Engine cooling fan

Post edited by: davel, at: 2007/11/29 23:36

So me and the ol KZ made it through the first season with the 1075 kit installed. The bike is a joy - finally. Many thanks to everyone at the forum and Jeff at Z1. This bike has a few unconventional features that worked well so I thought I’d post them when time allowed. The one detailed below is a cooling fan mod I made mid season. It works perfectly and keeps the 1075 from overheating in city traffic regardless of air temp. Before adding the fan this engine would overheat if it were stuck idling in traffic in hot weather. It never stalled or seized but it would start idling erratically and ping under load. The engine would then behave normally once it got moving (even if the air temp was 90+ degrees) just as long as air was moving over the engine it would run fine. This got me thinking about a cooling fan. I found a nice 7” fan made by Derale in the Summit Racing catalog. It is intended for car oil coolers and it moves alot of air. I ordered it with an optional coolant temperature sensor switch with adjustable temperature control. Since the bike already had an oil cooler I decided to install the temp sensor in the outlet side of the oil cooler. Logic being that if the oil coming out of the cooler were still hot, this means no air is moving over the cooler and the fan kicks on. Once air moves over the cooler the oil temp drops and the fan shuts off. I was able to use this setup during the last half of the season in city traffic and it worked perfectly! Bike ran great and never overheated. Fan would turn on if I was stuck in traffic in 80+ weather and shut off once I got on the expressway. Hope these pics and info are of some use.

The fan points directly at the middle two cylinders. It does a good job of moving alot of air (rated at 400cfm 4amp) over the hottest part of the engine.
Oil cooler (JC Whitney PN ZX381481X)
Derale fan (Summit Racing PN DER-16507)
Fan bracket (home made)

Post edited by: davel, at: 2007/11/29 23:52

Temperature sensor (Summit Racing PN DER-16749) mounted on the outlet side of the oil cooler

Fan relay with temperature adjutment pot (included with temp sensor)

Final Product

I never thought about adding a fan to a air cooled bike, but it seems to work just fine, neat ideaB)

davel, just curious... how is plastic fan assembly holding up between hot motor and very hot exhaust pipes?

I had the same concern when installing it but it's held up fine. The back of the fan (closest to the header pipes) is powder coated sheet metal. The front of the plastic fan shroud is about 2.5 inches from the cylinder block. It's been through hot days and rainy days and so far so good. The fan is high quality and meant for hash environments. Well worth the $70 paid.

The other concern I initially had was that an extra 4 amp electrical draw at idle might drain the battery but that hasn't been a problem either. Alternator seems to keep up fine and the fan doesn't kick on very often or for very long.

If the fan doesn't kick in very often or for very long then it's probably not needed, but I still like your thinking, it's a cool idea

Lorcan wrote:

If the fan doesn't kick in very often or for very long then it's probably not needed, but I still like your thinking, it's a cool idea

Well, I wouldn't recommend all the effort and energy in a rural or suburban setting but in NYC, where the occasional summer traffic jam is inevitable, it's worked out quite well. Though I usually do a pretty good job of making my way through traffic

Thanks for sharing this information about installing a cooling fan.

I've often thought how great it would be to have a cooling fan on my Zs here in Florida especially during the summer when it's 95+ degrees F and I'm stuck in bumper-to-bumper traffic ... and my Zs' oil temperature is approaching 250 degrees F.

ive been trying to find a small enough fan to mount between backbone tubes of frame above motor to pull cool air across topside of motor while sitting/idling.project #534678...........