BlownCorona Posted January 4, 2011 Share Posted January 4, 2011 So im building a scooter out of a bike frame i had built when i was younger, and a 50cc full frame scooter engine. i've got the engine mounted in really nicely and made up a sprocket to go from scooter axle to bike chain/rear gears. now i've run into a problem where when i start the engine (sometimes hard) it will idle really lumpy and wont rev at all, no matter where the throttle is. in fact if i open the throttle up it starts to kill the engine. then it will die and wont restart for another 10 minutes or so. i have a feeling this might be to do with the angle the carb is on, but ive positioned the bike so the carb is flat and it dosn't seem to fix it. I really want to get the engine running smooth before i start on setting up the gears and tanks etc.. Bit of info about the project. im in need of a cheaper way to get around and to my course this year and i had this engine in a little grass cart i built. the engine runs extremely well and although its a Chinese motor. i constantly had it on the rev limiter while drifting on grass and it was more than happy to cope. i plan on linking the engines output (with its centrifugal clutch, to the rear gear system from a mountain bike, giving me a 5,6 or 7spd scooter, depending on what wheel i go with. should in theory be good for skids in low gear and have a decent top speed in high gear. I built the frame when i was about 10. and thus will, im sure, need welding properly and please pay no attention to the terrible welds that are on it currently that where done with my fathers arc welder with the wrong sticks. these will be redone with my new mig welder. Quote Link to comment Share on other sites More sharing options...
jakesae101 Posted January 4, 2011 Share Posted January 4, 2011 was it sitting at all from when it came out of the grass kart try giving the carb a go over might not like being run with no air filter . or will it run better with the choke on ? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 4, 2011 Author Share Posted January 4, 2011 was sitting for about 2-3 weeks. i took the air filter off so you can see the carb in the pics. dosn't make a difference. however when the engine was in the cart. taking the filter off had the same effect as it has now minus the starting issues. and its got an electric choke, Quote Link to comment Share on other sites More sharing options...
jakesae101 Posted January 4, 2011 Share Posted January 4, 2011 have you checked for leaks between the carb and barrel Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 4, 2011 Author Share Posted January 4, 2011 nope but thanks for the point of interest. ill take a look at it at some point. not sure why there would be a sudden leak. im pretty sure its something to do with tilting the angle up, as it use to run horizontally Quote Link to comment Share on other sites More sharing options...
phr34kr Posted January 4, 2011 Share Posted January 4, 2011 Put rear of the bike up on something so that the engine is horizontal again and see if that fixes the issue? Quote Link to comment Share on other sites More sharing options...
cubastreet Posted January 5, 2011 Share Posted January 5, 2011 blocked main jet? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 6, 2011 Author Share Posted January 6, 2011 how do you clean scooter carbs properly? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 6, 2011 Author Share Posted January 6, 2011 sat the bike up on an angle so the engine was flat, still very hard to start/wont start and wont go past its rough as idle Quote Link to comment Share on other sites More sharing options...
10Speed Posted January 6, 2011 Share Posted January 6, 2011 airleaks? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 6, 2011 Author Share Posted January 6, 2011 had a look at the intake manifold and it looks ok, where else could it leak? also could running premix on and auto mix engine cause issues like this? Quote Link to comment Share on other sites More sharing options...
jakesae101 Posted January 6, 2011 Share Posted January 6, 2011 possibly unless you have removed all the gear to run it on pre mix Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 9, 2011 Author Share Posted January 9, 2011 so i may be back on track, put the oil in the oil bottle and just petrol in the tank, put in a clean spark plug and fired it up and it runs alot better, it revs up but is smokey as hell, i suspect that there is alot of unburnt oil in the engine as the plug that came out was soaked. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 30, 2011 Author Share Posted January 30, 2011 So i have made pretty good progress with this, the engine is running nicely, and the gears seem to work. Pics will follow I just would like to know, what sorta base settings should a little scooter carb have, its a mikuni something, can find out if it makes a difference? im pretty sure i messed them up when the engine wasnt running and its not getting the full potential from the engine. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted February 2, 2011 Author Share Posted February 2, 2011 Pictures - Just have to sort out tanks (probably done thanks to [i5oogt]), finish the gears, air filter, exhaust and welding, its about time this thing lit up the rear tire. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted February 14, 2011 Author Share Posted February 14, 2011 does anyone have a small scooter muffler laying around they wish to get rid of? Quote Link to comment Share on other sites More sharing options...
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