grimesy Posted August 14, 2009 Share Posted August 14, 2009 My Mikuni carburettor is intermittently leaking fuel through the overflow outlets. I have replaced the needle and seat and adjusted the float level several times without a great deal of success. I thought I had a win after adjusting the centre tang to be parallel with the tangs that the floats touch. When I reinstalled no fuel was leaking, took it for a short ride and still all OK after. Left the fuel tap on to see if it would stay that way - it did for an hour, then started leaking slowly. Tried again today and it started leaking as soon as i turned the fuel on. I don't understand why it would change - could understand if I hadn't replaced the needle and seat (which seals fine when I blow through the fuel pipe and actuate manually. Incidentally - may be important - problem seems to be less when I adjust the float level in the 'wrong' direction. by this i mean bending it down rather than up (up should cut off the fuel earlier. Am wondering if the floats are floating properly - but all looks pretty good, nothing obvious to my untrained eye! Below is a link to the Babbits online part diagrams - to see the exploded view of the carby you need to select Yamaha/Motorcycle/1977/ DT250D - then select the Carb view for the 250D.. Parts Diagram Appreciate any suggestions you all may have Mark Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 14, 2009 Moderator Share Posted August 14, 2009 Incidentally - may be important - problem seems to be less when I adjust the float level in the 'wrong' direction. by this i mean bending it down rather than up (up should cut off the fuel earlier. Mark No its the other way round, bending the tang down will shut off fuel later and so raise the level in the bowl. set the float level to the specified level, ensure the little spring loaded pin is not compressed as this measurement is taken. If you have the level correctly set and the valve is shutting off properly then the only other way the fuel can seep into the carb is through the sealing gasket for the needle valve (item 6 on the diagram), did you fit this gasket...is it intact?? ...Paul Link to comment Share on other sites More sharing options...
jordanscycles Posted August 14, 2009 Share Posted August 14, 2009 also make sure your floats float Link to comment Share on other sites More sharing options...
grimesy Posted August 18, 2009 Author Share Posted August 18, 2009 Hey Guys, Thanks for your help. Got it sorted, there were 2 probs.. 1 - didn't tighten up the seat properly - fuel was seeping around it. 2 - more adjustment on the tang - i was doing it correctly but the seepage was confusing the issue. Good calls from both of you - didn't consider that the floats mightn't have been floating, that suggestion made a lot of sense - however found both to be OK. Anyway took it out to a bush block at the weekend - gave it a good workout and was very happy with the result - first real riding i'd done on it. the bike was given to me after having spent 5 years in a paddock (where it stopped) then a further 5 years in someones back yard - when i got it had no seat or plastics, many dents in the tank, broken rings/piston seized clutch, bearings seized... the list goes on.. Cheers Mark Link to comment Share on other sites More sharing options...
Recommended Posts