P.Lew

New Member
I recently purchased a '78 CT70 that would only run when the choke was fully on. Everytime I turned the choke off, the engine would die. I am no mechanic, but feel like I can usually get these problems fixed. I took the carb off to clean it and make sure the jets looked good. Upon taking the carb off i noticed a little corrosion in the fuel lines from the tank. The carb, much to my surprise, was fairly clean and the jets looked decent as well. I gave everything a good cleaning and reinstalled the carb. Since everything looked good on the carb i figured my problem likely is due to the fuel lines being partially blocked from corrosion in the tank. I took the tank out of the body of the bike and cleaned the inside of the tank and put new fuel lines from the tank to the carb. I got everything reinstalled and when i went to start the bike the engine ran full throttle. I figured i reinstalled the throttle slide 180 degrees wrong into the carb body. I turned the throttle the correct way, the the slit in the slide facing the idle screw and it still ran wide open. I unscrewed the idle screw, almost completely out, to make sure that wasnt rubbing on anything. Didnt fix the problem. I disconnected the carb from the air intake and fuel lines, but left the throttle connected to see if the needle was moving correctly and everything seemed correct. Does anyone have any addition checks for me to resolve this issue?
 

TENACIOUS T

Member
So where did you get the rebuild kit from ? Any parts left over ? So you say you could see the needle - what about the slide ? Did it go all the way down ?
 

P.Lew

New Member
I did not buy a rebuild kit as i figured everything looked fine when i took the carb apart. I poked a wire in all the hole to make sure they were not plugged and cleaned everything with carb cleaner. The slide appeared to go all the way down when i reinstalled it.
 

69ST

Well-Known Member
If it won't idle down, then you've gotta figure out what's preventing the slide from bottoming-out inside the venturi. Leave the throttle cable in place, unbolt the carb from the intake, then look inside the throat. You'll be able to see the position of the slide. With the curb idle screw set to allow full closure, you should see little, or no, light through the venturi.
 

OLD CT

Well-Known Member
Did you remove both jets and the main jet holder to clean all the holes in the pilot jet / main jet holder? Sure hope you installed ''fuel filters''. Check the cable to see if it moved @ the adjustment on the top of the carb under the rubber boot. Check the slack adjustment also.
 
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kirrbby

Well-Known Member
Also, maybe check under the rubber boot.
IMG_20190114_170944211.jpg
Make sure the cable is properly seated into the brass adjuster, and not bumping against it.
IMG_20190114_171545798.jpg IMG_20190114_171610722.jpg
A little heat and WD-40 will make it easier to pull up the boot. You may not even have to pull it up to tell if the cable is seated.
 
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