Here's the same problem. I installed the EGT guage at 6" from the exaust gasket. I am jetting according to it. HPD's specs are between 800 and 900 degrees at 1/4 throttle, 1000 degrees at 1/2 and 1200 for a "very safe" WOT. 1250 is peak performance and 1300 is meltdown. I have the 38 pilot jet and EEG with the clip at the bottom.

My 1/4 throttle seems fine but the 1/2 to 3/4 goes about 100 to 200 degrees too high. WOT is at about 1100 degrees so I could lean it out a bit. Now what do I do???

I was thinking of richening the main jet since some of you said it affected midrange but then it would loose top end power which is already lower than peak performance and "very safe" level.

Could I just put a small washer under the needle clip as a spacer? It would be like putting the needleclip one or two notches lower.

I also played around with the air screw but it didn't sem to do anything. What would be the ideal setting for the air screw?

Any suggestions once again would be helpful. Tomorrow I check for air-leaks too.

Side question: Is 1/2 throttle = to when the slide is 1/2 open and so on???

 

Somebody throw me a crumb!!![img]i/expressions/face-icon-small-sad.gif[/img] Please...

 

For modified engines 1 turn to 1 1/2 turns out is normal, your needle jet also has say in how much gas passes through the main jet at any given time during throttle operation. the higher the needle jet is set the more gas it will let pass through the main jet, lower is the opposite, it will allow less gas to run through.

Yes half throttle means the throttle body is half way up.

Good Luck!!!

2000 SCRAMBLER 400 2X4

SCRAMDADDY400

 

Scramdaddy, Problem is that i have the richest needle available and it is set to its richest point. Some have told me to shave the needle and I have also heard about making it higher with the spacer. Would the air screw affect jetting a lot? maybe mine is out of whack?!?!

 

The air screw is mainly for fine tuning, if you have the richest needle jet then try going one or two sizes down on the main jet and adjusting the needle jet. The middle position is very common for a neddle jet to be set even on highly modified engines, try the main jet first.

2000 SCRAMBLER 400 2X4

SCRAMDADDY400

 

O.K. here's my old newby side coming out again. By going down in size...wouldn't that lean out my mixture even more? I was using a 175 main jet. If I go to a 172 or 170...wouldn't that just make it worse? I must be having a momentary lapse of reasoning... [img]i/expressions/face-icon-small-confused.gif[/img]

 

Yes a 172 and 170 is leaner, the best thing you can do rather than listening to all this computer mumbo jumbo is to get a new plug and a 172 main jet and a 180 to 185 main jet set the needle jet to the middle position and run the machine on a straight as fast as you can turn around and come back as fast as you can. Take the plug out and inspect for coloration, if the porsline is still white or white with spots of carbon you know its too lean, if its tan or beige like color your perfect, but if it's wet or black or both your too rich.

2000 SCRAMBLER 400 2X4

SCRAMDADDY400

 

Tomorrow I may just go try some other settings. I had an idea though: I have my airbox modded but re-plugged the extra hole in the baffle wall between the snorkle and the airbox. Some have told me that the extra airflow beyond the simple airbox mod affects only WOT range. I may just re-drill it and stick in the 180 main jet. Maybe the 180 will help richen up my midrange and the added air coming in will offset the richness at WOT. What do you think? Could work...[img]i/expressions/face-icon-small-shocked.gif[/img]

PS- I installed the EGT so as not to burn my arm checking the plug every 5 minutes. It is supposed to give me precise readings.

 

Xplor, you didn't buy the book I told you to did you? How high exaclty is your mid-range going? You have the clip in the lowest position right? Not the highest. I'm not familiar with that carb but I know on others you can change the tube that the needle goes down into. You may want to check into that. You might want to try that extra hole in the airbox, but I doubt you will need to change the main cause it's too rich. All these headackes are the reason my Scrambler is still stock!

 

Rob, I am hitting almost 1200 degrees in the midrange. It does not stay there but stays between 1100 and 1200. WOT is less, at 1100 about.