2005 Honda 400EX Jetting
 

I have a Dr.D. Slip on and it has a 148 main jet and a 38 Idle. I was told to go up to 160 Main and a 42 Idle.

The airbox lid is off with a K&N Air Filter.

What would be the best jetting for this application.

Aslo, if jetting is not right on a 4 stroke, could this cause clattering when the motor is under a load? It sounds like metal is bouncing around in the motor only if reved real fast then it does it for a second but mainly under a load like 3rd gear going up a hill the punching it, it clatters pretty bad but riding normal it doesn't.

Please help!!!!


Thank you!

2005 Honda 400EX Jetting
 

No on can tell you what jets to run, every machine is different even with the same mods, and your location makes a difference as well. The jets that you were told to use sound a little big for just a slip on IMO.

As for the clattering, that sounds like the valves need adjusting to me. If the jetting is off it can miss and sputter, but it shouldn't "clatter".

2005 Honda 400EX Jetting
 

I gapped the Intake Valves at .004 & Exhaust at .005. Is it better tighter than looser as far as perfromance and noise?

Thanks!

2005 Honda 400EX Jetting
 

Check your honda specs if you have a manual it should say in there if not contact a service dept or ask someone on here what the right clearances are and make sure you check the intake and exhaust etc and it depends on what jet manufacturer you got as some jet companies have different numbered jets but they could be close in number it depends on altitude and the company

2005 Honda 400EX Jetting
 

try a 155, that should be plenty, my 400 ex jumped about that when i Piped it.

2005 Honda 400EX Jetting
 

intake lash is .004 and exhaust is .005 like u said, good rule of thumb for any eng is tigher is better, doing that it keeps the valves oppen longer letting more air into the eng on the intake stroke and hold the exhaust vavle oppen longer to get rid of it all on the exhaust stroke. if you run them to tight u can run the risk of slaping the piston, not cool haha. on my 02 400ex i run them just tight enough that the feeler gage moves with miniumal but some friction. well keep us posted bowz