Carburetor Problems

Posts: 16 · Newbie Joined: 06 Jun 2008 Posts: 16 Pictures: 0

Hi,
I have a Baja Motorsports Dune 150 that has been giving me fits for so long I'm about ready to give up on it. What it does is leak fuel out the carb whenever the petcock on the tank is opened. I messed with it for a long time with no luck, and ended up buying a new carb, which immediately did the same thing! This makes me suspicious that the problem is not the carb, but something I didn't replace thats making the carb behave this way, but I don't know enough about this engine to figure it out. I'm hoping one or more of you can help me with this, and make me a hero in my kids eyes!
Looking at the attached picture of my old carb, the fuel is leaking out of the round hole that is at about 7 o'clock in the picture. The old AND new carbs both do this. Can anyone help me with this?
Thanks in advance,
Jim

Posts: 4286

sounds like the float needle is stuck or will not close. does the float needle move up and down in the seat easy? also might check the float level

Posts: 16 · Newbie Joined: 06 Jun 2008 Posts: 16 Pictures: 0

I've re-adjusted the float level many times on both carbs with no luck. I've also cleaned the needle and seat each time I've had the carb off, and checked the operation/sealing of both the needle and seat and the float. I don't have much experience with these particular carbs, but I've worked on many automotive carbs that have the same type of needle/seat/float, and I can't find anything wrong with any of these parts in either carb. Plus it just seems so unlikely (although not impossible) that a brand new carb would have the exact same problem as my old one right out of the box.
Does the float bowl need to overflow to have fuel coming out of the hole in the picture? I can't see how they are connected, except through the electronic valve on the side. Is it possible that this valve is bad and isn't closing when it should? Anyone know what the purpose of that valve is?
Thanks,
Jim

Posts: 4286

there should be a rubber hose on the side that makes a 90 degree bend, thats the overflow. the by starter valve or choke is the electric part on the side.

remove it and measure the length, hook 12 volts to it and let it sit for 10-20 minutes, then remeasure it.

Posts: 16 · Newbie Joined: 06 Jun 2008 Posts: 16 Pictures: 0

Posts: 4286

yes I ment the choke, sorry about that. after you remove the choke measure the length from the top of the black part to the tip of the needle. you will be looking to see if it get longer

Posts: 1893

Is it possible you reversed the lines going to the carburetor? Looking from the rear of carburetor, the left barb should be fuel and the right barb is the vacuum off the intake elbow.

Posts: 1684

Posts: 16 · Newbie Joined: 06 Jun 2008 Posts: 16 Pictures: 0

Thanks guys. I know I don't have the fuel and vacuum lines crossed. In fact, I know that I have everything hooked up correctly, because I took pictures of it before removing the carb and used those pics as reference when I put it back on.
I didn't have time last night, but hopefully I can test the choke valve tonight. I assume it should shut off fuel flow when no electrical is on, and opens to enrich the fuel mixture when the engine is cold? I'll report back what I find.
Thanks again,
Jim

Posts: 1893

The electric choke actually works backwards of the way you described. The choke is always energized when the the engine is running (powered off the AC stator line on GY6 engines and through the rectifier/regulator on CN250s). When the choke (not the engine) is cold, the pin is retracted and the carburetor enrichment circuit is providing additional fuel. When the choke body starts to warm up, the pin extends and blocks off the enrichment circuit.

You need to check two things:
1. Voltage is present at the connector when the engine is running
2. The choke pin extends after 10-20 minutes when voltage is applied