Carb flushing/cleaning and question about disconnected line

385 Views 33 Replies 7 Participants Last post by Buddy, 4 d ago

Hrk

Discussion Starter · 15 d ago (Edited)

2

Hi. So I bought 2005 VN750 that doesn't run after standing idle for a year or two fully understanding the risks. Now I'm learning the bike by going through manual and Checkered Floor Garage video. I'm an engineer so I enjoy learning new stuff, but I am totally new with bikes so I have some questions:
1. Is there a video on how to flush carburetors specifically for VN750? I'm thinking to flush, pour some SeaFoam and see if it helps before planning something more radical.
2. I read somewhere that injecting starting fluid could help. Is there a video or short instruction on how to do it?
3. While inspecting carburetor and fuel system I found this line that is not connected anywhere at bottom but has traces of being connected. Line goes from top of carburetor. What could it be? (Pictured from left side of the bike)

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Spockster

· #2 · 15 d ago

3 .. looks like a fuel line

2 .. starting fluid will only help if you're trying to start it, spraying into the carb intakes. It's probably not that great of a cleaner.

1 .. it's usually best to remove the jets for a thorough cleaning if it's sat very long.

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Hrk

Discussion Starter · #3 · 15 d ago

3. Fuel lines of fuel tap seem to be connected (all 3). So I guess I will have to remove tank to see what is that.
2. OK, I will try then. If I can start it, then it's already something. Then maybe SeaFoam in gasoline will help to clean?
1. Does this mean removal and disassembly of carburetors? Then I think I would need a help of mechanic.

Spockster

· #4 · 15 d ago

Jets can be removed with the carbs in place but it's tricky getting the JIS screws loose at an angle. Some people change them to hex screws for that reason. Otherwise, removal is the only other way.

The loose hose might be one of the carb vents. The fittings for the vents stick straight up out of the carbs (metal). The fuel inlets are 90 degree elbows (plastic).

Two vent hoses come out of the carbs to a tee fitting, then a single hose runs to a specific hole in the back of one air filter housing. Can't let the vent get any wind because that stops fuel flow at highway speed.

You can run Seafoam in the gas and you can inject it into the fuel inlets for soaking. It may not start very well on straight Seafoam so you'll probably want to drain it after soaking.

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Spockster

· #5 · 15 d ago

Keep in mind when starting... It's a vacuum operated petcock, so some cranking is just to get the petcock open, then you have to allow time for the fuel to fill the carbs.

So.. crank a few seconds, pause , crank, pause... Usually gets the fuel flowing.

It's the same thing if it sits more than a couple of days.

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Hrk

Discussion Starter · #6 · 15 d ago

Thank you. Will try in the nearest days.

PseudoPhil

· #7 · 15 d ago

Make it a habit to close your petcock when you park it.

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Checkered Floor Garage

· #8 · 14 d ago

PseudoPhil said:
Make it a habit to close your petcock when you park it.

Can you explain why it's a good habit to close the petcock when you park it? My previous owner told me to do the same thing when I got my VN750 in 2020...but I've actually never done this except for over-the-winter long term storage.

Checkered Floor Garage

· #9 · 14 d ago

Hrk said:
Hi. So I bought 2005 VN750 that doesn't run after standing idle for a year or two fully understanding the risks. Now I'm learning the bike by going through manual and Checkered Floor Garage video. I'm an engineer so I enjoy learning new stuff, but I am totally new with bikes so I have two questions:
1. Is there a video on how to flush carburetors specifically for VN750? I'm thinking to flush, pour some SeaFoam and see if it helps before planning something more radical.
2. I read somewhere that injecting starting fluid could help. Is there a video or short instruction on how to do it?
3. While inspecting carburetor and fuel system I found this line that is not connected anywhere at bottom but has traces of being connected. Line goes from top of carburetor. What could it be? (Pictured from left side of the bike)

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I'm glad my little YT videos are able to help you out. You are very welcome. Have you checked out this video of mine? Maybe it'll help you find out where that extra line goes. Try to find a T-fitting (like what Spockster said already) because I think this line goes there. Spockster said in a prior reply, "Two vent hoses come out of the carbs to a tee fitting, then a single hose runs to a specific hole in the back of one air filter housing. Can't let the vent get any wind because that stops fuel flow at highway speed."

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Hrk

Discussion Starter · #10 · 14 d ago

Checkered Floor Garage said:
I'm glad my little YT videos are able to help you out. You are very welcome. Have you checked out this video of mine? Maybe it'll help you find out where that extra line goes. Try to find a T-fitting (like what Spockster said already) because I think this line goes there. Spockster said in a prior reply, "Two vent hoses come out of the carbs to a tee fitting, then a single hose runs to a specific hole in the back of one air filter housing. Can't let the vent get any wind because that stops fuel flow at highway speed."

Yes, I have been watching specifically this video of yours, trying to identify what is this loose line. I could not. I will have to remove tank first, it should be easier then. I'm doing everything first time so it takes a lot of time.
P.S. Thank you for all your videos. Extremely helpful and well done.

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Checkered Floor Garage

· #11 · 14 d ago

Hrk said:
Yes, I have been watching specifically this video of yours, trying to identify what is this loose line. I could not. I will have to remove tank first, it should be easier then. I'm doing everything first time so it takes a lot of time.
P.S. Thank you for all your videos. Extremely helpful and well done.

You are so very welcome. And yes, these things take time. Especially when doing it for the first time. That's one of the reasons I started making videos. I was doing my second coolant flush...but since so much time had passed since the first one I did it was like relearning the whole process over again. Did I get all the screws? Where are they all located? etc. The first time I did the coolant flush I actually cracked open the 17mm oil drain bolt on the bottom of the crank case and oil leaked out a little. 😱

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mmart

· #12 · 14 d ago

Checkered Floor Garage said:
Can you explain why it's a good habit to close the petcock when you park it? My previous owner told me to do the same thing when I got my VN750 in 2020...but I've actually never done this except for over-the-winter long term storage.

The petcock needs vacuum to start feeding the carbs fuel but if there is anything “off” then gravity will take over. This will first flood the carbs and then make its way into the crankcase. I left mine open the first and only time I put my bike in storage and this is exactly what happened.
Its just a good preventative step.

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Spockster

· #13 · 14 d ago

mmart said:
The petcock needs vacuum to start feeding the carbs fuel but if there is anything “off” then gravity will take over. This will first flood the carbs and then make its way into the crankcase. I left mine open the first and only time I put my bike in storage and this is exactly what happened.
Its just a good preventative step.

Yes, if the petcock diaphragm goes bad, it will flow gas through the vacuum line no matter where the petcock is set.

I knew my diaphragm was bad but thought if I turned the petcock off the flow would stop. It kept flowing and overnight the crankcase filled up for the second time.

It's a good idea to check that vacuum line once in a while to make sure it's dry.

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Checkered Floor Garage

· #14 · 14 d ago

Spockster said:
Yes, if the petcock diaphragm goes bad, it will flow gas through the vacuum line no matter where the petcock is set.

I knew my diaphragm was bad but thought if I turned the petcock off the flow would stop. It kept flowing and overnight the crankcase filled up for the second time.

It's a good idea to check that vacuum line once in a while to make sure it's dry.

Spockster, I wish there were a way to download all your VN750 knowledge. But then again...learning comes from experience and you have a lot of experience with these bikes! I never knew about checking the vacuum line once in a while to make sure it's dry. To make sure I understand, is the vacuum line the one I have circled in red below? (the center/bottom petcock port?)

And by dry, do you mean it should be dry when the bike is on? Off? All the time?

Lastly, how does the fuel fill up the crank? Does it simply leak fuel into the carbs, then the carbs overfill, then the fuel leaks into the combustion chamber via the intake?

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Spockster

· #15 · 14 d ago

Checkered Floor Garage said:
Spockster, I wish there were a way to download all your VN750 knowledge. But then again...learning comes from experience and you have a lot of experience with these bikes! I never knew about checking the vacuum line once in a while to make sure it's dry. To make sure I understand, is the vacuum line the one I have circled in red below? (the center/bottom petcock port?)

And by dry, do you mean it should be dry when the bike is on? Off? All the time?

Lastly, how does the fuel fill up the crank? Does it simply leak fuel into the carbs, then the carbs overfill, then the fuel leaks into the combustion chamber via the intake?

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Yes, it's the center port.

The front carb is angled down toward the cylinder, the gas runs through the hose into the vacuum port on the carb and into the cylinder where it flows through the end gaps of the piston rings.

That vacuum port is directly in the venturi of the carb and gravity makes the gas flow to the cylinder when the bike isn't running.

I would check it after the bike has been parked at least a minute. Not sure if vacuum flow could cause it to be dry or not. Either way, it should never have any gas in it.

I was able to ride with the leak, it didn't run rich, but the gas flowed enough overnight that it ruined two oil changes. I did notice the shifter being sticky when all that gas was in there.

mmart

· #16 · 14 d ago

I had no idea it happened and I took the bike on I-295, the pressure of running it like that caused the oil to seep out of any place possible. I thought the bike was going to explode. I even managed to get oil on the rear tire, it was a mess.

PseudoPhil

· #17 · 14 d ago

Checkered Floor Garage said:
Can you explain why it's a good habit to close the petcock when you park it? My previous owner told me to do the same thing when I got my VN750 in 2020...but I've actually never done this except for over-the-winter long term storage.

In my case, I got my intake full of crud over-revving after an MCCT install, and the main jet valve got some gunk in it. After being parked for a few days gas had flooded the front chamber. When I tried to start it, compression forced the excess gas into the crankcase, costing me 4 1/2 quarts of fresh oil.

With the petcock in good shape and closed, only a few CCs in the lines can seep through the carb, preventing repeated flooding of the chambers or the need for extra oil changes.

taco_to_go

· #18 · 11 d ago

There is info here on how to do a simple blow back to unstick carb floats and possible remove debris. Search posts by now deceased "Wolfie".

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Hrk

Discussion Starter · #19 · 9 d ago

So I drained left carb, nothing awful inside, just 5 or so seconds of gasoline going down the drain line. But when I moved to right carb - I cannot get to drain screw. It sits behind two cables in the rigid harness(?) that I can't move aside, distance is so small I can't even fit a screwdriver bit. Is that something wrong with my bike or with me or there is some kind of special screwdriver that I'm not aware of?

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Spockster

· #20 · 9 d ago

Hrk said:
So I drained left carb, nothing awful inside, just 5 or so seconds of gasoline going down the drain line. But when I moved to right carb - I cannot get to drain screw. It sits behind two cables in the rigid harness(?) that I can't move aside, distance is so small I can't even fit a screwdriver bit. Is that something wrong with my bike or with me or there is some kind of special screwdriver that I'm not aware of?

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Not sure, maybe the bracket is bent? You're supposed to be able to drain the carb.

They do make a ball hex wrench that will work at an angle.

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