Poor fuel mileage

In my experience, when the t-stat begins to fail, my average mileage will begin to drop BEFORE I start seeing the bars transitioning from 3 to 2 or less when fully warmed up. I replaced my t-stat twice in my '04. I also witnessed a co-riders t-stat fail on his '03 during a 1,100 mile SS1000 ride from Seattle to WeSTOC in Minden, NV in 2004. My bike was 2 weeks old at the time. About 600 miles into the ride he started to notice his dash fluctuating between 2 and 3 bars. Mine was rock solid at 3 bars. As the ride progressed he was down to a steady 2 bars, then fluctuating between 2 and 1, then a steady 1. I don't remember if he ended up at no bars?? The temps dropped during the coarse of the ride and it rained pretty hard for the first 500 or 600 miles. But even as the weather warmed up and dried out his bars never returned. He had the t-stat change out in Minden before we rode home. He wasn't tracking his mileage at the time.

When my first t-stat failed I was already at the fluctuating between 3 and 2 bars point. When the 2nd failure occurred I noticed the drop in mileage before seeing any issues with the bars. I changed the t-stat and my mileage returned to normal.
 
adamk said:
In my experience, when the t-stat begins to fail, my average mileage will begin to drop BEFORE I start seeing the bars transitioning from 3 to 2 or less when fully warmed up.
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That's exactly the expected behavior.

The ECM is very diligent about running the engine rich to get it up to temperature and keep it there. The cooling system is efficient enough when you're moving to make it difficult or impossible, even when the weather is warm. The thermostat is supposed to stem the flow of heat out of the engine by closing; if it doesn't, the ECM will counter the heat loss by burning more fuel. I'd bet the richer mixture throws performance off just a bit, too.

You don't see any of this on the gauge until the combination of ambient air temperature, humidity and wind speed remove enough heat to overcome the built-in hysteresis. (I don't have anything to back this up, but my theory has always been that the three-bars position on the gauge has a lot of it built in.) In most places, the air temperature is high enough during most of the riding season that you won't see any indication, but once fall and winter set in, this starts to show up.

--Mark
 
mlheck said:
I will be following this thread as I also am having an issue with my fuel mileage. I have an 05 with 70k miles and it has always averaged 40-42mpg in combined riding. Last year it dropped to 36-38mpg. I also plan to change my thermostat even though it holds a solid 3 bars at all times. Air filter was cleaned last year. Might be an issue there, but haven't pulled plastic to double check it yet. I'm running a Turbo Tom fuel pressure regulator but might put stock one back in if I can find it.
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If you want company let me know. I need to change mine too. Maybe we can do it at the same time. Im not that far from you.
 
etalors said:
what are we supposed to follow.
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Search this site for how to do it. The HSM will have you remove the throttle bodies. TOTALLY not required to remove to replace the STAT.

Remove your Tuperware.

Follow HSM to remove the radiator. My HSM is pages 6-13 to 6-14. Once the radiator is out of the way the Stat housing is behind a bracket that once removed will allow you to split the housing and remove the STAT. Be prepared for a coolant spill/mess when removing the lower hose. Get a large catch pan.
 
Kevin_56 said:
Search this site for how to do it. The HSM will have you remove the throttle bodies. TOTALLY not required to remove to replace the STAT.

Remove your Tuperware.

Follow HSM to remove the radiator. My HSM is pages 6-13 to 6-14. Once the radiator is out of the way the Stat housing is behind a bracket that once removed will allow you to split the housing and remove the STAT. Be prepared for a coolant spill/mess when removing the lower hose. Get a large catch pan.
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Thanks Bro. BTW, are they having the tech event in Pardeville, this year. This is something I would have liked to do there under the guidance of some experienced folks.
 
Kevin_56 said:
Search this site for how to do it. The HSM will have you remove the throttle bodies. TOTALLY not required to remove to replace the STAT.

Remove your Tuperware.

Follow HSM to remove the radiator. My HSM is pages 6-13 to 6-14. Once the radiator is out of the way the Stat housing is behind a bracket that once removed will allow you to split the housing and remove the STAT. Be prepared for a coolant spill/mess when removing the lower hose. Get a large catch pan.
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Regarding the mess I started siphoning all of the coolant out of the radiator before removing the hose on the lower right side of the engine. Now when I remove the lower hose from the block to the radiator it's much easier to catch what drains out of the block as very little coolant is coming out of the hose, mostly it's just draining the block. It works well.
 
Ha 49.5 average on the parkway! It's very hilly around here.
The third thermostat was the charm.
 
First thanks to all you guys that helped me out and pitched in with advice!
I have a nice 2 up ride planned for today to bring Laurie about an hour and a half north to pick up a friends truck for him. He had a heart attack while up there, and got brought back twice. Seems OK now but he is not to drive for 3 months.
He is an ER doctor and was at his brand new job. Good place to have a heart attack it seems!
Anyway nice to have a ride planned. Bonus ride for New England in January for sure!
 
To close this out, Did a throttle body sync as well as the new new thermostat and all is well and smooth.
The end!
 
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etalors said:
my temp bar goes back and forth between 3 and two when riding below 50. Does that mean the T stat needs replacement. I get about 40 mpg hwy at roughly 75 mph.
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I had the same issue and I would think thousands of others. I changed the Radiator fluid I believe at about 20K on the ODO. It ran less going btw 2-3 bars and over the course of a few thousand miles consistently came upto 3 bars and stayed there. I now have just shy of 119K and it still is running at 3 bars. Problem solved.
 
I had the fluid changed at the dealer in 2014 about 12K miles ago. So its not like its very old. I am going to change it in april/may, since its been two years and up for a change now anyways. But most on the board believe that the Tstat is the culprit. I also experienced a drop in mpg right after I changed my air filter last year.
 
The engine running cold is an indication that the coolant is doing its job.

--Mark
 
When my thermostat went bad I never got above 2 bars even when temps were in the 60s and low 70s
 
I'm confused now. Some say one should always be at three bars. You are saying engine running cold (shifting between 2 and three bars is ok). If the temps are at 70, I am at three bars, no switching back and forth between 2 and three. If the temps are around 55-60, I do see 2 bars and then back to three. What is the consensus now? I have however as I said experienced a drop in mpg from 41 to about 39 at highway speeds (80 mph indicated).
 
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