My first bike 85 ninja gpz900R

[Blkmaroman]

I just got my first bike 85 Ninja gpz900R, and so far ive had to replace the battery, re soldierd the rectifier(rust ate through the wires) and cleaned out the carbs. It runs great now, and man its got alot of power. More power than i though and 85 would have, i pull the front tire off the ground in first and second. But its running hot, when im going down the open road it runs between half and three quarter, but in town it will run up to almost the redline. I pulled the airfilter out because it was falling apart, im thinking its running lean now and getting hotter than normal because of their being no airfilter but what do you guys think? The fan does come on and when i turn the key off it will stay running so i know its working. I was also wondering if you guys had a good (cheap) place to buy aftermarket parts like exhaust,individual filters for my carbs so i can take that pain in the butt air box off, tires and things like that.

[Blkmaroman]

Ive also noticed that if i have to crank it for more than like a second or two the starter will kick out and free spin, so i have to stop cranking and try again. Is my starter gear going bad?

[CTGPZ]

Might need a thermostat. Did you drain and flush the radiator?

[CTGPZ]

Congrats on the new bike BTW!

[Blkmaroman]

No, i havent flushed it yet. I figured id post on here while i was going through everything. Im leaving for vacation tonight and wont be back for a week, so im not gonna get to work on it for awhile which sucks.

[StarGate]

Sounds like a starter clutch is in your near future. As for the lean and running hot, I'll agree that sounds correct. That could be the air filter letting too much air in, or it could be dirty jets that have a coat of varnish on them and restricting fuel flow. Either way, try running a can of Seafoam thru with your gas and see if that cleans the carbs up. Also, get a new filter for the airbox. If you go to individual pod filters before you get it running right, you're just asking for multiple headaches. Get it running right before you start to modify it. That way, at least you know what you are fighting and why you are fighting it.

Thats my 2 cents worth and I'm sticking to it.

[JonProphet]

I want to see pics of this beast.

-JD-

[E.Diane]

I have an '85 that used to run hot too. Get some pics up after your vacation and let's get started!

...Diane

[Ericthejet]

Air filter will have very limited impact on bike temp. Replace with an OEM and scrap any plans to go with pod filters, trust me on this one.
Flush the coolant out and do a chemical clean of the cooling system with aluminum safe flushing agents. I flushed my system out 3 times with my mixture. Replace with 60% H2O and 40% coolant and follow repair manual instructions for refilling.
I have 2 of these bikes nd they are a great machine. Parts are available but a bit harder to find.
Basic stuff can be found at "oldbikebarn.com".

Some technical bits for you to read, well worth your time.

GPZ 900R COOLING FAN SYSTEM
Send the Missus and kids on a day trip to the Outer Hebrides lock yourself in a room and have an ice-cold beer at your fingertips - you'll need it! The cooling system on the 900R is fairly complex and cleverly designed, but with a little patience it can be understood to help with those all too common overheating problems - I'm sure that we've all had the temperature gauge in the red at some stage, and wondered why the fan hasn't come on !
The following text hopefully will help you grasp the logic and operation of the system to enable you to tackle any possible faults with gusto and confidence ! Good luck !


The cooling fan circuit consists of three temperature sensors, two relays, and of course the fan. The system automatically provides three modes of operation and to differentiate between them we will consider these as ignition off, ignition on (normal) and ignition on (standby). Whereas each mode utilises different sensors and power supplies, we shall see that the two relays are powered and in use constantly. Let's now look at the modes of operation:
Ignition off Mode

With the ignition off, the first temperature sensor, the 97 C switch, is armed and if the coolant is at 97 C or above, the fan will be commanded to run until the temperature falls to below 97 C. (Note - this sensor is not active with the ignition on during normal operation.)
It is therefore normal for the fan to run when the ignition is turned off with the engine hot.

Ignition on (normal) Mode

Throughout the ignition on (normal) mode, the 97 C switch is disabled and the second sensor (110C) on the thermostat assembly is armed. This will signal the fan to run if the coolant temperature increases to 110 C. Once the temperature decreases to below this threshold, the fan will cease.

Ignition on (standby) Mode

For the last mode, the third sensor actually measures oil temperature and switches at 120 C. This appears to be a fail-safe feature which switches temperature sensing from the 110 C switch to the 97 C switch if:
1. The 110 C switch is defective (we have to assume that if the oil reaches 120 C, the coolant temperature is above the 110 C threshold, therefore the 110 C sensor has failed).
2. The oil temperature rises due to a problem in the oil cooling system.

Under either of these conditions, the 97 C sensor will be activated to prevent cooking your engine. This will command the fan to run until the coolant temperature decreases to below 97 C.

Relays

The first of the two relays, the Fan Switch Relay is situated adjacent to the headlight and determines which sensor is used under the prevailing operating conditions. It routes an earth signal (if temperature threshold exceeded) from either the 97 C or the 110 C sensor to the Fan Relay (situated adjacent to the fuse box) to bring on the fan. Failure of either of these relays will render your cooling fan system inoperative.

Sensors

Both of the engine coolant temperature sensors function in exactly the same manner, in that the resistance is inversely proportional to temperature - in other words the higher the temperature the lower the resistance. This is in contrast to the oil temperature sensor, which works in the opposite way - the resistance is conversely proportional to temperature, the resistance increases with temperature. The coolant sensors provide an earth when hot, the oil sensor provides an earth when cold. Remember this - it is invaluable when troubleshooting.


Troubleshooting the system

Before you go tearing the bike apart, first determine if there is a fault - does the fan run when it is supposed to ? If you have read this far you should a fair idea of what is supposed to happen and when. Let us start with a very simple check which does not require fairing removal etc, but it will prove about 90% of the cooling fan system system.

Turn the ignition on, (no need to start the engine) disconnect the black wire from the 110 C sensor on the right-hand side of the thermostat and ground that connector to earth. The fan should run. Refit the wire back on the sensor. Be careful not to snap the terminal off the sensor, they're delicate!)

If a fault persists, and you suspect component failure, then the place to start is the fuse box, check, the main fuse, the horn fuse, and the fan fuse, each of these has a role to play in the cooling fan circuit.

Remember that overheating can be caused by problems other than component failure, such as, chafed wiring, air locks, sticking thermostat or a particularly bizarre electrical problem.

Two 3ft lengths of wire with crocodile clips at either end is invaluable when troubleshooting, as they enable you to provide power from the battery, to virtually any component on the bike.

COOLING SYSTEM COMPONENT BASIC FAULT-FINDING
Remember that the status of the ignition switch is critical during most of these checks.

To prove the fan. and To Prove the Fan Relay (Situated adjacent to the fuse box)

With the ignition off, disconnect the fan switch relay. (adjacent to the headlight). from the 6 pin connector, earth the Red & White wire. The fan should operate. If it doesn't the fault lies either in the fan, or the fan relay. Disconnect the two pin connector from the fan, apply 12 Volts directly to the fan. If the fan fails to spin the fan is faulty. If the fan spins, then the fault lies in the Fan relay, or, there is a solitary blue and white wire supplying the fan relay from the rear of the fuse box, this connection often snaps as it is particularly prone to corrosion, remove the fuse box and check this wire.
To prove The Fan Switch relay (Adjacent to the headlight)
With the ignition switched off, disconnect the yellow wire from the 97C switch (rear LH side of the radiator and touch it to earth. The fan should operate. Reconnect the wire.
With the ignition switched on, disconnect the black wire from the 110C switch (side of thermostat housing) and touch it to earth. The fan should operate. Reconnect the wire.
If the fan fails to operate when checking the 97C sensor (yellow wire) it must be assumed that the Fan switch relay is at fault. This can either be replaced, or checked further using the diagnostic checks given in the manual.
If the fan fails to operate when checking the 110C sensor, the fan switch relay, or the oil temperature sensor may be at fault.
To prove the Oil temperature sensor
With the ignition either on or off, disconnect the multiplug connector from the fan switch relay and using an ammeter, check for continuity between the Green & yellow wire, and earth. If there is no continuity, it must be assumed that the oil temperature sensor or the wiring to it is faulty.
To Prove the 97C & 110C sensors
It is a very clumsy process to prove that these sensors are working properly, the procedure for this is featured in all of the manuals.
But let common sense prevail. If the system is not working with the ignition on, and you have proven all of the other components by following the above checks then the 110C switch must be at fault. If the fan does not come on when the engine is very hot, and the ignition is off, then the 97C sensor must be faulty.

Nb:- Remember that if the oil temperature sensor is faulty, it will switch the reliance of the cooling system (ignition on) mode from the 110C sensor across to the 97C sensor. In this case the 97C sensor will bring the fan on if the ignition is on, wheras normally it only operates when the ignition is off.

[Ericthejet]

Index of /pdfcat

Parts index, UK sourced.
Ninja 900's sold over there for 17 years.
Call UPS?

[Mango7]

Eric knows what he's talking about!

I just spent 5 hours replacing the mirrors on my '84 (3 trips to the hardware store!...dropped a bolt down into the nether regions). Hoo Wee!

Yes, the Ninja runs very hot, or appears to. I heard that the water temp rarely gets to over 210F. What color scheme do you have? Love to see pics.
I'll post mine as soon as I get her cleaned up

Kurt

[Rick_in_P.A Wa.]

on my gpz9 I added a toggle for the fan, didnt cut or splice any wires in the sys, and it cured my over heating woes, only needed it wile stopped.
Great bike, a real mile burner in stock form with a real kick in the pants at about 3300rpm, I miss mine terribly

[stocksj]

Congrats, wouldn't mine getting myself since I like the old bikes. Maybe one day.

82 Gpz750

[Blkmaroman]

I checked out my fluid and its nice and green but i still plan on draining and flushing it. I think my problem is that my fan isnt running when my motor is. But as soon as i turn it off the fan will come on. I felt behind the fan being careful of my fingers and i could only feel air when it was turned off. so i think thats my problem. Ive got some pics, there not to great but it wont let me manage my attachments to put em up.

[Blkmaroman]

My 97degree sensor is obviously good since my fan will come on when i turn off the ignition, so why does it not make it come on when the ignition is on. I thought it was supposed to switch it from the 110 or 120 to the 97 if they go bad, and its not running when the key is on so i assume they are bad but its not going to the failsafe and running off the 97?

[Blkmaroman]

The only pics i have

[E.Diane]

The fan on mine never kicked on automatically until it got to the mark all the way to the end of the white zone or in other words, about a needle width to being full red.

I put in a manual switch for when I'm running in traffic so I can kick the fan on at about 3/4. If you want to test that your fan works with the bike running, ground the wire coming off the sender located in the thermostat housing. For my manual switch, I just tapped into this wire and grounded the other side of the circuit.

Watch sticking your fingers in the fan with the bike off. When I park mine, and shut it off, the fan usually kicks on for a bit, shuts off like it's all cooled down and then kicks on again like it is possessed.

I Like the bar end mirror. Can you see out of it? I'm sick at looking at the inside of my elbows and was thinking about trying some.

For pics, I find it easiest to upload them to somewhere like PhotoBucket and copy the IMG tags into my post.

[Blkmaroman]

Ive been thinking of just putting in a manual fan switch, thats probably what ill do. I can see great outta the mirror, i can see pretty much everything behind and beside me in it and im a big guy but i dont block it at all.

[Blkmaroman]

i grounded the wire coming off the sensor on the side of the thermostat housing today and with the key on the fan will kick on, so im guessing my sensor is bad?

[E.Diane]

It's either bad or just doesn't kick in soon enough? Like mentioned, mine wouldn't turn the fan on until the temp gauge was a needle width from fully red. By that time, it was usually too late to bring the temps back down.

Taking a look at my service manual, on rising temperature, the fan switch should activate at 225 to 235 degrees F. On falling temp, it clicks off at 219 degrees. That's pretty hot.