cooling is really weak

[Black wing]

so a week or so ago my cooling system took a ****, thrmo switch went and even on the high way it was barely cooling.

 

so i wired my fan to a spare switch on my handle bars till i can get a new one, but i replaced the thermostat and flushed the coolant today

 

the bike cools great while driving again. was able to just cruise around with the fan off barely even reached over half the temp gauge, got back and let it idle for a while with the fan on and it held fine at half.

 

then i turned of the fan and let the temp climb to about 3/4 and turned the fan back on. it then held at 3/4 without dropping any.

 

what would cause for such weak cooling. could my water pump be suspect? and how would i test it without taking everything apart

[frankd]

How warm was it when you were riding? How clean is your engine? If it's covered with crud, it'll run a bit warmer. Today it was about 70F here, and when I was cruising about 50MPH and 2 up, mine indicated a little over 1/4 of the meter scale. Are you using 50% water, 50% anti-freeze?

[Black wing]

its 17C and the engine and cooling system is clean. i havent had 1/4 scale while riding in over a month

[Condor]

I'm not sure if the '86's had a metal or plastic impellar in the water pump, but if they are plastic you might have lost a blade??

 

Another thing to check is if the drain valve was left in the 'on' position after cleaning the cooling system...

[Black wing]

The 86 appears to have a metal impeller and a plastic drive gear. And the drail valve is turned so that the little ball is in the top hole

[speakerfritz]

see chapter 5 on how to test your 25 year old cooling system. my bet would be the thermost...but go thru all the tests. My second guess would be the radiator is full of crud from 25 years of use.

 

http://www.yamahaventure.nl/1999-Royal-Star-TF-Service-Manual.pdf

[Condor]

The 86 appears to have a metal impeller and a plastic drive gear. And the drail valve is turned so that the little ball is in the top hole

 

Metal is good... Since I don't have a drain valve sitting in front of me to look at, and I haven't had to deal with one lately, is yours on or off? Some of the plastic hex lettering will get pretty beat up over the years, but there's actually an 'off' on them to be aligned with the diamond pointer on the housing. When the valve is in the on position the coolant by-passes the thermostat, and will actually cause the motor to run warmer than normal.

 

[Black wing]

i'm not certain but it does appear the bypass is on, so i will turn it around tonight and see if that helps.

 

edit: just got back after turning off the by pass and that DID NOT WORK at all made things substantially worse even with the fan on at all times the bike was about to over heat after barely 10 minutes of riding

Edited July 3, 2014 by Black wing

[Black wing]

So ive taken the water pump off and it seems fine beyond a few extra mills of slop from the sheer pin. No excessive wear or blockages anywhere. I know the fan temp switch is shot what role does it play in displaying temp on the gauge? Could that bypass be screwing with the reading?

 

When I place a multimeter on the power to the temp gauge I get 5.9 volts between the lead and the splitter it screws into and when I touch it directly to the splitter the temp needle pegs to the top of the scale. What are the benchmarks that sensor should be reading at?

 

How can I test the temp gauge and sensors to see if its just electrical messing with me cause im getting mad and this is getting expencive

Edited July 7, 2014 by Black wing

[frankd]

Is your ENGINE clean? If you've had an oil leak, a lot of crud accumulates on the engine, preventing the air from cooling the motor. Believe me, I realize that the Ventures are 'water cooled', but they still dissipate a lot of heat in the air that moves over the engine.

 

If you're wondering about the accuracy of your temperature gauge, measure the temperature of the motor and compare it to the temperature gauge. You could use an infra-red thermometer. Harbor Freight has both of them for a decent price. Or you could put a small thermometer in the radiator cap opening of the radiator. The fan switch has no effect on the heat gauge. It only turns on the fan (through a relay) when the temperature gets up to about 205F. On a Mk II, that's about 3/16" below the top of the green band on the gauge. On a Mk I, it's right at the top end of the green band.

 

http://www.harborfreight.com/catalogsearch/result?q=thermometer