TOPIC:

I have had no luck diagnosing the noise emanating from my cylinder head. I do know that it is not the valves hitting the pistons, or the valves hitting one another. The head appears to have been clearanced, so the cams have room enough to spin, still it sounds like a diesel - horrible rattling.

My bike is a 1976 KZ 900 with a 1075cc MTC piston kit installed and I am using .385 lift cams, Z2 grind. The valve sizes are stock.

Does anyone know of any good bike shops that have experience working on modified KZ engines in Northern California? I live in Reno, NV and I have a truck. I am willing to travel to get this problem fixed, as it appears to be beyond my capabilities. I may even be willing to go to Southern California...

try APE:whistle:

check the crosses that are up inside the valve cover itself.

nads.com wrote:

check the crosses that are up inside the valve cover itself.

they should have cleaned those up when they clearanced the head.try it without the valve cover on ,yeah it will drip some oil but its low pressure.if you dont mind shipping it i know a real good machinist here in omaha whos doing both of my motors.

is it a solid even sharp tic tic tic

or is it more a jumble of rattling and not so sharp and distinct.

if the latter, change your fuel if it is old and check you ignition timing.

Post edited by: Duck, at: 2006/06/26 16:14

Thanks for the input. Yes, I removed the plus signs from the cover. I ran the engine without the cover and the noise was still there. The gasoline is fresh and the timing is set. The noise is a loud rattling - literally sounds like a diesel. I'm thinking it could be valve lash? I would rather have an expert listen to the engine rather than disassembling it and shipping it. I did check with APE and am waiting to hear back...

You said it doesn't feel like there is any interference when you turn it over by hand.

Here is what I might try next. It's really hard to say, not being there to see and hear...

Take out the plugs, squirt a little light oil in the jugs, spin it with the starter and see if it rattles. Use a really good battery and/or jumper cables from your car/truck wth a good battery.

If it doesn't even hint at rattling I might go back and look at the timing. Retard it by about five degrees and make sure that it's not advancing too early.

Some other wild and crazy ideas...

Did you put the BB kit in? Did head gasket hang over edge of bored jugs? Did pistons come really close to head gasket? Did pistons extend beyond the top of the block? Did you remember to torque the head bolts or are they on hand tight? Did you remember to put the wrist pin retainers in? Did you use 18mm pistons with 17mm pins

-Duck

My guess is that if you have the timing on the fire mark, it is too advanced and the rattle is coming from the combustion chamber. Try backing it down signifigantly and youll know the intsant u start it wether it is the death rattle or not. The compression ratio must be known also. Gotta have oil up there too.

Post edited by: nads.com, at: 2006/06/27 01:28

Valve clearance tends to decrease as the head wears in but if you are just setting up the bike, recheck clearances as tooooo much clearance will set up a tremendous clattering. You will also ruin your cam lobes if your clearances are too great. I am sure no one else has ever put in the wrong shim (old man has old eyes) but if you do and have about .5mm of clearance the noise is quite impressive and it doesn't take me long to get that valve cover back off and check to see which shim I put in was wrong bwhahaha

Oh yeah, Nads.com was pretty much on the mark as far as the rattle possibly being a timing issue with spark coming way too early... The noise I refer to in my suggestion is a click click or clack clack where the noise Nads.com refers to is a rattling noise like the sound of ball bearings in a metal bucket if you shake the bucket (shake, not stir!).

Post edited by: wiredgeorge, at: 2006/06/27 09:23

Thanks to all you guys for trying to help a dummy like me! The one area I have not looked at was the ignition timing, other than double checking the setting. Right now it is set to fire right on the F mark. I will try retarding it and check the results. Up until now I have blamed the retardation of the builder, but maybe the engine timing could be at fault. At least that is an easy thing to try.

I remember putting in the pistons (way back in 1999)and the wrist pins were definitely the right size. Also, I used the nylon buttons rather than circlips. The head gasket was the right size, with no overlap.

If it does turn out to be the timing I will be quite relieved.

Still, if anyone knows a good shop close to me, I would not mind some input from someone who can hear the exact noise and knows a lot about these engines.

wiredgeorge wrote:

Valve clearance tends to decrease as the head wears in but if you are just setting up the bike, recheck clearances as tooooo much clearance will set up a tremendous clattering. You will also ruin your cam lobes if your clearances are too great. I am sure no one else has ever put in the wrong shim (old man has old eyes) but if you do and have about .5mm of clearance the noise is quite impressive and it doesn't take me long to get that valve cover back off and check to see which shim I put in was wrong bwhahaha

Oh yeah, Nads.com was pretty much on the mark as far as the rattle possibly being a timing issue with spark coming way too early... The noise I refer to in my suggestion is a click click or clack clack where the noise Nads.com refers to is a rattling noise like the sound of ball bearings in a metal bucket if you shake the bucket (shake, not stir!).<br><br>Post edited by: wiredgeorge, at: 2006/06/27 09:23

I read the instructions on your website about checking valve clearances. Very nicely written and easy to understand. I am going to double check the clearances on my bike, but I was wondering what clearances are acceptable? Are the stock clearances still the appropriate measurements even though I no longer have stock camshafts?