Kart YZ-125 Engine running leaner, spark plug still wet and chipped reeds

RAFO

Member
Jul 18, 2005
1
0
Hello guys,

I am shifter kart racer with just one season of experience and I am still in the process of learning my YZ-125.
My YZ-125 is ported for short tracks and I have a Swedetech straight intake manifold. The reed cage is the stock YZ-125 year 2000 (four petals total) with Carbon Tech low tension reeds (142LT). The carb is a Keihin PWM with a pump around system. I've been told this is is the best intake combo.
For exhaust I have an RCE T3 pipe with an RVL titanium 12" silencer.
Spark plug is NGK BR10EIX
I race in Florida (at sea level pressure and like 90-100 F temp)
After my on-line research, I think I've got the proper method of reading spark plugs, by looking the ring that forms around the base of the insulator with an otoscope. So, I have started to lean down my engine up to a point were I run out of smaller main jets. I started from 165 and now I am at 150. However, the spark plug still looks wet and the dark ring at the insulator base is about 1~2mm tall.
Also, I have started to experience reeds problems. Last race I had reeds failure. The engine won't pull from the bottom range and when it hits 12,200 rpm it makes a cracking sound and acceleration is flatten out (usually It could go as high as 13,000 and still pulling). After inspection of the reeds I found that the corners were chipped to the point that I can see through to the other side of the reed cage.
Last Saturday (testing session) I replace the reeds for a new set of Carbon Tech low tension reeds (142LT) and chipped them again in just five laps.

Can somebody give me a clue of what is going on. I have a race next weekend and I am not certain if a new set of reeds will solve the problem. I am not sure if the reeds problem is related to the jetting, because it looks that the engine is still running rich.

Thank you!
 

steve125

LIFETIME SPONSOR
Oct 19, 2000
1,252
0
The 150 sounds lean, I would think to stay in the 160-165 range.

Anyway, excessive turbulence and or excessive carb angle in the intake is the no.1 reason the reeds chip if all else is OK. Are you running reed stops? and have you noticed that the reeds are chipping at the same location/position on the reed block every time?
 

CharlieT

Member
Dec 7, 2004
17
0
Does sound a bit on the lean side, with the crackling/going flat. Remember, a broken/chiped reed can artifically richen the mixture. You may want to go to a higher tension reed. Low tension reeds can have a tendency to flutter at high rpm, such as you run in your shifterkart. A higher tension reed may not be as responsive at low rpm, but can resist the high rpm flutter
 
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