Ricco Posted June 26, 2017 Share Posted June 26, 2017 Apologies for this being a bit long winded, thought it best to explain in full. I've had a Yamaha RS125DX for a month now. I've had one of the 2 following problems quite regularly since: Either: Petrol flows from the carb overflow when I stop, engine floods. Or: Bike runs fine for a couple of miles then bogs down and dies. This happens quicker if I rev the bike harder. After waiting a minute or two the bike starts again, same thing happens a couple of miles down the road. I think both problems are caused by the same thing: The float needle isn't moving in and out correctly. It's either doesn't move far enough up and fuel overflows, or doesn't move down enough, not allowing enough fuel. Does this sound about right? I've cleaned the carb out loads of times. The tank was rusty inside when I bought the bike so I cleaned it out and fitted an inline filter. I cut the first one up after a couple of weeks, there was very little stuff inside it, I'm fairly confident the petrol getting through is fairly clean. I want to replace the float needle and its seat but I'm really struggling to find one. The Haynes manual lists the carb as a Mikuni VM 24 SH. Neither Wemoto nor Yambits sell this carb repair kit, and my wider search came up with a blank. I could buy a complete new copied carb from China for 20 quid delivered but don't really want to put any Chinese stuff on it, you know? I would expect the parts I want are probably the same on some other Mikuni carbs, which may have repair kits available. Is there any way I can cross reference the needle and seat against other carbs to see if they will fit? Any other ideas? Many thanks. Link to comment Share on other sites More sharing options...
slice Posted June 26, 2017 Share Posted June 26, 2017 Found this took me 10 minutes..! http://www.ebay.co.uk/itm/73-YAMAHA-AT3-125-NEW-KEYSTER-MIKUNI-VM24SH-CARBURETOR-MASTER-REPAIR-KIT-KY-0151-/400790156786?epid=1691209920&hash=item5d50f475f2:g:Rl8AAOSwr81UQDwh Complete repair kit from the US. Loads of others on the net but the repair kit is a bit more difficult to find. Mikuni Japan will supply you direct as well. Link to comment Share on other sites More sharing options...
Ricco Posted June 26, 2017 Author Share Posted June 26, 2017 Thanks I saw that, but was put off by how long delivery takes. I'm still using the bike most days, having to take the carb off half the time! I've just noticed that Wemoto are offering a carb repair kit for the 1975 RS125. My Haynes manual suggests that all the RS125's have the same carb. Emailed Wemoto to confirm but they can't, say they can't access the OEM diagrams, whatever they are. Anyone know what these diagrams are, could I maybe find them on the net? Link to comment Share on other sites More sharing options...
nayruf Posted June 26, 2017 Share Posted June 26, 2017 http://www.wemoto.com/bikes/yamaha/rs_125/75/picture/carburettor_complete_repair_kit/ try this! 1 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 26, 2017 Moderator Share Posted June 26, 2017 You said the tank was rusty, there may be rust between the fuel inlet stub and the float valve seat which will cause havoc! 1 Link to comment Share on other sites More sharing options...
slice Posted June 26, 2017 Share Posted June 26, 2017 There you go Nayruf found one in the UK and about the same price, good one..! Airheads comment is spot on to, rust is tricky stuff, get's into all the little places and fucks all your previous work up. Link to comment Share on other sites More sharing options...
Ricco Posted June 26, 2017 Author Share Posted June 26, 2017 1 hour ago, nayruf said: http://www.wemoto.com/bikes/yamaha/rs_125/75/picture/carburettor_complete_repair_kit/ try this! Yes that's the one I saw. No guarantee that it fits (see previous post) but Wemoto have said they'll take it back if it doesn't fit. Got to be worth a go. 1 hour ago, Airhead said: You said the tank was rusty, there may be rust between the fuel inlet stub and the float valve seat which will cause havoc! God it never ends does it! If there is, how can I get it out? Link to comment Share on other sites More sharing options...
finnerz89 Posted June 26, 2017 Share Posted June 26, 2017 3 hours ago, Ricco said: Yes that's the one I saw. No guarantee that it fits (see previous post) but Wemoto have said they'll take it back if it doesn't fit. Got to be worth a go. God it never ends does it! If there is, how can I get it out? Might be best to have it ultra sonically cleaned somewhere, shouldn't cost much and might well do the trick Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 26, 2017 Moderator Share Posted June 26, 2017 4 hours ago, Ricco said: Yes that's the one I saw. No guarantee that it fits (see previous post) but Wemoto have said they'll take it back if it doesn't fit. Got to be worth a go. God it never ends does it! If there is, how can I get it out? It's not difficult, you'll probably see the rust particles when you unscrew the float valve seat if theres any there, compressed air would blow it out, if you don't have access to compressed air you could possibly attach a tube to the fuel spigot and blow down that if there is rust there? Link to comment Share on other sites More sharing options...
Ricco Posted July 1, 2017 Author Share Posted July 1, 2017 There was some rust when I unscrewed the valve seat, plus bits of what looked like epoxy. I guess someone must have put expoxy in the tank sometime (badly). I don't think we smashing lots of nuts and bolts around the tank would have helped much, but there you go. I received the carb repair kit. Unfortunately, the float valve in the kit is a larger diameter so won't fit. I'm a bit stuck. There are no legible markings on the float valve so I've really no idea what I'm looking for. One option is to get a copied carb from China for 20 quid delivered. Hopefully the float valve and needle will fit mine or otherwise, I could put the whole carb on. I'd rather not introduce Chinese to this bike if at all possible. Otherwise, is there a place in the north west where I could physically take the part so someone knowledgable could identify something suitble to use? Link to comment Share on other sites More sharing options...
slice Posted July 1, 2017 Share Posted July 1, 2017 Don't know about the North West but just try your local bike shop/repair, they are usually only to pleased to offer advice on what to fit and where to find it, they might even offer to get it for you (at a price..!) and then if it don't work you can take it back. Just a suggestion. Where are you in the world? someone might know a local place near you if you tell us what part of the world you live in..! Link to comment Share on other sites More sharing options...
Ricco Posted July 1, 2017 Author Share Posted July 1, 2017 Cheers I live on my narrow boat, different places around Cheshire, near Nantwich at the moment. Might drop into the bike shop in Middlewich, they seem quite helpful. Link to comment Share on other sites More sharing options...
slice Posted July 1, 2017 Share Posted July 1, 2017 Sounds like a plan, best of luck to you. Someone out there will help if they can, not all bike shops are full of arseholes who only want your money and can't be bothered to even say "thank you". So where are you keeping your bike then? Must be a bugger finding somewhere to store it and work on it. Not noted for space on the deck of a narrow boat. Link to comment Share on other sites More sharing options...
Ricco Posted July 2, 2017 Author Share Posted July 2, 2017 It is a bit tricky but I carried my last bike around for 4 years without it falling into the cut! Basically I welded a rack across the back of the boat, 4mm steel channel. A shorter piece of the same slots into this, pivoting to allow for variations in the towpath height. It's a bit tricky, the boat is 6 foot 10 wide, bike is 6 foot 4, with rear light assembly removed. I also need to remove the front footrest assembly, this interferes with the rudder steering, and wedge the rear brake pedal down with a block of wood. I've been through hundreds of locks without a problem but you do need to be careful, it's a bit tight. I know it's not the best environment for a bike but needs must, and I always cover it. 1 Link to comment Share on other sites More sharing options...
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