Cylinder Head Temp Sender Locations

[conquest87tsi]

Last summer I mounted a temp gauge to my bike. Originally I wanted to measure engine oil temp and final drive temp. I wanted the FD temp since I did the XS750 FD mod and I noticed how hot my original FD was getting (probably just a little paranoid). I have been looking all over to find a robust SP3T switch so I could also measure cylinder head temp. All SP3T switches I have found are tiny and cheap junk. I ended up settling for a SPDT switch and am measuring engine and FD oil temps.

I am wondering if anyone has any ideas or experience on a good place or sensor for measuring cylinder head temp. I have seen the ring terminal ones for a spark plug, but am not fond of those senders as I have read that they do not last long. Maybe a good place to drill and tap for a sender? Any ideas are greatly appreciated.

[Rasputin]

You could try to send Rooster a PM and ask him how he mounted his. I have not seen it myself but he has some custom gauges and electrical going on apparently.

[jwhughes3]

I checked into this. I researched aircooled airplane engines. I think the ring sender will work ok if you give it a chance.

John

[bikerphil]

For a while I had a BBQ grill thermometer mounted to the cyl head, a round one about 1 3/4" diameter that would normally be mounted on the lid of a grill. I took the nut that threaded on the back and ground it down on two sides so it could be forced in between two of the cooling fins on the right side center of the head. The sensor end would just hang in air space between the fins but not make any physical contact. The hottest head temperature I ever saw was 400F in a traffic jam when it was 95F outside (summer in S. Florida). At this temperature I had to keep the RPM's up to prevent the motor from stopping (semi seize). Normal temps would run about 200-250 depending if you were moving or not. I do not run this gauge anymore, I feel there is no real need to know the temp of an air cooled engine, it fluctuates all over the place, JMHO, HTH

[conquest87tsi]

I agree Phil, it is definetly not a necessity. But if I had only done things to my bike that "needed" to be done..... well I guess I would have a lot more free time and money, and lose a hobby.

Functionally the gauge is more or less worthless. I realize this. What am I going to do if I have abnormal temps? At most stop for a smoke and then ensure myself the guage has malfunctioned and ride on.

I guess I was bored and didn't have anything broken so I had to find something to add. I do have some thermocouples laying around, just haven't thought of a good way to mount them. In between the fins between 2&3 seems like a good place. Wonder if JB welding the sender to a fin would work. I have a twisted pair and a probe thermocouple. Probably would want to use the probe for that.

[Schming]

IMHO it would be worth the time and effort to install and wire such a device only if its function were to activate strategically positioned fans to help deal with extreme temperatures in certain low speed operation. Otherwise these engines, tuned right, and with the superb oil on the market today are the time tested phenoms we so lovingly admire.

JAT, You may want to pick yourself up a project XS11 of another flavor to use up some of that extra time and money

[conquest87tsi]

Trust me Schming, I'm looking for another project. I am actually on the tail end of a F I just finished restoring. Just need to remove a broken exhuast stud (got to quit going to the gym) and waiting for my dad to get the tank, side covers and fenders painted. Now I'm in the market for something smaller. Like a xs400 or maybe RD350.

[TADracer]

Concerning a place to measure head temp, to me the most logical place is at or near the plug. The plug also acts as a heat sink to transfer heat from the combustuion to the head. Taking the temp right at the plug will give you insight on how your heat range is acting for your particulat setup.

[Schming]

Concerning a place to measure head temp, to me the most logical place is at or near the plug. The plug also acts as a heat sink to transfer heat from the combustuion to the head. Taking the temp right at the plug will give you insight on how your heat range is acting for your particulat setup.

x2, the inboard cylinders would most likely convect the highest reading

[CaptonZap]

Wonder if JB welding the sender to a fin would work. I have a twisted pair and a probe thermocouple. Probably would want to use the probe for that.

I think you will find that JB Weld would not be appropriate for this application. The engineer from JB told me that the resins used in JB Weld start to soften around 230-250 deg F, and your fins will get hotter than that on occasion.
A friend builds SCCA VW engines, and breaks them in on a dyno, and so, must change the instrumentation easily from one engine to the next. He has two head temp gauges, and the thermocouple (TC) wire junctions are soldered to a folded piece of baling strap, which is then forced down between two fins. The TC junction is on the outside of the strap, so that it is in contact with the fin, and if you leave excess solder, the blob can be filed down so that you have more surface area to contact the fin, and quickly conduct more heat. Lead free solder melts around 430 deg F, and you do NOT want your heads to get that hot, so soldering will work. As long as the two wires in the TC are wound around each other, so that they are in intimate contact with each other, the solder has no bearing on the operation of the TC junction, other than to hold it to the spring clip. You want the junction to be down in the fins as close as possible to the solid portion of the head, so you may have to play with the form of the clip and the position of the TC junction on the clip to get it down in there. Here again, a lot of surface area of the junction will help the temperature transfer, thus accuracy.
Four TC probes could be wired to a rotary switch, which would then feed the gauge, and allow observations in differences in temperatures at various points on the engine.
The indicated temperatures wouldn't be 100% accurate, due to the added cold junction on the switch, but for comparison purposes, it would be within a degree or two, and that would be accurate enough.
Unless this project is leading to a Doctorate degree.
CZ

[81xsproject]

I have had FI for a few years now and have yet to find a good solution for this. Like you, I'd like to find something better, like a place to drill tap. I also have yet to find any place that seemed to be a good representative for 'warm up.' Most of what I have tried around the head seams to be up to temp before the bike is running like it's TRULY warmed up. If you find a good solution, please share.

[clcorbin]

Have you tried attaching the sender to the carb bank? The head is going to warm up very fast, but I suspect that a cold carb would still cause it to run a bit lean. Might get the response that you are looking for.

[bikerphil]

For the FI setup on our air cooled engines, I would think you would need to somehow have a sensor monitoring the oil temperature to let the computer know when the motor is fully warmed up. JAT