running rich once engine warm

[chatty katty]

Have a newly rebuilt engine with 15 miles on it. Engine runs fine until it gets warmed up (220 degrees) in which it boggs down like the chokes on or something. It ran fine with 120 main jets last summer. Got 116's in now and even with the cold weather it runs very rich. Any ideas?? I took apart the carbs since it last ran good in the fall. Any internal parts in the choke mechanism I could have messed up when I cleaned out the carbs?

[md86]

Rebuilding the engine will create more vacuum than it once had , sucking more fuel . If the carbs are fine , coils are fine , all that crap , then just keep tinkering with the jetting until it's right . I knew a dude with a stock pre 750 with a full exhaust that had his dyno-tuned , and ran best with 105's .

[chatty katty]

So higher compression = sucking in more fuel? Why does that not apply to air consumption as well?

[md86]

Good question . I've been told that a newly rebuilt engine sucks more fuel . That's all I know . If it seems to be running rich , tinker with the jetting . Be nice if you had access to a dyno/EGA to be sure , but whaddya gonna do .
BTW , how do you know it's getting to 220* . Seems to me a Katana will run hotter than that being air/oil cooled , and they ain't usually got temp gauges on them . You bolt one of them on ?

[TRH1]

Have you checked your float heights as this is important, you can make the mixture leaner by lowering the floats by 1mm, this worked for me.Best of luck.

[chatty katty]

"BTW , how do you know it's getting to 220* . Seems to me a Katana will run hotter than that being air/oil cooled , and they ain't usually got temp gauges on them . You bolt one of them on ?"

I took the temp readings with a laser temp gauge. Normal operating temp for my bike is around 270-290 degrees. When it reaches 220 it starts running bad.