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DT175 running on choke only


mcferreira100
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Hi..started a new thread on this. The bike only runs with choke out..soon as choke is in it starts to die. Swopped over the choke from another DT but made no difference. I have cleaned the carb twice now with carb cleaner and compressed air, as well as replaced the float valve and checked float height due to petrol coming out overflow.. All orifices and jets seem to be ok. Need some help here. My next step is to swop over carb from another DT to see if that cures it.

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.. All orifices and jets seem to be ok.

Presumtion" the mother of al f*kups, that pilot must be blocked,,,Its the pilot that takes the throttle first,, as venturi speed rushes thru - then fuel is drawn thru main jet bye the needle, only when wide open [ throttle] does the size of the main jet become important,,, :grin:

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But I checked..both jets look ok.

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Couldnt get it out..but can see light thru it...does that not mean its ok?

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if you couldnt get it out but can see light through it the jet must be clear but how do you know the little passageway is clear through to the venturi?

did you spray carb cleaner down and witness the passageway is clear?...see the diagram I posted in your other thread

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The pilot jet has small hole up the sides also. they must be clear, take it out ,,,use a good quality driver,,

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Still no joy..got the pilot jet out..again carb cleaner and compressed air everywhere..and I mean everywhere..fuel still coming out of carb overflow. Can it not be sucking air?..are the jets not suspect? Think I need to take it to a carb specialist.

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Take the float and put in a container of gas and weight it down for a hour then see if it floats. If it floats then you haven't set the float height correctly or the needle and seat are worn.

When you cleaned the carb did you note the number of turns on the pilot screw and correctly reinstall it? Just because the fuel end is clear dosen't cancel out the air side of the circut. Also did you remove the emlusion tube( the brass tube that the main jet fit's into) the pilot is responsable for 95% of the idle but the main will be pulling fuel past the emlusion as well thats why you have to adjust your idle by the height of the slide

Using spray carb cleaner is fine for a carb that was in use daily to remove the small film that can build up but to fully clean a carb that has been left to go to jelly/crustations you need to soak the carb for days or have it ultrasonic cleaned.

Throw it in a buccket of deisel for a couple of days,or what i doo is use a jug with a lid just big enough to fit the carb and fill it with carb cleaner,fire up the lawn mowwer and set it on,poor mans ultara sonic vibrator so to speak.

The only difference between a "carb pro" and anyone else is experience and careful instalitaion of the parts,tuning a carb is a different matter but if your using the original carb then it just needs to be fully cleaned and assembled correctly,proper turn's on the pilot and float height are the 2 most important.

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Good advice here and lot`s of things i`m not aware of..emulsion tubes??..didnt know there must be certain no of turns on the pilot. I just tightened it back in. I have fitted new needle and seat and set float height to 21mm as per the manual.

Decided to swop carbs with the other bike and its running a lot better. So at least I can be sure its the carb.

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..didnt know there must be certain no of turns on the pilot. I just tightened it back in.

Its the Air screw he means , outside left on carb body, Airhead will post a piccy of carb adjustment , soon ,, :yeah:

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Airscrew I know..all the way in and 1 and 1/4 turns out. What is this emulsion tube?

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The emulsion tube is the brass tube that the main jet locates into , wheres airhead wi that diagram,,, :eusa_doh:

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Swopped carbs and spent the day putting everything back on the bike to get it road legal..but something still not right..goes better but still tends to prefer choke. Going to ride the hell out of it for awhile and see if it gets better. She pulls like an XT500 with a good clutch. Will see if I can get this emulsion tube out of the original carb.

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Took it for bit of a run today..amazing how these little bikes pull..front wheel pops up 1st and 2nd and she goes on to 100km/h quite easily. So running well under full throttle, but idling very erratic. If I pull choke after a run she does die which is good. Idles high for awhile then wants to die.

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Airscrew I know..all the way in and 1 and 1/4 turns out. What is this emulsion tube?

1 and 1/4 is just a rough starting point for adjustment this is where tunning a carb comes in to play. To get it to Idle better try 1.5 turns on the pilot air screw or inbetween,you should post a picture of what screw you think is the pilot air screw is just so we are on the same page,if you turning the idle screw than it won't make it any better.

The emmie tube is removed from the top side of the carb ,slide removed main jet removed then push it out.It's the part that the needle slides into as you can see there is verry small holes that if blocked will mess up the mix

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There you go. Will try 1 and 1/2 turns.

jhio.jpg

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