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Motorcycle Repair/engine cooling


I recently purchased 1986 1100 shadow. how  warm must the engine get before the cooling fan operates ? I performed   the grounding  test in my repair manual, and the fan ran, but it seems the gauge  reaches  the upper   3/4 across towards red around town, but never in,  nor has it seemingly overheated, but  I have never witnessed it running otherwise.. paranoia? lol compared to my truck, the temp seems to move around more....
thanks, Frank

Frank, these bikes don't carry much coolant in them, so it is easy for the needle to fluctuate, especially where you live.

DO check the coolant level in the bike at the radiator cap, not just the coolant filler tank.

The fans normally pop about 195 degrees I think. I had the fan switch on my 89 NT650 die last year. Didn't come on in hot weather after I came off the freeway, then it puked coolant out, but the needle never red HOT and the fan didn't turn on. According to the forums, Honda fan switches are problematical so I would track one down and install it, along with a new thermostat, as long as you are draining the system. The parts are probably all original and at 28 years old, need some attention.

I added a toggle switch, to run in parallel with the coolant fan circuit, so I could flip it on, if I sensed problems after the fan switch replacement. The bikes generally run pretty cool, so the fan seldom kicks in, unless the weather gets hot or you are putting a lot of miles on the highway, packing double or something like that.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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