stage 2 (old #) cam and bad jetting

[Don_Carnage]

I stripped the threads on my stage 1 cam and put in a new cylinder and 426 11:1 piston and stage 2 cam. Jetted it perfect and one ride I lost my airbox lid. Ever since I jetted it for that it always had a sputter in the bottom rpm. I rebuilt the bike but not the motor, got a new carb and lid. I Jetted it the same way as before (155-3rd clip-3.5 turns) and now it has a really hard time to start and still has the sputter. If I hold the throttle just a touch it will fire up easily but let off and its done. sounds rich to me but the plug says grey/tan. Any ideas?

[400exrider707]

Originally posted by Don_Carnage
I stripped the threads on my stage 1 cam and put in a new cylinder and 426 11:1 piston and stage 2 cam. Jetted it perfect and one ride I lost my airbox lid. Ever since I jetted it for that it always had a sputter in the bottom rpm. I rebuilt the bike but not the motor, got a new carb and lid. I Jetted it the same way as before (155-3rd clip-3.5 turns) and now it has a really hard time to start and still has the sputter. If I hold the throttle just a touch it will fire up easily but let off and its done. sounds rich to me but the plug says grey/tan. Any ideas?

Im kind of confused by your post, but I bet if you bump your pilot to a 42, move your clip on your needle down to the 4th position, and have the screw out 2 1/2 turns. You should be good. What other mods are done to it?

[Don_Carnage]

I've got the 426, 11:1, the stage 2 cam, pro cirquit ti-4 pipe and magnum rev box. it only bogs in the lower throttle. If I stay at steady pace and close the throttle it starts to sputter. and only since i jetted it without the lid. now that i have the lid it still sputters down low.

[bwamos]

Sputtering is usually from being too rich.
Probably just need to lean up your mixture screw and/or pilot.

[bradrenea]

Well, if you now have an airbox lid and left the jetting as it was without the lid then it is too rich. I am not sure what you meant by "I jetted it the way it was before", but I took it to mean you jetted it like it was before you got the new carb and airbox lid.

[Don_Carnage]

It is jetted the same way is it when I had my lid, then took it off, jetted it and the idle-3/8 throttle sputter started. Now that I have the lid and the same jetting as the last time I had a lid the sputter still continues. I've tried the 2nd,3rd, & 4th clip, and a range of 2-3.5 turns on the screw on all the needle positions. my choke seems to do nothing and it will only fire up with a few cracks on the throttle before i start it. Even then i have to stay on the throttle a little or it will die, choke or no choke. On my 416/stage 1 cam engine I used 155/3rd/3 turns out and it worked like a dream. now on my stage 2 and 426, I can't seem to get it right. We don't have snow yet and I'm missing valuable time.

[bradrenea]

Mine does the same thing as yours but it is fine when it warms up. Mine has the choke removed, but I just have to pump the throttle a couple times and start it. I do have to keep giving it gas until it warms up, then its fine. Does yours still "sputter" after its warmed up?

[cals400ex]

i would make sure you have no leak in your exhaust system where it mounts to the head or where the silencer meets the header or in either of your air boots. both of these can crack and cause problems. make sure everything here is tight too.

[Don_Carnage]

It does still have the low end sputter when it warms up but not half as bad. I'm going to the shop to check the plug again, but last time it was a dark tan. the first time it was a bright orange color and got it to turn tan by turning the screw out. I had a rip in my old boot between the carb and head but that has been fixed a long time ago. maybe another? I did have a small exhaust leak between the header and silencer but it doesn't leak enough to make any black residue on the pipe and you can't hear it, but i'm giving it a full inspection on my day off.