Raptor Carburetor Print Step Sheet

 

  1. Remove throttle shaft and butterfly assembly.
  2. Cut or machine throttle shaft within tech specifications
  3. Re-assemble and set throttle to maximum opening. Install #52 test jet and adjust needle valve out 1½ turns counter clockwise.
  4. Attach assembly to flow bench with air filter adapter, connect a manometer line to short pick up tube.
  5. It’s important to set-up, calibrate, and adjust flow bench accurately for comparison analysis. A good performing carburetor should be used as a machine calibration standard.
  6. Provisions should be made to record high and low airflow and fuel draw values. (A carburetor flow analysis matrix chart will be forthcoming.) Record atmospheric conditions.
  7. Run pre-print flow test and record values. Adjustments will have to be made to throttle valve stop tab to set maximum airflow. An accurate fixed low speed throttle position, and reduced airflow value identical to the set-up standard, must be maintained during low speed discharge hole testing.
  8. Remove carburetor, disassemble, ream and prep throttle bore.
  9. Machine and true pump cover.
  10. Re-assemble printed carburetor, re-install a #52 jet, turn needle valve out 1½ turns, and attach to flow bench.
  11. Re-run flow test and re-adjust for maximum airflow as needed. Record air and fuel draw values for high and low speed. (Air- flow for low speed test must be identical to carburetor used as a set-up standard.)
  12. Make an analysis comparing data recorded against the original set-up carburetor flow values.
  13. Compared to the set-up standard carburetor, if the fuel draw shows richer on top than the bottom, ream the high-speed discharge hole smaller than the maximum allowed (under .062). Ream the idle hole to .025" (under .028")
  14. If fuel draw was richer on the bottom than on the top, ream the low speed discharge hole under the maximum and the high speed close to the maximum diameter permitted. Re-run flow test. Continue to ream holes in small steps until close to the set-up test carburetor values are achieved. Each step diameter change, to the discharge holes, requires multiple flow tests to insure accuracy. (Enlarging one hole to increase fuel draw, always takes away fuel draw from the other.)
  15. To make final fine tune adjustments, switch throttle shafts, plates, alter pick up tube inside diameter or bend the throttle shaft stop tab.

Notes: A good carburetor can be destroyed by automatically drilling the discharge holes to the maximum tech diameter permitted before air- flow testing.

There are some carburetors that are just plain bad. No amount of work will ever make them work well.

Rookie and Junior carburetors require different flow values to provide the best performance than a senior class carburetor does.

Exact air- flow values depend on the machine and inches of water column used. Habitually using the same good performing carburetor, as a set up standard, will eventually lead to accurate results.

Low speed checks must be done with reduced, but consistent set-up airflow values.

Always remember to allow for variances in atmospheric conditions. Some machines do not automatically compensate for these factors.

It’s more important to achieve correct air/fuel ratio than it is to be concerned only with maximum air- flow.

It takes from one to three hours of shop time to complete blueprint and flow operations on a WKA spec carburetor. (Perhaps we are slow.)`

We realize we didn’t tell exact blue print operations; modifications or numbers for flow mix rates. This is something you will have to work out for yourself. Hope this may be of some help.

Good luck and thanks for your interest.

Yours in karting, Rick at Rix

www.rixkartengines.com

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