WTF replaced throttle cable - now won't start

David Williams /

Ok, the damndest thing. Last week my moped ran great... until the throttle cable broke inside the carb. I removed the carb and spark plug (to be cleaned) and waited for the new throttle cable to come. (I cleaned the head of the spark plug with a wire brush to clean it off) (Also, my fuel valve leaks internally, so it tends to flood the carb over long periods) Today after i installed the new throttle cable and got everything back together, it wouldn't start. Fuel delivery is fine, compression, spark, all good. I also noticed fuel was getting into the exhaust header. When i removed the spark plug to take a look, it was all wet with gas. The odd thing is that when i remove the spark plug and check for spark it's fine. Could the timing be off? Even though it hasn't been touched in a week?

Re: WTF replaced throttle cable - now won't start

Jason Luther /

regap the plug, or just get a new one. did you put all of the pieces back in the carb? -jason

Re: WTF replaced throttle cable - now won't start

Bruce Wilkinson /

Take the carb apart and make sure that the float is free and the slide is moving freely. bruce

Re: WTF replaced throttle cable - now won't start

David Williams /

Hey guys,

Yea, I put the carb back together with all the parts in tact. When I tested my moped, I also tried another carb (I have a 12mm and a 14mm). When I put them together, the slide and float looked to be operating fine. One thing though, the bowl gasket was disintegrated, so I screwed it on with a ratchet pretty hard. It seems like the carb is letting way too much gas into the cylinder and it's seaping into the exhaust when I try a few good cranks...

I'll recheck the carb again and regap the plug. ::crossing my fingers::

Re: WTF replaced throttle cable - now won't start

Sounds like you have a couple of problems with your carb.

First, sounds like you may be sucking too much air through that defective float bowl gasket. Air leaks can make starting difficult or impossible.

Second, the float needle valve sounds like it needs to be replaced. The float needle valve is attached to the float and is supposed to move upward and blocked the flow of gas when the bowl is full. The float needle valve has a rubber like pointed tip that becomes worn with a ring indentation and will no longer stop the flow of gas.

You can order these parts from Ike's Bike or Moped Warehouse or your favorite moped dealer

Re: WTF replaced throttle cable - now won't start

David Williams /

thanks zippy! I'v ordered some new gaskets including the bowl. I took the carb off and completely apart. The float needle valve was a little worn, so i'll order up a new one as well.

Is it possible that the carb was putting so much gas in the cylinder that it wouldn't even fire?

THanks

Re: WTF replaced throttle cable - now won't start

Yes too much gas could keep it from starting (flooding), Depends on the weather conditions in your area at the time you are trying to start it.

I've seen them leak so bad, gas runs out the tail pipe when it is just sitting, not running.

While you have the carb disassembled clean the chamber where the float needle valve slides up and down. Sometimes varnish gunh can build up inthere and obstruct the full range upward movement of the float needle valve. This would agin cause the flaot needle valve to seat properly and gas to continiously flow through.

Re: WTF replaced throttle cable - now won't start

David Williams /

Ok, I took the carb apart and did some minor cleaning, but i didn't clean the fuel port where the float needle valve slides. I'll clean that next. Attached is a pic of the float needle valve. There doesn't seem to be a lot of wear around it. I'll wait and see what happens when i clean the needle valve chamber.

Thanks

1081409443_floatneedle.jpg

Re: WTF replaced throttle cable - now won't start

It is difficult to tell but best to replace the float needle valve if you are having a flooding problem.

It doesn't take much of a indentation in the tip for the gas to find a way to seep through.

Best to bring components up to oem specs when you are trying to correct a problem.

Anyway good luck with your project and let us know when you get the carb parts and hopefully that will solve the problem.

Re: WTF replaced throttle cable - now won't start

David Williams /

I'll be sure to post my progress. Thanks for all the advice! :-D

Re: WTF replaced throttle cable - now won't start

make sure your thorttle is working by looking at the carb off the intake with the airbox off, make sure its moving up and down and closes all the way

Re: WTF replaced throttle cable - now won't start

Bruce Wilkinson /

Another thing to check. The float can have a groove worn into the channel where the needle rubs. Thus the needle can get stuck at an angle and not seat properly. Check for wear on the float. bruce

Re: WTF replaced throttle cable - now won't start

David Williams /

Ok, I checked on my moped again, and it looks like gas is leaking out of every seal on the carb. The bowl gasket, the two gaskets on the fuel inlet to the carb, and even the seal around the primer valve button. The mechanics of the carb seem fine. I also realized in the beginning, when I replaced the throttle cable, i also filled the gas tank. I know the fuel valve does have an internal leak (new one on the way), but would it be pushing too much fuel into the carb. because of the full gas tank?

Re: WTF replaced throttle cable - now won't start

Part of the problem is a full tank. Won't your petcock valve shut off?

The real problem is your float needle valve. It si like the flapper valve in a toilet tank that won't close properly.

If you have any lawn mower shops near you, go see if they can sell you a plastic 3/16" inline shut off valve. You can put this on the fuel line AFTER the tank fuel petcock valve and BEFORE the carb. This will stop the flow of gas when the moped is sitting, not running but won't solve the problem of the defective float needle valve when the fuel petcock valves are open and the moped is running.

Re: WTF replaced throttle cable - now won't start

David Williams /

I've got a new fuel petcock ordered and on the way. Once it gets here I'll give it another go. Since i took the carb. off, it shoudl also give the engine some time to dry out from all that excess gas.

Thanks

Re: WTF replaced throttle cable - now won't start

Like Zippy said.........you need to repair the float and/or the needle valve or seat or at LEAST clean it and the float bowl. The fuel should not force its way past that float as long as the gas cap is venting. don-ohio (:^)

Re: WTF replaced throttle cable - now won't start

David Williams /

Ok... I replaced the fuel petcock and bowl gasket.... and I cleaned the float valve... but it still won't start. It did sputter for about 4 seconds before dying. After that it wouldn't even burp. When I try cranking on the engine a few good times, fuel starts dripping from the exhaust pipe where the header meets the baffle. When I took the exhaust pipe off and tried cranking away, a spray of gas formed on the pavement below. Should it be using this much fuel?

Thanks

Re: WTF replaced throttle cable - now won't start

Bruce Wilkinson /

No. If the gas is leaking like that then the needle is not closing off the gas flow. Is there any gas on the outside of the carb ?If not then it's inside the carb. bruce

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