Mid range runs hot

After putting about 800 miles onto my bike since I finished getting it running, I have a had a trouble with the engine getting too hot during operation around 4-6K rpm. When running below that point the engine stays very cool. After calling around to a few bike shops in town, I have been told that my floats may be improperly set, jets may be wrong size or I may have the wrong size needles. Everything on the bike is stock except for the replacement of wear items. Where should I start looking? Should I raise my floats a little?

 

What makes you think it's running hot in a particular RPM range?

In regard to the floats; there is a spec for float levels. If they were set to spec to begin with, that shouldn't be an issue. If not, then by all means wet-set them, to spec.

When the carbs were rebuilt, did you break the rack and replace the throttle shaft seals?

 

While I am riding if I keep it below this rpm range I'm getting a head temperature of around 225-250 degrees Fahrenheit. When cruising with the throttle higher, I am getting close to 300 degrees Fahrenheit. The carbs have new shaft seals and have been wet set to 3mm + or - .5mm.

 

What is the correct head temperature spec you're shooting for? Where did you get it?

Higher RPM = more fuel = more heat to dissipate. I'm surprised it doesn't heat up more than that.

 

I called a local yamaha dealer and some to a person in the service department. He told me that 280 degrees is about the max I should be seeing on the head.

 

are the cylinders and head painted or bare?
if the guy you talked to said 280 and your getting close to 300, your not far off, 10%.
since it's air cooled, no head temp can be quoted without considering ambient temp. it's got to run hotter when it's 90 rather than 50

 

Where/how are you measuring the temp; and more importantly, why?

I've never seen any sort of specs in any of my Yamaha literature including the EGA manual.

 

The head I stripped and the cylinders are painted. I'm just trying to make sure that I'm not going to cause damage running it like this.

 

OK, that covers "why" but how/where are you measuring?

I honestly think you're getting worried over nothing; a lot of XJs came with "naked" heads and painted cylinders:



(Ignore the arrows and lines, those were from a YICS discussion.)


Go ahead and run it as hot as it's gonna get; then shut it off and have a peek at the plugs after it cools down. I'll bet you find no signs of "overheating."

 

I'm using an infared thermometer and am taking readings around the spark plug.

 

I think you're becoming overly concerned about a non-issue. If the bike isn't "misbehaving" and you aren't blueing pipes nor have any other signs of running hot, then just keep an eye on the plugs. If they constantly indicate a lean condition, then investigate.

But you didn't create a problem by stripping the head and painting the cylinders.