Thread: 1970 CT70 NO Power without choke open

I was hoping someone could give me some advise on why my bike seems to have no power. I have a ct70 with a 88cc big bore kit, new valves, new exhaust, and a carburetor that I just spent $100 rebuilding and tuning for high altitude "original". I thought that would work and the guy who sent it to me had it on a test bike going 40 MPH!! The bike starts great but only has power when I open the choke. I have tried everything to get it to run and it will not even rev up unless the chock is opened up. When I ride it, the bike will go like 15 MPH. It seems to peg out and have no torque. It has no power but yet it has a new coil, spark plug, points and condenser, etc. I have completely restored the bike and can't get it to run right. I could really use some help trying to figure out the problem. Thanks.

The pilot jet is too small or it's clogged. You might want to back out the fuel screw a turn or two first to see if that may help.

I believe it has a #58 installed now after the rebuild. Is that too small? I think the guy rebuilding the carb was trying to lean it out. What size would you suggest? Thanks

Your main jet has got to be partialy plugged for it to only run decent with the choke on. Just my opinion.

I Live right at sea level a #62 jet works about right with a #35 pilot jet and the clip in the middle grove on the needle. I would check the brass tube the main jet screws into, It has some small holes in the side too mix fuel and air and if their pluged up it wont run very well. good luck Grant

It's definitely a jetting issue. Pilot, needle, and main jet. If it improves with the choke on than the bike is jetting too lean on one or all three circuits.

You are SURE yor getting full fuel flow and that your FLOAT is set correctly. These to items will also cause a bike to run like a turtle....

I must be reading this wrong? Choke open is how its supposed to run. Choke closed is for cold starting only. It should only run correct and well with choke open...

Thanks for all the advise, I will try messing around with the jets and the needle setting which is at the top now. When I said choke open I meant it is pushed towards the air filter OPEN all the way. I think it should be closed after warm up but it will quit then due to no gas/throttle response. I have a couple bigger jets in the #60 range I can try out. What is the smaller jet you were talking about??? Like I said I just got the carb back on the 24th completely rebuilt so I don't think anything is clogged and he ran it on a bike of his, and it ran great, so why is mine such a dog????
Thanks again.

The choke is supposed to be open when it is warmed up, not closed. You only close the choke to start a cold engine only. It is supposed to be open all the time!!