Part power drop out

[jetmechmarty]

I tried to burn my bike down last fall. With all the things life throws at you, I'm only just getting to sort it out.

It feels like I am losing one cylinder at about half throttle. I could be two, but I seriously don't think so. It won't accelerate up a hill and seems to be the same throttle position when it drops out. The drop out is independent of RPM.

I replaced the number four carburetor. I used a body from a XS650. The carbs were dropped off and the work was done by a professional that I trust. I put everything together and rode the bike even though it was awful. Yesterday I took it to the shop where the work was done and had the carbs synched. That was a major improvement.

My awful solder job on the advance wires is still holding. The vacuum line is plumbed to the #2 carb. I replaced the scorched wiring.

Before the fire, this bike screamed. Now, it's a dog. Where do I go before I remove the carbs again?

[xs11bobber]

Check the voltage of the hot wires with a DMM (all reds, red/yellows, red/whites, orange, and grey). Is all power there when at idle? I'm thinking you may have the issue consistantly, but you just notice it the most or a lot more.

If electrical checks out, then maybe it's a fuel problem. Maybe a shot diaphragm? Carbs are thoroughly clean? Since you mention that #4 was replaced, I'm assuming they were torn down. Check ALL jets(Fuel and Air) for clear passages. Could be a multitude of things all trying to be diagnosed at the same time. HTH

[jetmechmarty]

Since I made the post, I pulled the spark plugs. #4 has a white electrode. The other three are light gray. I will try to raise the float height tomorrow and see if that helps. I'm suspicious that it might be running out of fuel when I open the throttle.

The #4 carburetor body was replaced. All of the parts were interchanged from the original as the donor was from an XS650.

It runs fine if I don't open the throttle beyond half way. I don't expect it's electrical. I'd like it to be.

[DGXSER]

Sounds like they are al running a bit lean with four being the worst. Do you have access to a colortune? Perhaps it would help to look in and see what is happening at those throttle positions.