ST1100 - She's Giving Up Smoking Like A Cigar But Now She's Hot!

bdalameda said:
Does the fan come on when it is supposed to? If so and the temperature does not go down I would suspect that the thermostat is not opening enough. At least with the Evans coolant you won't boil over and the higher temps won't hurt the engine. I've run Evans in a motor that the water pump impeller failed and was able to ride the bike in the desert almost 20 miles severely overheated and the engine was not harmed at all.
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Fan comes on as it should - the bike never overheats it just runs hotter than a ST1100 normally does.
 
Let's do this again -
1. It does not overheat - the fan kicks on when it should (the needle is about 1/4 off the right mark).
2. It does not run hot at first - if I start in the garage and let it idle until the fan kicks on (gauge at 1/4 off right mark), then go ride the gauge settles back to a 1/4 off the left mark - which is normal for a ST1100.
3. If I continue to ride and get into some traffic or push it hard and the gauge gets to 1/4 off the right mark, it will never get lower than 1/2 (12 o'clock) regardless of how quick and how much air flows across the radiator (i.e. 40 miles on the slab at 75 mph no traffic).

The issue seems to be that once it runs for a while and gets hot once, it can never cool off properly.
When you turn the bike off and let it set till it cools, the gauge shows 1/4 off the left mark as it should once it warms up a bit.
The issue for me if it is a component failing, I don't want to be on a trip when it finally decides to go south.
And once again -

1. New Honda Thermostat with about 2,000 miles on it - working fine with the previous engine.
2. New Honda Temp sensor with about 2,000 miles on it - working fine with the previous engine.
3. Original Honda Temp Gauge - working fine with the previous engine.
3. Water pump only has 23,000 miles on it.
4. Evans Waterless Coolant at proper level.
5. Swapped radiators caps and made no different.
6. Appears to have good flow if you run with the radiator cap off.
7. Radiator is the same one that was working fine with the previous engine.
8. Blew the engine passages out with compressed air before I installed the engine - got good flow for the air.
 
Uncle Phil said:
Let's do this again -
1. It does not overheat - the fan kicks on when it should (the needle is about 1/4 off the right mark).
2. It does not run hot at first - if I start in the garage and let it idle until the fan kicks on (gauge at 1/4 off right mark), then go ride the gauge settles back to a 1/4 off the left mark - which is normal for a ST1100.
3. If I continue to ride and get into some traffic or push it hard and the gauge gets to 1/4 off the right mark, it will never get lower than 1/2 (12 o'clock) regardless of how quick and how much air flows across the radiator (i.e. 40 miles on the slab at 75 mph no traffic).

The issue seems to be that once it runs for a while and gets hot once, it can never cool off properly.
When you turn the bike off and let it set till it cools, the gauge shows 1/4 off the left mark as it should once it warms up a bit.
The issue for me if it is a component failing, I don't want to be on a trip when it finally decides to go south.
And once again -

1. New Honda Thermostat with about 2,000 miles on it - working fine with the previous engine.
2. New Honda Temp sensor with about 2,000 miles on it - working fine with the previous engine.
3. Original Honda Temp Gauge - working fine with the previous engine.
3. Water pump only has 23,000 miles on it.
4. Evans Waterless Coolant at proper level.
5. Swapped radiators caps and made no different.
6. Appears to have good flow if you run with the radiator cap off.
7. Radiator is the same one that was working fine with the previous engine.
8. Blew the engine passages out with compressed air before I installed the engine - got good flow for the air.
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UP, it's a strange one innit.
Is it possible there was a bit of crud in the old motor that has dislodged and is either blocking the thermostat or radiator flow. Although can that be explained by the fact it only happens after it gets properly warm.
I.E. why can't it settle down to a third on the temp gauge?
I agree with your experience with regards to where the gauge should sit but obviously doesn't.
I think I would check just incase some shite moved and if I could find nothing else use it as my local bike until I knew it wasn't going to let me down.
Good luck fella and if this is the bike you're shipping to old blighty get it fixed before you come.
Upt.
 
Do you really know what your coolant temp is? If not is there a conversion kit to remove the factory temperature sensor and replace with a digital sensor that give real coolant temp? I guess the other question would be does the fan operate off of the temp sensor that is connected to the gauge or is there a separate sensor for the fan?
 
I'm pretty certain from memory they're separate sensors. Again from memory one on the thermostat housing the other on the rad.
But if you fit a digital gauge won't it just show what UP has already found and the gauge is thought and tested previously to be good.
Upt.
 
Phil, It sounds like a sensor/temp gage problem. I'd probably buy a cheap thermistor like the one below and tape one to the thermostat housing, another to the radiator. I think you can use a digital voltmeter to read the temps (not sure, but both my Fluke and Ideal DVMs came with thermistors that plug in to the meter). Once I'd set up a separate temp sensing system, I'd go for that ride and see what temps I get.
 
My train of thought is to see which parts and behaviors of the bike indicate actual over-heating, and which, if any, exhibit non-overheating conditions.

How about a probe-type thermometer, dial or electronic, dipped directly into the radiator coolant, since the system doesn't require pressurization?

Standard trouble-shooting is a process of elimination.
 
Uncle Phil said:
3. If I continue to ride and get into some traffic or push it hard and the gauge gets to 1/4 off the right mark, it will never get lower than 1/2 (12 o'clock) regardless of how quick and how much air flows across the radiator (i.e. 40 miles on the slab at 75 mph no traffic).
Click to expand...
So temp raises (slightly) once you start to request more power hence burn more fuel...

This has odd parallels with the radiator issue on my '96 Toyota...
Flying down the Autobahn at 100mph I noted the needle of the temp indicator hanging like 2mm higher then normal...
Slowing to 50mph in a roadwork section, needle went down to normal again...
Free road, speeding up again (requesting more power/more fuel burning), needle again slightly higher as normal...

Closer inspection unveiled that corroding fins expanded, crushing the aluminum pipes of the radiator just so much to cause a slight increased resistance/lower flow volume...

Other possible issues coming to mind
- too lean mixture (= running hotter), PAIR, air leaks, carb settings... (you mentioned reinstating the PAIR system on that engine...)
- issues of pre and post '96 components (oil cooler)...
 
Cogmeister said:
You've fixed it
Have you thought about just riding it?
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See post #211 -

"The issue for me if it is a component failing, I don't want to be on a trip when it finally decides to go south."

Understand a 'trip' over here could be 1,000+ miles from the Holler. ;)
 
Sure sounds like a problem with the gauge, sensors or electrical system. Did you check all the grounds? Try grounding the temp sensor wire and see how the gauge reacts. Once it saw an issue with a temp sensor when the sensor had too much teflon tape on it and it could not ground properly so the readings were crazy. Probably a long shot but who knows.
 
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