get a Haynes manual and read up on doing an oil pump bleed, and think about a clear oil line kit from Yambits for peace of mind.
Servicing intervals kind of depends how and where you ride but I'd start with a few air filter elements from Yambits (as good as genuine but half the price, if you get a few you can wash and re-oil them in rotation) and a cable oiler for £4.99, and order a gearbox oil drain bolt and some copper washers from Fowlers (£2 genuine). These are designed to stretch and break if overtightened, a PITA as you have to get the clutch cover off and wind out the broken part but better than needing new crankcases. Everyone overtightens these so it's one of those things worth buying genuine. Tightening torque is 15Nm so get a 1/4" drive torque wrench from a cycle shop (under £20 as so much stuff on MTBs has torque values now) and this will be good for most of the bolts around the bike like fork/axle clamps etc.
Look around for a good deal on a box of BR9ES spark plugs, and fit an NGK LB05EMH plug cap (the type moulded into one piece of rubber).
Have a really good look at the chain and sprockets and use quality replacements if in any doubt.
Get a grease gun for the rear suspension linkage bushes and there are posts on here showing you how to fit them to later bikes' swingarms/relay arms where Yamaha deleted them.
Get 5 litres of Gunk/Jizer to wash the bike, and 5 litres of WD40 with the free spray bottle from a motor factors; after washing throw old towels over the wheels to protect the tyres/brakes/spoke nipples and just WD40 the whole bike, specially around the engine/carb/shock/wiring. This protects it and makes it easier to wash next time, as well as preventing common DTR problems like seized carb mixture screws etc.
A MX bike stand (the type where you wheel the bike over it and press a pedal to raise it) makes everything a lot easier, specially chain maintenence and oil level checking.
Hope all the above doesn't put you off but a lot of bike shops these days aren't really up to speed with 90s two strokes so it can be of great value and very rewarding to get into doing all this stuff yourself.
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Is engine braking still bad for the engine with oil injection?@mbmO8 Good question, within reason the short answer is no.
Closing the throttle at high engine speed is one of the problems Autolube solves because the pump being driven by the crankshaft means it's still delivering enough oil to prevent seizure.
It's fairly common on competition bikes running premix for them to seize if you chop the throttle at high rpm, like at the end of a long straight at a beach race for example.
To be honest I wouldn't be adding extra oil to the fuel as this can actually cause engine damage by creating a lean running condition; a percentage of oil mixed with the fuel equates to that percentage less fuel right across the engine's load and speed range. Autolube is one of the most reliable lubrication systems ever made; if you're worried, double check your oil pump adjustment/delivery rate and get an oil pump rebuild kit from Yambits if the pump is rebuildable. And run a genuine throttle cable as those £12 pattern ones aren't great.
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Dt 230 Lanza top end@gary76 This is probably a better way of doing it to be honest: https://www.aeb-developpement.com/en/910-complete-mxe-250-aeb-engine
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Dtr 2001 hose warming pipes@Michaelashbrook As others have said it doesn’t make any difference which hose goes where, and they’re not really needed in a country like the UK with mild winters. However they also serve another purpose which is to make the cooling system self-bleeding when refilling as the one on the thermostat housing comes out above the actual thermostat, so all you have to do is fill the radiator slowly and you end up with no trapped air (this is why bikes like the 350LC and a lot of MX bikes have bleed bolts on the head and barrel etc.). So it’s useful to just run a single hose from one banjo straight to the other and bypass the carb; you still retain the self-bleeding cooling system but it’s a lot easier to get the carb off for cleaning, jetting and float height changes etc.
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Is zeeltronic still going@gary76 I think mine took about 3 weeks to arrive via DHL when I bought it directly from Borut, and I received tracking numbers etc. Just seen your other post, have you checked your spam folder for confirmation emails etc.? I forget that sometimes when ordering stuff lol
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WTF??? hole on bottom on engine@Calum I think it's something like that yes, that part of the crankcase is just an empty space.
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WTF??? hole on bottom on engine@mbmO8 All DTRs have this, can't remember the reason for it offhand but it's nothing to worry about.