Starving for Gas

MB-Monkey

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Nov 19, 2008
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now that i have done all the things i can think of to solve the problem i am asking for a little help.

I have had the motor running well for about 2 weeks of break in. I leaned out the mix after a hundred miles and discovered the plug was too dark and oily so i replaced it. The fuel filter looked muddy so i replaced it.

The motor seems to be starving for fuel. I have the CNS carb on it and it was performing fine then i noticed the performance dropping off lower top speeds and ow it seems starving for fuel.

I took the carb off and took off the bowl nothing in it i removed the jets and made sure they were clean so i reassembled the carb and gave it a shot.

I can choke the motor out and it will stall. I have seen others that have had air leaks and i am getting some carb cleaner and silicone but not real clear on what to seal.

Does anyone have some pics of what needs to be sealed i am dying can't get it to go more than 15. with the gradual on comming of the problem i am kind of stuck.

Any help is welcomed.

scratg
 

MB-Monkey

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Nov 19, 2008
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Yes fuel seems to be flowing fine now thru the new filter and into the carb bowl. if shut the petcock (i love that word) and open the bowl drain the fuel drains out as it should if i pull the line off right before the carb it flows as it should so i am kind of leaning towards it being an air leak as if the motor is sucking so much air it can't put enough fuel in it. this problem has developed from a well running break in period kit. i want to seal up the motor case with silicone but i am not sure which areas to seal
 

MB-Monkey

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Nov 19, 2008
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i have adjusted the mixture screw and it will change at idle but won't rev more than once and bogs down. The setup had been working just fine until the preformance drop.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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a dark plug doesn't mean the engine is starving for fuel....
I don't know much about your carb, but usually you can buy jewelers drill bits & drill it out, one size at a time & see if it starts running better?? If not you can solder the jet closed & use smaller drill bits to make the hole smaller & see if that makes it run better...
 

georgeknight

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Sep 26, 2008
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a dark plug doesn't mean the engine is starving for fuel....
I don't know much about your carb, but usually you can buy jewelers drill bits & drill it out, one size at a time & see if it starts running better?? If not you can solder the jet closed & use smaller drill bits to make the hole smaller & see if that makes it run better...
This might save you a few dollars. I use a drill bit set I got at the local welding supply. I think it was $8.00. It's for cleaning the tip on a cutting torch. It comes with a varity of small bits.

George
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
This might save you a few dollars. I use a drill bit set I got at the local welding supply. I think it was $8.00. It's for cleaning the tip on a cutting torch. It comes with a varity of small bits.

George
I took the jet into my local hardware store; found the drill bit that was the exact size as the jet, and then bought the next 6 bits larger & smaller... for about .50 cents a piece...
 

MB-Monkey

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Nov 19, 2008
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ok let me see if i can explain this a little better

the bike setup has been working just fine. So i don't think it is the size of the jet. the CNS carb has a bigger jet in it and it was working just fine.

When i start the bike the motor will idle just fine. I can adjust the air/fuel mixture and the motor responds as it should.

when i try and ride the bike it is not really getting the rpms like it used to. and it won't go over 15.

This is why i think it is an air leak more than a carb problem
 

misteright1_99

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Mar 21, 2008
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I would try turning the air screw in 1/2 turn, less air. If it has been running good with the carb then I wouldnt think there is an air leak. The temperature fluctuations lately you might have to adjust the carb daily depending on the temp. Another thing I have read in some posts is loose motor mounts create a foaming of the gas in the carb bowl, creating a lean condition, just a thought.......
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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A air leak won't matter at WOT... (the engine is sucking all the air throught the wide open throtle body, not the tiny cracks)
It might be running too rich; If it was running good, then just started running bad; you might have some dirt in the float needle...
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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Also, if it has an air leak, it will have a white or grey looking plug.

However, to seal the engine, run a bead of silicone along the place where the two case halves go together after you clean it all real well.

Also, take off the manifold where it bolts to the jug and seal both sides of the gasket there.

If the carb has AIR screws, they turn in to richen, out to lean. Most only have that type of screw of the low end though.

How the compression? Have you pulled the head and had a look at the cylinder walls for scoring or burn marks?
 

Goat Herder

Gutter Rider
Apr 28, 2008
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Also if you were playing with different air filters these CH realy need to breath got to have high flow.
 

MB-Monkey

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Nov 19, 2008
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i just sealed up the case and air intake with silicone gray high heat. I took apart the carb and made sure the jets where clear and put everything back together. Motor didn't seem to respond when i sprayed carb cleaner i was hoping i could ID where or if there was a leak. After it dries i will give it a go and see if has made a difference. I have a stock carb that i have not tried yet i guess i will drain the tank first and refuel with new gas. That idea just came to mind. That would suck if this turns out to be a ethanol issue.
 
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MB-Monkey

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update

I drained the tank and refueled, cleaned the old plug regapped and installed, sealed the intake where the carb meets it, and gave it a shot and still i have the same issue. while draining the gas it didn't seem to be as free flowing as i would expect these is no screen on the petcock (i love that word) but there is a newly installed fuel filter. I guess next i will try and put a straight gas line from the tank to the carb and see what happens but the bike just won't rev at all.
 
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MB-Monkey

New Member
Nov 19, 2008
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Manchester TN USA
i just pulled the inline filter and ran a straight line from the tank to the carb and it is still not pulling fuel. the line wasn't filled all the way after a short ride and the motor would not rev. If i pumped the fuel line with my fingers the carb would take fuel in and the motor will rev until the bowl gets light then it won't if i pump it again it will rev up a couple of times then bog down again.

It just seems like the carb is not pulling enough fuel in to keep the bowl full when i had the carb apart the float was working fine i guess tomorrow i will switch out with the stock carb to pinpoint if it is the carb or not

any more thoughts on the matter after the updates?
 
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POPS

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Sep 8, 2008
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Sounds to me like the petcock has gone south??? I think the fuel line should fill up with fuel all the time??? Maybe someone with more experance will comment on this...POPS .Just another thought...The breather hole in the gas cap might be plugged ?
 

Train

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Dec 2, 2008
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Arcadia, CA
i just pulled the inline filter and ran a straight line from the tank to the carb and it is still not pulling fuel. the line wasn't filled all the way after a short ride and the motor would not rev. If i pumped the fuel line with my fingers the carb would take fuel in and the motor will rev until the bowl gets light then it won't if i pump it again it will rev up a couple of times then bog down again.

It just seems like the carb is not pulling enough fuel in to keep the bowl full when i had the carb apart the float was working fine i guess tomorrow i will switch out with the stock carb to pinpoint if it is the carb or not

any more thoughts on the matter after the updates?
i'm having a similar problem that started today. the carb just doesn't seem to be pulling fuel down. i had installed an inline filter and once that was on it stopped pulling fuel. after i replaced it with a straight line, it still wouldn't pull any fuel.

any suggestions?