"Ping" sound after pilot jet change - '99 KDX200

[paul6585]

'99 KDX 200 Air box lid is removed and silencer is stock. I ride near sea level in NJ. Jetting was 45/155. I recently added a pro circuit pipe, did WOT chop then changed main to 152. Air screw was 3 turns out (since 1 yr when I purchased) and low end a bit sluggish so I switched pilot to 42. Engine seems more responsive on low end but now I have a distinct pinging sound when lugging around at low rpm and I am concerned. I recall a recent thread mentioning pinging but can't find it. can anyone provide some insight?
I also went through a new set of brake pads in about 100 miles (mostly mud) is this normal? I am fairly new to dirt bikes.

 

[dirt bike dave]

How many turns out was the airscrew with the 42?  Seems like the 45 at 3 turns out would be as lean as the 42 all the way in.  What about your needle?  Stock? Stock position? 

Lugging around at low rpm is the easiest way to make an engine ping, and it if runs good everywhere else and only pings then, your jetting must be pretty close.  I'd look to fine tuning like raising the needle (put the clip on a lower groove) one notch or turning in the airscrew a little.  Weather conditions can also be a factor.  If you were well jetted for poor summer air and were riding on a cool day with good air, that could have contributed. 

Re: brake pads, mud is much harder on pads, but the stock KDX pads usually are pretty long lived.  In extreme conditions, 100 miles might be about right, but you should normally get much better life than that on the stock pads.  If you are unknowingly dragging your brakes (pedal to high?) or have some air in the system (seems common on Kawasakis), that could certainly shorten pad life. 

FWIW, aggressive compound aftermarket pads will wear much faster than the stock compound.  IMO 100 miles in the mud would be about the best you could expect from a real aggressive pad.   The only time I put race pads on my KDX they wore out in about 2 hard trail rides (approx 120 miles). 

 

[paul6585]

Air screw was 1.5 after switching to 42 pilot. Needle is stock and set at mid clip. My concern was that pinging indicates a lean condition. Is a lean condition a concern at low rpm or just mid-high rpm? thanks

 

[dirt bike dave]

Pinging / pre-ignition / detonation is bad anytime.  Imagine someone banging a tack hammer on your piston right before tdc.  Most engines generate their highest combustion pressures and combustion champer temps at low rpm with heavy loads, so pinging is most likely to occur then.  It is an indication of excess heat, lean jetting, improper timing or poor fuel quality. 

If you know your fuel is good and you have no reason to suspect timing as the culprit, that narrows it down some, especially if you just made jetting changes and the bike didn't ping before.  By turning in your Airscrew you'll be getting a little more cooling fuel and oil in there, and that may be all it takes.  I would say the first thing to try would be turn your AS in 1/2 turn or so and see if it helps. 

 

 

[CaptainObvious]

New to dirt bikes you say. Pinging at low rpm you say.

2 strokes make a normal "ring-ding-ding-ding" sound at idle and low rpm's. This sound has the same cadence as the rpm. Pinging, as in preignition, is more intermittent.

Which do you have?

 

[paul6585]

I say "new" to dirt bikes since this is the first dirt bike that I have owned with what I consider to be a significant amount of hours on i.e. 100+ hrs. The sound is definitley not the "ring- ding- ding" as you say - I am familiar with the 2-stroke sound. The sound I am getting is definitely more of a "ping- ring- ding".
Thanks for all of your help. I will go at it from here.

 

[23jayhawk]

At the risk of this starting to sound like a SNL skit, I've always found that when the low end jetting is dialed in (i.e. crisp & sharp), I get a ting-ting-ting sound when I motor along at a steady low-load, part throttle opening. It almost sounds like someone tapping on the expansion chamber with a welding rod.

It basically sounds like you're getting 100% combustion of the mixture. No, it's not 100%, but the sound is much more crisp than when the low end is a bit fat. The individual firing pulses are much less distinct sounding when it's on the rich side.

As far as whether you should be concerned over being too lean, my experience is that you'll encounter a lean bog before getting too far in that direction. If you're getting crisp throttle response and the bike basically rips on low end, perhaps you've simply found a good jet set.

 

[andrew]

Regarding your brake pads, if you use the Kevlar compound then they'll wear out in double quick time in the mud. I got some once and they lasted TWO rides! Get the sintered metal pads - they are a lot harder on your disc but they'll last a long time.

Cheers,
Andrew