Don't Fear Changing the ST1100 Thermostat!

Slasher

Slasher

Joined
Aug 23, 2012
Messages
583
Location
Lexington, KY
Bike
1998 ST1100
The day I first saw and rode my new to me 1998 ST1100 the seller started it right up and left the choke open for what seemed like a long time as he explained that it was a "very cold natured bike". Not having had an ST before I took him at his word because the bike otherwise ran and rode beautifully. The bike followed me home and I have been loving it ever since. The cold natured part was really starting to bug me though. So I came to my trusty ST owners site and everybody says... "Its not the thermostat". I checked everything else and all was well but I just couldn't believe that this bike ran this cold all the time. The gas mileage wasn't what I expected either. I am a pretty experienced shade tree mechanic and any time a car runs like this... its the thermostat. Through some research I found that the Stant 13868 thermostat was a direct fit for the ST1100 (even the stant website confirms this). I went to Advance auto parts and picked up the T-stat for $5.99 and went home to "operate". I pulled the saddlebags, right side middle cover, right side inspection cover, shelter, right side fairing pocket, and the plastic shroud on the front of the thermostat housing. The thermostat sits basically under the radiator cap. After I had access to the thermostat housing I used a turkey baster to suck out enough coolant to get below the thermostat housing. Using a 1/4" ratchet with a short 10mm socket and a short extention I was able to remove the two bolts on the housing and extract the old thermostat. That sucker was stuck wide open! I was happy to see this because it confirmed my suspicions. The rubber o-ring gasket looked fine so I left it in there and reassembled everything with the new t-stat in place. Topped the radiator back off and fired it up. She warmed right up nicely, and I observed the flow in the radiator increasing after awhile confirming that the new t-stat opened as it should. Put all the tupperware back on and rode to the gas station to fill up. The temp gauge now sits inside the normal range bracket instead of on the low side of the gauge. The jury is still out on the mileage but it has to help. The best part of this is, from start to finish, it only took about an hour! So if your ST is "cold natured" like mine was, for an hour and $6, you can warm her up! YMMV Yadda yadda yadda
 
Slasher said:
The rubber o-ring gasket looked fine so I left it in there and reassembled everything with the new t-stat in place.
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Wow, mine was flat as a pancake, surprised yours was reusable. I tried to reuse it because I had to wait to special order a new one, but as I expected, it leaked badly.
 
I guess it would've been more accurate form me to say "the o-ring didn't have any cuts, breaks, or tears". Mine was pretty flat too. I really wanted to coat it with silicone grease but I didn't want to push my luck pulling it out of the housing. I also have the benefit of a custom gasket company a few miles from the house that could've made me an o-ring if things went bad wrong so, I just went with it. I watched it like a hawk once I pressured it up but, no leaks.
 
Many thanks for your post. I took my bike out on it's first ride today. Noted my temp gage staying near the cold zone on the freeway. When I was at idle while parked the gage would creep up near half, but a throttle blip would make it dive to cold again. "Thermostat" I thought. Drove it back home and got the Stant 13868 for six bucks at Advance Auto Parts. If you were to use the Honda Service Manual technique you would be two hours of body work and another hour or so to remove the housing. I just removed the parts you stated and the overflow tube. All the other hoses stayed on. You have to fiddle the housing a bit to get the inner housing bolt off, but it did. I just shot the new one right in without a new O-ring as well. Same condition as yours. No leaks when put back together. You saved me a bunch of time, unnecessary labor and cash. I took about a little more than an hour only due to the fact is was still hot and needed some cool down time. Put the tupperware back on and gave a 30 mile road test with a normally operating temp gage. As you say, no fear!
 
Glad I could help! You'll find your STeed will get better gas mileage and run a lot smoother now that it isn't freezing all the time!
 
Hmmm, the one thing I did differently was take the o-ring out to try and buy a replacement for it at various local dealers and auto parts stores.

Perhaps if I had just left it in the housing it would have re-sealed, but it looked pretty flat after 16 years in the housing. It only takes a minute to try, so in hindsight I should have given it a shot anyway.
 
Slasher said:
Glad I could help! You'll find your STeed will get better gas mileage and run a lot smoother now that it isn't freezing all the time!
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I got 52.6mpg once being very careful and steady on an all freeway run last year. Seemed to run no different. I just caught it right away this year, thankfully.
 
I had the same condition on my saturn sl2, low temp reading, new t-stat fixed last fall. Will be pulling my st1100 out of winter storage this wkend!!!
steve
 
craigstys said:
I got 52.6mpg once being very careful and steady on an all freeway run last year. Seemed to run no different. I just caught it right away this year, thankfully.
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I get 47 on the interstate with the cruise control set at 76. With the bad thermostat and the massive clearview windshield I used to have, I'd get 37.
 
craigstys said:
Drove it back home and got the Stant 13868 for six bucks at Advance Auto Parts.
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At first I went to Autozone, they don't carry Stant. Just searching Advance Auto Parts website and the part number shows " no match found". I'd like to get a couple spares since I've just noticed that mine is stacked. Needle just doesn't even get to the middle of temperature meter even in heavier traffic.
Just googled it with no avail.
Mark
 
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maximark said:
At first I went to Autozone, they don't carry Stant. Just searching Advance Auto Parts website and the part number shows " no match found". I'd like to get a couple spares since I've just noticed that mine is stacked. Needle just doesn't even get to the middle of temperature meter even in heavier traffic.
Just googled it with no avail.
Mark
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I went to NAPA for mine. You still want to order a new o-ring though. Keep that in mind or you will have to tear into things again.

I want to say the one that I used was for a 1986 Honda Civic.

Here is more info

http://home.insightbb.com/~mmartin36/Hose.htm

Sent from my Nexus 4 using Tapatalk 2
 
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Man, thanks for this thread. I just got my 2002 ST with 16k miles. I have only put 75 miles on it. But the damn this runs ice cold. And I can't get the idle right either. I figured it was the Tstat. But I needed comformation. I will be getting a Stant tomorrow. THANKS!
 
acoloreo said:
Man, thanks for this thread. I just got my 2002 ST with 16k miles. I have only put 75 miles on it. But the damn this runs ice cold. And I can't get the idle right either. I figured it was the Tstat. But I needed comformation. I will be getting a Stant tomorrow. THANKS!
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I have found setting the idle can be quite tricky. You can't even begin to try and set it until the engine is at normal operating temp so a new thermostat should help. Seems like I had to set mine a few times before I was happy with it. I'd set it, ride a couple days, adjust it a little, ride a couple days, finally it settled to where I wanted it (1000-1200). Congrats on your new STeed, you got the last year for civilian model 1100's. (police model was still available in '03)
 
I am sure I can get it set right after the new Tstat. By the way, is the idle adjuster seem hard to turn to you? Or is there something wrong with mine?
 
acoloreo said:
I am sure I can get it set right after the new Tstat. By the way, is the idle adjuster seem hard to turn to you? Or is there something wrong with mine?
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Mine is turning just right. Not too tight, not too loose. It's easy to grease it just take off the "tank". I've did mine and have used and new spare. If yours is bad, PM me and I can ship one to you right away.
Slasher, thanks for your advices.
 
acoloreo said:
I am sure I can get it set right after the new Tstat. By the way, is the idle adjuster seem hard to turn to you? Or is there something wrong with mine?
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The adjuster does not turn easy. I think this is intentional, if it was too loose the vibration of the engine could change the idle and that would be bad! It also only turns so far. I can go up to 2000 (when syncing carbs) but then it stops turning. So it should be tough but don't force it if it stops turning. If you want to lubricate it, this is the other what the other end looks like. ImageUploadedByTapatalk1366976793.353109.jpg The two cables on the left are the throttle cables and the idle adjuster is at about the 1 O'clock position. As mentioned above, you can gain access to the throttle drum by pulling the shelter and its located on the left (shifter) side of the bike just behind the air cleaner.
 
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