puzzled by 350X problem

[geaux350x]

I'll try to make a long story short.......I purchased a dead 350X and had what I thought was a very good mechanic restore it. Most of the engine is brand new crate parts (lower, transmission, complete head with valves, jug and piston, & oil pump). Side covers, strator, cam, and all the other goodies were in great shape. The only modifications to the bike are a DG freeflow pipe and K&N air filter, which were on the bike when I purchased it.

THE PROBLEM I'M HAVING: The bike seems to be running lean. We have tried to re-jet the carb., having started with the factory 135 jet and incremented up 5 sizes at a time until we reached 170, which the bike should not have even started at that point. We have moved clip on needle to all positions, adjusted and changed pilot, adjusted air screw, and every possible combination you could possibly imagine.

The bike starts on 2nd or 3rd kick every time, and idles beautifuly. However, when accellerating quickly, it falls on it's face. Also, when letting off the throttle, it pops as it slows. I've pulled the plug out, which is usually a little black, but I've seen worse. Now I'm not sure if the bike is running lean or rich. It could be fouling the plug at idle and not while running. I'm wondering if I may be having an electrical issue or is it fuel to air, like we've been trying to tune?

I've exhausted all my resources, so before I smash the thing to pieces, DOES ANYONE HAVE ANY SUGGESTIONS?

[dads]

have you tried factury jets and lowering the needle.

or running with the lid off the air fillter.

[geaux350x]

Yes now I'm back to factory everything.

[dads]

and it still falls on it's face??

[geaux350x]

If I accellerate slow it's usually ok.If I get on it yes.Allways pops when slowing down.I've done so much in adjustments I must be missing something or looking @ the wrong thing. TKS

[dads]

I had a prob. like that and lowered the needle to stop the over fueling.
on the piolot screw the fac. setting is the starting piont for fin adjusting.
I blip the throttle to see if it hesitates then adjust the pilot a little. one way then the other till it's good. it should not be more than a 1/4 turn from fac. setting.

[geaux350x]

I'll move the needle again and start over. do you think it could be a lack of consistant fire. I'm just wondering now if there is something else.

[dads]

not if it runs good. falling on it's face when full throttled is fuel prob.
poping can be air leek in exh. or if you running a full flow exh just air getting back in and setting off the unburned gases.

[dads]

are you valves set right and decopretion set right

[geaux350x]

The valves were checked on the new head before assembly.I haven't put enough time on the motor to addjust yet. I'm not sure what you mean about compression,I do know there is plenty and a new decomp cable?

[geaux350x]

Sorry the valves were checked after assembly.

[bones200x]

Popping when backing off throttle means pilot screw too far in or jet is too small. I never really go by 1/4 turn on srew from factory. I use that as a REFERENCE point. Once you start modifing, Then stock isn't enough.
This is what I would do to check. RECHECK valves.(have seen just valves cause numerous problems).. Check spark.(COLD and HOT). The let warm up. adjust pilot screw to highest idle. bring idle to factory setting.
Try a hotter plug just to check. Make sure no air leaks in intake. Have you tried cleaning carb? Maybe it has trash somewhere in circuts????

[Mr. Richard]

just so you know,,, the pilot screw on a 350x is gas not air,,, so it works backwards to what you would think,,,, the more you screw it in the leaner it makes the idle mixture,, the manual says screw it out 2.5 turns,,, set the idle with the idle screw then screw the pilot screw in till it dies,, then screw it out one turn,,,, the main jet has no effect on any throttle position below a half ,, so if you feel it is lean on the bottom a larger pilot jet would be in order,,, if the plug is black it really doesn't represent anything unless you are doing a plug chop,,, then it will change colors to show true jetting

[NOS_350X]

If your running a 170 main you NEED to go with a larger pilot. One of my 350x's is just ported, with a pipe and its at a 185 main 65 pilot. Just rember looking at the plug does nothing, you must plug chop.

[geaux350x]

Thats all good info.Ihave went up on the pilot but I guess I'll start over again.At the risk of sounding like a dumb a** how or what is a plug chop.

[NOS_350X]

do a search for a plug chop, you will find what you need.

[dads]

plug chop. you need running room.
put in a new plug. run it like you racing though all the geares.
when you hit top speed high geare hit the kill switch.
then pull the plug and see what color the porsalin is

[Dracus124]

This is for a 2 stroke http://www.dfn.com/benkaren/plugchop.html

I imagine it's the same thing

[bones200x]

My way might not be as accurate. I usually do it in 3rd pinned. I don't have room to do 5th around my house. It seems to work. But, you have to be able to hold it for atleast 100 yards my way.
It takes at least 4-5 plugs to get right. But, the ones you use, you can keep as spares. I don't cut mine. I use flashlight to check.

[random-strike]

This is for a 2 stroke http://www.dfn.com/benkaren/plugchop.html

I imagine it's the same thing

thats basically the jist of it.

as bones200x said, on a 4 poke just doing one gear will be fine as long as it runs enough to actually make the mark

[likestrikes]

Are you certain that there is not an air leak between the carb to the boot or the boot to the head? I'd take that boot off and stone it perfectly flat along with the mating head surface. Then replace the oring just to be sure.