K11 Owners Group

[N41EF]

Since I don't think the coolant has been changed in the recently purchased bike, I'm looking at doing a drain/flush/fill sometime in the next week or so.

I read wha seems like a dozen threads about coolant, and have settled on VW G12 since I have several gallons and I know it's safe for steel/alluminum/copper systems. Zerex G-05 would be my second choice. I also happen to like the color pink, makes the bike go faster.

I'm thinking about replacing the thermostat with a lower temp one. This is a very popular upgrade in the Porsche places, running a 165 or 170 degree thermostat instead of the 180 or 195 original ones. The 986/996 engines have problems with IMS bearings and seals and the though is that a lower temp is better on the seals as wel as wear on bearings. The ECU should compensate for the slightly lower temp, the oil, coolant and such are cooler. I also hope this keeps me a little cooler in the southern heat. Is the stock thermostat 180 or 195?

I think I'd like to start with a 170 thermostat, in a fail safe design, with either the jiggle pin or I'll drill a small vent hole to make the fill and vent easier. I read the thread about the Toyota version so will start at one of the big boxes first.

I did a 30 minute ride tonight with a blast down I-20 in it. Air temp was 65 degrees, the temp gage was about two needles width right of center, heated up just a little when I slowed down in traffic before getting home. I used an infared thermometer and the cylinder head was 170, the crank side was 168, After reading about heat problems and blanket fixes, I'd just as soon the bike ran 10 degrees cooler.

[Flying Duck]

OEM thermostat is 185.

All putting a lower temp thermostat in will probably do is run the engine and it's components at a lower temperature. The heat from combustion that needs to be dissipated will still need to be dissipated. Basic thermodynamics. I doubt the heat to the rider will lessen to any significant degree, the radiator will just generate it sooner/more often when the lower temp thermo kicks in.

The Motronic will probably put out more fuel to compensate for the lower engine temperature so it may hurt mileage a bit. (Not that that really matters on a motorcycle.)

And then there's the fact that the engine, fuel system and ignition system were all designed to run with 185 degree thermo. By he time the 4V Ks were designed the heat thing was a well known issue so I'd guess that if the design engineers thought they could mitigate it by designing a system that was optimized for running at a lower operating temp then they probably would've done it.

The 4V K bike design has been on the road for over 20 years now with lots of tinkerers trying lots of different things (including lower temp thermostats) to address the heat issue. I don't think anyone has ever come across a silver (or even lead) bullet to address it.

One idea I have but have never pursued would be to redo the relay box and get it out of the way so that some of the heat can flow out under the rider and exit behind him/her.
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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)
Buy parts HERE

[N41EF]

Thanks for the input Duck. I'm always amaized at how much knowledge there is floating around on message boards like this.

I'm new to the K bikes but a gear head from way back. Some of this is guess, some of it is wive's tales. In the 80's the auto industry started using higher temp thermostats to raise the overall temp of the engine, to get the combustion chambers hotter to make it easier to pass an emissions test. I rember Chevy went from 180 to 195 thermostats in the SBC in the late 80's as computer controlled fuel injected cars became popular. The higher temp thermostat also stayed shut longer, made the car heat up quicker and again helped the car for emissions purposes. This was all fine when the cars were new, but as radiators got fouled and systems older cars started over heating and blowing hoses or just dumping out the cap. Chevy also had an issue with "lifetime" coolant known as DexCool, which in reality needed to be replaced every 5 years at least. A comsumer fix was to install a 180 thermostat to increase the margin between where the car operated and the overheat point.

Most of my personal experience with cooling modifications comes from the P cars. Factory was 185, but the GT2 and GT3 cars had 160 thermostats from the factory. They were designed as street legal race cars and were more set up for track use, the factory wanted them to run cooler to last longer. LN Engineering sourced the 160 thermostats and sells it as a kit for the cars, their dyno testing concludes that the lower temp (after an adaption period) makes more power on the dyno due to the lower engine temo and there by lower intake air temp. The ECU compensates for the lower temp and does enrich the fuel mixture slightly, but does adapt to what is "normal" and leans back out. My 986 had about 50k miles when I installed a 160 thermostat, I saw my car run cooler, and fuel milage went up a bit, nothing major. My goal there was to lower temp to protect the plastic seals on the IMS bearing.

My goal with the K bike would be to lower the engine temp 10 degrees or so to increase the margin to overheat. Yes the thermostat would open at a lower temp but I would think the lower temp water flowing would be cooler on my feet. Cooler temps means the oil lasts longer, engine seals last longer, and hopefully the hoses and such as well. Since there is an O2 sensor it should learn to lean the bike back out after an adaption period.

The relay box does seem to block air flow. Any initial thoughs on how to change it?

[Flying Duck]

"Margin to overheat?" Not sure what that means but regardless of what thermostat you use the Motronic will turn the fan on a 221 degrees to keep the bike from overheating. If I were to define a "margin to overheat" it would be between the 221 degrees when the fan is supposed to come on and the 239 degrees when the warning light comes on or the 248 degrees when the radiator cap blows. Neither of those events are anywhere near 185 degrees.

Increase engine oil life? To what end? Do you intend to extend the change interval by a few hundred miles? With a stock thermostat, a properly maintained K bike will run for hundreds of thousands of miles. I've never heard of one failing from oil-related issues.

Extend the life of seals? I suspect the number of heat cycles and age have more wear on seals and other parts' lives than reducing the operating temperature by ten degrees.
_________________
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)
Buy parts HERE

[N41EF]

Been working too much and finaly got to this. Installed a 170 degree thermostat part 7214-170 from O'reily's. Was 17.99 plus $5 to order it to te store. The thermostat was original at 85c or 185f, so the new thermostat was 15F cooler. Fail safe means if it overheats it locks full open. It also has a jiggle valve to help bleed air out of the system, I was able to fill it completely full though once the initial half gallon or so was in it did slow down quite a bit. I reused the original gasket, the Nissan gasket was not the right one for the bike.

I used Zerex G-05 since that what I think was in it, the old coolant had a brownish tint to it prob from corrosion. I used just under a half gallon each of G-05 and distilled water including the overflow tank.

Test ride this morning the "normal" indication on the gage went from the mid scale line to one full line below that. Sitting in traffic temp did creap up as it did before, got to about midscale then dropped once I took off again. The heat on my feet and lower leg was much better, and I could tell when I stopped for traffic and it heated up again. When I returned the cylinder head temp was 165F only about 5 degrees cooler than before.

I did verify the fan comes on as it should, just before the gage gets to the red mark. Part of this idea is to keep me the rider cooler, and to operate the bike at a lower temp that just makes things last longer. I intend to maintain the same oil change intervals and such. With the ECU running in closed loop after a few hours running it should lean back out to a normal O2 sensor reading. I use Fuelly to track milage, will let you know how it works out.
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2014 R1200RT Water Cooled
2001 R1100S Light
1993 K1100LT. Nissan Ice Blue.(Gone)