Valves hitting pistons?

Hello everybody,

I am new to this forum and I am hoping to get some advice from experienced KZ engine builders.

I have a 1976 KZ 900 A-4. I modified the engine as follows:

Replaced the stock cylinder block with a KZ 1000 block; had the cylinders bored and installed a 1075cc MTC piston kit. I then had the cylinder head worked on by replacing the valves, guides, springs, etc.

I then installed .385 lift cams, as was recommended by the shop that did the machining (Cope Racing). Well, I started the engine for the first time yesterday and I heard a very loud clicking sound from the top of the engine.

So my question is: is a .385 lift cam tall enough to cause the valves to hit the pistons? Both Cope and the cam manufacturer stated it was NOT, but I would like some other opinions.

I ran the engine twice, both time for about 30 seconds at idle. With the noise this loud I don't want to run it again until I know what the problem is. For all I know, I may have bent the valves already...

Any input would be appreciated.

Post edited by: Scoot Jockey, at: 2006/06/19 12:29

Post edited by: Scoot Jockey, at: 2006/06/19 12:29

kind of wonder if the cam chain is loose or the valves are way loose, if the valves hit the pistons they are bent and I dont think it would run, plus you would be popping out of the exhaust and carbs if it did

did you clear the cam cover for larger cams? i ground the x's off mine.( on the inside over each cam lobe)

I don't have much experience with high lift cams but I would advise you to check valve clearances as a clearance that is excessive will set up quite a racket.

Yes I ground off the "X"'s from inside the cover.

Could you please advise the procedure for checking valve clearances?

Post edited by: Scoot Jockey, at: 2006/06/19 14:33

when the piston and valve kiss you have reached the ooop-s zone . it is wise to turn the engine over by hand several times before you use the electric start:
cam chain, cam chain adjuster, valve lash, lobe interference with head or cover. then the worst.. piston to valve contact. all maka lots o noise when not built right.
on 900 head you must use clay and check piston clearance to valves after .380" of cam lift. set valve to piston clearance at .065" with thicker head gasket or cylinder spacer. get extra gaskets because you need to torque it down to test. at that lift different valve springs are required as well. I use megacycle for my hiperf cams and have gotten the info from building a similarly modified engine as you have described.

Post edited by: trippivot, at: 2006/06/19 14:50

Post edited by: trippivot, at: 2006/06/19 14:51

www.wgcarbs.com/269767.html

Whoever assembled the head should have set preliminary clearances based on valve stem length but this will change as soon as you tighten things down and run the engine a bit.

I would suggest that the cams are out of time. There is no chance that a .385 lift cam would cause the valves to hit MTC pistons. Our .410s and .435s will clear MTC pistons.

Was the tappet bore area clearanced for the cams? We have never sold those small cams, but our .410s require cam clearancing.

There is also the chance that the sound you hear is the valves touching each other. Also easy to do if the cam timing is off.

Jay

Post edited by: APE Jay, at: 2006/06/19 15:15

Hey thanks to everyone for offering their thoughts. I appreciate the feedback. I did turn the engine over by hand many times and never heard any noises. I wish now I had tried checking for impact with clay prior to assembly.

I will definitely start by double-checking the cam chain to see if the tension is still correct. Then I will make sure the cams aren't hitting the tappet area of the head.

If these areas are okay, then I will check the cam timing. I hope those valves aren't hitting each other. I am also considering running the engine with the cam cover off (just for a few seconds) to see if there are any contact points there.

I started this project many years ago and I wish I just would have went with a stock 1000cc setup. Oh well...

If you had the valve work done and used stock size valves, you shouldn't have valve to valve issues if the cams are in time.

It is when oversize valves are installed, and whoever is doing it doesn't know what the minimum distance between the valves, when they are on the seats, that the Kaw needs, to avoid contact.

Well supposedly the valves were cut down to stock size, so assuming the machine shop knew what they were doing that should work in my favor. I had the work done many years ago (this project took way too long). I'm not even sure Cope Racing is around anymore. I know their website no longer exists.

I still have the cam timing kit, so it should be easy to check the timing. I just have to watch the video and refresh my memory.

Thanks again for your feedback. All of this information has helped me think this problem thru...

i would pull valve cover and inspect shims. perhaps one was forgotten or is not seated in bucket. ditto for the camshaft bearings. a shell could have gone missing. heck, they may have left out a spring. you can check cam timing and chain while you're there. for clearance, measure with feeler guage at greatest clearance. book spec on the 1000 is 0.002" minimum 0.006 inch maximum. suspect 900 is the same.

Post edited by: Duck, at: 2006/06/19 19:17