[tk2stroke]

I've been tinkering with my 2008 TTR 110 to get some additional performance such as opening up the airbox, optimizing jetting, new piston/rings, and lapping the valves after more than 500 hours. The bike was running great after the mods and then after removing the head and polishing the port, the bike now is running like shit. It starts and idles fine, but once you rev it up or place it under load it's sputters as seen in the video.

I figured during the re-installation fo the head and the carb, I must have made a mistake somewhere. Since then I've replaced the spark plug, carb (from loaner bike) and even swapped the head from a fiends stock TTR and nothing has helped. I've confirmed the timing is spot on after having done it previously on several occasions. At this point having ruled out air flow, timing, fuel, and spark I figure it may be coincidence that it's something electrical.

It's a long shot, but hoping someone has experienced this and has some ideas.

New video by Tom Klein
WTF did I miss, help!

 

[jack_song]

when you port your head it may require larger main jets or it may be poor porting and its restricting air of not mixing air and fuel together properly

 

[jack_song]

and what size carburetor are you using
bad spark plug ?
cdi or coil

 

[jack_song]

try slowly reving it, if sometimes it revs out that means your main jet is a little lean

 

[tk2stroke]

Sadly, I've confirmed everything you mentioned. I simply polished the ports and to confirm it wasn't related to any of my head work, I tested the bike with a 100% stock head and the exact same sputtering was encountered. I'm using the stock carb and tried various jetting settings before going back to my known jet setting that was working perfectly even after the my head work. Additionally I tested another purely stock carb from my buddies TTR-110 and no success here either.

The Spark plug was also changed 2 times and confirmed at proper gap.

Also tested the CDI from my buddies loaner bike, but I have not swapped the coil. This is a good shout-out and def my next test to rule it out.

Slow reving yields the same result with sputtering happening at about 30-100% throttle under load or not.

I get the sense that it's timing related even thought he timing is dead on balls accurate and verified from my buddies loaner bike. It's maddening and a challenging problem I have on my hands.

Thanks for the suggestions