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Overheating and valve train noise.

Old 06-22-2011, 06:53 PM
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Overheating and valve train noise.

Just got my '98 VTR1000 about half a month ago. It's my first street bike so my knowledge is limited on it and I'm having a small issue. I took the bike into a local shop and had them go over it and they mechanic told me I have some valve train noise and that my valve train might need to be adjusted. I'm not sure what all this entails but any advice is welcome. Also, I rode for a more extended period than usual today and my oil temp was just getting into the red. I let it cool and did the same thing and it happened again. The coolant level checks out, but one of the previous owners rigged up a toggle switch for the radiator fan because the temp sensor is broken. However, the toggle switch was on the entire time. I'm not sure why exactly this is happening, but again, all advice is welcome. Look forward to hearing from you guys!

Last edited by Big Shepp; 06-22-2011 at 06:58 PM.
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Old 06-22-2011, 07:01 PM
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It's actually a water temp sensor in this bike.

Something's not right with your cooling system. When you toggle the rad switch, does the fan turn on?

If the fan turns on, personally my next step would be to see if the coolant is flowing. I do this by opening the radiator cap (careful if the bike is hot!) and letting the bike idle till the thermostat should open... maybe 15 min or so, or the halfway mark on your temp gauge. You should see a "flow" of the coolant in the cap. If not, then it's either your water pump or your thermostat.

Water pump is pretty easy to check, but you have to drain the coolant. Drain the coolant, then take the cover off of the water pump (it's the little cover on the right side of the motor with three hoses coming off of it). Try to spin it by hand- if it spins, it's broken. If it doesn't, turn the motor on briefly, and it should spin.

If that's not it, then it's probably a thermostat issue. This is the part of the bike that opens up to allow the coolant to flow to the rads when the temp gets hot enough.
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Old 06-23-2011, 09:32 AM
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I usually leave the toggle switch on, and the fan turns on and off with the switch. I'll take a crack at your advice to check out the cooling system and leave another post if I have any more questions. Thanks!
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Old 06-23-2011, 09:40 AM
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Not sure how much the mechanic looked into the noise or if they're related, but there's a slight chance he heard a broken water pump?

Also, I'd look into getting the fan switch back online. How good are you with electrical? It's not too hard to diagnose a bad switch with a stock wiring setup.
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Old 06-23-2011, 05:40 PM
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Well the previous owner told me that the temp sensor (or as you properly called it the water temp sensor) broke. He wired up a toggle switch into the original wiring so as to manually trigger the fan because the sensor no longer did. He said the only reason he didn't fix it was because the sensor costs about 80 bucks. Before I went out and spent the money for a new sensor, however, I wanted to see if the experts on here had a better diagnosis.
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Old 06-24-2011, 08:28 AM
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The service manual (found in the KB section of the forum) has a procedure to test your sensor so that you can verify that it is bad before spending any $$. All you need is a ohm meter and a pot of boiling water.
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Old 06-24-2011, 09:35 AM
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Also, that temp sensor is a fairly universal part-they've been using it since like 1987 in their bikes (same part number: 37760-MT2-003). Any Honda sensor with "100" stamped in the side will work. I think that that 100 indicates that it triggers at 100* Celcius, which is about when the fans switch on with this bike...

http://shop.ebay.com/i.html?_nkw=Cbr....c0.m270.l1313

Like Lazn said, you can check yours first, too. Also, sometimes the ground wire is faulty, making it look like the switch is broken. The way to test this is to touch the tip of the wire to some metal part on the radiator- the fan should switch on when you do this.
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Old 07-14-2011, 02:58 PM
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So I started checking into ya'll advice today and here's what I found out. The temp sensor has a 75 stamped on it and that's about when it opens. I put it through the test the manual describes and it worked like a charm. Next I checked the water pump and it wouldn't budge and then spun with the engine on. I didn't check to see if the coolant is flowing yet, but when I followed the manual's instructions for flushing the coolant, i couldn't get the reserve tank to empty. I'm not sure if this is a blockage or what, and I intend to check it with the method 7moore7 suggested just as soon as I get the gas tank and the airbox back on. (I'm in the middle of installing CCTs, but found out I need the spark plug tool, so it's on order.) I do have another question however. I pulled the toggle switch off and removed the non-factory wires but now I don't know what to do with them. Here are a few pictures I took of them.







That piece circled in red is the piece the previous owner was talking about, obviously not the water temp sensor. Anything you guys have for me is always more than welcome. Oh and these pictures are of the right radiator. And if someone wouldn't mind posting pictures of the proper setup of these wires I'd appreciate it.

Last edited by Big Shepp; 07-14-2011 at 03:02 PM.
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Old 07-14-2011, 03:22 PM
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I'd check your thermostat next...

This is a part that is on the left side of your bike (inside the frame) with one hose going to your left rad and one coming from your water pump and a couple going to your carbs.

The way the cooling system works is that the water pump circulates water throughout the engine while it's warming up. Once it reaches a certain temp (something like 160*F), the thermostat opens and allows fluid to circulate through your radiators. If this piece is not functioning correctly, then water does not circulate through your rads and keeps getting pumped through your heating up motor. It also doesn't flow passed your fan switch which could be the reason why your fan isn't turning on. The temp sensor is in the same housing as the thermostat, and reading the temp of the water circulating through the engine, which would also explain why you're getting high temp readings (and the fan not being effective, as it's cooling water that's not circulating through your engine)

You can take the cover off the thermostat (2 or three bolts, can't quite remember) and pull it out and test it in a similar way as your fan switch. You heat it up in water according to the manual, and it's supposed to open at a certain temp.

Last edited by 7moore7; 07-14-2011 at 03:26 PM. Reason: Grammer... past vs passed is a killer.
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Old 07-14-2011, 03:36 PM
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The only thing these guys have forgotten is replace the radiator cap.
It could be the original cap from '98 and if it is not allowing you to build pressure, it could be the cause of all your problems.
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Old 07-14-2011, 04:05 PM
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You mean you don't do all of the hard stuff first, mike?

Completely forgot about the rad cap, although now that the coolant's out I'd probably check the thermostat anyway.
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Old 07-15-2011, 09:56 AM
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OK, here's what I've figured out by looking through my service manual and a VTR parts diagram. The pictures I put in my last post are of the radiator fan switch, part number 37760-MT2-003. The thermostat I've checked at it worked fine. I used the procedure on page 6-10 of the service manual to do so. One issue I've discovered is that the siphon tube (the tube that runs from the reserve across the top of the right radiator and into the filler neck) won't drain the reserve tank as per the instructions on page 6-5 in the service manual. I get the nagging feeling that I have a clog in my radiator hoses somewhere, so if the coolant flow test fails I'll be taking the entire cooling system apart. And 8541hawk great idea. I never would have thought of that, most of my mechanic experience is on my '08 'stang so original parts wearing out isn't something I'm used to. I'll be sure to order a new cap with my next trip to the dealer.
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Old 07-15-2011, 10:20 AM
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Hmmm, I got a little mixed up in there. So,

Thermostat is working, opens up at 75*C.
Water pump is working correctly from your tests.
Fan switch has not been tested.

Air in the system, or a cap like 8541Hawk said, can cause a lot of problems. I would buy a few gallons of distilled water and just flush it out. Turn the bike on and pour it in the rads. When I flushed mine, I let it heat up, then took off the water pump cover and watched the water all come out... then put it back on and put more distilled water. Then waited for it to heat up again and watched inside the cap for flow. Then emptied again. When you put coolant in, with the bike on, go through all of your tubes and squeeze them with your hands and hit them with the handle of a screwdriver or adjustable wrench. This gets all of the air out of the system. Sometimes it takes a little while.

Hope this helps and I'm not confusing you more!
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Old 07-15-2011, 11:27 AM
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No that seems like it should work to identify the problem. I'm going Monday to order a few parts including the cap and a new radiator fan switch, so hopefully I can do this test sometime next week. Thanks again for all the help.
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Old 07-15-2011, 05:19 PM
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I experienced the same blockage with the coolant reservoir hose that you're experiencing. The coolant should drain from the reservoir easily once the hose is removed from the fitting near the radiator cap. I had neglected to change the coolant on my VTR and as a result the reservoir was coated with brown sludge and the reservoir hose was blocked with it. It was bad enough that I couldn't determine the level of coolant in the reservoir.
I used a bottle brush to clean the reservoir. I forget what I used to clear the hose. It's important to be sure you don't remove the hose from the reservoir during the process because it's a PITA to remove the reservoir to reattach the hose.
The blocked hose is a problem but I doubt that it is the sole problem with the cooling system on your bike.
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Old 08-07-2011, 06:32 AM
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An update here. I seem to have fixed the cooling system. The issue was a simple blockage in the reserve tank. (I managed to crack it in removing it so I had to order a new one) I did a flush & clean of the cooling system and now it works great. I Just have one more issue. The fan toggle switch that is located on the top rear of the right radiator is still not working. I bought a new switch, but I have no idea which wires go where. Here's a picture of what I'm looking at.



I figure the wire with the green arrow pointing to it is the one that hooks directly to the fan toggle switch, but I have no idea where the wire with the red arrow pointing to it goes to. I figure it's some sort of ground to complete the circuit, but I have no clue where it hooks up. A picture of the proper location would be fantastic. Really I could use a picture showing how to rout both these wires too, but if no one has that I can figure it out. Thanks again guys.
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Old 08-07-2011, 10:08 AM
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Originally Posted by Big Shepp View Post
An update here. I seem to have fixed the cooling system. The issue was a simple blockage in the reserve tank. (I managed to crack it in removing it so I had to order a new one) I did a flush & clean of the cooling system and now it works great. I Just have one more issue. The fan toggle switch that is located on the top rear of the right radiator is still not working. I bought a new switch, but I have no idea which wires go where. Here's a picture of what I'm looking at.



I figure the wire with the green arrow pointing to it is the one that hooks directly to the fan toggle switch, but I have no idea where the wire with the red arrow pointing to it goes to. I figure it's some sort of ground to complete the circuit, but I have no clue where it hooks up. A picture of the proper location would be fantastic. Really I could use a picture showing how to rout both these wires too, but if no one has that I can figure it out. Thanks again guys.

You're probably going to have to pull back some of the protective sheeting on the wire and trace it to see what it is, or was. Since it's been modified, there's no telling if it's stock, or hacked. As for routing the wires, in the front of the manula, there are some routing diagrams. Check those to see how to run them.
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