Any Carb gurus in the Indy area?

[jjohn3845]

Hello all. I just finished a 6 year project on a 73 XS (TX)650
I’ve just spent 2 days trying to tune the thing. I had the carbs rebuilt buy a motorcycle tech. They are really clean at least. I installed mikesxs electronic ignition and set timing, cam adjusted and set valves. The eazy stuff I know! The bike starts on first kick just falls all over itself mid throttle on. I’ve tried different pod filters and velocity stacks now I’m trying with no filter. I installed a set of 4 inch baffles in exhaust with a 18” tale pipe hooked to factory headers. From what I can tell the carbs are factory vm38s with 130 mains and 42.5 pilot jet. Is there someone I can pay to fine tune this puppy in the Indy area. May is crazy busy for me and I’m so excited to ride the thing.

 

[5twins]

The RPM area you refer to would be considered the midrange and that is mostly controlled by your needle setting. Most carbs have their needles set in the middle #3 (from the top) slot but your '73 set differs. It should be set in the #4 slot (from the top). If the tech who did your carbs has just general carb knowledge and isn't really familiar with XS650 carbs, he may have set the needle wrong, in the middle #3 slot. Like I said, that would be normal for most carbs, but not these.

 

[jjohn3845]

Thanks for the help. It was in the #4 I’ve moved it to 5 and 2 setting with just a little change. The #2 setting moved the stumbling to a little higher rpm. The exhaust tips are black heavy carbon. I’m confused. I read the manual on this site 3 times. With the float set a 25mm black smoke puffs out exhaust pipe at idle so I moved it to 27mm and it was better. Hopefully that’s not hurting it.

 

[5twins]

Your carbs are running very rich for some reason. They shouldn't be with stock jetting and your mods (pod filters, more open exhaust). Have you inspected the needle jets? They have an o-ring on them and should be a snug press fit into the carb body. If the o-rings are bad (or missing) and the jets are loose, they can suck fuel around the outside instead of just through them as they should. I guess it's also possible the jets are worn.

 

[jjohn3845]

Quess I’m going to take them apart again tomorrow. And check that out. Thanks