1st tank good, 2nd tank starving

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FreeWheeler

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Jun 22, 2010
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I ran my first tank and refilled it before it ran dry, but now the fuel line and filter are empty and it only runs off what's in the bowl. It seems like vapor lock or something, will run lean and then quit, idles at high rpm. The only difference is refilled the tank.

What's the likely solution?

Here's a picture of what the fuel line and filter looked like when it ran good.
 

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biken stins

New Member
Jul 11, 2008
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Was a filter still on the petcock ?
Pluged filter ?
Blow some air where hose was. And/or clean the tank.
Get another in line filter ready, drain the bowl before replaceing.
 
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FreeWheeler

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Jun 22, 2010
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I took the tank off and tried to drain it through the petcock, it wouldnt until I shook things up. I drained it, got some regular premix and swished it around in the tank and drained out the filler hole.

I also removed the petcock and there was a piece of crud which I blew out. I refilled the tank through a piece of clean sponge. I also blew through the inline filter which was difficult until I went against normal flow and then it cleared. There were noticeable big chunks of crud in the filter.

I also checked tightness of screws on carb and everything was tight except where I screwed on the carb to intake. It had loosened. I used a gasket silicone when I installed. The gasket was still holding things, just the collar screw had loosened.

Holding down the primer button gushes fuel through every spot it can find.


So, youre saying replace the filter and remove the bowl, drain it?

Where can I get a filter which is cleanable by just unscrewing replacing paper element?
 
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F

FreeWheeler

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Jun 22, 2010
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Here's the latest. After doing all the above, it still didnt flow. I took the fuel line off, drained it, blew it out again. I put it back on the tank and blew through it until I couldnt any more and the bubbling sound stopped. I put the line back on and gave it rapid CPR compressions between the carb and the filter. I dont fully understand, but fuel started filling the filter and the lines and the air bubbles went into the gas tank. Now, the lines are full and the filter is full.

What the heck did I just do?
 
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biken stins

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Jul 11, 2008
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Sounds lke your tank had a bunch of crud in it. Always a good idea to clean it before mounting.
Your filter did its job by catching the chunks. they are replaceable.if you get a glass one secure it well so it don't brake.
carb being loose at intake will affect preformance. Did you make sure the studs were tight into the head before bolting intake on ? They can come loose also.
From what you said about fuel coming out of every spot. could be a chunk is stuck inside carb causing it to stick.
If you got it running might clean the bowl. Small grit can be drained out through the drain screw.
If still gushing bottom half carb removes with the 4 screws. Carefully remove as not to brake gasket and clean larger chunks out. If still gushing you will need to adjust the float. May be pictures in another post somewhere on the forum.
Good luck. This is a common problem but a easy fix once you have done it
 
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FreeWheeler

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Jun 22, 2010
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What the heck did I do? Apparently not enough.

I ran it about 1.25 miles and it ran good and then the same thing. If I give it enough time, fuel gets into the carb and it runs again, so I guess the filter is clogging. I'll replace the filter and make sure I filter the gas at fillup time and not run it below the hump in the tank.


Thanks, biken just saw your suggestions and will keep at it.
 
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GearNut

GearNut

Active Member
Aug 19, 2009
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It sounds to me like you have alot of rust or other other debris in the fuel tank. Rusty tanks are common in these kits. You may need to clean out the inside of the tank by:
1. Drain all fuel from tank and remove from bike.
2. Remove fuel valve and plug mounting hole with suitable plug. A whittled down wooden stick will work in a pinch.
3. Put a handfull of small screws or pea gravel in the tank through the filler hole.
4. Partially fill tank with HOT HOT soapy water and put filler cap back on.
5. Shake fuel tank like you want to kill it. Rotate tank all directions as you shake it. The idea is to get the screws or pea gravel to scrape all surfaces of the inside of the tank clean.
6. Take a rest and shake the tank some more.
7. Drain the tank out of the filler hole.
8. Stick a garden hose inside the filler hole and turn on the water. Turn the tank all directions to thoroughly rinse the insides clean.
9. Take a rest and rinse the tank some more.
10. You must do a final rinse with 90% denatured alcohol or WD40 to remove all traces of water from the tank and prevent rust from forming.
11. Replace fuel valve and reinstall tank on bike.
12. you can figure out the rest.
 
tommyboy1442

tommyboy1442

Member
Nov 25, 2009
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chicago
go to sick bike parts and buy a heavy duty fuel valve, or go to your local ace hardware store and get one. the stock chineese fuel valves arent worth the metal. just another bad design by the Chinese. can we just stop importing chineese already? we go through them to save money, but what good is saving money when the product isnt worth **** anyways. i miss those words "made in u.s.a.".....
 
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FreeWheeler

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Jun 22, 2010
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Thanks, I will end up doing all these things probably so glad you spelled it out. In the meantime, I got it running and kept watching the filter and line. Going along and I could feel it running lean so I opened the cap and the line filled up again and it started running right.

What I really dont get is how I ran an entire tank and never touched the cap or had a single hiccup in fuel flow.
 
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FreeWheeler

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Jun 22, 2010
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I put a bunch of miles on it tonight and it ran good as long as the tank cap was loosened. I dont get that, really dont. I dont like riding with the cap all loose. I hit a pothole and the cap flew off into the weeds. I spent the next 10 minutes trying to figure where the thing would fly. I found it and headed home but ran the tank too low and now I'm back where I started. Need to get more premix before I fill it again.

One thing I did after riding was I unscrewed the throttle at the carb and then hand tightened it. There are more threads showing than before. I had installed it with pliers and didnt crank on it, but got it tighter than by hand only. I'll test the idle screw and see if it responds.

The first tank was like a honeymoon, all problems were obviously something I did.

Forgot, I never installed the filter that goes into the petcock - couldnt even tell what it was, just a piece of plastic that looked carb related but carb was assembled so i left it in the bag.
 
GearNut

GearNut

Active Member
Aug 19, 2009
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San Diego, Kaliforgnia
Aaaahhh! Your cap is not venting! It should be able to let air flow in so as not to cause a vacuum in the tank as fuel flows out. I would drill a teeny tiny pin hole in the center of the bottom of it. Bottom only! Do not drill a hole all the way through it. The center bottom "vent chamber" of the cap should all ready be able to vent around the rim of the cap.
 
2door

2door

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Sep 15, 2008
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FreeWheeler said:
Forgot, I never installed the filter that goes into the petcock - couldnt even tell what it was, just a piece of plastic that looked carb related but carb was assembled so i left it in the bag.
Click to expand...

The in-tank filter is not necessary IF, you're using an in-line filter between the tank and carburetor. The little filter that is provided in the kits aren't bad but hard to get to to clean. You can blow air back into the tank to clean it but then the dirt will just plug it up again eventually.
As for your fuel cap not venting take GearNut's advice. To explain why the fuel doesn't flow, put a straw in a glass of water, put your finger over the end and lift the straw out of the glass. The water stays in the straw and will until you take your finger off (vent) the straw. This is an oversimplication of physics but it will demonstrate the need to vent the tank for you.
Tom
 
Bikeguy Joe

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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I'll refer you back to post #2 where the first thing I asked is "Cap venting?"

Drill a hole in the bottom center, and then blow through it, if it doesn't seem right, drill a hole offset in the shiny top part of the cap. fairracing31 has a post somewhere around here (Classic Posts?) for properly fixing this problem.
 
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FreeWheeler

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Jun 22, 2010
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Maryland
Thanks everyone for the fixes and explanations. I didnt understand "tank venting" until I took a closer look at the tank cap. Yup, not venting. I replaced the filter with a slightly bigger one and so far no visible crud. I'll try fairracing31's cap fix. Thanks again.
 
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FreeWheeler

New Member
Jun 22, 2010
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Maryland
2door said:
Keep us informed and let us know if things work out for you. Good luck, have fun, ride safe.
Tom
Click to expand...
Tom, Bikeguy, everyone, thanks again. I think I might have fixed it. I put the cap on snug and tested the flow out the petcock and it was drip drip, of course. I took the gasket off and cut two nothces without going beyond the outer diameter of the gasket. The gasket looks just like the top of the tank. I placed the gasket on the tank with the notches lined up with the tank notches, then put the cap on. I tested the flow at the petcock and it gushed. I guess I could lock the gasket in position with some silicone if needed, I'll see.

I'll see how it rides tomorrow. I also pulled the plug and overall it's been running jet black rich, but with fuel flow problems I know it is lean at times.
 
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FreeWheeler

New Member
Jun 22, 2010
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Maryland
It Vents!! Took it for a ride, long enough to get the problem and no hiccup. I guess the gasket swolled up after the first tank and putting 2 notches in the gasket lets it vent around the side of the "vent cylinder??" and over. I tried to spill gas by tipping and sloshing and nothing came out the cap.
 
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