carb issues

[saskct70s]

hi there, just rebuilt the carb on '77 ct 70 and when i start it up it revs right up high..the throttle cable appears to be working ok and ive checked where the needle screws into carb....any thoughts?

 

[69ST]

Sounds like you've reached the CT70 owners first rite of passage...installing the slide "backward" with the guide groove on the wrong side. When this happens, the throttle cannot close.

 

[saskct70s]

hahaha....ya im a newb at all this for sure!!! ok so what is the slide and what is the correct method racerx?

 

[saskct70s]

ok so i figured out what the slide is and it seems to only fit one way in the carb. it only slides down fully when the groove is in the right place it seems....checked the air box boots to see if i had leaks and they look good....not sure what else to check....could the pilot air screw be too tight or loose? i turned it to tight then backed it off 2 turns...

 

[69ST]

Trust me, we've all gone through this, at some time or other.

Look into the carb inlet and visually verify that the slide can reach to bottom of the venturi. If you can still see light getting under it, with the throttle in the closed position, you'll have to figure out what's preventing it from closing. It's possible that the throttle cable isn't seated at one end, carb cap, or inside the twist-grip assembly. Unless you've replaced the carb or something in the throttle assembly, the correction should be pretty simple.

The pilot airbleed (a.k.a. idle mixture) screw should be set 1-1/2 turns out from lightly seated, as an initial setting. You can't dial-in the idle mixture until the engine is at full operating temperature.

There's a second adjusting screw, the throttle stop/curb idle. That's what limits how far the slide can close. You set that by idle speed, engine up-to-temp.

 

[saskct70s]

YEEHAW.....i compared the slide to the slide on the 76 which has relatively the same carb and the one i was using was half the size... found the correct one and installed it and she runs like a dream....Thanks very much racerx

 

[saskct70s]

ok i got a little over confident....it started several times and idled nicely...adjusted carb screws a touch....then tried the throttle a bit....seems to bog down or very little response...adjusted screws some more....engine slowed down and now wont start...gonna pull plug and see if its flooded now

 

[saskct70s]

when we say to tighten the carb screws to tight then back them off i am wondering if one turn is equal to 360 degrees or 180 degrees....i know this may stupid to ask but ....

 

[dirtbkr188]

1 turn is 360°, personally, I use 1/2-turns (180°) x 3 to get the initial 1.5 turns OUT from seated, and make my fine-tuning adjustments in 1/4- turn (90°) increments.

 

[saskct70s]

ok so after rebuilding the carb again and using a thin wire on the jets i have gotten the '77 to idle nicely but when i give it some throttle it seems to bog out? i have swapped the slide and needle and this seems to have no effect. any thoughts?

 

[awm]

It may not be a carb issue at all. Have you checked the gap on your points ? If they are to close it will throw your spark timing off and will minick a carb issue. I dealt with this issue, adjusted the points and it reved up.