a9 camshaft & Big Port Valve Head By gy6fandan (Read 1,851 times)

[gy6fandan]

Just saw a video on a guy that installed an A9 camshaft and has a problem.

Just want to make sure I don't have problems like him.

Cant find specs (way of measuring A9 cam) prior to install to make sure its not faulty / actually an A9.

My upgrade will consist of the A9 cam and Big Port Valve Head with stainless steel valves and High Compression Valve Springs Rated to 12,000 RPM .

Just curious what this guys problem may be and how I can "AVOID" the problem with my setup.

A9 camshaft problems

Thanks for any "BEWARE" / "LOOK OUT FOR" info upfront ....

Like timing mods / valve spec changes, etc. with my planed upgrade.

[glavey]

This is just an educated guess, but I think either the guy's valves are really loose or the valves are being pushed too far into the combustion chamber because of the higher lift on the new cam and causing the valves to very slightly hit the piston.

I haven't upgraded my cam or head/valves, so I cannot say if you will have the same issue or not. I think it would be wise to measure the distance between the valves and the piston before you start the engine for the first time with the new cam and head.

[gy6fandan]

glavey --> Thanks and... how do I measure valve to piston clearance before I install this thing because I am clueless on that.

[jct842]

If it was me, before I ever started it the first time I would roll over the engine by hand with spark plug out feeling for any resistance. If you set the valves for the .005 clearance and on both strokes of the engine.... piston at the top, intake and exhaust, push down on the valve stem to see that it can still move in toward the piston top a little before hitting it. Should the valve touch the piston it needs to come apart and get some relief ground into the top of piston before starting the engine or you will end up with bent valves. I am not sure exactly how much between properly adjusted valve and piston but thinking it needs at least .05" to be sure there is never a chance of touching it while running.

[jct842]

Not sure the guy in video will have much left to salvage with that much racket going on. He should have checked clearance before starting it.

[Alleyoop]

Folks, do you really know how this stuff works!! Only way a piston is going to smack a valve is if it is way out of time and then only if for some reason the valve is being pushed open to much which is pretty hard to do.
Lift on cams is minimal at best it is the duration of the lobe on its high spot that determines how long the valves are kept open for more or less air and fuel and exhaust.
Alleyoop

[gy6fandan]

Alleyopp --> thanks and good video.

My concern was since I am installing a "different" cam - A9 cam - and Big Port Valve Head with stainless steel valves (and because someone else mentioned checking clearance)I thought a defective new part was possible. Better safe than sorry since its my third head in 7k miles.

ebay item (head) = GY6 150cc High Performance 63mm Taiwanese Big Port Valve Head (NON EGR)
solde by scooterelments-rcgalore

[Alleyoop]

Not a problem bud, if your concerned then by all means check the clearance this way you won't get an ULSER