Operating Temps and a carb sync question.

Was wondering if there are specific Operating Temp for these bikes. Obviously it changes due to conditions of weather and traffic. More or less I am looking to find a safe range for the engine temp. Sitting in traffic I can feel heat off the engine. Its hot but not so hot your skin will stick. I at every couple of traffic lights quickly touch the side of the head just below the spark plug to see how it feels. Usually its to hot to hold my hand on for more then a sec but not hot enough to cause instant burns. My hands are really tough because I am an auto tech and used to handling hot metal parts and all that. So I put my laser on it and it seems to be from 220 to 280 depending on the conditions. Do these temps sound like they are within range? I would think this is good for a air cooled machine but I am not a XJ pro just yet. I want to continue to learn and make sure I am doing all the right things for this bike. It is a hell of a lot of fun to ride and I want to keep it healthy.

Also, on another note, whats the symptom insinuating the carbs need to be synchronized? I know my carbs are clean and my plugs all are nice and dark and it idles great. I have an issue that I am predicting is due to the carb sync. No lack of power but I just seems to have a sort of lack of continuity in the acceleration unless you really mash on the throttle. Def not hesitating but if I had to guess differing amounts of air might be the culprit. I can just hear differences in the cylinders under mild accel and loads.

Thanks in advance

 

You didn't specify which XJ but we'll assume you're talking air cooled and if so, don't worry about the temp. Yamaha's biggest market in the '80s was (and maybe still is?) California, the air-cooled bikes do fine there and I suspect it's a lot hotter with greater regularity there...Carbs: Maybe. First thing to do is check/adjust valve clearances before carb fiddling. Also check your rubber intake manifolds for cracking/leaks. They ALL crack (eventually) but not always all the way through. You can use an (unlit) propane torch or starting fluid to probe for intake leaks while bike is idling, if the idle suddenly rises it's sucking in your "test fluid." Check petcock filter screen for cloggage, check petcock vacuum line for cracks/leaks. Run bike for a while on "Pri" and see if the issue is still there, could be your vacuum-operated petcock is becoming "lazy" and needs rebuilt. After ALL the above pass muster, especially valve adjustment, then carb fiddling can begin.

 

Hey,
It is an air cooled bike. 83 XJ750MK with 13900 on it. No intake leak and I believe not the petcock because I dismantled and cleaned and rebuilt that little piece when I got the bike. I have good vacuum to the petcock too.

I live in Maryland and I noticed some fumes Not smoke coming off the motor this morning. No leaks what so even. I haven't ridden this bike in wall to wall traffic and I felt like I was worried about overheating the bike. Very possible it wasn't getting hot enough prior to bake the paint completely.

I realized today that I don't know what all the positions on that petcock actually do. Maybe someone could straighten that out for me. Also, i realize that it might not be anything worry but I still want to know what temp range this thing should be in. Its about 85 and sunny here and in stop and go traffic what would be acceptable is what I am after.

 

If it is teh same as my XJ650

Pri - Allows gas to flow into the carbs without the vacuum activating.

On - Allows fuel to run into the carbs when the bike is running and the vacuum is running.

Res - Allows the petcock assembly to use it's lower hole allowing the lower end of the fuel tank - For the "oops i forgot to fill up" moments