K11 Owners Group

Wigomas · Joined: 09 Jul 2010 Posts: 20 Location: Dorset, England

I built a kitcar a while back using a BMW 2.5 engine which overheated like crazy.
The problem was that the thermostat couldn't keep up with rapid raises in temperature.
At a junction the engine would get hotter, the fan would cut in at 88°C, but the car would go into meltdown.
The rad was big enough, water pump was new, fan was big enough.

The solution came when I experimented with the thermostat.
I drilled a couple of 3mm holes at the top of the flange of the thermostat, where, on some older cars there used to be a 'Jiggle' pin.
The little bit of by-passed coolant through the holes was enough to solve the issue.

Hold on, reader. I'm going somewhere with this.

I guess modern 'stats shut off the flow to the rad to help warm-up, but in the above case, by the time the 'stat started to open, the engine temperature was raising too fast for the 'stat to open fully and for the rad to catch up.

Anyway, in really hot weather, K1100's do get a little hot.
Now I know that the fan is man enough to cope and the motor cools down quite quickly.
But I found that when I drilled a 3mm hole in the 'stat, the fan doesn't cut in quite so often as it used to and warm up is just as quick.
The motor runs a little cooler on the move too.

Thoughts anyone?
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K1100LTIC

gladstone · Posted: Fri Jun 24, 2011 5:20 pm Post subject:

If it runs cooler doesn't that means it will run richer? My LT was running one segment cooler than normal in steady running, and the exhaust was black and it used to occasionally backfire on the overrun. I put in a spare used thermostat and it runs nearer to normal with no backfires. Not sure if the exhaust is any lighter.

Cheers
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1993 K1100LT (x2!)
1998 R1100R - gone
1994 R1100GS - gone
1990 K100RS 16V - gone

Wigomas · Joined: 09 Jul 2010 Posts: 20 Location: Dorset, England

It doesn't seem to run richer. The plug reading is nice and toasty brown. The ECU works it out, I spose.
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K1100LTIC

Rafal · Posted: Mon Jun 27, 2011 7:44 am Post subject:

DaveVoorhis · Posted: Mon Jun 27, 2011 8:02 am Post subject: Re: Thermostat tweek.

Wigomas · Joined: 09 Jul 2010 Posts: 20 Location: Dorset, England

The kit I built was one of these;
http://www.marlinsportscars.co.uk/sportster/

It uses a rad from an early M20 engine which is just enough to keep it's cool. but only just.
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K1100LTIC

drikko · Posted: Mon Jun 27, 2011 8:19 am Post subject:

That looks real cool!!! Very Happy

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K1100RS '97
Laverda RGS 1000 '84
Jim Young Trailer Sailer 5.7M WB

DISCLAIMER:- Anything I say may have been when I was drunk so please don't take it personally.

'Bigamy is having one wife/husband too many. Monogamy is the same.'
Oscar Wilde

Wigomas · Joined: 09 Jul 2010 Posts: 20 Location: Dorset, England

It is, now that I'll solved the overheating. HaHa.

It weighs just under a ton with 190bhp and steers like a skateboard.
Real fun to drive.
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K1100LTIC

Tim (Midland Section) · Posted: Tue Jun 28, 2011 4:59 pm Post subject:

Seems like a good idea to me:-
a) If it doesn't prove successful, it ain't a lot to restore to original. £20 for a stat here.
b) Will be easier for any air to escape after servicing or boil up.
c) Those in hot climates who have fitted the "fan mod resistor" may find this idea compliments that mod.
d) IMHO if the engine does indeed run cooler it will only be a small percentage. I reckon the gauge reading change is due there now being a continuous water flow, rather than on/off.
e) I too, am old enough to to still own thermostats with the "jiggle pin" which under flow, should rise to block the hole.

If it works for you carry on.
HTH
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Regards Tim,

Grey haired riders don't get that way by pure luck
1996 Guzzi Cali3 LAPD
1972 750 Commando
G6HRN
#485