Blow back thru front left carb

[totalcomfort]

Just got a 07 in neglected shape, pulled carbs and cleaned them and checked float height. Carbs were not very bad but bike would only idle with choke on. After cleaning carbs idle smoothed out but still had a random miss. Changed plugs and checked for spark at all cylinders all checked good. Took bike for a short run and it was weak till it hit about 3k then started pulling good, but could tell it was down on power. Bike rev’s out good to 9k. The weird thing is I have blow back thru the front left carb As your sitting on bike. All other carbs are drawing good at idle but that is pushing pressure back thru the carb. Do I have a stuck valve? Bad cam? Any ideas?. Thanks for any and all help.

 

[MaxMidnight]

The first thing I would do is to synchronise the carbs and if not already done so do a full service.
The PO may have been fastidious in the servicing but there again....
It would be worthwhile running some fuel system cleaner through to see if that helps.

If the problem persists then check that all four cylinders are firing at idle (Helpful hint: An IR thermometer make this task far less painful that using your fingers to test).
You may need to do The Shotgun or even have the carbs ultrasonically cleaned.

 

[Parminio]

It would be worthwhile running some fuel system cleaner through to see if that helps.

Get a can of Seafoam. Put it in your jacket pocket or backpack. Run the bike down to where the warning light turns on, then flip to reserve and ride to the gas station. Pour about half the can in and fill up with super unleaded gasoline. Run that tank out and do the same thing with the other half of the can.

If it's not sorted out by then, it's not going to be and you've got another problem.

 

[Fire-medic]

MaxMidnight is correct on checking firing, but instead of using fingers on the header pipes he warned about, spray a spritz of water and a hot pipe will immediately vaporize it, a non firing pipe will allow it to drip/run down the pipe and then you know. If you have an infrared thermometer as he suggests that's best.

I suspect a clogged pilot jet in that cyl carburetor. When it clears up by 3K, that's a good indicator of it being a clogged pilot jet. He suggested a carb synchronization and setting air mix is part of properly functioning carbs.

 

[totalcomfort]

First of all thanks for all the help, I checked pipes and all were evenly hot, running sea foam in it during all the test runs. I have some other plans for this bike later on, so decided to send them to Sean. Going to have him fix them up and install his kit in them. Looking for some cops right now , figured if I have to work on it go ahead and get stuff done this winter. I want to get it ready for spring and not have to do anything but put a LOT of fuel in it. Still have to do fork seals and bushings and will put progressive springs in when I get to that project.