Bill and Joann, right. I exchanged emails with him awhile back and got them mixed-up with Sully Dirt.

 

I don't want to hijack this thread, but I have a question or two that relate.

I have 2 symptoms with my bike that would indicate (I think) that I am running lean. First, my header pipe has blued quite a bit, which I understand from folks here would imply hotter than normal exhaust gasses, which would indicate a lean condition. Second, I get a little bit of "stuttering" when cruising at around 35-40mph with the tach at about 4500-5500rpm. This is extremely subtle. Actually, for the longest time I was convinced it was a front suspension issue because it really is more like a slight bouncing of the front end. The engine sounds smooth, but I think there is just the slightest bit of hesitation in this range.

My setup is as follows: #130 main jet (recently upgraded from #128 - some improvement), stock pilot jet (#40 on order from ronayers.com), N1TC need at 3rd slot (recently moved from 2nd slot - some improvement). Double snorkel & Muzzy exhaust. I live at about 1000 ft. above sea level.

I have been proceeding under the assumption that I need more fuel, thus the move from the #128 to the #130 and the clip change. Both have had some improvement, even clearing up some lean pop on decel that I did not really think was there but now I see it was because the decel is much smoother. I still have the bounce in the mid-range to some extent, though, so I am about to put in the larger pilot.

I raise this question here because Marty suggests more air. I don't really know how to diagnose the different between lean versus rich. I know I need to pull my plug, which I haven't done. Other than that, does it sound like I am barking up the right tree with getting more fuel in there, or I am going in the wrong direction?

Thanks,
Chris

 

Yep, that's the gentleman! Fine fellow. Not too many folks you feel comfortable sending a $300 piece to to work on. He's the exception.

Looking forward to getting the carb back. I'm hoping this week! I want to see what it will do for the KLX!

 

Chris,

I keep going back to the HMF Engineering website and reading the commentary by MotoZ about removing the airbox lid altogether and getting 1.5 hp! I mean that's pretty cheap horsepower.

Is the KLX250S a well set up motor that has been "corked up" on both ends to meet EPA requirements? I'm starting to believe this to be true.

Adding fuel and air is making it better.

I had a bit of "whateveryouwanttocallit" with the KLX above about 8000 rpm. But it went away with the HMF pipe. I might just pull the airbox lid this evening to see what happens.

I hate to say it, but unless you're running some sort of 'sniffer' you are not going to really know rich or lean. Remember, it can be rich down low, lean in the middle and rich on the main jet.

I do believe Nobrakes was looking into a "Poor Man's Mixture Diagnotic" tool made from an O2 sensor. Any additional information on that would be very helpful. Maybe we can hook up a Palm Pilot to something, connect it up to our bikes and have the ability to record it as we make a run, holding it at certain throttle openings to find out if we need more on the bottom, more in the mid-range or more jet. That sure would be a nice addition.

 

Well, that does it. I am going to pull my lid tonight as well. I have resisted it because I like the idea of being bulletproof regardless of what I run into, but the fact of the matter is that unless I make a big mistake, I am not going to be in water deep enough to cause a problem.

Marty, I think you have hit the nail on the head. I think I am good down low and on the high end, especially now that I have the larger main jet and more agressive needle position. I think once I add the larger pilot, it will give me a little more room on the air/screw (currently pretty much maxed out at 2.5 turns out) which will hopefully smooth things out a little in the middle. If not I will move the clip another notch on the needle. Actually, I will probably go ahead and do that when I am in the carb next anyway.

I am realizing that we are just going to have to figure this bad boy out by trial and error. I definitely agree that more seems to be better in the air & fuel categories.

Thanks,
Chris

 

I'll let you know what I come up with. I need to get the sensor and see how big it is. Depending on its size, and how to fit it, I am thinking about buying a separate Muzzy mid-pipe section and mounting the sensor in that. With that, I'd be able to install the modified mid-pipe with the sensor in place, take my readings and get the jetting correct, then replace the mid-pipe with an unmodified one. This is just a thought - not sure if I'll need to do that or not, but the sensors need to be a ways down the pipe and in or near the header pipe. The separate mid-pipe that the Muzzy uses would be a convenient mounting point and hopefully not cost too much to buy an extra one. Otherwise, I think you'd need to make some sort of long tube to get the sensor far down into the pipe from the tailpipe opening at the end and get some wire with high temp insulation.

 

Awesome! I have a feeling it will do wonders.