My 19 year old son put a race cam (only) in his stock '01 400ex without consulting me or an engine builder. Upon startup, he bent 2 intake valves. He called the cam manufacturer (webcam) and was told he needed different valve springs and guides. He took the parts and head to the local honda dealer, who installed them into the head, along with 2 new valves.

Last nite he re-installs the head, and, upon startup, hears the same clacking noise (like piston to valve contact) that he heard b4.

Shld we take the whole bike to the dealer for diagnosis? Replace the piston? with what?

Help!

 

Before you take the engine back apart make sure the valves are adjusted.It is easy to mess up on the adjustment,& they can be very noisy.

 

Check to make sure the cam sproket bolts are on good, and make sure you havn't rotated the motor backward even the slightest bit.

 

sonny verifies valve adj is per spec, and piston is tdc on correct stroke.

We're dissapointed that the dealer didn't know that the piston needed to be changed for the new cam, in spite of us asking specifically.

 

save your self some major exspense take it to the dealer before you damage many other part's ..it should only be a small charge to install the cam and putt the timming corectly for you .

 

and second dont install that cam !! it will not work with a stock motor ! it is designed to work with high comp piston !!

 

I agree with the last comment. The big cam needs a piston. Now for the next problem...With the big cam in the 400ex, you need valve springs. Problem is, most of the springs on the market have way too much seat and lift pressure for your application. What problems can you expect??? The rocker arms will fail. Either get springs with a lower installed height pressure or you will need the rockers hard faced.

 

As usual, you guys are correct.

Upon re-re-examination, son found that the crank was not at tdc.

Bike now runs well, with lots more h-p. Son knows he'll need to harden his rockers and replace the piston soon.

Really appreciate your contributions!

May God Bless America.

 

Doo,

If you are smart, you would not run the 400ex for one second without replacing the rockers.

Your rockers are wearing as we speak and the 400 recirculates the metal filled oil into the rod and other critical engine components. You are asking for really big problems.

 

dont listen to the hard facing thing ...ive been racing a 450lrd built ex for the hole season and just took off my head cover yesturday to adj timming and my rockers look perfect and Im runnig a preety rad cam ...and second if you do were out the rockers in five years or so you can buy new ones cheep