help me tune my carb.

[79ATC110]

Ok guys I need some help! I'm in the process of finishing my rebuild of my '79 110, and need help setting the carb. It idles nice and smooth once its warmed up... when I get on the throttle it does fine at low RPM, but when I hit the mid RPM range it putters, but once it gets into the higher RPMs it takes off and runs great. I've played with both the adjusting screws and the needle clip...but I'm really not sure what I'm doing, any ideas!?! I know I can adjust the needle clip up and down, but I dont know what screw does what on the carb, I need help!

[Unclediezel]

Sounds like the carb float may be a "TAD" low. Low speed is fine , but when you go up the range , A transition occurs between Pilot and main jets. if your bowl empties out momentarily , the engine will sag and clear up once the fuel level is equalized. If this is not a modified rebuild - Get a svc manual and set the carb up stock, It will be much easier to troubleshoot a problem if "The Variables" are known to be correct.

[TeamGeek6]

Try to find out what the original jetting is and see if something has been changed. Look at Sudco.com and/or if its a Keihin, keihin.com and you should be able to find this information.

Sounds like its too rich on the needle. Dropping the needle farther into the main jet makes the midrange leaner. Wide open throttle is usually only on the main, depending on the carb, because the needle is lifted completely out of the main.

My R had a leaner needle installed and I didnt know it - a previous owner was chasing this same problem and it turned out not to be a jetting problem.

Could also be too rich on the transfer jet, if it has one. Transfer is what gets the engine from idle up to the main jet by supplying extra fuel when you open the throttle off idle. If the transfer is too rich, the spark plug could be fouling a bit when it crosses transfer.

My 86R did this (bogging off idle and midrange) because the float was too high. It was loading the spark plug up off idle and it took a while to clean the engine out.

Before getting too deep in carburetor, make sure the spark plug is clean, or new. A fouled spark plug can do strange things. If it runs OK at high speeds, I doubt the ignition is at fault, but it cant hurt to put a timing light on the engine to make sure the ignition is working correctly.

Two things to keep in mind when chasing a problem like this:

1.) both a too rich and too lean situation can act similar - both can cause power loss
2.) at high speeds, the engine heats up and can cover up a too rich or too lean condition. IT may seem to run OK at high speeds but still be way out of whack.

[79ATC110]

Ok so I'm still playing around with the tune...could some one tell me what each scew on the 110 does, I have a manual but cant seem to find a good descripition of what they do. I know #1 and #2 are jets of some sort, and #3 is the needle clip but thats about it!

[Unclediezel]

1 is idle speed -2 is mixture ---3 -under that cap is the throttle valve. inside you will find a small hairpin clip that snaps onto the needle . the needle has grooves in it to raise or lower the needle out of its seat.
Its usually best to set them to the Mfr settings before you tinker . that gives you a baseline , and a place to go back to when things go wrong.