Float level... Switch the carbs between your 2 ds's just to check...

 

That is an excellent idea - Thanks

 

OK, so I was at the dunes again on Saturday testing my Baja X that dies while climbing. I did go through the gas tank, cleaned it out, and made sure there was nothing limiting the tank breather tube.

I also changed the oil and now have the right amount of the right stuff in there, but it still dies when ridden aggressively.

When my son rides the bike (fairly aggressive) it dies, but when my wife rides the bike (she is not very aggressive) the bike works fine. I think this points fairly conclusively at a carb issue

So, the next thing to check is the float level and then pull the carb to see what is up. I will be doing this soon as I have a trail-riding vacation planned in two weeks.

 

It definately sounds like a low float level. That is where I would have started. Under hard riding the float goes dry and cant keep up with the fuel demands. If your just cruising around its able to keep up...

 

Thanks for the confirmation, yes I probably should have started there but the oil needed to be changed and it is easier to check the tank breather tube, so that is where I started and then had no more time before my trip.

Always start with the simple stuff is my motto. Because low float level and partially restricted breather tube carry many of the same symptoms, it just makes sense to start with the breather and making sure the tank is clean inside and the petcock is flowing.

 

So here is an update. . . The 2004 baja X was at the dunes and did OK when it was ridden nice and easy, dies when ridden hard. Except now there is a new development.

The bike now will start, but it will not run for very long before it dies. While it is deciding to die, it backfires quite a bit and then it just goes down. Doesn't seem to matter what RPM the engine is at either.

Yes, I have now checked and cleaned the entire fuel system from the engine all the way up to where you put the gas in. Carb is clean, float level is just about right (the clear tube test tells me that the flot level is right below where the fuel-line enters the carb). Removed the jets, cleaned them, pshed cleaner through all the channels in the carb, etc. Petcock and tank are clean, and there is nothing obstructing the gas tenk vent hose.

I am starting to lean toward a faulty CDI box. However, I am thinking that maybe the valves need to be adjusted. But really don't know how to tell if this is the problem.

If the valves need to be adjusted, I would really appreciate a link(s) towards threads or online instructions of some sort. That would really help.

Thanks in advance for any help you can give me.

 

So I just read somewhere that having the valves out of spec wil not necessarily make the bike run crappy or shut down. Now I am really confused.

What is the deal here?

 

If your carb is truly working correctly (AGAIN, TRY SWAPPING THEM), then I have another suggestion for you.

In my Kid's Sunl, the voltage regulator went bad and was pumping too much voltage to everything - making everything hot and causing the overheated coil to stop providing spark and the engine would die. After 10 to 15 minutes, the electrical system would cool down and would fire up like everything was fine - until it warmed up again and this would repeat. A tell tale sign (A multi-meter can tell you as well) is a battery that is juicing (gassing) and running dry.

Again, I would try swapping carbs first, then you can chase electrical demons.

 

I have now tried all of those things. New CDI, swapped carbs, 14.6 volts charge when running (about 20 seconds is all I get before it dies). The bike got a new top-end before I bought it - I am wondering if the timing is off or something internal? I read somewhere that spark plugs or the coil can go bad and cause issues close to what I have, so I am checking those things next.

I will have to find some instructions for checking / resetting the engine timing and chain - maybe the chain was not set right or has skipped a tooth?

 

Quick update - I pulled the spark plugs this morning and found that neither of them have any gap at all, the ground electrode has been pushed right up against the center post. No wonder it is not running. I don't know if the piston did this or if whoever installed them dropped them or something.

I am now looking to see if there are other issues like maybe the head was planed when the rebuild was done, so the plugs now stick in too far, or if there is something in the cylinder.

I plan on (a) checking inside the cylinder, (b) using a thrust caliper to measure the headspace between the cylinder and the plug hole, and (c) putting in new plugs with the correct gap and maybe a few indexing washers if I need them to keep the plugs away from the piston.

I will post to let everyone know what happens.