Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
techtalk:evo:carb02 [2020/01/22 05:54]
ixl2relax [Diagnosing CV Carb Issues]
techtalk:evo:carb02 [2020/02/18 23:52] (current)
ixl2relax [Carb Farts (coughing)]
Line 358: Line 358:
  
  
-At this point, we need the engine to be warmed up to normal operating temperature to continue tuning the carb. A cold engine may operate quite differently once warmed up, therefore, tuning the carb while the engine is cold is not valid. Since we set the idle screw very low, you may need to use the throttle or enrichener to keep the bike running...+At this point, we need the engine to be warmed up to normal operating temperature to continue tuning the carb. A cold engine may operate quite differently once warmed up, therefore, tuning the carb while the engine is cold is not valid.
  
-Start the engine and use the enrichener for the first 1-3 minutes ​while you take the bike for a 10-15 minute ride to warm the engine fully. Then be careful of the burn potential while working around a hot engine. Make sure you have no intake leaks in the manifold seals by using an unlit propane torch to flow propane around those seals. The engine idle will alter if an intake leak allows propane into the manifold.+Start the engine and use the enrichener ​if the engine is cold, for the first minute or so, while you take the bike for a 10-15 minute ride to warm the engine fully. Then be careful of the burn potential while working around a hot engine. Make sure you have no intake leaks in the manifold seals by using an unlit propane torch to flow propane around those seals. The engine idle will alter if an intake leak allows propane into the manifold.
  
 ==== The Idle Drop Method (IDM) ==== ==== The Idle Drop Method (IDM) ====
Line 366: Line 366:
 The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM. The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM.
  
-With the engine ​idling, set the idle speed as low as the possible ​for smooth engine operation. Lock the idle speed with the throttle grip lock rather than changing the setting of the Idle Set Screw (which should still be between the Idle Port & the Transfer Ports).+If you have previously set the throttle plate, between the idle port and the transfer ports, using the Idle Set Screw, you may need to roll the throttle slightly to keep the engine ​idle. With the throttle grip, set the idle speed as low as possible, yet still smooth engine operation. Lock the idle speed with the throttle grip lock (rather than changing the setting of the Idle Set Screwwhich should still be between the Idle Port & the Transfer Ports).
  
-Now carefully reach under the carb and adjust the IMS in very small increments, turning it counter-clockwise (as if looking up from below). This is enrichening the fuel mix. Listen for the engine speed to begin falteringSTOP adjusting the screw. Now begin turning the IMS clockwise ​in very small movements. ​Calculate ​the amount of movment in 1/8 turn increments (1/2 of a 1/4 turn = 1/8 turn). Listen for the engine speed to begin faltering due to a lean condition. STOP adjusting the screw.+Now carefully reach under the carb and adjust the IMS with very small increments, turning it counter-clockwise (as if looking up from below). This is enrichening the fuel mix. Listen for the engine speed to begin faltering, then STOP adjusting the screw. Now begin turning the IMS clockwise ​with very small movements. ​Listen for the engine speed to return to running well and then begin faltering as you continue to turn the screw clockwise, which will create a lean condition. When it falters, STOP adjusting the screw. 
 + 
 +Do this several times to be sure of your results and to calculate ​the amount of movment in 1/8 turn increments (1/2 of a 1/4 turn = 1/8 turn) that represents this range, from too rich to too lean.
  
 (Note: If you can't find a fall off until below 1/2 turn out, you need a smaller Slow Jet. If you can't find a fall off in idle until beyond 3-1/2 turns out, you need a larger Slow Jet.) (Note: If you can't find a fall off until below 1/2 turn out, you need a smaller Slow Jet. If you can't find a fall off in idle until beyond 3-1/2 turns out, you need a larger Slow Jet.)
  
-Now, use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well.+Use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well.
  
 You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again. You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again.
Line 378: Line 380:
 The goal is to have the engine properly idle from the Slow Jet & the Idle Mixture Screw rather than by opening the throttle plate with the Idle Set Screw or throttle grip. Once you are satisfied that you did find the proper setting, you can turn the bike off. The goal is to have the engine properly idle from the Slow Jet & the Idle Mixture Screw rather than by opening the throttle plate with the Idle Set Screw or throttle grip. Once you are satisfied that you did find the proper setting, you can turn the bike off.
  
-Now check to see how many turns you must go (clockwise) until you GENTLY seat (closed) the IMS. WRITE DOWN THIS SETTING. That's it - You completed the Idle Mixture Screw setting using the Idle Drop Method.+Now check to see how many turns you must go (clockwise) until you GENTLY seat (closed) the IMS. **__WRITE ​DOWN THIS SETTING.__** That's it - You completed the Idle Mixture Screw setting using the Idle Drop Method.
  
 You can now release the throttle lock. Start the engine & adjust the Idle Set Screw (it should require very little adjustment) for the proper idle speed, typically, between 950 & 1050 RPMs. You can now release the throttle lock. Start the engine & adjust the Idle Set Screw (it should require very little adjustment) for the proper idle speed, typically, between 950 & 1050 RPMs.
Line 405: Line 407:
 **Some considerations:​** **Some considerations:​**
  
-A) Even when tuned correctly, cold engines are more likely to have carb farts than after they warm up. It is easier to create a lean condition when you open the throttle and gulp a large amount of cold air. If you ride off while the engine is still cold, expect to have farts. When the outside temperature is cold, you may also notice more carb farts for a longer period for the same reason. Trying to set your tune to eliminate carb farts that occur under cold conditions is likely to lead to excess fueling. ​Be sure to warm up the engine.+A) Even when tuned correctly, cold engines are more likely to have carb farts than after they warm up. It is easier to create a lean condition when you open the throttle and gulp a large amount of cold air. If you ride off while the engine is still cold, expect to have farts. When the outside temperature is cold, you may also notice more carb farts for a longer period for the same reason. Trying to set your tune to eliminate carb farts that occur under cold conditions is likely to lead to excess fueling. ​Instead, be sure to fully warm up the engine ​before tuning.
  
 B) You __should__ need the enrichener to start a cold engine. If you don't need it, your carb settings are too rich from the start. Go back to the general tuning stage and get this corrected before looking at carb farts. You may not have carb farts if you are that rich (which is not a good solution). B) You __should__ need the enrichener to start a cold engine. If you don't need it, your carb settings are too rich from the start. Go back to the general tuning stage and get this corrected before looking at carb farts. You may not have carb farts if you are that rich (which is not a good solution).
  
-C) HD added an Accelerator Pump on the CV40 in 1989 to help minimize carb farts by squirting extra fuel into the carb when you first twist the throttle. However, the EPA settings on the carb create a general lean condition which tends to increase the problem. This is another reason to do a proper tune on the carb, getting the overall Air-Fuel-Ratio (AFR) right, before addressing carb farts. Be sure the Accerator Pump is squirting a good spray into the carb, directed at the needle.+C) HD added an Accelerator Pump on the CV40 in 1989 to help minimize carb farts by squirting extra fuel into the carb when you first twist the throttle. However, the EPA settings on the carb create a general lean condition which tends to increase the problem. This is another reason to do a proper tune on the carb, getting the overall Air-Fuel-Ratio (AFR) right, before addressing carb farts. Be sure the Accerator Pump is squirting a good spray into the carb, directed at the needle ​to break up the stream into a spray.
  
 Every carb and engine is slightly different. Pay close attention to when & how you are getting carb farts. Use a thorough and patient approach to finding where the problem is located and choosing the right solution. Every carb and engine is slightly different. Pay close attention to when & how you are getting carb farts. Use a thorough and patient approach to finding where the problem is located and choosing the right solution.