I have a 1050 dominator on the motor and it is burning "big time" rich. The jets are 92 and the carb was purchased from a gentleman who raced. I've heard of stagger jetting and that in some cases it works to good advantage. I'm not sure it would help this "rich" condition but what are the thoughts on this. As always, thanks in advance. Motor is Stage II iron head, 12.69 CR.
Hi Len, Just a wild guess here, but when you say the motor is running "big time rich" I'll bet you're referring to idle and perhaps part throttle conditions. If so, don't try to tune with the main jets. It's a good bet that the primary throttle plates are opened too far at idle, excessively exposing the idle transfer slot, thus causing an overly rich condition at idle. Remove the carb, drain the bowls, and flip it upside down on the workbench. Have a gander at the relationship between the primary throttle plates and the transfer slots. If more then .040" of the slot is exposed (visible from the underside of the carb) you're going to have problems. Close the throttle plates until just .020" is showing. Adjust the secondaries to the same position. Set all of the idle mixture screws to one turn out from fully seated. Now re-install the carb and start the motor. If it will idle, great. If not, adjust both the primary and secondary speed screws the same amount until the motor will just barely idle. Now move to any of the (2 or 4 depending on model) idle mixture screws and adjust (in or out as necessary) to achieve the highest idle rpm possible. This will also co-inside with the highest vacuum reading, so if you'd like to use a vacuum gauge you can do it that way too. Back off the idle speed screws (primary and secondary same amount) to the lowest possible rpm that the motor will stay running and move to the next idle mixture screw. Adjust it, just like the first, to achieve the highest possible idle rpm or vacuum reading. Now back off the idle speed screws again and move to the next idle mixture screws. Keep repeating this procedure until you've adjusted each of the mixture screws twice. Then set your final idle rpm using the idle speed screws, keeping the primary and secondary adjustments the same. Less is more--if you run the idle speed up too high you'll again expose too much of the transfer slot and re-create the rich condition. Jet main metering for best mph, or go for a light brown color on the center electrode insulator after a clean full throttle pass. Sometimes additional work on the air bleeds is necessary to correct this condition (make sure they're not clogged with dirt!), especially if a really hairy camshaft is being used, but this usually gets the job done. -Ron Rygelski Red Line Oil Racing
Staggered jetting continued Hi Ron, it's nice to hear from you again. Ya, still doing the same project after more than a year. I printed out your response, ran down to the shop today and proceded to follow your advice to the letter. In summary, I found the problem, you hit the nail on the head, the secondaries were open way too much at so called idle. Also I found the mixture screws were turned out a full 4 turns. After all the adjustments were done per your detailed instructions, it's great, absolutely great. I really appreciate it Ron. it seems to me this may be the 3rd or 4th time you've helped me out of a jam over the last year or two. Me thinks I owe you big time. Anyhow, thanks again for your most welcome help.:beer Len
Yeah, thanks Ron (you ARE still around). Len's pushing hard to get that bad boy to Vegas in November and I, for one, will be disappointed if he shows up without the Stage 2.
