Fuel Flow Problem -- APC Mini Chopper - Pocket Bike Forum - Mini Bikes
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post #1 of 55 (permalink) Old 03-31-2011 Thread Starter
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Fuel Flow Problem -- APC Mini Chopper

My 43cc APC Mini Chopper (well it might be a chinese clone) seems to have a fuel flow problem. It will run for only 30 seconds by using starting fluid and then stalls.

After trying to start (pull cord or electric) I lose fuel flow to the carb. I get fuel flowing to the carb again by applying suction with a straw to the fuel line and immediately attaching it to carb. I end up repeating this process of trying to start, losing fuel flow, and applying suction to get fuel flowing to the carb again.

NOTE: Attempting to start seems to be what kills the flow. If I remove the line after priming (without trying to start) the fuel flows out of the line.

OTHER NOTES: When I got the mini chopper the primer bulb was destroyed so I bought and installed a new carb (15mm venturi opening) and fuel line kit with filter stone last month. I installed the black tube on the curved supply fitting and the clear tube on the straight return fitting. Also, have a new plug in it and fresh fuel and 2 cycle oil mixed at 1:32 ratio.

Anybody know what I am doing wrong? Or how to fix the fuel flow?

Thx,
Matt
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post #2 of 55 (permalink) Old 03-31-2011
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Re: Fuel Flow Problem -- APC Mini Chopper

It probably needs a quick clean at the intank filter and bumped up on the lsn richer....a fast simple carb clean couldnt hurt either

open the fueltank by removing the cap and with a piece of coat hanger fish out the intank fuel strainer/clunker on the black line and if discintigrated replace it aswell as wash out the tank...if dirty simply clean it with carb cleaner and replace back into tank making sure theres no kinks in the line when dropped in.....

Remove the carb

Take out the lowspeed needle which is the slotted brass screw on the carb throttle rotator where the cable connects to.................



...Its set tight with epoxy and must be reset with 1hour set epoxy again to prevent the setting from wandering from harsh engine vibes while giving time for finetune adjustments if needed when you get it running...

take out the hsn on the carb side and dont lose the thin washer , metal spring or small rubber-o-ring attached to it..

Take carb cleaner in an aerosol can and stick the straw into the hsn hole and hold the throttle wide open and spray 2-3 3-5 second bursts into the carb then clean up the outter body and old epoxy from the low speed needle

mix up a very small bit of jb weld and put it on the threads of the brass lowspeed needle and screw it all the way down and back up 1 5/8 turns and leave it..

install the hsn into the side of the carb and set it to 1 1/4 turns out....

set the barrel rotator to 1.5mms open with the small philips idle screw and reinstall the carb making sure that the gaskets for the intake on the purge port hole lines up with the hole in the carb and that you install the carb lines back on correctly...the black line with the clunker filter is hooked to the large port on the carb and the clear line is the small nipple port...If gaskets look questionable make new ones out of .025" thick rolled fiber rubber gasket material and a sharp razorblade,,,having a hole puncher is bonus too

If that dont work the diaphragm may be too dried to pump correctly and a new carb may be needed..

Does your chopper look like this one?


Last edited by CAM2; 03-31-2011 at 03:42 PM.
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post #3 of 55 (permalink) Old 04-01-2011 Thread Starter
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Re: Fuel Flow Problem -- APC Mini Chopper

Thanks for the instructions. I have a question though. Is the high speed needle "mixture" screw?

Second...this is a new carb. Is it common for new carbs to have a bad diaphragm?

My chopper is similar style but a different chopper than your link... this is what it looks like (but mines black):

http://www.truckaddons.com/images02/...hopper_LG2.jpg
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post #4 of 55 (permalink) Old 04-01-2011
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Re: Fuel Flow Problem -- APC Mini Chopper

Ok well in that case the dried lines will be a problem because they shrink first before they dry up.....

Then the other thing would be to check your carb install again.....Theres a small hole in the intake manifold that must be clear so the engine pressure can pump the diaphragm in the carb to get fuel into the engine..The gaskets can be easily put on wrong at either the engine block or at the carb..Theres even members who put the carb on 180 degrees on wrong.Make sure the lines are on the right nipple ports too...Large port is for the black fuel feed line..

Take pics and post how its mounted now...

The screw on the side is a mixture screw for the high speed side....the one on top is for startup and idle a/f mixture control......
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post #5 of 55 (permalink) Old 04-01-2011
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Re: Fuel Flow Problem -- APC Mini Chopper

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Originally Posted by svt_ct View Post
My chopper is similar style but a different chopper than your link... this is what it looks like (but mines black):

http://www.truckaddons.com/images02/...hopper_LG2.jpg
Mine started out looking like that one...I was given two pieces of crap for free and decided to make a suburban ghetto hopper chopper out of one by chopping them up and ratting one out with a bit of Redneck low budget style thrown in...........




Last edited by CAM2; 04-01-2011 at 02:18 PM.
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post #6 of 55 (permalink) Old 04-02-2011 Thread Starter
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Re: Fuel Flow Problem -- APC Mini Chopper

I got it running....fuel supply and return were reversed. When you said the large fitting is the supply it got me thinking. Thanks again CAM2.

When I got this mini chopper it was mostly apart. I was misled as to how to connect the supply/return connections by page 9 of this scooter manual: http://www.neoscooters.com/pdf/trex602a.pdf
I thought it would be accurate because it is a 43cc carb and the carb picture on page 6 looks the same. I guess its an error or their fuel line colors are reversed.

Quote:
Originally Posted by CAM2 View Post
Mine started out looking like that one...I was given two pieces of crap for free and decided to make a suburban ghetto hopper chopper out of one by chopping them up and ratting one out with a bit of Redneck low budget style thrown in...........
I did not realize yours is the same bike, just chopped. Thats cool...I like it. Two motors on one bike is also really cool.
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post #7 of 55 (permalink) Old 04-02-2011
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Re: Fuel Flow Problem -- APC Mini Chopper

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Originally Posted by svt_ct View Post
I got it running....fuel supply and return were reversed. When you said the large fitting is the supply it got me thinking. Thanks again CAM2.

When I got this mini chopper it was mostly apart. I was misled as to how to connect the supply/return connections by page 9 of this scooter manual: http://www.neoscooters.com/pdf/trex602a.pdf
I thought it would be accurate because it is a 43cc carb and the carb picture on page 6 looks the same. I guess its an error or their fuel line colors are reversed.


I did not realize yours is the same bike, just chopped. Thats cool...I like it. Two motors on one bike is also really cool.
Thanks man for the good words and hoped it would be something simple and it was also no problem;-you did the actual work..Good job getting it fixed up and running.........Have fun with it...


EDIT: I just got done going over that website you posted and alot of tuning stuff is misleading especially where it shows the screws used to tune the carb...They forgot the lowspeed needle placard and forgot to mention it...No wonder alot are having troubles getting them tuned in.............

Last edited by CAM2; 04-02-2011 at 09:45 AM.
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post #8 of 55 (permalink) Old 08-08-2012
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Re: Fuel Flow Problem -- APC Mini Chopper

Hey I'm Working on My Mini Bike Chopper Thing Look's Just like that.. The Engine Has Great Compression But.. it Don't idle???? i can Only start it when i Spray Starter Fluid in the Carb .. But i Tor Apart the Carb it Looked Brand New Clean!! i was amazed but i Cleaned it anyways.. and i tryed starting it.. but it wouldn't start without me Spraying Starter Fluid in it.. when i let go of the Gas it Cut's out.. as Long as i Hold it.. it will Keep Running??????????? Please help
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post #9 of 55 (permalink) Old 08-08-2012 Thread Starter
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Re: Fuel Flow Problem -- APC Mini Chopper

I had the same symptoms and my fuel supply and return lines were reversed. Check your lines. The black supply line goes on the fatter nipple and the clear return line goes on the thinner nipple. If that doesn't work I would follow CAM2's advice above on cleaning and setting up the carb.

'?? APC Mini Chopper
'99 Ford Contour SVT
'07 Harley Street Bob - FXDB
'78 Winnebago Minnie Winnie
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Re: Fuel Flow Problem -- APC Mini Chopper

Hey how are you I'm new to this web site an have never posted anywhere be4 so sorry if this is not the right place to ask an if it is plz help me to the right place to post. Let me start off by saying that the bike with the twine engine looks mad, i seen it a week a go an I have to ask on help with makeing my lil bike work with to motors on it, so if u could can I have some more pics an any advice for someone new to makeing coutm bikes. All so duZz it work good is there anything to look out for. Thanks for all ur time an sorry if I'm being rude at all I don't no how this all works. Mikey
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Re: Fuel Flow Problem -- APC Mini Chopper

Welcome to the forum and adding two engines to a single frame is pretty straight forward......You just have to heve tools like a saws-all,drill,,welder and a few others...

Both engines are mounted so the forward engine is staggered right 5/8" more than the rear engine so it makes linking the two together easier...

On my project the rear engine was already aligned and afixxed so it was natural to stagger the engine outwards but most would mount them perfectly inline................

For my project after it was built it was necessary to refine the design and add some space between the engines...In my future plans I tend to have two dominator revpipe designs on both of the engines,,hp walbro carbs,,velocity stacks and a lil more agressive powerporting to really make them rev higher to get even higher topend speeds............








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Re: Fuel Flow Problem -- APC Mini Chopper

Wow thanks 1st off for the fast reply an a big thanks for your time. One quick Q... Have you got a dule cog on one of the engines or did u make something up?
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Re: Fuel Flow Problem -- APC Mini Chopper

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Wow thanks 1st off for the fast reply an a big thanks for your time. One quick Q... Have you got a dule cog on one of the engines or did u make something up?
I made something up............I used a 17tth freewheel sprocket I modded to fit so its easier to push around...the 17 tooth sprocket is larger than the stock 12tth so i get nice topend speeds......On the outside I have the stock 12tth sprocket

The sprockets are sandwiched together on the shaft using a bolt and a washer.....It took a machine shop to drill and tap the shaft because its really hardened which was surprising to me........

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Re: Fuel Flow Problem -- APC Mini Chopper

I have question on a mini chopper. After reading the threads and double checking the black hose to the bigger nipple on carb. All is good there and I siphoned it to run freely before reinstalling, however I cannot get fuel flow into the primer bulb when pumped up? Any ideas? thanx, Scotty
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Re: Fuel Flow Problem -- APC Mini Chopper

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Originally Posted by scotty1031 View Post
I have question on a mini chopper. After reading the threads and double checking the black hose to the bigger nipple on carb. All is good there and I siphoned it to run freely before reinstalling, however I cannot get fuel flow into the primer bulb when pumped up? Any ideas? thanx, Scotty
Sounds like the orange one way check valve in the primer bulb isnt doing its job...



Have you checked to make sure the return line is clear?

A new carb is like $10.00 shipped..

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Last edited by CAM2; 03-09-2019 at 09:24 PM.
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Re: Fuel Flow Problem -- APC Mini Chopper

cam2
Both fuel lines are new. With Filter
How would I I'D the carb for parts or a replacement?
For $10.00 a new one would prolly be easier, maybe?
Where would I start looking?
I don't even know the manufacturer.
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Re: Fuel Flow Problem -- APC Mini Chopper

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Originally Posted by scotty1031 View Post
cam2
Both fuel lines are new. With Filter
How would I I'D the carb for parts or a replacement?
For $10.00 a new one would prolly be easier, maybe?
Where would I start looking?
I don't even know the manufacturer.
The carb is a 15mm WYK192 walbro knockoff.

You could pay 10 bux for just the carb alone or a lil more for one with a velocity stack plus hp airfilter too....

Good Luck

https://www.ebay.com/itm/15mm-2-Stro...YAAOSwvjtceEv4

https://www.ebay.com/itm/Carburetor-...sAAOSwEzxYRLVE

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Re: Fuel Flow Problem -- APC Mini Chopper

Cam2 ,
Thanks for the info and the lead. Ordered it and should be in a week or so.
Will tell how things go after I receive it and install
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Re: Fuel Flow Problem -- APC Mini Chopper

Great information on the mini chopper 43cc engine starting problems. I picked up two of these bikes for a song. One is gas and the other is electric. Both are ruff but the gas one was more complete so I attempted to fire it up and it does run but with problems. I am going to attempt to restore it back to original as much as possible. I have a running custom one with a 212cc Predator engine, fat rear tire and peanut fuel tank. The thing goes like a bat out of hell. Anyone out there have an extra fake fuel tank they would like to sell?
Thanks for the info posts,
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Re: Fuel Flow Problem -- APC Mini Chopper

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Originally Posted by oldguyminbikeNUT View Post
Great information on the mini chopper 43cc engine starting problems. I picked up two of these bikes for a song. One is gas and the other is electric. Both are ruff but the gas one was more complete so I attempted to fire it up and it does run but with problems. I am going to attempt to restore it back to original as much as possible. I have a running custom one with a 212cc Predator engine, fat rear tire and peanut fuel tank. The thing goes like a bat out of hell. Anyone out there have an extra fake fuel tank they would like to sell?
Thanks for the info posts,
Oldguyminibikenut
Welcome to the site....I checked my spre parts and it seems I may of thrown it out or put it somewhere in a really good spot..............

I'd love to see the 212cc one you built...I was gonna do one but opted to go with a twin 43cc design.

Im pretty sure you can get a fueltank cover from fancy scooters or ebay..

Fancy Scooter: Gas Scooters and Electric Scooters Retail and Wholesale

Good Luck








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Last edited by CAM2; 03-21-2019 at 01:01 PM.
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