Fuel Starved 60cc with 20mm carb By hitshane (Read 1,217 times)

[hitshane]

So,

    I am driving like a bat out of hell to work along the same road for about ten miles. Half way either way my 60cc taotao starts to lose power. Lowering the throttle fixes the loss of power. It's not over heating and plug chops look great. It starts great and takes off like crazy. The idle is rich, the mid is a little lean and the top end is rich. Makes those takeoffs great! After 4 blocks im at 45MPH and it creeps a little faster where the needle is on the left turn signal and the tran's whine's pitch gets higher.

    I have a new carb with the floats double checked. I have new fuel and vacuum lines and a new petcock, with a huge fuel filter. I blasted the fuel cap with ether and air and that is the only vent for my tank. It has a keyhole in it. I have the air filter clean and the air plug pulled out. I have the best spark plug and the valves are between .003 and .004". I have stock airbox and exhaust with some Pirelli Tires.

The way the fuel cap turns with a key to unlock it I can't see a good way to drill a hole into it. Do I need another fuel cap? With a syringe at the petcock vacuum line the fuel pours out just fine. The engine response is great and it has no surges or backfires of any sort. Should I put the airplug back in the airbox and see if the increased suction will help? Should I get an after market fuel cap and drill a large hole in it?

Can someone with inadequate fuel delivery problems chime in please. The lines and filter are full of gas when I get home. I don't see any vacuum leaks. I checked with starter fluid.

-Shane 

[drahken]

maybe your mid needle is lean and your main jet, full throttle is rich. it started to slow down? what did it do as you held it floored? was it running fine, then it started to make a bboooouugh sound? if it did, the next time, it doesnt hit or anything when it does that, doesnt fire a lick, if it does that, hold it, hold the throttle wide open there, where its at. If, then it starts to backfire and it pops out of your exhaust, then your rich. for sure.

id say it loads up after, however long on your ride, and then starts to get too rich. the bike goes because your lean on the needle to get you up to full throttle.

i had a bike, it ran a dellorto carburetor, and i ran it for a long time and it never showed overheating according to my cht gauge, or having, toooo badd of running issues.

make sure to tune the mixture right, and check needle height and main jet. dont know how many needles you got.
what needle clip setting are you at? thatd be a good question.

Before you do this, check what position the air?fuel mixture screws at, so you can return it to that, and have it so in case if it doesnt work better, you can adjust it back
To tune the mixture, make sure to, do it at right around 1800-2000 rpms. little high on idle speed. change the idle speed, with the idle speed screw, make it just a high idle rpm speed, 1800-200rpm. then, adjust your mixture adjustment screw, to get the highest idle rpm. if it starts to raise the rpms, as your adjusting, let it get a little higher then lower them back down to around what you started at, back with the idle adjust screw. then go back with the mixture screw adjusting. make sure your screw is somewhere between 1 1/4 turns out to not, a lot over 1 3/4 turns out. adjust for highest rpms. once got. use the idle adjust screw, again to lower the rpms back to a normal idle speed. like whatever you set yours at.

[jct842]

Put the plug back. All engines today must have an aircleaner in order to run right.

[Bashan]

Well run it with the cap loose and if it doesn't fizzle it's a venting problem.

[hitshane]

So, I have not been on any long rides as I work about 9 blocks from my house. I went to buy my wife an anniversary gift today and it started losing power again. It feels like the brakes are engaging or something is holding the scooter back. I have to let off the throttle to get the power back. I am fuel starved! I took off the gas cap and continued on my way and it still did it after a few minutes at WOT. I made it to the jewelry store and on my way home it started doing it again. I pulled over and opened my stock air box and put the air restrictor back in hoping maybe this would solve the problem. Nope, 2 minutes later it was doing it again. I have no vacuum leaks and the fuel flows fine with a suction test on the petcock. I have pulled off the carb before and the float is as high as I can set it. The fuel filter is massive and probably holds a half a cup of gas in it. The entire fuel system is downhill from the tank to the carb. Could the petcock be not big enough? Power band is great from idle to WOT. Scooter starts and runs great otherwise. Gas consumption is great. The plug looks fine. The valves have been set twice and checked twice since then with no change in gap. I find lots of these posts about fuel starvation and not really any solution besides blocked vent lines/caps, bad fuel petcock, and dirty carbs. I have none of these problems. Losing power on a 45MPH road in traffic is no fun... HELP!
-Shane

[Alleyoop]

What size main jet have you got in the carb?

[hitshane]

32 Pilot jet, 91 Main jet. 60cc, 20mm carb. Stock (derestricted) airbox and stock exhaust.

[Alleyoop]

That should be more than enough for a 60bbk, Are you sure IT IT NOT TO MUCH FUEL?

Do this open it up at wot open throttle and when it ACTS UP BACK OFF THE THROTTLE 1/8 to 1/4 of an INCH AND HOLD IT THERE.
NOW PAY ATTENTION TO WHAT THE MOTOR DOES:
A. Does it speed up
B. Does it settle down and just runs good there
Alleyoop

[drahken]

i had a problem, alleyoop has a good suggestion there, his test. uh, my bike was rich i found out. when id hold it wide open, itd run good, for a good half a mile maybe even a mile. but after it warmed up some and stuff, id be going along pegging it, held wot. then all of a sudden, bwaaooohhhh. if i didnt let off the throttle, usually, id hear a loud, pow from the exhuast. i was rich. i lowered the jet one size at a time until it didnt do that no more. i had a temp guage that told me my temps and i was all good. but id hold the throttle when this kept happenning, wide open, when itd happen then, evenutally like maybe 10 seconds later, not letting off the throtlte, to see what would happen. Pow. exhaust would go. backfire. figured, from the gassy smell, the smoke, and the freezing cold intake manifold temp when i touched it right when it done this, or short after after i stopped it to touch it, it was cold.

a thing you could do to check for fuel starvation, are you running clear gas lines? stop it as soon as it stops, and check the line to see if its empty.

[hitshane]

If I let off a little bit while its braking fast, it wont catch up or do anything right away. If I catch it right when it starts it will smooth out where im holding the throttle. Sometimes pumping the throttle does nothing just complete loss of power. It never pops or surges, it just loses power and the RPM's drop...

Last time it did this I cleaned the carb and thought I had bad gas and drained it, then with new gas it worked fine. That happened two times and now a third. I only fill up like once a month. I drive the scooter locally every day to and from work 2 miles round trip. What are the odds I got bad gas 3 times out of the last 5 months?

I took my pilot off tonight, because after I replied to this post today, it was idling like crap sounding really rich and low, so I took off the carb. The pilot jet was clogged and long story short I grabbed a new one from a local shop. I put it on and its idling great, but now it wont rev it just dies. I feel like if I changed the gas out it would work fine. The fuel was fine for the last week since I filled up and is still full. I really don't get it. Everything along the fuel system is new. If changing the gas doesn't work out tomorrow I'll just put it up until I get a new carb, because even if I get the bike back running like I have the last two times, I will still have the WOT fuel issue...

-Shane

[drahken]

try finding what carb or bike yoru bike copied if its a copy and get the original equipment, from honda, or yamaha. whichever one, works, fits.

[Alleyoop]

Well you do what you want, I suspected the main jet was to big which is what most people do thinking dump a crap load of fuel and I will have a storming machine(NOT). That is why I asked for the jet size,
and your problem is running to rich, try an 80 or 85 main jet.

[hitshane]

I cleaned out the carb again with air and blasted every nook and cranny. I reran the fuel line without the petcock and installed a manual shutoff and capped the vacuum line. Drained the fuel and got fresh gas. It fired right up but wont idle. I have to hold the throttle about halfway and it just sputters and does a rat tat tat tat rat tat tat sputtering like. It almost sounds like a 2 cycle dirt bike. It is blowing white unburned gas out of the exhaust. Everything is exactly how I have had it since I got the new carb installed by a local dealer. They installed the jets for the bike and it ran great except for the 3 times it has had issues. Cleaning it and fresh fuel have always fixed the issue.

I will look for a different carb. I'll go for your recommendation of a 80-85 main jet. There must be something wrong with the carb I have that is an intermittent problem. Either that or the engine has a valve that sticks sometimes or something. The carb does not have that many parts and I have had it opened up 3 times now in the last day. Nothing is missing or out of place.

Thank you guys for all of your help so far!!!

-Shane

[Guitarman]

Drain all your gas out into a gas can. Take the fuel tank off and look inside it. How much crud do you see? CLEAN it out REALLY clean. Had the same problem on a Ducati and it was crud in the tank. Its real small and can get past the filter but clogs the jets. You have to use a good solvent to really get all the crud out. If it's a cheap plastic tank, then just replace it.

[hitshane]

So, I bought a new carb for $23 from a supply store close to me. It is the 20mm with the metal top. The jets it came with are not numbered. I tried to run it as is and it wouldn't start. I pulled the jets from my carb and installed them. Started right up! I messed with the mix and idle screw and got it as good as I thought I could, but it seams too rich at idle even with a 32 pilot jet.

Scooter runs smooth through the whole range, but it lacks the responsiveness it had before. I think the old carb had an air leak or something, then some of the passages must have got gunked up. I was probably running lean before and boy did it go! So, being as the dealer I got the carb from tuned it with that problem, my needle and main are most likely too rich. It has a 32 pilot and a 91 main jet with the needle in the middle. Should I lean out the needle a notch and drop the main jet to an 80 or an 85 (or was the scooter supposed to be this sluggish the whole time ?

Any recommendations would be great! It is a 2013 TaoTao 60cc...

-Shane