XJ700 temperature

I have never had an xj with a temp gauge. I installed the vapor and it is working correctly as I verified with a infrared thermometer. What should these bikes be operating at on the highway at around 70mph. In town it stays around 250-260 on a 90+ degree day. On the highway I see over 300 degrees. Is this normal?. I have colortuned and synced and all is good there. Plugs are a bit on the rich side but better than lean. Just want to make sure I won't ruin my new baby. I just finished a summer long build on her. Its a 1986 XJ700 by the way.

 

At what point on the engine are you measuring this temperature?

 

*Deleted*

 

I have it hooked to the head stud but up front. Where would you suggest hooking the temperature sensor. Its too small for the spark plug. I do notice the rear is much cooler than the font since the exhaust exits the front. The exhaust temps are well above 400 which is every bike I have ever measured. I just want to make sure I don't blow up my fresh build.

 

I know this is an old thread but since it was on this specific topic I figured I would ask on this one instead of starting a new thread for the same topic.That way if anyone else has this problem or question it would be easier to find than having to search 2 threads. Plus I am new so I do not know the most efficient way to do things in order to have things properly located and receive the right feedback/ replies, yet! lol.

Anyways, 4freese was asking about, what I am assuming, is his XJ700 'N', since he mentioned he never owned on with a temp gauge. My question is how likely / do they have a tendency to overheat? I know they are simply air-cooled, and not having a radiator or temp gauge seems a bit risky, so should I worry about my 85 XJ700 N overheating?

 

if you want to measure engine temp i would think that the best way would be to measure the oil temp. It is my understanding an oil cooler can be put on these bikes. tapping into the input cooler line would give a temp that was consistant with whole engine as opposed to one point of the outside block which could be affected by wind.

if you want to get creative maybe 2 probes inside the YICS passage from both sides by drilling through the plug bolts.
or a probe mounted inside the valve cover
you would do better to collect data then you could record temps at different speeds, air temps where riding just to check against.
you could use thermal resistors which change resistance with temp.
thermistors
http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/Sensors/TempR.html
you can get creative with them and the location end of oil plug inside oil filter ect...

 

It is almost impossible to overheat an air-cooled engine. You'd have to be running quite lean, and running the engine quite hard on a very hot day, or run it with almost no oil in the sump.

 

Ok great, thanks for the info k-moe. I was wondering when I bought my bike how it was cooled and discovered on these threads that the 2 years of the XJ700s didn't have radiators, so I was curious to see if that was advantageous or possibly harmful to my bike. After your response, why the heck did they ever start equipping bikes with radiators versus leaving them air-cooled?

 

Thanks for the thorough answer XJ550H and link to the diagrams. A bit over my head, but one day I will probably have to sit down and learn all that stuff anyway!

 

Water cooling has advantages for power production and emissions. A water cooled engine has passages near the valves, which allows heat to be removed much faster. That fast removal of heat allows for higher compression, different valve timing, and in short- greater power production per CC without damaging the valve train. The water cooling the cylinders also has advangates in the overall weight of the engine. An aircooled engine tends to be heavier because there has to be enough mass to quickly draw the heat away from the combustion chamber and cylinder walls in order to keep the metals from melting and fusing.

If you want a fantastic exploration of engine design and engineering that is written in laymen's terms get a copy of Top Dead Center (1 and 2) By Kevin Cameron.

 

Well as I have read on many threads and as I just read again, you seem to know your stuff. Thanks again and I will check it out.

 

I just know what other people have taught me.

 

and that wealth of information is something that we can all hopefully lean from you.
I now look forward to another book to add to my reading

 

Holy Heat Batman! (since we're on the subject) Just came in from a short ride around town. It is litterally the second run I've done with the bike since the carb rebuild/bench sync (air/pilot screws to 2.5 turns out from seated), new brakes, new tires and valve shims swapped to spec... Much thanks to Hogfiddles, Len @ XJ Forever and the kind and knowledgable people here... I have to sync the carbs & do a color tune.

The first run was only 7 miles, then shutdown. Sat for a few hours, then startup and run 7 miles home... ran flawlessly.

She starts up good and I'm able to remove choke after a min or two of warming up. She'll hum just over 1k real nice. Tonight though, after about 20 min of riding, her idle was dropping and she stalled a couple times at lights and stop signs. At one point had to keep just a teeny twist on the throttle to keep her from stalling again... Scary at a 4 lane intersection... Seemed like the longest red light I've ever sat at... Ugh.

The raging heat coming off this thing is concerning me. Granted, I know air-cooled engines can get really hot compared to their water cooled cousins, but even the carbs were too hot to touch when I came in tonight... And you can forget about touching that starter... I'm so afraid of "cooking" the components that are more susceptible to heat damage. When I rolled into the garage, there was a HINT of smoke in the air that i could see wafting in front of the headlight. Not a lot... more like perhaps oil on the case burning off?

I'm hoping that after the color tune & sync, the temps will be less of an issue.

So...

1.) Maybe she's too lean?
2.) Should I sync before color tune? Or vise versa? Does it matter?
3.) Would the temperature (if indeed it is hotter than it should be) affect the idle?

I'm including a pic of the plugs that I took after the first ride the other day. Can't touch them right now...

Thanks.
XJ700