2007 Trailboss 330 backfires and loses power mostly on hills or under a load. I bought 3 brand new. one has always run poorly the other two run great. It backfires and loses power/bogs down. Occurs most when climbing a hill. Took it to the dealer I got it from but they didn't fix it. I've adjusted the low idle but that didn't help. So I purchased the 2007 Trailboss 330 service manual. after reading the manual I don't think it's a problem with the main jet since the other two run great. Always run all 3 at the same altitudes and temperature. I read about an adjustment with the float, the choke and the throttle cable. Any one with experience please throw some advise my way. I'd appreciate it. Not sure where to start.

 

Jetting could be the same,but you could have some dirt/trash in the carb partially stopping the jets. I would eliminate this first. Make sure the the main and pilot jet are clean and open,and also the float needle and seat,either clean or replace.Plus check that valves are at .006 intake and exhaust. If carb is ok then could be other problems causing backfiring /loss of power. Make sure carb intake boot is not cracked or split also,could cause running lean/backfiring. Check these out first. Keep us up dated. OPT

 

Yeah, I guess I'll tear into it this weekend. It has been doing this since the first weekend we took it out and i took it to the dealer right away. but no help. I'll check it all out. by the numbers. I'm leaning toward the float adjustment but the truth is I have no idea. I hear that you need a float adjustment tool, i've also heard that the stock setup on most mikuni carbs is the float tab set parallel with the bowl flange. So when you hold the carb upside down your float tab (the brass lever the floats use to close the needle) should be perfectly parallel with the flat surface that the float bowl mates to. if it is not parallel then take a small screw driver and adjust it by bending the brass tab until the float arm is parallel. read that on a post earlier... So I guess I'll find out if working over the carb will fix it.

 

I never used a carb tool. I've adjusted em sideways,upside down and seems like inside out trying to adjust the BST40 carb trying to keep em from leaking,but you have the good old BST38 and as you said just have the bottom of the float assembly parallel with the carb body and you should be ok as far as the carb. Hope this solves your problem. Keep us up dated. OPT