406 jettingg problem Where to start....

[wildwheelerb200]

hey whats up i had a 440 in my 400ex but now i down sized to a 406. I was wondering if anyone knew about where to start with the jetting.

I have a 406 weisco 11.1 piston stage 2 hot cam stock valves and ports with full exaust with intake.

does anyone know about where to start for jetting it. Pilot jet ,main jet and air/fuel mix anyones help is great. thanks sam-

i would like to know how this works out because when i need a rebuild i am going with a 406 9.8:1 piston possibly a xr400 or a stage 1 hotcam. I have a 158 keihin main in right now and I only bought jets up to 162

[rideracelivemx7]

40 or 42 pilot and id do a 165 main. and try that. but question for you, why did you down size? i thought the 440 wasnt all that impressive for such a big kit and price tag. but a 406? did you do it for reliability or did you have a series of unfortunate events lol

[wildwheelerb200]

I did it for both reasons. I have a 440 jug with over sized studs and i waped the cylinder 2 times and blew the copper head gasket about 4-5 times in 1 year. I think the 440 is not worth it. Your better off with a 416 or 426. The 440 is not what they are made to be. Bigger bore less effecent fuel burn and all a 440 is is tourque monster. and not alot of top end. It burns alot of fuel and isnt worht rebuilding every 2 rides with a 40$ head gasket and your time.. The 406 cylindar is what i could find and is a reliable set up.I would have wanted to go with a 416 but that what i found. I want a little more power but dont want to rebuild it every 2 rides...

[rideracelivemx7]

bummer dude, I have yet to have a problem with my 440 besides dropping the intake valves but that was expected. I ride mine hard and show it off infront of my stock riding friends when im not on the yz. but that sucks you had that many problems

[wildwheelerb200]

yea i ride it very hard and push it. I dont have the $ to get a 450 so i just keep fixing it so its never let me down on the trails or nothing it just always happens right when i get to the truck so i caint complain about it.

[wildwheelerb200]

170 main with a 42 pilot with air/fuel 2.5 turns runs perfectttttttt

[xtullyx16]

man that sucks to hear that u had so many problems with ur 440.. my friend has a 3mm stroker 440 and has the oversized valves and all that and only thing he had problems iwth was his stock head studs got loose and blew a head gasket and then he used heavy duty and loc tite and solutioin solved hes been racing it all this year! knock on wood tho.. you never know