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Post by dan50 on Aug 26, 2016 11:12:16 GMT -5
Mech, what's the difference between a vacuum fuel pump and a vacuum petcok?
Iwould like to got to a gravity fed system with a manual shutoff. Does anyone know where to get the hook up to the fuel tank. My Dongfang is exactly like a Taotao ATM50-1 (just like Brent's).
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Post by dan50 on Aug 26, 2016 11:17:38 GMT -5
I ordered a new lower front running light for $10. My Dongfang uses Taotao ATM50-1 parts. The lens is good, but the socket got melted when the bulb blew (the bulb was black). I have a bulb in there now, it still works. The lens also comes with the wiring harness, socket and reflector. I ordered LED bulbs to replace the regular ones.
In a short time, except for the turn signals, all the rest of my light including headlight are LED's. Turn signals will be LED's in the future.
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Post by dan50 on Aug 26, 2016 11:24:10 GMT -5
I installed a set of PowerMadd hand guards. They mount by unscrewing t6he mirrors, put the bracket under the mirror and tighten the mirrors back up. They do keep quite a lot of wind off your hands. I really like them.
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Moat
Scoot Member
Posts: 88
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Post by Moat on Aug 26, 2016 16:13:48 GMT -5
Mech, what's the difference between a vacuum fuel pump and a vacuum petcok? Hey Dan - not Mech, but... A petcock is just another name for a valve. Turns your fuel flow on or off. These require gravity to function - i.e. the fuel tank has to be located higher than the carburetor's float bowl in order to supply the pressure required to deliver the fuel. Most scooter petcocks are the automatic, vacuum-operated type that don't require you to turn it on/off manually every time you ride (like all motorcycles used to be back in the day - mid 70's and earlier). It applies intake manifold vacuum from the running engine to a small rubber-impregnated cloth diaphragm which lifts a valve off of it's seat, allowing fuel to flow. When the engine is not running, the valve returns to it's closed position (via a small spring), and fuel flow stops. Handy - but can be trouble prone; i.e. pinhole fuel leaks in the diaphragm can suck fuel directly into the intake manifold via the vacuum line, causing an unexplained rich mixture - or the normal lower vacuum from large throttle openings sometimes being insufficient to lift the valve fully off of it's seat (spring too stiff?), causing lean mixture/fuel starvation at WOT. Reasons why some (wisely) change to a manual petcock. If the fuel tank is located lower than the carb's float bowl, a fuel pump is required to move the fuel uphill, to the carb - scooters usually being vacuum-operated as well, with a similar rubber/cloth diaphragm (without the valve) that's a bit bigger in order to provide sufficient pumping force using the intake manifold's rapid pressure pulses. Vacuum pumps incorporate check valves of some sort, in order to keep the pump primed and pumping fuel in one direction only (towards the carb). Petcocks have no such check valves. Similar troubles as above can apply to pumps as well. Both usually have the same input/output ports - i.e. one vacuum line, a fuel inlet and fuel outlet - and can look quite similar, too. Bottom line... Tank low = pump Tank high = petcock Bob |
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Post by FrankenMech on Aug 26, 2016 19:46:35 GMT -5
Good job moat!!!  I agree it would be very wise to replace that vacuum operated petcock (valve) with a manual one. Fuel starvation (lean) and surplus fuel (rich) will cause almost the same symptoms. There are threads here in the tech section that go into the differences and testing. Stumbling and loss of power result from both. I dislike vacuum operated parts and controls. I still have nightmares about the early 70's cars with a pit of snakes under the hood. Fixing that stuff was a nightmare. I was a mechanic in a service station back then. One does not see many early 70's cars on the road unless they were heavily modified. The cars all died for want of some $2 valve or an inch of vacuum hose. Cars still die today from want of a $2 plastic part, plastic parts SUCK! I still remember vacuum operated windshield wipers too... I have an auxiliary electric fuel pump on my scoot. |
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Post by dan50 on Aug 26, 2016 19:47:46 GMT -5
Thanks Bob. My tank is higher than the carb. I would like to find a manual petcock just to do away with the vacuum garbage. That way It's easier to diagnose fuel problems.
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Post by dan50 on Aug 26, 2016 19:55:44 GMT -5
Fuel starvation (lean) and surplus fuel (rich) will cause almost the same symptoms. There are threads here in the tech section that go into the differences and testing. Stumbling and loss of power result from both. Plug chop about 2 weeks ago was showing brown color (just a hair rich) where it's supposed to be. I put in a new plug and the plug chop today shows white, lean. I haven't touched any settings on the carb, so I'm sure the problem is in the fuel system. The fuel filter is brand new, just changed to see if was the filter, it's not. So, that leaves the petcock or fuel line. My Dad had a car that ran bad, after new carb, filter and pump, it turned out to be the rubber fuel line. It was disintegrating on the ID of the line. I just bought new fuel line and will be putting it on as soon as my scoot cools down (rode about 25 miles to test). Thanks for the help guys!! Dan |
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Post by FrankenMech on Aug 26, 2016 20:02:49 GMT -5
Ethanol in the fuel causes that rubber disintegration inside the fuel line. Older fuel line was really bad when exposed to alcohol. The newer fuel line formulations with different elastomers (rubber) works better. Chinese fuel line is NOT ethanol proof. They don't use ethanol in their fuel made from food. Feeding people is more important to the rest of the world.
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Post by dan50 on Aug 26, 2016 20:13:15 GMT -5
How true Mech. The farmers that plant the land around my Dad's place grow corn for the ethanol plant. It's not really edible, cross-bred for alcohol. That's about 6,000 less acres of food, and that's just 1 farm!
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Post by dan50 on Aug 26, 2016 20:44:09 GMT -5
OK guys, I found an issue that I hope will cure my problem. I opened the carb access panel under the seat (handy), and I pulled the vacuum line off the intake manifold. The scoot started to starve for fuel shortly after that. I put the vacuum line back on and after a few seconds to fill the float bowl it ran fine.
The issue I found was there was no clamp on the vacuum line off the intake manifold. the vacuum & fuel line off the petcock both have clamps. Plus when I removed the vacuum line it was about 1/2 way off the hookup. I put a clamp on it and the scoot started idling real fast. The rear tire was spinning (scoot on the center-stand). I had to back off the idle screw quite a bit to get a reasonable idle.
My thinking is, without the clamp on the vacuum line, at WOT, it was not getting enough vacuum through the line to the petcock. I will test this in a bit.
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Post by dan50 on Aug 26, 2016 20:57:38 GMT -5
I removed the 1k contra spring and installed a new stock contra. I also put the 5 gram rollers back in the variator. I checked the bushing in the variator and the drive boss, there is no slop so neither are worn out (although I do have a new drive boss as a backup).
This setup seems to be the Holy Grail for my Dongfang. Stock contra with 5 gram rollers. On a 25 mile test run, I couldn't tell at what speed the variator fully opened, which is a good thing. I can take off at 1/2 throttle until about 25mph or so, then open the throttle to accelerate faster. All the way to 35mph, the acceleration was smooth and I couldn't feel the engine bog. Before, when the contra opened at about 15 to 17mph, the engine would bog as it wasn't in it's powerband at that speed. Now when the variator fully opens, the engine is well into it's power band and will accelerate smoothly up to about 36mph (into a 5mph headwind).
I will do some more testing to see if I got it right (see post above), but I am confident that I do have the correct tune on my CVT.
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Post by niz76 on Aug 26, 2016 21:39:47 GMT -5
Nice! Sounds like you're getting some of the bugs worked out. It's such a pleasure to ride a nicely running, nicely tuned scoot!
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Post by dan50 on Aug 26, 2016 22:35:30 GMT -5
The vacuum line wasn't the cause of the fuel starving. Tomorrow I will change the fuel filter as well as the new fuel line when the scoot is cool.
The fuel filter is full of gas, so I'm sure the petcock is working.
It might be an electrical problem. I just changed the spark plug and it might be a bad one (hard to believe, it's a NGK). So I will put another plug in it. If that doesn't fix the problem, it might be a bad coil or CDI.
The confusing part is that it just started happening. Just after I changed the spark plug and started to tune the CVT.
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Post by dan50 on Aug 26, 2016 22:44:22 GMT -5
Nice! Sounds like you're getting some of the bugs worked out. It's such a pleasure to ride a nicely running, nicely tuned scoot! Yes it is. I am confident that I have the right tune on my CVT. Now I have resolve the issue of the engine cutting out on me. Either starving for fuel at high throttle, or something electrical. |
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Moat
Scoot Member
Posts: 88
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Post by Moat on Aug 26, 2016 23:49:14 GMT -5
I would like to find a manual petcock just to do away with the vacuum garbage. I've seen these for sale at my local hardware store (sorry FrankenMech... it's plastic!) - Briggs & Stratton - plastic fuel valve Although I like the look of these - appears it'll bolt right up where my ATM50's OEM petcock resides (although I have no idea of the quality) - Cheapo manual petcock on Amazon Or something like this, maybe mounted with a few band/Adel clamps - Motion Pro brass fuel valve Bob |
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