no start, backfiring through carb, new engine

[hondamxerd]

i recently put a 430 kit in my 99 400ex, now it wont start, it just backfires through carb, tried all of the following,
new plug
new gas
verified timing was correct
valve specs correct
wiring correct
nice blue spark
good flow of fuel through tank and carb, nice stream out of carb

even tried to drift start it, although then you can hear an audible valve noise

it has an aftermarket cam, which i did not install to begin with, is there a different istallation or setting for an aftermarket cam, meaning do i put the timing a few teeth advanced or retarded from factory specs?

dont know just shooting in the dark

[Fast350ex]

I have the same exact problem as you with my used 400 (440), someone put a curtis sparks cam and chain before I got it and it won't start, it makes a sharp sucking noise through the air filter. Sometimes I get it started and I have to keep the revs higher than idle or it will shut off, and I've tried everything you've tried, I'm planing on a jet change to see if that helps.

If anyone has any advice for me and hondamxerd it would be greatly appreciated.

[K_Fulk]

Mine was doing the same thing as yours was this summer. The timming was off one tooth. Since my flywheel was lightend i couldnt see the flywheel mark. So when i put it together i put it together with the piston all the way up and tdc was actually about 2mm on the down stroke.

If your flywheel isnt lightend rotate that to the t mark in the little window.
Make sure the lobes are facing down on the cam.
Line up the sprocket and install the chain and sprockt.
Install the chain tensioner.
And rotate the motor left one revolution untill the t mark is back in the window and make sure the timing marks still line up 2 parellel marks flush with the head and the other pointing up.

[cals400ex]

yes, check the timing again. make sure both of the air boots holding the carb on are tight. also make sure there are no cracks in them. i noticed my aftermarket ignition box makes the problem worse too.

[hondamxerd]

thanks, i will try this again tomarrow, i appreciate everybodys info