Am I running lean on new Mikuni VM TC Bros carbs?

[1973 TX650 Chopper]

I'm a newb and I've learned a lot already on this forum and am really grateful. My 1973 TX650 is nearly finished as I just completed a pamco ignition upgrade along with new Mikuni VM roundslide 34mm performance carb kit by TC Bros. I have the bike running and have driven it a few times. I've set the timing and done everything else like cam chain tension and valve clearance.

I believe the bike is running lean according to the symptoms. It starts and runs somewhat normally but when I drive it, there is no power when just cruising along at a steady speed in the middle of the power band. The lower end of the power band seems mostly normal and if I push it hard in first or second gear through the middle, then when it gets to the top range of the power band it seems to really respond and take off with power. It's just sluggish and unresponsive in the middle power band range. From what I gather on the Mikuni carb PDFs I've found is that the needle may need to be adjusted to supply more fuel to the motor during half open throttle.

These are the brand new Mikuni carbs from TC Bros. I hate to start messing with them if it's possibly something else I'm overlooking. I thought these would be pre-adjusted to work well. I have the Mikes XS pod filters and open exhaust although it's a bit longer than the super short pipes. Is there anyone who has any insight or experience with this? Any help is appreciated as I'm so close to having this bike dialed in. Thanks again.

 

[5twins]

I think you're going to have to mess with the carbs. They are aftermarket performance carbs and pretty much always require a little fine tuning. Take notes and make little changes one at a time. I guess the place to start would be to try needle setting one above and one below where they are now, see what works best. Be aware that main and pilot jet sizes also effect some of the midrange. They bleed over or overlap into it, pilots into the lower portion, mains into the upper portion.

 

[grizld1]

Click the "Tech" button. Select the menu for carbies. Click the link to the VM section of the Carb Guide. If you don't understand it, read it again. Repeat until it makes sense; it won't make any more sense if I write it out again just for you. Check the jetting you got against the baseline there. Follow the instructions. If you still have problems after doing all of those things, I'll try to help you.

 

[Max Midnight]

Before starting to 'adjust' it would be prudent to do a plug chop.