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Old Today, 01:14 PM   #1
MATTY's Avatar
Joined: Jun 2014
Oddometer: 294
Hot --r 45 ?

I picked up a 1980 R45 about 6 months ago it had been sat for 20+ years has around 10. 000 miles on it from new.
I just got it mot tested and on the road last weekend, it was cold but i braved the weather and went for a good old blast to blow the cobwebs out of the old girl. The exhausts are in poor shape they seem to be rotten on the inside and its throwing bits of rust out and its a little louder on one side than the other but everything else seems fine with only one concern from me, the engine feels very hot, it is not running lean from what i can tell, and it is smooth running and brisk enough for a little engine.
Any ideas on the hot running, its my first BMW ever and not sure if they all run a bit warm or what.
IUts warmer than anything i have had before and i have had a great many bikes over the years, any advice because frankly its scaring me and last thing i want is a problem developing. It did 400 miles over the three days and its not showing any change in how it sounds performs etc just this heat issue. HELP!!!
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Old Today, 02:09 PM   #2
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Joined: Feb 2013
Oddometer: 632
That's curious as the very last thing an R45 should do is run hot.

If you think about it give or take a few barrel fins an R45 has much the same cooling area as an R100 and yet it develops only half the power. If all is well it shouldn't run hot in the summer never mind the winter.

How did you diagnose it was running hot ? A quick measurement of the oil temperature after a ride might confirm if it's really hot. Normally it wouldn't even be up to temperature in the winter.
A man haunted by a fixed idea is insane. He is dangerous even if that idea is the idea of justice - Joseph Conrad
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Old Today, 02:26 PM   #3
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Joined: Mar 2012
Location: Cave Creek AZ
Oddometer: 496

Heaters - in the winter the cylinders take on their 2nd roll as heaters for the rider - sound like it is working.

Seriously get a digital IR temp gauge to read the temperature of the cylinders - I have done on my bikes when running correctly and use it as a guideline for any problems but I don't have the normal temp reading on me now - maybe someone else will chime in with what is normal.

Temp gauge is also good for trailer wheel bearing / hubs
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Old Today, 03:32 PM   #4
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Joined: Jun 2014
Oddometer: 294
It just feels to radiate heat more than anything i have had, it just seems hot i cant be more specific than that at this stage, it does tick when its cooling down and seems to do that more than other bikes too, maybe its just the fact the barrels are stuck outside the frame more or something, you have got me thinking now. I wondered if it is retarded on the ignition or something like that, its on points, i have not touched them other than a quick clean of the contacts it starts fine and apart from the exhausts which are basically history, and a little popping on overun i put down to the disintegrating exhausts i cant see how its running at all bad.
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Old Today, 03:36 PM   #5
I like everything.
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Joined: Sep 2012
Location: SLC area, Utah
Oddometer: 639
Whenever I had a lean condition that made my temp go abnormal, my header pipes would glow enough to let me see (76 r90/6). If you're starting easily, revving well, and have a shortage of back pressure, I'd say maybe you're just feeling the radiant heat of some metal in front of you. Not to be contrary, but an r45 would likely hold heat for a lot longer than the r100, as there's a ton more cast iron in it and the bore is further from the cooling fins. Presuming a similar operating temperature, it should stay warm for a demonstrably longer time.
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Old Today, 05:11 PM   #6
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Joined: Nov 2008
Location: Northern VA and Guatemala
Oddometer: 279
This is a little off topic but you're the only person I know of that owns an R45!
Could you tell me what numbers are stamped on the side of your carbs? Would you take a picture of the carbs and how they connect to the heads?

Someone told me years ago that is the set-up you have to replicate to run CV carbs on an R60.

Thanks in advance!
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