rh-dt100 Posted September 7, 2011 Posted September 7, 2011 Hi Can I have some pointers to help me with my latest problem in getting my DT100 on the road? Having got it up and running (well enough to get its MOT and able to be used at low revs) it refused to pull from mid range, 30 mph max. I have now looked at the possible reasons I have stripped out the exhaust and decoked it, lots of carbon, but no difference on the road. I sent off the carb to be ultrasonically cleaned and it has been returned re set, with new jets etc I also cleaned out the tank and fuel filter at the same time Now having re fitted the carb it will not start, noithing, no sign of life. I have a healthy spark but a wet plug. I also noticed fuel coming from the overflow. So could the needle jet be stuck open? Where should I set the mixture and air screw (assuming they are wrong) and what else should I check? Fuel is getting to the carb no problem. Any advice much appreciated!
Moderator Airhead Posted September 7, 2011 Moderator Posted September 7, 2011 Try a new plug first even though it is sparking. open the fuel tap and close it...you do have overfilling issues. you may have flooded the crankcase somewhat with attempts to start it so leave the plug out overnight to allow evaporation. use choke but no throttle or very little
rh-dt100 Posted September 8, 2011 Author Posted September 8, 2011 Try a new plug first even though it is sparking. open the fuel tap and close it...you do have overfilling issues. you may have flooded the crankcase somewhat with attempts to start it so leave the plug out overnight to allow evaporation. use choke but no throttle or very little Hi It seems my problem is the float height, I am getting either too much fuel or none at all. Spent all day tying to set the height but I can not find a middle setting, any suggestions on how to set it correctly please
Moderator Airhead Posted September 8, 2011 Moderator Posted September 8, 2011 Hi It seems my problem is the float height, I am getting either too much fuel or none at all. Spent all day tying to set the height but I can not find a middle setting, any suggestions on how to set it correctly please The float height may be out but it really shouldnt stop it from starting...you could always switch the tap off when the carb is full. It may be that the throttle stop screw (the knurled one) isnt in far enough to allow air through, especially as the carb has been stripped. as for float height adjustment dont try doing it with the carb fully inverted because the weight of the float will push down the spring loaded pin in the needle valve, rather...turn the carb on its axis just until the float touches the pin without pressing on it and then measure the distance from the float bottom to the surface the gasket mates to on the carb body (below the gasket with the carb inverted), you will see a cut-out notch in the flange to aid measurement. Remove the float if adjustment is needed and bend the central tab slightly to achieve the correct measurement. This may give you an idea but use the measurement given for yours
rh-dt100 Posted September 8, 2011 Author Posted September 8, 2011 Hello Thanks for this, to be clear it did run but it was pumping fuel out of the overflow. After I tried to adjust it no fuel at all, then back to overflowing, a bit of a see saw, all or nothing! I will try again this weekend......... instead of smashing it with a club hammer.......I was very tempted!
Moderator Airhead Posted September 8, 2011 Moderator Posted September 8, 2011 I am wondering about the condition of the reed valve now, next time you get the carb off have a look there...maybe the petals are bent or seating on dirt and thus you are getting back pressure in the carb...its an easy check so have a look-see. You could also try it without the air filter fitted in case it's dirty or blocked, it will be fine for a small run around the block but obviously not prolonged use. also what did you mean all or nothing...of course you dont mean the overflow? nothing would be good there
rh-dt100 Posted September 8, 2011 Author Posted September 8, 2011 Hi The air filter had turned to mush, so I tracked down a genuine part from the Netherlands The reed valve looked ok (removed it a few weeks ago) but I will look again, maybe I will post a picture. My propblem was initially overflowing (the bike started then stopped), then no fuel at all getting into the bowl depending upon my setting of the float. The best information I have been able to find is a setting of 20mm float height, Mr Haynes does not give a measurement. Following your advice I have measured it and it seems to be set at 22mm, so I guess that might be the problem. I am off to the Beaulieu National Autojumble in Hampshire at the weekend, I will be looking for a geunuine workshop manual, they turn up from time to time Thanks again.
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