Yamaha C3 Stalls

5973 Views 16 Replies 4 Participants Last post by nast70, Sep 9, 2019

nast70

Discussion Starter · Aug 14, 2019

My sons yamaha c3 stalled today and left him stranded. It has done it twice for me, but I just figured it was me, 3 times my kids weight and 4 times the length of ride he took it on.figured it was too hot.
We changed oil, air filter and spark plug. Seemed to be fine. It stalled on him a couple times out with his cousin this weekend, but started after 10 or so mins if cooling off.
When it stalls, it's usually taking off from a stop. Like it's not getting fuel. Fuel pump runs when key is turned on, so it's working. Is there a fuel filter somewhere? Nothing is shown in the service manual.
Nothing comes up online for the motor.
It's a 2007 C3 (50cc).
Any help would be appreciated

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Retired Guy

· #2 · Aug 14, 2019

When it quits, check the fuel pump right then and see if its still working. Drove me nuts (explains a lot) trying to figure out what was happening on a Ninja a few years ago.

Sometimes I could ride all day with no problems. Next day I might not get a quarter mile and it would quit. Then it might quit twice more trying to get home. I thought it was something electrical because when it quit, it was like turning the key off. It was the fuel pump.

Good luck with it.

nast70

Discussion Starter · #3 · Aug 14, 2019

The pump was our first thought as well. My son knew that and said when he turned the key on the pump cycled.
I am leaning towards a bad fuel filter. It is mentioned in the service manual in the FI system description, but I cant find any other specific reference to one in the rest of the manual. And be damned I could see one anywhere inside the last time we had the cowels off. Saturday we will be visiting the local dealership for some other stuff and have a talk with the service guy there.

Retired Guy

· #4 · Aug 14, 2019

I had to replace the fuel pump on my Yamaha Royal Star Tour Deluxe. While doing that, I found my fuel filter. It was in a place that it would be hard to find and it made no sense to me why it was tucked away like it was. It looked old.

I bought new fuel line and "re-plumbed" the fuel lines. Now when the seat is removed, the new fuel filter can easily be inspected as its in plain sight.

I also learned my bike doesn't even need a fuel pump until it gets down to about a half tank of fuel. (Its got carburetors). So now I carry a piece of fuel hose in my left saddle bag. Petcock to carburetors, if above half tank, start up and go.

hogcowboy

· #5 · Aug 15, 2019

Retired Guy said:
I had to replace the fuel pump on my Yamaha Royal Star Tour Deluxe. While doing that, I found my fuel filter. It was in a place that it would be hard to find and it made no sense to me why it was tucked away like it was. It looked old.

I bought new fuel line and "re-plumbed" the fuel lines. Now when the seat is removed, the new fuel filter can easily be inspected as its in plain sight.

I also learned my bike doesn't even need a fuel pump until it gets down to about a half tank of fuel. (Its got carburetors). So now I carry a piece of fuel hose in my left saddle bag. Petcock to carburetors, if above half tank, start up and go.

I give. What is the fuel line in your saddlebag for then if the fuel pump is there for the less than half tank times? I'm lost as to why you are carrying it then. Doesn't the petcock in the on position work for the whole amount of fuel in the tank then if the pump is working?

Good work though on getting the filter where you can easily see or change it. Or in doing that did you create a problem with the half tank volume issue? Like I said, I'm confused for why you are carrying fuel line in your saddlebag and when or why you would use it.

Critter

· #6 · Aug 15, 2019

To bypass the fuel pump if it has quit, around a half tank fuel will no longer flow past the pump if it isn't running (gravity?) But with a direct line from the tank to the carbs it will continue to flow enough fuel to be rideable

Retired Guy

· #7 · Aug 15, 2019

When the problem first happened, and I suspected the fuel pump, I read how to just run a line from the petcock to the carburetors, and if above a half tank, the bike should run. Before doing that, everything was factory, as far as I know, (I bought the bike used).

This was supposed to be one way of diagnosing a faulty fuel pump. I think it was on a Yamaha Venture forum where I read about this. So I got two, two and a half feet of fuel line and tried it. It worked, above half tank it would run, drain it to less than a half tank, it wouldn't run, at least not very long.

It was then I got a new fuel pump (and filter) and re-plumbed everything so the fuel filter was easily seen. So I don't believe I created the situation. Why bypass the fuel pump? I don't know. Maybe fuel won't flow through a faulty pump? I do know if the pump quits again, I can bypass it with a short piece of hose to get me back on the road.

So, like carrying a plug kit in case of a flat tire, I'll carry a short piece of hose in case of another fuel pump issue. Coiled up and laying in the bottom of a saddle bag, it doesn't take up much room.

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hogcowboy

· #8 · Aug 16, 2019

Critter said:
To bypass the fuel pump if it has quit, around a half tank fuel will no longer flow past the pump if it isn't running (gravity?) But with a direct line from the tank to the carbs it will continue to flow enough fuel to be rideable

So why not just leave installed rather than carry it around in the saddlebag? Maybe it would be obvious if I saw it installed.

Retired Guy

· #9 · Aug 16, 2019

Bypassing the fuel pump only works if there is more than 1/2 tank of fuel.

nast70

Discussion Starter · #10 · Aug 16, 2019

Retired Guy said:
I had to replace the fuel pump on my Yamaha Royal Star Tour Deluxe. While doing that, I found my fuel filter. It was in a place that it would be hard to find and it made no sense to me why it was tucked away like it was. It looked old.

Had a conversation with the tech at the local dealership about this. He said after doing everything we did "cheap stuff first, then move on from there", we found the fuel filter on the drawings. It is part of the fuel pump and cannot be changed on its own. We can try to clean it and see what that does.
I think we will run some Seafoam through it first before we start tinkering with the pump/filter. A replacement pump is a $400.00 bill from the dealership if we need.:frown:

Retired Guy

· #11 · Aug 16, 2019

My dealer wanted $232 for a new fuel pump. I didn't have an extra $232 laying around at the time. So I went to O'Reilly's Auto Parts and bought a low pressure fuel pump for about $65 (if I remember right) and a new fuel filter.

They've been working for over a year now. I don't know how much pressure is needed on a fuel injected bike, but that info shouldn't be too hard to find out.

nast70

Discussion Starter · #12 · Aug 19, 2019

Well we tried one more trick before taking out the fuel pump. Filled the tank and added Seafoam. Shook the bike a bit to mix it in the tank, and left it to idle for 20mins.
My son took it around a loop around our neighbor hood, about 4km total each time around. He did that 6 times, or until he was dizzy he said!
It didn't stall or hesitate on him, and he note a bit more pep in the take off, and bit higher speed. We might be onto something here. It will take about a week of his regular riding to burn through that tank, then I think we will do one more and see what happens on the third tank of no additives.

nast70

Discussion Starter · #13 · Aug 22, 2019

Well, turns out it was the pump. It got him to football practice, but wouldn't start to get him home. A quick trouble shoot in the parking lot figured that out. $40.00 later from Amazon and we will get the new one in a week or 2.

Retired Guy

· #14 · Aug 22, 2019

$400 from the dealer, $40 from Amazon. That's a bargain!

nast70

Discussion Starter · #15 · Aug 22, 2019

Retired Guy said:
$400 from the dealer, $40 from Amazon. That's a bargain!

Um....yeah!
And the amazon one isn't the cheapest on there. They had $20 units, but i'd be weary of it. This one had the best reviews from folks that have our machine. Feel pretty confident its will work. It's also not the most expensive one. Don't see a need to throw $100.00 into it when he's only going to drive it one more summer then get his DL.

hogcowboy

· #16 · Aug 23, 2019

Now that a pump has been mentioned, that might be the problem with my cheap Chinese Bennche UTV. It started being hard to start then a few days ago totally refused to. Carb cleaner does get it started but it won't continue. So it's a fuel delivery problem of some kind. I've been focused on looking for a filter that might be plugged but maybe the fuel pump has given up. Could also be injectors but I can't see all of them at once. So fuel pump has more promise and thinking back, I don't think I hear it anymore. Don't have a service manual on the cheap thing. But this is the first problem that it's had so not too bad really. Time to do some investigation. Maybe our Chinese expert can help.:surprise: :sad: Just kidding.

:smile:

nast70

Discussion Starter · #17 · Sep 9, 2019 (Edited)

Well, its up and running. I gotta say it was a total head scratcher, and i'm still not sure why it works now vs why it didn't before. This is what we ended up doing:
First we ordered the new pump and filter assembly. The new filters were not compatible with the current pump holder assembly, so we just swapped out the pumps.
The pump ran the first time the key turned on, that's good. It didn't start. Okay, might take some time to get the fuel up through the line. Keyed it on and off several times more. Still no start. Tried one more time and not a peep from the pump. Maybe it overheated? Left it for an hour then went back. Still nothing. Swapped out the pump for the old one, same thing nothing. Now I'm thinking there's something else wrong electrically. Lets start with the pumps and move from there.
Hooked each to an old 12v battery I have, both ran like they were supposed to. In my mind I'm thinking I bought a new pump for nothing now. Focus on the wiring, plugs and injection system. Over the next few days it was tinker here and there.
Not the plugs, all the connections have power. Look a bit closer to the pump plug. Cant cross the wires, the spades are different sizes. Otherwise it would be pushing air into the tank instead of sucking fuel out. Verify that by hooking the pump directly to the battery. Fuel comes out of the pump. It works. Lets put the fuel line back on and see if we can get fuel up the line to the motor. It does. Lets try starting it like this. It lights up perfectly. Let it run like that for a minute, turn it off, disconnect the outside battery, hook up everything properly and try starting it. It runs perfectly.
My best guess is the fuel line is around 12" long and maybe air locked. The pump didn't have enough umph to push the fuel through. That would mean it's running on less than 12v. The pump directly to the battery pushed fuel and filled the line. That was Saturday morning. He's had it out 2-3 times since and had no problems. All that still doesn't quite explain why the pumps quit working, unless there was a loose connection that my fiddling and farting around magically solved.

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