Tachometer Shows Hot Running engine

[Prospect]

Hello everyone, I brought back to life a 75 gl1000 a few years ago after it had been sitting 20 years. The bike runs great and everything works well except the cooling system. This is my first water cooled bike and I'm not sure what to think of what I'm seeing.

As shown in the picture the temp indicator shows as running hot. The fan turns on. However, when I come home and open the radiator cap the coolant is not overly hot and the engine does not seem very hot either. When I turn off the bike the fan keeps running for about 60 seconds and then it turns off. The coolant is new and at the correct level. According to the manual the fan is supposed to turn on around 100C or middle of temp indicator. My question is whether this is normal for a GL1000, for the fan to turn on after about 10-15 minuets of city riding.

Another issue is, the tachometer is original and slow to respond. The RPM needle does not respond to engine rpm but rather it hangs in one spot before eventually setting down (20 seconds or more). See picture of needle hanging after bike is shut off. Should I open the tach and rebuild or buy a replacement? I've worked on cb750 tachs before and understand they are hard to open but definitely doable.

I love the GL1000. Such a comfortable ride and lots of power. I'm not sure which I like more my cb750's or the GL1000. I'll have to put in a few hundred miles in before making the verdict.

Thanks

[digger]

10 to 15 minutes of city driving when the air temp is high will make my fan run. If it doesn’t get into the red zone to the right it isn’t overheating, looking at your pic it seems to be in the upper range of normal (the wider section of white) If you have a infrared thermometer you could check the temp at the thermostat outlet and see what you actually are running. As for the tach, when I first got mine it was slow/lazy acting, but just running it cured that. You can open the tach and lube it, read more here viewtopic.php?p=753800&hilit=Lazy+tach#p753800 and/or look up how-to rebuild gauges in the main menu.

[digger]

Oh, I almost forgot. In case you haven’t done so, replace the timing belts. You stated that you brought it back to life a few years ago, just making sure that was part of the resurrection process. You can see pics of the carnage in various photos on this site. Enjoy riding your beautiful piece of history.

[Prospect]

Thanks so much digger. I appreciate the advice. Great to hear that my bike is behaving normally.

When I mechanically restored the bike I did do the timing belts along with rebuilding the brakes and carbs, final drive (greasing), cooling tube o-rings, valve adjustment and a few other things. It was a lot of work but I got a good understanding of how complex this bike is compared to the other bikes I worked on. It really is like a car.

[gltriker]

Post#5[/color ]
PostPquote=Prospect post_id=825839 time=1719430910 user_id=26234]
Hello everyone, I brought back to life a 75 gl1000 a few years ago after it had been sitting 20 years. The bike runs great and everything works well except the cooling system. This is my first water cooled bike and I'm not sure what to think of what I'm seeing.

As shown in the picture the temp indicator shows as running hot. The fan turns on. However, when I come home and open the radiator cap the coolant is not overly hot and the engine does not seem very hot either. When I turn off the bike the fan keeps running for about 60 seconds and then it turns off. The coolant is new and at the correct level. According to the manual the fan is supposed to turn on around 100C or middle of temp indicator. My question is whether this is normal for a GL1000, for the fan to turn on after about 10-15 minuets of city riding. YES In fact you may be riding along at higher groundspeeds in hot weather and notice the cooling fan is running then, too.

Thanks
[/quote]

I am attaching a link to another Topic wherein a fellow member was puzzling over the same questions about temperature gauge display details. See the marked up illustration in that link. Most beneficial (from my viewpoint) is the conversion of the Honda GL1000 Shop Manual cooling system, theory of operation illustration of engine running temperature reading numbers from Celsius to Fahrenheit.

https://ngwclub.com/forum/viewtopic.php ... 83#p820983

I also have to inquire when the cooling fan continues to run after you " turn off the bike", you are indeed shutting the engine down with the right handlebar OFF/RUN/OFF switch, only, and leaving the Key Switch in its Run position. That's how I always allow the cooling fan to dissipate heat until the radiator cooling fan turns off.
If you watch the temperature gauge needle slowly move to lower coolant temperature numbers, and where the thermal fan switch, which is located on the thermostat housing, finally shuts off the radiator cooling fan, you will become comfortable the cooling system is operating correctly.

Note my advisement to Jai there, too

[redglbx]

On the slow tach,,, I’ve had a couple of my bikes do that and even pulled the gauge apart to clean & lube. My 81 CBX was the worst but I never pulled that one apart. I’ve found that if you carefully drill a small hole where the cable stem meets the housing and squirt some lube in it will fix the slow response problem.

Couple of things to be mindful of, coat the drill with grease to minimize any chips going into the gauge and you need to really be careful to only drill deep enough to get through the outer skin of the stem only. Also once you lube it do not turn it over or you may get oil on the gauge face and ruin it. It may take several oil applications to get enough oil in to completely resolve the sluggishness. I’ve done this on a number of Speedo’s & tachs with good success.

On the overheating thing, if you’re not pushing fluid you’re probably not overheating. A couple of things to check are the hoses making sure that they are not sucking closed (old hoses) , replace if needed. A new cap may help. Check that the fan is actually spinning fast enough to move some air, mine was very sluggish and I replaced mine with a small hi performance pancake fan with an adjustable thermo switch. And the last thing I would check is the actual radiator as most of these used a silica based coolant when new before Honda decreed silica coolant taboo.

The problem with silica based coolant is that they use “silica sand” in the coolant to theoretically sand blast the inside of the coolant system to keep things clean. Great idea that really didn’t work well, the problem is that the silica falls out of suspension and settles in the low spots restricting good flow, it’s that yellow/orange mud that you find in the bottom of the radiator, not good. So I suggest taking the radiator to a good radiator shop and have it boiled out and then only use silica-free coolant….finally with the heat we’re seeing most places I don’t think you’re really all that bad, also ignition timing has a direct affect on engine temp, specifically being over advanced.

that’s my .02

[Prospect]

I took the bike for a longer ride and the temp comes down a bit with the fan running so that's a good sign.

I'll tackle the tach using the method redglbx mentioned. It seems the least intrusive and worth a try.

Thanks for all the info.

[pidjones]

You should also check the 7 volt level.

[redglbx]

Yep, do PID’S suggestion on the 7v regulator first.

[Sidecar Bob]

Silicates in coolant are not "silica sand", nor are they intended to scour the cooling system. They are a silicon based compound that increases the boiling point of the coolant and in fact in ferrous engine blocks they actually coat the metal and protect it from corrosion.
The more I learn the less I tend to believe this. No-one has been able to find any mention of this in any Honda manual. It does, apparently, appear on the label of Honda coolant, but there is no evidence that it wasn't put there by someone in marketing (whose job is to sell people more than they need) as opposed to someone in engineering (whose job is to provide the information needed to keep things running properly). Some Silicate free coolants are not compatible with "yellow metals" (like the brass in our rads) and could potentially do a lot of harm. Some long life (silicate free) coolants will, over time, dissolve the solder used to hold brass radiators together. And finally, Joe-the-Bike (who lives in Queensland Australia) put over 210,000 Km on his CX500EC with regular bargain priced ethylene glycol coolant. Many 'Wings went much farther than that before they invented "silicate free coolant".
But it doesn't matter much anymore because you would be hard put to find coolant that actually contains silicates these days anyway.

When I mechanically restored the bike I did do the timing belts along with rebuilding the brakes and carbs, final drive (greasing), cooling tube o-rings, valve adjustment and a few other things.

I hope you aren't saying that you added grease to the final drive or that you think that squirting some grease into the zerk fitting next to where the final drive meets the swingarm will do anything for the final drive (all it does is lubricate the splines where the driveshaft meets the FD - and fill the swingarm with grease).
If you have never changed the oil in the final drive do that sooner rather than later. Note that it should be an oil intended for use with hypoid cut gears (I use 80W90 and it seems to work OK).

[CYBORG]

I use 80-90, and change it every oil change. Works welll for me. And have been known, usually during winter maintence, put the Thing with the splines on the rear wheel, and coat the splins with moly grease

[Sidecar Bob]

I use NLGI #2 lithium based grease with moly additive (= regular Moly-Lithium grease you can get at any auto parts place) like the FSM recommends. In fact, it is the only grease I use on the bikes except for silicone grease (required for the brakes & a few other odds & ends).

[CYBORG]

same here

[redglbx]

The grease zerk on the swingarm in front of the final drive is nothing more than a marketing tool, it will not grease or lube your splines. If you pull the final drive off you will find a shield that actually directs the grease away from the splines and merely into the swingarm tube, does nothing !

You must actually pull things apart and physically smear the grease ( I only use the Honda moly lube) on the splines, the zerk does nothing but make you feel better about it.

Cooling, if you pull the radiator out and physically look in the bottom you will find a yellowish gritty mud coating (whatever the f**k that is) and if you haven’t had the radiator cleaned for a while it will be fairly thick. It tends to restrict the coolant flow & cause the bike to run warmer, have a good radiator shop clean it out.

[Sidecar Bob]

At least the swingarm won't rust from the inside