200x jetting issue after top end rebuild

[mtsnieg]

Redid my top end, .25mm over, new piston, new valve job. I ran one tank with a 125 main jet. NOTHING above 1\3 throttle. Through the gears up and down. Ran like a champ.

Now I'm starting to get on it some. Put in a 135 main jet. Lean, lean lean. Above 1\2 throttle it cuts out. Engine gets warm. Pull the bran new plug, light brown lean! Mixture screw 2 1\2 turns out.

I'll go tomorrow morniing to get a couple bigger jets, I don't mind at all. Wisconsin is 25 degrees average during the day when I'm ridin.

Bigger than 135 sound right? I've re-adjusted valves, timing a couple times, they're all right on.

Getin efin frustrated, gotta turn some laps tommorrow, gotta.

[rdlsz24]

Do you have any mods? 110 is stock. I would be surprised if you needed to go that big unless you have a lot of mods.

Rob

[mtsnieg]

As the engine is now it it back to stock. Just an Answer slip on muffler. My plug is light brown LEAN. All summer I ran a 115 main with a haggard 130 psi engine all day long. With an XR200 cam. I don't get it. Carb is SPARKLY clean. Not a whole lot of replies or ideas or such. WTF, I guess I'll dump a 110 stock main in it in the morning and see what happens.

[ATCrider42]

Are you running with the stock airbox? Maybe try pulling the lid off and see if that helps.

[mtsnieg]

Are you running with the stock airbox? Maybe try pulling the lid off and see if that helps.

I would think that would allow more airflow and lean it even more.

I'm totally stumped. Just re-checked timing and spark advance assembly. All right on. Could I be running too big a main jet and overfueling it? Idles great and runs good up to 1\3 throttle where it cuts out. It's 25 degrees right now, cold start it took a minute and a half for the engine to warm up to operating temp. Should take 3 or 4 minutes at least usually.

Fuel petcock working properly, nice clean fuel filter, full tank of premium.

[Yamaha_Rules69]

It could be an air leak. Start the motor and use starting fluid and and spray it around the top end gaskets, and take particular notice to the intake boot attaching carburetor to the motor. If there is a leak, there will be a hesittion when the starting fluid hits the leaking area when the motor is running. Another thing I would try is a new spark plug, and check the coil to be sure the wire is connected properly, and you can OHM the coil out to test the resistance to see if it is good. I had a bad coil on my X one time, and it did the same as you are describing. Specs via service manual. Good luck!

[mtsnieg]

Still having the same problems.

Last weekend with a 130 main is was running ok. Still breaking up on the top end a bit. Engine running hot.

Yesterday, 130 main, simular outdide temp it was breaking up really bad above half throttle. Really bad. Still runnin hot. Too hot.

Just pulled the coil. Primary coil measures .8 - .9......Manual says .2 - .8
Secondary coil measures nothing. Manual says 3 - 5k

Could this be my problem. Starts and idles great. Runs good to half throttle. Called my usual moto shop and they say OEM and aftermarket coil in discontinued. Not available. Looked on Egay and I found em around $25.

Not sure on what to do here. Try an Egay coil?

[rdlsz24]

Did you ever try the smaller main jet, and if so how did it go?

Rob

[mtsnieg]

Did you ever try the smaller main jet, and if so how did it go?

Rob

No I have not. I will trt it and report back.

[rdlsz24]

ok cool. It's worth a shot. If it runs even worse at least you can rule it out

Rob

[mtsnieg]

UPDATE

I removed the spark plug wire from the coil and re-checked it. Secondary coil measures 4.25k, right on.
I trin off a quarter inch of the spark plug wire where it goes into the coil and re-attatched it.
Now it measures almost 9k. WTF? Way too high.
Jump the secondary with a piece on regular automotive wire and test, it measures 4.25k. Right on. WTF?

[rdlsz24]

Any updates on this mtsnieg?

Rob

[mtsnieg]

I have it running pretty good with a 120 main jet right now. Haven't really run it much in the last two weeks. 50 degree weather wreaked havok on the lake and tracks. Hopefully this weekend will get some laps in.