what is the best way to do a plug test ???and were to set the air/fuel mixture screw to start out [img]i/expressions/face-icon-small-confused.gif[/img]

 

Hawley, It's always a great idea to do some jetting runs.....heck, even w/ a stock bike. You'll want to find a good 1/4 mile stretch, and some shut-down area too. Start out holding a constant 1/4 throttle steady as you can for the entire 1/4 mile. Use your electrical killswitch on the bars to kill the engine whill still maintaining that throttle setting. Coast to a stop, and read your plug. White is lean, black is rich, and cocoa brown is the sweet spot. The small airscrew is located on the side of the carb, that controls the idle-1/4 throttle range. Turning it in richens the mixture, and turning out leans it. Don't go out beyond 3 turns, if you can't get it dialed in w/ the screw, changing the pilot jet would get you in the correct range.

The next two jetting runs are held steady at 1/2, then at 3/4 throttle. These two ranges are adjusted by moving the clip up or down on the needle inside the slide. Moving the needle to a lower clip position richens, and oposite for leaning.

Finally, the WOT (wide open throttle), this is adjusted with the main jet. Make sure to have ample enough shutdown area. [img]i/expressions/face-icon-small-smile.gif[/img]

 

thanks for the help on this..

 

You're very welcome. [img]i/expressions/face-icon-small-smile.gif[/img]

 

hey modquad,

thanks for the valuable info

ross[img]i/expressions/face-icon-small-smile.gif[/img]

 

Modquad

I just finshed doing the plug test today. the plugs look like a brown color.but what I am trying to fix is the hesitation I have at take off.when you set still and crack the throttle it bogs for a while then opens then comes alive or if I need to stop on a hill and try to take off I need to power brake it to get it started up the hill.
I did your testing on the plugs and each time the plug looked good..any other suggestions would be apprecited thanks Scott[img]i/expressions/face-icon-small-confused.gif[/img]

 

hawleywood400, Does it bog or hesitate at any throttle opening, coming off idle? If so, the air mixture screw still needs more adjustment, sounds too lean.
carb tuning
Read more about it here.

 

Well I don't know a bunch about the 400's but the 250's are notoreious for the low end bog. part of this is because they are a piston port engine with no reed valves. So mabey your reed valves are bad has it always been like this? or just since the mods the clucth engagment needs to match the rpm where the pipe starts to make power. I see it's all hot seat stuff so they should have set you up right. mabey you ride more extreem than others they have to try for a good allaround cluthing do you know what weights and spring your primary clutch has? If your reeds are good let us know whats in your clutch will get it clutched to your likeing I ended up with a box full of springs and weights to get mine right.

Jeff
2003 Trailblazer250 RcR stage1 Milled Head

 

checked the air mix screw it was 4.5 turns out screwed it all the way and backed it out 1 turn to start have not been able to run it do to not enough time in the day...hopefully I can run it Saturday....let you know how it turns out


Thanks all for the input

Hawleywood400