zrpilot
01-07-2012, 07:05 PM
Guys,
As many of you "veterans" know I rarely get back here, but today I read caseywoods5's post about the trouble he had getting his 400EX to run right with the 450R carb.
I want EVERYONE who is considering making this upgrade to know that it is VITALLY important to use the existing hot start components and simply use the silicone to seal off the top of the hot start hole.
Also please read and understand my jetting post, (http://www.exriders.com/vbb/showthread.php?s=&threadid=394028&perpage=10&pagenumber=1) I wrote it for those of you who may not understand jetting so you can diagnose your jetting troubles. Please understand where you are having problems (ie: idle, mid-throttle, wide open) and concentrate on the appropriate circuits that effect your problem. For example don't put a 220 main to solve an idle problem.
Everyone focuses on what the main jet is, but in reality a main jet has little to do with overall performance. Nope, assuming the carb is installed correctly, has the float set right (VERY IMPORTANT), the hot start is sealed correctly( AGAIN VERY IMPORTANT), then the pilot is most important for idle issues, while the needle is important for 1/8 throttle to 3/4 or more throttle, while the main most important for 3/4+ throttle.
I keep seeing things that I have to make a helpful list (please feel free to add yours)
1) Don't check jetting by revving in neutral at a standstill, IT WILL STUMBLE and COUGH!
2) Don't idle or rev in neutral because your HEADER WILL GLOW RED, especially at dusk or night! Even IF your quad is jetted perfectly! All jetting changes should be made while putting a load (riding or dyno) on the motor.
3) Replace every part you can afford. Don't go cheap, piece of mind means a GREAT running quad. In otherwords, if I WERE doing a carb upgrade I would replace the float, hot start, all gaskets, ETC...
4) IMO the needle jet is more important then the main jet...
5) With today's unleaded fuel, reading a plug is VERY difficult, and probably means the plug would need to be cut (or chopped) apart to check where the insulator meets the steel to get an accurate reading.
6) A 6 point main jet change made VERY little difference on my quad on the dyno with an air fuel meter! For proof please read:
http://www.exriders.com/vbb/showthread.php?s=&threadid=394028&perpage=10&pagenumber=1
7) Fully warm up the engine before making any jetting judgements.
8) The 400EX is VERY tolerant of jetting (assuming it is NOT detonating)... and honestly it doesn't have HUGE gains on jetting.
9) Every motor is different, ask for baseline advice, but go out and ride yours then change your jetting until it runs to YOUR satisfaction!
Whew... I am sure there is more, but that is all I can think of...
As many of you "veterans" know I rarely get back here, but today I read caseywoods5's post about the trouble he had getting his 400EX to run right with the 450R carb.
I want EVERYONE who is considering making this upgrade to know that it is VITALLY important to use the existing hot start components and simply use the silicone to seal off the top of the hot start hole.
Also please read and understand my jetting post, (http://www.exriders.com/vbb/showthread.php?s=&threadid=394028&perpage=10&pagenumber=1) I wrote it for those of you who may not understand jetting so you can diagnose your jetting troubles. Please understand where you are having problems (ie: idle, mid-throttle, wide open) and concentrate on the appropriate circuits that effect your problem. For example don't put a 220 main to solve an idle problem.
Everyone focuses on what the main jet is, but in reality a main jet has little to do with overall performance. Nope, assuming the carb is installed correctly, has the float set right (VERY IMPORTANT), the hot start is sealed correctly( AGAIN VERY IMPORTANT), then the pilot is most important for idle issues, while the needle is important for 1/8 throttle to 3/4 or more throttle, while the main most important for 3/4+ throttle.
I keep seeing things that I have to make a helpful list (please feel free to add yours)
1) Don't check jetting by revving in neutral at a standstill, IT WILL STUMBLE and COUGH!
2) Don't idle or rev in neutral because your HEADER WILL GLOW RED, especially at dusk or night! Even IF your quad is jetted perfectly! All jetting changes should be made while putting a load (riding or dyno) on the motor.
3) Replace every part you can afford. Don't go cheap, piece of mind means a GREAT running quad. In otherwords, if I WERE doing a carb upgrade I would replace the float, hot start, all gaskets, ETC...
4) IMO the needle jet is more important then the main jet...
5) With today's unleaded fuel, reading a plug is VERY difficult, and probably means the plug would need to be cut (or chopped) apart to check where the insulator meets the steel to get an accurate reading.
6) A 6 point main jet change made VERY little difference on my quad on the dyno with an air fuel meter! For proof please read:
http://www.exriders.com/vbb/showthread.php?s=&threadid=394028&perpage=10&pagenumber=1
7) Fully warm up the engine before making any jetting judgements.
8) The 400EX is VERY tolerant of jetting (assuming it is NOT detonating)... and honestly it doesn't have HUGE gains on jetting.
9) Every motor is different, ask for baseline advice, but go out and ride yours then change your jetting until it runs to YOUR satisfaction!
Whew... I am sure there is more, but that is all I can think of...