Yerf Dog 3206 Go Cart Troubleshooting

Yerf Dog 3206 Go Cart Driveability Problem

Shortly after I drove my Yerf Dog 3206 go cart for the first time, I began to notice a driveability problem.  The GY6 engine would hesitate slightly at higher RPM's.  The problem persisted and seemed to get progressively worse.  Since I've had the opportunity to work on many different engines over the years, I began with some basic troubleshooting to try to track down the problem.  After checking many likely culprits, I finally discovered something!  The go carts fuel filter was almost totally plugged up with plastic shavings that were accidently left in the tank during manufacturing.  The go cart gy6 engine only had maybe 7 hours run time at this point.  When I saw this, I figured that this must have been it - the engine was starving for fuel.  Here's what I found in my fuel filter...

GO CART FUEL FILTER PLUGGED WITH PLASTIC SHAVINGS

At the time that I discovered the plugged fuel filter, I decided to upgrade the fuel tank to the Carter XTV go carts tank.  I did this not only to gain more fuel capacity but also to eliminate the Yerf Dog tank design which tended to leak fuel out of the cap vent.  CLICK HERE TO READ MORE ABOUT THE CARTER XTV GO CART GAS TANK UPGRADE.  So, I installed the new tank along with some new fuel line and a new inline filter.  I figured that now my go carts GY6 engine would finally run right!  WRONG!

The problem was still there!!!  I was really getting stumped on this one.  I thought that maybe some tiny particles of plastic has made it past the filter and lodged themselves within tiny internal carb passages.  This was a bit of a stretch, but I has already checked out many other things and wasn't sure what to do next.  It seemed very clear to me that the problem was with the go carts carburetor.  I say this not only because of the way the engine acted, but also because when I pulled the spark plug to read it, the center insulator tip was white showing a very lean air/fuel mixture.  This was particularly suspicious because I live at an elevation of about 1 mile above sea level (~5200ft).  At this elevation, carbureted engines tend to run very rich because there is less oxygen in the air, and a simple carburetor can not adapt for this and adjust the A/F mixture like a more complex fuel injection system.  So, I strongly suspected something was not right with the fuel system.  Unlike many of the engines I've had to troubleshoot in the past, this go cart GY6 engine was nearly brand new so it made the problem more puzzling.  Most of the engines I've worked on have been old and there were many areas to suspect as possible sources of problems.  On this new engine, it was a little more of a mystery - especially since I had already checked, double checked, and triple checked the most likely causes.  What changed...  what was different...  what could possibly be causing this - especially on a nearly new engine?!?! 

I removed the carburetor from the go cart and took it apart.  I did not find anything inside that would indicate a contamination problem.  Even so, I removed the main jet and partially disassembled the carb and blasted out the passages with carburetor cleaner and compressed air.  I put it back together and took the go cart out for a test drive again.  Although the hesitation problem seemed to be less (probably coincidental), it was still there.  To make matters more confusing, the hesitation and sputtering were getting progressively worse.  Not only was it isolated to high engine RPM's anymore, but it seemed to be occuring sooner (at lower RPM's).  I was really puzzled.  I won't go into every detail, but I checked, and re-checked, and checked again the areas that were most likely causing this.  Still, no change!  I was beginning to get very frustrated with my new go cart!

Finally, I decided to dig in and remove the carb and take it apart again.  This time, I took it apart even further.  I could see nothing wrong that would explain the problem with my GY6 engine.  Just as I thought that I was done and there wasn't much more I could do, I decided to remove a small cover off the side of the carburetor.  This small, round cover had a fitting with the vacuum line attached to it.  I figured that this was just an open vacuum chamber/passage inside, and the first time I just bypassed this figuring there was nothing in there worthy of checking.  When I took the cover off, I discovered a spring and diaphragm.  I'm not talking about the big diaphragm at the top of the carb that actuates the main needle in and out of the main jet.  I had already checked that big diaphragm earlier and it was fine.  This smaller diaphragm (about the size of a quarter) was different.  It appeared to some sort of "pump" that ran off of the vacuum pulses from the intake manifold.  This smaller diaphragm is located behind the small round cover with the vacuum hose attached - located toward the top of the carb in the picture below...  

DEKNI PD24J GO CART CARBURETOR

When I removed the small diaphragm, I saw a BIG problem!  The diaphragm is made of a fabric mesh type material that is overmolded with an rubber-like elastomer.  It appears that this particular diaphragm was defective, and the overmolded rubber was separating from the fabric underneath.  The rubber material was cracked in a few different areas and peeling off.  Basically, the diaphragm had holes that were progressively getting worse as the rubber was separating further from the mesh underneath - making the leak worse and worse.  That would explain why my go carts GY6 engine was progressively running worse and worse.  You can not see all the areas where the diaphragm is cracked in this picture, but you can see one of the worse areas (around 8 o'clock) where the rubber has separated from the fabric mesh underneath creating a big leak....  

LEAKING CARBURETOR DIAPHRAGM

Finally, I found something that could explain the hesitation and driveability problem of my go cart!  I spent many hours troubleshooting and thinking about this problem, and I was beginning to get very frustrated!  It was especially frustrating because the problem was getting worse and the go cart was barely driveable toward the end.  It just sputtered, coughed, and bucked when I applied the throttle.  Earlier, I could not find anything that would be causing this... it just didn't make sense!  Hopefully, this detailed description will save others the HOURS of troubleshooting that it took me to get this far.  Even better... hopefully this problem will be very isolated and other owners of these go carts will not have to worry about it.  The nice thing is that this small diaphragm can be checked relatively easily without even removing the carb - which unfortunately I am now an expert at doing!  All that should need to be done is simply remove the 2 screws holding the throttle cable bracket to the carburetor, move the cable aside, and then remove the 2 screws from the small round cover.

IMPORTANT UPDATE 12/22/03:  I wanted to follow up on this GY6 driveability problem.  Once again, Yerf Dog Customer Service was very good.  All I really needed was the small diaphragm, but they did not have that individual part in stock at the time so they immediately shipped out a whole new carburetor for my go cart.  I installed the carburetor and the engine ran better, but some of the high RPM sputtering was still there!  To make a long story short, I began to do MORE troubleshooting and I finally ran across a big culprit of all my driveability problems.  There was a loose electrical connector on the primary side of the go carts ignition coil.  In the picture below, I have drawn an arrow pointing to the ignition coil connectors that I am describing here....

On my gy6 engine, the lower connector was loose.  It was still "connected" but when the engine would vibrate more at higher RPM's, the loose connection began to go intermittent and the ignition was firing erratically.  My lower connector on the coil was badly pitted from the arcing of the intermittent connection.  I cleaned the connection with some abrasive pad and sandpaper and then took some pliers and gently crimped down on the female connector (while it was disconnected) to tighten up the fit with the male blade connector on the coil.  You have to be careful not to apply to much pressure with the pliers or else you can smash the female connector.  I made sure that these connections were clean and tight and then I took my go cart out for a test drive.  FINALLY THE HIGH RPM SPUTTERING WAS GONE!! 

If you are experiencing a driveability problem on your go cart with the gy6 engine sputtering and not running right, then be sure to check ALL your electrical connections to make sure they are tight.  There are more electrical connections underneath the plastic black box on the driver's side of the engine.  Obviously, based on my own experience, I would strongly recommend checking your ignition coil connections first and make sure that they are nice and tight!  I am not sure if swapping connectors (switching polarity) on the primary side of the coil would cause any problems, but it would probably be best to take note which connector is on which blade before disconnecting them so you can put them back the same way.  Just for reference, on my kart the lower connector had a purple wire.  

BACK TO MAIN YERF DOG 3206 & 3209 GO CARTS PAGE                              BACK TO SITE HOME PAGE

MORE POWER!...   THE ULTIMATE SOURCE OF POWER