big bore and stroke jetting issues

[kakorb]

i recently had a bearing failure so i stroked and bored my yfz 3mm stroke 3mm bore and put stage one cams in it. had the oil mod done, and cut my stock exhaust in half and rewelded it with all baffles i could retain for back pressure. it was jetted for a fmf titanuim pipe which was destroyed when bike went over backwards riding a wheelie. had a 180 main jet and 52 pilot. neoedle only has one clip. pro have get a diff needle. anyway i put a 190 jet and 58 pilot to start. with the 180 52 the bike would be hard to start and idled only half time warm or cold. pipe would get orange transparant idling and orange half to wide open. clear to the muffler and shoot flames out. now the bike wont idle no matter where the fuel air screw is and but the pipe is red to elbow now and idles on choke but kicks up idle spark plug light and dry any suggestions elevation is 1000 to 2000 i believe

[kakorb]

so i stuffed a 198 main and 52 pilot and air fuel screw out 2 turns pilot one turn out and she idles for minute or two then stalls header gets red clear back past heat shield need to figure out clips on needle cause mid seems to be worst area now and run it to see how main jet does but seems better than has been.

[kakorb]

turned the fuel screw out another half turn and she idles good but the header still gets pretty red not sure what to do now

[ldjbuff]

U live by a dyno by chance?

[06yfz]

you're jetted way, way to rich for your modifications my friend. assuming your not using dyno jet jets that is... Go down to a 48 pilot and a 170 main and see how it does. Also change one thing at a time when it comes to jetting. your pilot jet controls idle to 1/4 throttle, needle 1/4 throttle to 3/4 throttle, main 3/4 to wide open throttle.

[GSWEAR]

First off I don't know anything!8|

Get your jetting somewhat normal as already mentioned (these guys know a lot more about that than me).
Once you have done that do the 3 things you always do on a 4 stroke before major troubleshooting, install new plug, check valve clearance and cam timing, also verify you have a strong spark at the plug (ok maybe 4).
If any of these is the issue or contributing to the issue you will just chase your tail trying to find it as will everyone else.

As I already said I don't know anything but something sounds fishy here.

[kakorb]

With how it is now it runs really good but backfires when come off throttle. Would that be needle or pilot jet and how should I change them. No offense but a 170 would put a hole in my piston as hot as the pipe and jug got. Timing good. Had new plug when started and cked shims when put cams in.

[06yfz]

Originally Posted by kakorb

With how it is now it runs really good but backfires when come off throttle. Would that be needle or pilot jet and how should I change them. No offense but a 170 would put a hole in my piston as hot as the pipe and jug got. Timing good. Had new plug when started and cked shims when put cams in.

Do you have a temp gauge on your bike? If not you have no idea as to if it was to hot or not. These things put out quite a bit of heat. Backfiring on deceleration is usually a lean pilot however your pilot jet is way larger than most run. I would check for air leaks around the carb boots and the exhaust gasket. Those can cause a lean condition making you use a larger than normal pilot jet. I would also double check your timing and valve clearances while your in there.

[silverado2nv]

06yfz is right...you got to remember that the added stroke and bore is going to create more vacuum thus it may require leaner jetting....when I went from a 471 to a 501 I actually had to lean up the needle and main jet

[JDiablo]

yeaa mang wayyyyy to rich for sure

[Mr.Haulass]

mixture screw = screw to left for more fuel, screw to right for more air. Start out at 2 1/2 turns out/open. Lean = to much air. I'd try 170 or 175 main 48 pilot and make sure air box lid is off & stays off. Easy to change mains from bottom of bowl. Im sure someone will correct me if im wrong. lol