On the road in Vegas. Just came from death valley. Bike was cool, like 178. When I stopped for a pic, it spit a little water out the overflow. Then when I started back up, it ran 183. This cycle continued, spit a little with 5 deg temp rise till I was at 220. I am thinking radiator cap, but wanted a second opinion.

Maybe a sticking thermostat causing a restricting in flow...   I'm sure someone with more knowledge would chime in.

Cheers
Ron

Rad Caps do wear out.... We replace the factory rad caps on our big CAT diesel gensets with caps that have a higher pressure rating to keep them from burping over when just shut down and then replace these caps every couple of years for the same reason.

I did some desert riding, in those conditions, the stock cooling system was right at over taxed.  When your bike puked fluid, the lower fluid level explains the higher temp.   The radiator cap should hold the pressure as long as the cooling fan come on and stays on long enough.  Make sure the fan is running and replace the cap.  That dry air does not absorb much heat as it passes the radiator fins.   I had a bad time riding two up in Arizona with a strong tail wind, The fan ran the whole time and I was very gentle on the throttle.   If it would have started puking fluid, I would have had to wait until the sun went down or the wind quit.  Good luck

Thanks - I am loaded heavy and two up.  I am going to replace the cap in Texas, the next stop not in a campground. (nobody stocks these, are they like super unique or something?) and I am going to put in one of the replacement lower temp fan switch referenced in earlier posts.  I don't have my service manual with me.  Could someone tell me where the fan switch is located?

Thanks guys!

Fan switch located left side of the radiator on the back side. You could also put a switch in parallel with the fan switch and turn it on whenever you want.

Fan switch is on left rear of radiator.  You can see with side panel in place but will need to remove panel to replace.

The local auto parts store can have or can get one for $24.  The one I bought is about 1-2mm longer and operates at a little lower temp but is barely noticeable in when it kicks on and off.

Remove middle side panel to replace.  No need to drain coolant if you are quick or can temp plug radiator.

You can test the unit by placing in a pan of hot water and make sure connectivity begins/completes before 212 degrees.  I forget the actual specs.

There is another thread by me with more details on which part numbers are said to work.

Jim

Sounds like it was overfilled to start with. Keep riding it and see if it mellows out.

On the road in Vegas. Just came from death valley. Bike was cool, like 178. When I stopped for a pic, it spit a little water out the overflow. Then when I started back up, it ran 183. This cycle continued, spit a little with 5 deg temp rise till I was at 220. I am thinking radiator cap, but wanted a second opinion.

Most parts houses will have these
switch, cooling fan - Borg Warner: TFS500, Facet: FS8404, Filko: TFS-1, Four Seasons: 35934, Wells: SW504
radiator cap (32mm ID x 16mm deep neck)  - Carquest :33028, NAPA: 703-1443, Stant: 10227, Stant: 11227(blister pack)
Thermostat    Stant: 13368, Stant: 35368 (blister pack)
thermostat o-ring - 32mm OD x 25mm ID x 3 mm    Pep Boys: 29368, Carquest: 31068, NAPA: 142,  Toyota: 16401-63010, Mitsubishi: MB221855, Futaba: R124,

Do not mess with that thermostat while you are on the road unless you absolutely have too as a last resort!   If it has not been disassembled lately (ever), the o-ring will look like a little bead of black bubble gum.  A few have said they changed it with out removing the carbs.  Yeah, good luck with that.  You may get lucky and be able to get a good seal if you can get it all out - there's just very little room to work with.  There is a second smaller o-ring you will probably need but I don't have the info.  It will leak after being disturbed.

The fan switch got me also last year.  Just before it quit working, it would seem to come on a little late.  Didn't loose coolant though.  You will loose a couple ounces of fluid when you change it.  Had the new one ready to screw in.  Maybe it's a good time to drain and refill the coolant since this happened just to make sure its properly mixed.  Buy the premixed non-silica green stuff (or your preference).

P.S. - Read the big black note again.  I hope this works out well for you and enjoy your trip.  I'm in VA and would love to be out there no matter what the heat is.  Don't forget to check your tire pressures too.

I had to mess with my stat on a trip, but I did make it to my brother's house, with a 40x60 well equipped shop. I had picked up Stant stat, opened it up, discovered the nice goo. I sealed it up with Permatex Form a Gasket #2, the non hardening stuff. Lasted about a year and a half(20,000 mi). The reason it let go is my radiator cap gasket had swollen after being in existence for 7+ years. When revving the bike north of 9 grand one day, I sprung a leak in the Permatex, from the cap not releasing. Better the Permatex than the radiator. I'm now running a 195* stat, I like the way it works, and it does work fine even in our nice upper 90* summer days.

Hello Uglydog, I'm curious, what method are you using to get the specific temp numbers?   I recently installed a Koso digital instrument on my 95, an alum in-line pipe, just downstream of the original thermostat housing.
  So I could compare numbers to what i see on the orig equipment gauge with just Hot/cold indication.
A couple thoughts about cooling systems, as on any system, it should be clean inside, no scaly stuff, etc. Also, at highway speeds, the negative pressure on the outside of the fairing is important, as is of course the positive pressure in front of the radiator.  Do you have high-way pegs, with your legs blocking part of the exit vents in the fairing?  I've seen this happen on the KLR650 with guys running tank panniers.
Pure anti-freeze wont cool as well as water, but of course we need some of the additives for corrosion and anti-freeze in the winter.  50/50 works pretty well IMHO.
And, one other thought, your fan blade ok, not slipping on the motor shaft?  Blade tips melted where they pass close to the headers?

Just throwing some ideas out for consideration.

Good luck to ye.

Sorry I left out something before I hit send;
 IMHO, puking at 178F, certainly the cap is a good place to start. 

Good luck and ride safe.