Spits and sputters.

[Jbroderick91]

I have an 01 blaster I got on trade with a blown top end. When I first got it it would
Spit and spitter untill the band kicked in and it had all kinds of power once it kicked in. Come to find out I the top end was shot. So I rebuilt the top end with a fresh cyclinder and stock 66m wiesco piston. After a number of heat cycles I hopped back on her and gave her a ride. I noticed with the new top end it seems to have the same spitting and sputtering problem then the band hits and throws you back. I've had the carb off and apart multiple times. Cleaned it and cleaned jets. Still having no luck. Went riding this past weekend and since the lay time I've had carb off its not as bad. Like I said once I get into the band it's great and has ton of power but it bogs untill then. Any ideas?

 

[Jbroderick91]

Right now I am currently running a toomey B1 exhaust came with the bike. Carb had a 310 jet and I just jumped up to a 320 main. It's a lot better with the 320 but issue still present. I run a klotz oil at 32:1. My needle clip is in the middle position. To me it seems like it's not getting enough gas? Mabey the petcock is Gettin plugged up? Bought a rebuild kit I pulled the carb off again tonite. I plan to bring to work tomorrow and rebuild the carb. Check/ set the float height.

 

[Fast6hand]

Plug chops will confirm the main jet. Sounds like your in the ballpark.

What was your air screw set at?

Clean air filter?

Old/new gas?

Did you clean jets with thin piece of wire and air?

Are they genuine Mikuni jets? I know those rebuild kits aren't typically genuine.

What's your compression?

Is the top end one of those cheap kits off EBay?

 

[deeeebeeeeee]

^ to add to these

An easy way to verify rich or lean at a particular throttle position, is to reach down and pull the choke while at the throttle position it sputters at. Make sure you are on an open area. If it's running lean it should pick up at half choke, rich it will start to die.

One thing I didn't find in any write-ups on the subject but has helped me is to try full throttle in a higher gear at low rpm, see if it pulls smoothly, if so then you know it is not rpm related, and can do the same with various other throttle positions to pinpoint where the issue is.

Keep in mind that your pilot jet and air screw feeds fuel across the entire throttle range, I have found fhey can make a noticeable difference up to as far as half throttle, especially if they are way out of adjustment.

 

[Jbroderick91]

I'm definitely running lean by the ping I'm getting under load. And jets are genuine mikuni from jets r us.