strange popping on decel 02 426F


5 replies to this topic
  • rufusz

Posted April 28, 2008 - 11:28 PM

#1

Hi

I've recently did a whole rebuild on the engine, fixed the 5th gear throwing out problem and installed an HotCams exhaust cam with autodecomp and the bike now does strange popping on decel. Beside that it runs better then before (did shimming on the exhaust valves also and on valve 1 of the intake, the rest was ok). So on strong accel and then decel, it starts a series of rapid popping. Before changing the cam it popped fewer times like 2 seconds between poppings, now it's like gunfire 1/second or maybe a little faster :eek:
Any ideas what could cause this? Timing must be right, installed like this :
old intake cam with I punch mark aligned to cylinder head, hot cams exhaust cam one punch mark aligned with cylinder head, other at 12'o clock.

  • 426 NOOB

Posted April 28, 2008 - 11:44 PM

#2

Hi

I've recently did a whole rebuild on the engine, fixed the 5th gear throwing out problem and installed an HotCams exhaust cam with autodecomp and the bike now does strange popping on decel. Beside that it runs better then before (did shimming on the exhaust valves also and on valve 1 of the intake, the rest was ok). So on strong accel and then decel, it starts a series of rapid popping. Before changing the cam it popped fewer times like 2 seconds between poppings, now it's like gunfire 1/second or maybe a little faster :eek:
Any ideas what could cause this? Timing must be right, installed like this :
old intake cam with I punch mark aligned to cylinder head, hot cams exhaust cam one punch mark aligned with cylinder head, other at 12'o clock.


Popping is a sign of a lean condition or an air leak. Usually when you do any performance mod, especially a pipe or cams, the motor will become lean. I would suggest that you play with the air fuel screw and if that doesnt make the bike rich enough, go up a size on the pilot or main jets. Hope this helps

  • rufusz

Posted April 28, 2008 - 11:49 PM

#3

1. Air leak where?
2. What do you mean to play around with air/fuel screw? How do you know when is the setting right?

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  • 426 NOOB

Posted April 29, 2008 - 12:01 AM

#4

1. Air leak where?
2. What do you mean to play around with air/fuel screw? How do you know when is the setting right?


When you replaced the rebuilt motor in the bike, you had to put the air boots back on the carb from the airbox and from the carb to the head. These are possible air leak spots. When you mess with the air/fuel screw you can lean and richen the motor out, depending on which way you turn the screw. You need to go richer, when the motor stops popping on decel, you have found the right mixture.

  • 426 NOOB

Posted April 29, 2008 - 12:05 AM

#5

forgot to mention turning the air fuel screw counter clockwise will richen the carb, this is what you need.

  • grayracer513

Posted April 29, 2008 - 06:17 AM

#6

1. Air leak where?

In the exhaust system, usually. It has nothing to do with lean mixture in that case, and everything to do with the basics of combustion.

2. What do you mean to play around with air/fuel screw? How do you know when is the setting right?


http://www.thumperfa.../jetting.htm#PJ





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