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Some water temp sensor data points.

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Flying Duck
PsyKotic Waterfowl

Joined: 27 Jan 2005
Posts: 9537
Location: Bumf***, WA

PostPosted: Tue Aug 03, 2010 1:28 pm    Post subject: Some water temp sensor data points. Reply with quote

Local guy having issues with a K100RS4V:

- When hot, the bike stutters/floods past half throttle.

- Fan never comes on.

- Exhaust smells like fuel.

- Mileage has gone to crap.

I suspected that his temp sensor might be going. Since I got that parts RS running (which I assume has a good temp sensor since it's only got 24k on it) and it uses the same water temp sensor I thought it might be interesting to compare the resistance at various temperatures. I used the same BMW temp gauge on both bikes to remove any variance there.

Anyhow, it does look like he's got a bad temp sensor but I thought I'd document the readings I got at K11OG in case someone might find them useful. Note that the 94+ bikes use a different temp sensor and Motronic so this data may only be applicable to 93 and earlier K1100s and K100RS4Vs.

In order to measure the resistance from the temp sensor for each bike I disassembled the Motronic connector so I could shove a multimeter probe in with the violet wire from the temp sensor. (Note that when the bike is on the Motronic grounds it out so readings were taken by turning the bike off and measuring the resistance between ground and the violet wire.)

The "good" bike - 93 K1100RS:

More or less stone cold: 850 ohms

1/2 on the temp gauge(major hash mark to the left of the straight up one): 223 ohms

5/8(straight up): 178 ohms

3/4 (major hash mark to the right of the straight up one): fan kicks on at 143 ohms

The "bad" bike - 91 K100RS4V:

Didn't measure it cold since he rode it here.

1/2: 214 ohms

5/8: 197 ohms

7/8(start of red zone): 140 ohms and fan still hasn't kicked in

So it looks like his temp sensor is a wee bit off and fooling the Motronic into thinking the engine is colder than it really is and overfueling. I'll update this thread once he's replaced the temp sensor.

(Disclaimer: I wouldn't take the specific numbers as gospel but I think they're useful from an order of magnitude perspective.)
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
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Flying Brick Rider

Joined: 05 Jan 2009
Posts: 257
Location: Wroclaw, Poland

PostPosted: Wed Aug 04, 2010 2:46 am    Post subject: Reply with quote

I had a similar issue, the discussion was here on forum. A bad temp. sensor should generate an error cod of ECU. Check the connector of the sensor.
Here is the link with my measurements, K110RS 1995, the sensor with pigtail:
chart ling, two temp. sensors + simulation

There was a temperature sensor type change around 07/1993, old ones are "short", new ones have a pigtail with a connector! Old type cost ~ $40, new one ~$85 - an expensive piece of 25 cm of wire with a connector Confused

Soon I'll add data for temperature gauge sensor, as I have a new one. After I have destroyed genuine Wink.

Best regards
K1100RS is a real beast (in Marrakesh Red)
K75S is a real beauty - she has gone Sad, but not to far Smile.

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