Leaking Carb on 1987 VT700C - Honda Shadow Forums : Shadow Motorcycle Forum

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Old 06-14-2007, 02:01 AM   #1 (permalink)
BT
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Default Leaking Carb on 1987 VT700C

Hi Guys, I just bought a 1987 Honda Shadow VT700C two days ago. I used to own this bike in the earlys 90's and it was a 750 instead of 700. The bike starts fine and run pretty well too. I noticed there's oil stain mark on the cylinder and trace it to the carb. Got a rough quote from the local honda dealer and they said it could be rust from the tank causing all this and I'll need to get the carb rebuild, flush the tank, replace all fluids and oil and it'll cost me $500.
I've been riding the bike and there's no lack of power and it runs and idle fine. I was told by the previous owner that he rebuilt the carbs 3 years ago.
The temp gauge is not working as well. After about an hour of riding, it finally have some reading (about half way) and then it went back down to C mark again and never came up since. I've open up and check the contacts and tighten all screws in the tachcometer and even push in all the socket behind the head lamp and it's still not working, where else have I miss that I should have look.
I'm going to get my manuals soon and hope that I can fix all the problem with help from you guys. Thanks.
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Old 06-14-2007, 08:55 AM   #2 (permalink)
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Welcome to the group! I know you'll enjoy the bike once you get all of the initial quirks worked out of it. I have a question about your carb leak: is it wet, or is it dry? Namely, is it still leaking, or is it just a stain from a previous leak?

I would run some Sea Foam through it. If it's something little, like a bit of crud under a seat or something, that will clear it out and save you a rebuild. If you take the tank off, which isn't tough, you can flush it yourself for about $5, if that. But, I don't think rust in the tank is the problem. This model has a full inline fuel filter, so I doubt any rust shale could make it to the carb and cause a leak. But, while you have the tank off, you could rebuild the carbs if you felt so inclined. Search this forum for the removal procedure. It's a bit tricky since the air box is integral to the frame and non-removable. I got my two carb kits for $55 for both. A few hours time, a can of carb cleaner, and they're back business. But if they were rebuilt 3 years ago, it sounds like they just need some Sea Foam.

As for the temp gauge: what was the outside air temperature when you were riding? On mine (which is working as designed, and others will vouch for this behavior as well) the needle never comes up past C unless it's 80 degrees out or more. Even then, it only comes up past 1/4 if you're stuck is traffic. My ride in this morning was 49 degrees, and across the entire 42 mile trip, the needle never moved. Not even a little. Unlike car, this bike has not only a radiator, but also cooling fins. Unless it's really hot out, the cooling fins are doing most of the work, and the radiator is just there for looks. Only when you're stuck in traffic at 90 degrees does the radiator and coolant come up to bat. Then the temp gauge will tell you how you're doing.

Start the bike, and let it idle for 20 minutes. If the temp gauge doesn't move then, then you know it's broken. it will also be a good test to see if your fan works. It should click on just before the needle get to the red.

--Justin
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Old 06-14-2007, 11:05 AM   #3 (permalink)
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Hi Justin, It looks more like a stain on the carb. But I saw a few drop of gas mix with oil drip under the bike after a long ride. I've not seen it drip again though.
How do you use sea foam? Do you just mix it with the gas in the tank? I removed the tank yesterday, the tank looks fine and there's no sign of rust. Is there a way to replace the fuel filter? Or do I need to?
The outside temp was around 85 when I wrote outside and the temp gauge didn't even move. I check the fan and it's working fine. And I guess the gauge should be too because I saw it move once. Could be some bad connection, where else should I check? I'm still trying to locate the thermos to check the connection.
I bought some Spectra 4 oil, plugs and oil filter and I'm going to rplace them today. Should I also change the coolant? The bike's mileage is 22800 miles.
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Old 06-14-2007, 12:35 PM   #4 (permalink)
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Sea Foam is mixed right in the tank. Dump in 3 - 6oz and top the tank off.

The thermostat is under a plastic cowl on the right side of the bike, right in front of the fuel tank. It's under a little plastic hood (4 bolts, I think) and the coolant hoses run unto the bottom of it. It's also the same piece as the coolant fill neck.

I'd drain the coolant and refill it with a Silicate/phosphate-free coolant of your choice. Silicates will kill the water pump.

The combination of oil mixed in with whatever is leaking interests me. Where is the oil coming from?

I wonder if your thermostat is stuck open. That might account for the odd temperature behavior.

--Justin
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Old 06-14-2007, 02:34 PM   #5 (permalink)
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Perhaps the fuel bowl gasket is the problem. I would pull them out and look at them up close to be sure. If the PO used cheap Chinese kits. could be the problem.

Gonz
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Old 06-14-2007, 02:50 PM   #6 (permalink)
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HI Justin, Found the thermostat, and short it to ground, the temp gauge move up ok. So I need to check the thermostat. I'm waitng for delivery of my manual, got myself a 86 Shadow VT700C manual. Should be the same as the 87 I hope. I'll have a look at the carb again when I receive it. Anyway, what's the best way to check the thermostat?
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Old 06-14-2007, 03:12 PM   #7 (permalink)
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Just fix the gauge, it was just a missing mounting bolt for the unit. Put a new one in and the contact made and ran the engine for a while and the temp gauge is rising. This bike seems to have a lot of missing bolt and nuts. Just replace acouple and now I found out the tank front two bolts are missing. I'll have to check with the previous owner about it.
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Old 06-14-2007, 03:47 PM   #8 (permalink)
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Quote:
Originally Posted by BT
HI Justin, Found the thermostat, and short it to ground, the temp gauge move up ok. So I need to check the thermostat. I'm waitng for delivery of my manual, got myself a 86 Shadow VT700C manual. Should be the same as the 87 I hope. I'll have a look at the carb again when I receive it. Anyway, what's the best way to check the thermostat?
Ah! Okay, I think we have a clash of terminology. The thermostat is the mechanical device that opens around 185 degrees and allows coolant into the radiator. The temperature sensor is the little capsule that fits into the thermostat housing and sends a signal to the temperature gauge so the needle moves.

The thermostat should have no electrical connections at all; it's 100% mechanical. A loose not on the temperature sensor could make it not work.

Okay, I think we're all set.

When you pull the thermostat out, put it in a pan of water on your stove, and put your wife's candy thermometer in the pot too. (Warn her in advance, and then go buy one since she won't let you use her good thermometer for testing motorcycle parts! ) Suspend the thermometer in the pan, as well as the thermometer, so they they don't touch the bottom. Fire the stove up. Around 175-185 degrees the thermostat should start to open, and it should be all the way open (8mm if I remember correctly) around 200 degrees. If yours does this, then it's just fine. Clean it up, and pop it back in. You'll probably have to get a new o-ring (sort of hour-glass-shaped o-ring) for the thermostat housing, since after 20 years, they tend to flatten out and leak when you put them back together. It was $5 when I ordered mine from the dealership. However, some Permatex gasket sealant held it together enough that I could still ride while I was waiting for it to come in!

Glad you're getting that old bike back on the road. It's a good bike!

--Justin
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Old 06-15-2007, 01:17 PM   #9 (permalink)
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Hi Justin, Sorry about that, I use the right terminlogy when I can manual. I guess the mounting bolt for the whole thermo unit was missing and once I put it in, the ground contact was made and it work again. I've not check the thermostat, I'll do that later.
I just change the engine oil, oil filter and spark plugs. I pour in 3 litres of Spectra Golden 4 oil and it still didn't reach the dip stick line. How much oil do you need. It only drain out 2.5 litres of oil though. Where did all the oil go? How much do you really need if you replace the oil filter, I know there's a different in amount whether you replace or not. Thanks
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Old 06-15-2007, 02:05 PM   #10 (permalink)
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If I remember, mine took something around 3.2 quarts. Be sure you check your oil with the bike on the center stand, or while someone is sitting on it, holding it level. If you check it on the side-stand, you'll end up overfilling it.

--Justin
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