Supermooser

Cool thanks mate :-) Any advise on cleaning/unblocking pilot jet? Much appreciated

Hi again people! I've just started the bike for the first this summer :-) I had to clean the spark plug connections but other than that it started/runs pretty well, but only with the choke open! As soon as I close the choke I can hear the engine start to struggle, and then die pretty quickly. The revs do not pick up when I turn the choke off, even momentarily. I've read on here that I may need to clean the carb or that maybe some of the rubber boots on the carb may need replacing? Is this right?! It's a Yamaha DT125 R, around 1990. The only other thing that may make a difference is that the power valve is not operating. The bike has been stripped of batterie etc hence no power valve. It has been fixed open about half way but this was the case well before the choke problem/cut out started. Any help for this silly amateur would be much obliged :-)

Hey folks. I’m just getting myself back into biking and have bought a DT125R (2001) to start off. The bike has been stripped of all road parts for full time off road use. When I bought it I was told the power valve does not open/close, and has been set mid way. Apparently this is because some part of the electrics &/or the battery has been removed (there is no battery). When I first got the bike this was fine, but now I would like more low/high range power to do jumps etc. Can anyone help me restore the power valve to open and close automatically as it should? Any help/advice appreciated

My bike starts and runs fine for about half an hour - then it cuts out. If i kick/push start the bike at this point it will not start. When I checked the spark plug at this point there is no spark. If i leave it for a day/week and try again - I can see the plug is sparking again, having altered nothing! However, when I replace the tank etc and run it for about half an hour it does exactly the same thing again! I think it may be a coil problem but the coil looks fine/not loose/cables etc. I've replaced so many unnecessary parts on my bike trying to solve problems incorrectly - Is there any way I can test my coil before getting a new one ?

If a HT lead is the lead between the coil and plug cap then there's no movement at either side/firmly secured. The whole coil/lead/plug cap seem very solid and in good order. Is there any way to test a coil before buying a one? I've replaced so many unnecessary part son my bike it's frustrating and quite costly!

My bike has started virtually first time for the last 6 months. The other day I started it and ran it for about ten minutes and it just cut out like there was suddenly no spark coming from the plug. I pushed the bike home and checked the spark was firing and it was not. It is a relatively new spark plug which has worked fine for the last month. I did try the old plug to see if this worked but it did not. I removed the seat and petrol tank to have a look at the wiring and could find no loose or disconnected wires. I left the bike for a couple of weeks before having a look again. Somehow, after doing nothing other than that that I have said I could see the plug was sparking again. I excitedly replaced the tank seat and seat to take it for a ride. After about 10 minutes running time and riding a 1/4 of a mile - exactly the same thing happened - it seemed like the plug just stopped firing. Once again I pushed the bike home. I am now thinking it is an ECU problem or a coil problem? Any ideas folks? I've checked eBay and I can get a coil for about £10, however the ECU is about $40+, otherwise I would just buy them both and hope this resolves the problem. Can anyone give me any advise on how to check the coil and ECU before getting a new one? - Or any advise on this problem???

Funny - It was alright actually, was only the dust seal making air noise. Friend of mine who's a mechanic happened to have a look and bled it in 30 seconds so nice and tight (after I'd put the fluid in the nipple via injection). Funny watching someone that knows what there doing. He released the pedal from the master so was pumping the master by hand (as more sensitive and had a better pump distance). Then instead of undoing/tightening the bleed nipple - he undid it slightly and just put his thumb over the end of it when required. Only took him a min and made me feel a little stupid haha! All's well that ends...finally, will have a proper burn tomorrow :-) Thanks for your help everyone :-))

Right folks.. I used the syringe method and filled the system with fluid fine. When I then went to bleed to stiffen up the brake, I heard a noise of air coming from the master cylinder. When I investigated further I found a small hole in the bottom rubber seal on the master cylinder. As I pumped the brake/tried to bleed, I could hear a jet of air coming in/out of the seal. I presume this is where I'm loosing pressure? If this is the case - do I need a master cylinder repair kit (aprox £20), just a new master cylinder rubber seal set (if available), or shall i just buy the complete used master cylinder on eBay (also around £20)? At least I feel I'm moving forward... slowly

Thanks mate. If I leave the caliper on and use a syringe, do I need to pump the peddle at all or just let it travel up through the cylinder to the resevoir on its own/with syringe pressure? Does it matter whether the pedal is up/down? I leave the reservoir cap off yea? I'll give it a go on Saturday

Hey that sounds good - nice. How does the air escape though - from the piston/master? I presume I leave the top off the reservoir? How does the fluid pass through the master cylinder up to the reservoir? Doesn't matter I suppose, but it does?! I suppose you could do it the other way injecting from the reservoir pipe and leaving the nipple undone p.s Nice photo

Haha ok - pipe it is So you reckon I can just bleed it and the pressure will return? If so, how long/many times do I need to bleed usually? Last time I seemed to do it ages and began to wander whether it was working! After the first pump/bleed (which expelled loads of air), very little/almost no air came out when repeated procedure, although this was before I rebuilt/caliper and replaced piston/seals

Oh really, Kinna like bleeding. So bleeding should bring fluid back into master cylinder from resevoir when cable connected and pressure? Or do I need a midi vac or whatever it's called

Haha yea - indeed

I had thought of this but haven't tried. Good point I suppose. The only reason I haven't done is that someone told me that if I connect the cable to the caliper, unscrew the bleed nipple and pump the foot brake 30+ times- brake fluid would/should spirt out the nipple and need replacing in the reservoir. When I tried this before I rebuilt the caliper/piston, it didn't - so i presumed I had a problem with my master cylinder. Also, if it is supposed to pump fluid out doing this I would have thought it would have pumped fluid out of the cable I disconnected from the caliper! Spent too long trying to repair back brake now - driving me nuts haha!

Could you possibly have a look at my new post titled: DT125R - HELP! Brake Fluid not draining from Reservoi... Thought you may be able to help?! Thanks

The caliper isn't connected remember. I'm just trying to see if the master cylinder pumps brake fluid from the reservoir but it doesn't! The master cylinder seems to be functioning but the reservoir doesn't empty no matter how many times I pump the brake. Presumably the brake fluid should be being pumped out where the cable should be connected to the caliper - but isn't!

I've just rebuilt the rear brake calliper on my 1999 DT125R, but BEFORE I RECONNECTED THE CABLE at the cable to the calliper at the calliper end (with bolt and copper washers), I thought I would check that the master cylinder was correctly pumping fluid from the reservoir - through the master cylinder - and along and out of the tube I had disconnected by the calliper. No matter how many times I pump the rear brake pedal/master cylinder, no brake fluid comes out of the disconnected end of the cable, and the level of brake fluid in the reservoir remains the same! Do I need to rebuild my master cylinder and/or renew the seals, or is there something obvious I am missing? I cannot understand why the master cylinder is not working now/pumping brake fluid properly through the system, as it was working fine before I removed the rear brake calliper! If I do need to rebuild the master cylinder, is this an easy thing for an amateur (such as myself) to do - with the help of Mr Haynes anyway?

Hi mate thanks. Did see that one but mine was actually this one... http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=380297831020&ssPageName=ADME:X:RTQ:GB:1123#ht_500wt_717 you might not be able to see it as I bought the only one! Just re-fitting mine now - fingers X'd!

I ended up having to drill it out! I took it to a motorbike shop who said they tried using a pneumatic pump and it wouldn't budge. I drilled a small hole in the centre of the piston and enlarged it bit by bit. When the hole was big enough I tried to prize out the piston. I broke a drill bit and a screwdriver but could still not prize it out or budge it a little. I could see one of the rubber seals/washers had come out of place and been jammed back in the tiny gap between the piston/chamber. The only way I could heat or remove the rubber without heating the whole section of the caliper was to drill a few times into the piston base - heating it up immensely. Eventually the rubber heated/melted and the piston actually rotated out of the chamber as I removed the drill. Finally! :-) Just need a new piston now...

I bought a Yamaha DT125R which was stolen/recovered but has no VIN number. I'm desperately trying to find out what year it is to order parts etc, and simply out of interest. Does anyone have any ideas?

I have a DT125 R, approximately 1996 or there about (the bike is stolen recovered and has no vin number). I had to replace the piston/seals in my rear brake caliper. In the Haynes manual diagram it shows a shim between the piston and the actual break pads. The shim is shown in a similar shape to the pads. Either I did not have a shim in place before I disassembled the caliper, or my shim is a round metal washer type - as this is the only part I have not found a home for when replacing the rear wheel and break caliper etc. Can anyone tell me if a shim is required? If a shim is required, could my (aprox 3mm thick) round metal washer be it?! I have looked on the internet to find a shim/picture for a DT125R and have been unsuccessful. No one seems to sell a rear brake shim and I can not find a photo to see if my washer is the shim. The Haynes manual diagram also shows a pair of pad springs that I also do not think were there before I disassembled the brake. Are these necessary also or not? Ps my rear break was working fine before I replaced the piston. Pps If anyone knows how to ascertain the year of my bike without a vin number this would also be a great help

My rear brake caliper piston is super stuck in the caliper. It's sunk quite far in and without even a millimeter protruding to be able to pull it out. I know you can reconnect the brake cable and try to use the brake peddle to pop it out but it doesn't seem to work. I've heard about heating the caliper and not the piston and then trying to pump it out but this has not worked either! I've hear mention of using a foot pump but I cannot work out how to connect the pump to the caliper! Can anyone help??

I'm renovating a DT125R and had to replace the rear wheel. Now I have done that I CANNOT GET ANY PRESSURE FROM THE REAR BRAKE AND THE BRAKE DOES NOT OPERATE. The rear brake caliper is fixed to the wheel spindle, so when I removed the wheel I (probably incorrectly), I disconnected the rear brake cable from the caliper so that the caliper could be removed connected to the wheel spindle. I have now read that I have made some errors in the way I removed the wheel and in particular the rear brake caliper. The rear brake cable that I disconnected from the caliper has obviously leaked some brake fluid whilst the wheel was replaced. Now I have replaced the wheel/caliper and reconnected the rear brake cable to the caliper, the rear brake arm swings almost freely with no pressure and does not apply the brake. I have tried to bleed it to remove any air/ but because there is no pressure it does not seem to even pump the brake fluid out of the bleed nipple, although I can hear air being projected from the bleed nipple when i operate the foot lever/brake. Can anyone help me as I am dying to ride it again but not without a rear brake. One additional point - does anyone know why the caliper removal is not included in the instructions for removing the wheel or at all in the Haynes manual. The caliper doesn't even exist in the diagrams of the rear wheel/spindle etc and is not mentioned in removing or replacing the wheel - hence my error

I'm renovating a DT125R and had to replace the rear wheel. Now I have done that I CANNOT GET ANY PRESSURE FROM THE REAR BRAKE AND THE BRAKE DOES NOT OPERATE. The rear brake caliper is fixed to the wheel spindle, so when I removed the wheel I (probably incorrectly), I disconnected the rear brake cable from the caliper so that the caliper could be removed connected to the wheel spindle. I have now read that I have made some errors in the way I removed the wheel and in particular the rear brake caliper. The rear brake cable that I disconnected from the caliper has obviously leaked some brake fluid whilst the wheel was replaced. Now I have replaced the wheel/caliper and reconnected the rear brake cable to the caliper, the rear brake arm swings almost freely with no pressure and does not apply the brake. I have tried to bleed it to remove any air/ but because there is no pressure it does not seem to even pump the brake fluid out of the bleed nipple, although I can hear air being projected from the bleed nipple when i operate the foot lever/brake. Can anyone help me as I am dying to ride it again but not without a rear brake. One additional point - does anyone know why the caliper removal is not included in the instructions for removing the wheel or at all in the Haynes manual. The caliper doesn't even exist in the diagrams of the rear wheel/spindle etc and is not mentioned in removing or replacing the wheel - hence my error

I'm renovating a DT125R and had to replace the rear wheel. Now I have done that I CANNOT GET ANY PRESSURE FROM THE REAR BRAKE AND THE BRAKE DOES NOT OPERATE. The rear brake caliper is fixed to the wheel spindle, so when I removed the wheel I (probably incorrectly), I disconnected the rear brake cable from the caliper so that the caliper could be removed connected to the wheel spindle. I have now read that I have made some errors in the way I removed the wheel and in particular the rear brake caliper. The rear brake cable that I disconnected from the caliper has obviously leaked some brake fluid whilst the wheel was replaced. Now I have replaced the wheel/caliper and reconnected the rear brake cable to the caliper, the rear brake arm swings almost freely with no pressure and does not apply the brake. I have tried to bleed it to remove any air/ but because there is no pressure it does not seem to even pump the brake fluid out of the bleed nipple, although I can hear air being projected from the bleed nipple when i operate the foot lever/brake. Can anyone help me as I am dying to ride it again but not without a rear brake. One additional point - does anyone know why the caliper removal is not included in the instructions for removing the wheel or at all in the Haynes manual. The caliper doesn't even exist in the diagrams of the rear wheel/spindle etc and is not mentioned in removing or replacing the wheel - hence my error Help!!!