Valve noise when hot
 

I just went through and did the cam chain tensioner replacement job.. All went well except now the bike sounds great when cold.. just perfect.. when it heats up I can hear what sounds like valve lash noise. My logic tells me this makes no sense as you would expect noise when cold to go away when hot. Could this be something with the cam bearings... incorrect torque settings. I used molly grease and did not have a torque wrench that goes to 25lb but I am sure they must be close... I am going to get a stethescope to pin point the noise... but very annoying.

RE: Valve noise when hot
 

The valve lash goes up when the engine is hot.

RE: Valve noise when hot
 

I was under the impression that as the metal of the cam and follower expand it would reduce the valve lash not increase it.. But why do you say it would increase with heat?

RE: Valve noise when hot
 

It is the alumin in the cylinder head that expands muchs more than steel, pulling down the valves and lifting the cams when engine is hot.

RE: Valve noise when hot
 

Ummmmm - I believe jemenon is correct. The valve train expands when hot, thus lowering clearance between cam/follower/valve. Valve clearance set too tight when cold means a valve that won't seat properly when hot. That is also why, in general, exhaust valves are set looser than intakes. Exhaust valves run in hot exhaust, intakes get cool fuel/air blowing over them, thus exhaust valves expand more requiring more initial clearance.

It's doubtful the cam has anything to do with the noise you hear unless a cam bearing cap was cracked during installation and has lost oil to one or more cam lobes or a bearing (don't ask me how I know that can happen. Okay?). An oil feed passage may also be blocked. I'd suggest taking the cam cover off and checking to see that oil is getting everywhere it should. You might even want to start it up and watch to see if oil gets to everything. Just make a temporary shield of tinfoil to put in front of the camchain so you don't spray oil all over the front of your engine while running with the cover off.

I wouldn't ride or run it until you've checked out the oil situation. Cams are expensive. Cam bearings are cast into the head and are also expensive to replace. You either find a great machinist who can bore out what's there and build you new ones, or you buy a new or used head.

Good luck, and I hope I'm way off base.

RE: Valve noise when hot
 

Aluminium expands about twice as much in heat as steel. That will definitely make the lash on intake valves to increase with heat. There are numerous of examples where an alumin head engine with below zero play on intakes are hard to start and runs bad when cold, but runs OK when engine is warm. People are often confused by this symptom as they many times believe the lash goes down with heat, which it doesn't, and don’t figure out the intake lash is too small. Regarding the exhaust valves, I don’t know if the steel valve or the aluminium in cylinder head expand most when engine is warmed up, or if its about an even race between them regarding thermal expansion. Perhaps some have measured the cold/hot exhaust lash and can tell.

Another concern why exhaust have larger lash, except for getting more time to cool down, could be the long term wear. The valves will chew themselves up in the head during time and at one point the lash will be zero or negative if not adjusted periodically. If the exhaust where to have zero lash before the intakes the engine head had to be pulled to fix burned exhaust valve/seats. When intakes come first to this point, it is recognised before damage has occurred, and it’s normally just to adjust them back to spec.

RE: Valve noise when hot
 

R1000: You are correct when you state that valve clearances on OHC, aluminum engine increase with heat. A google search came up with three sites that agreed with you, and two that didn't. To settle matters I checked the valves on my '91 1kF, then warmed it up until normal operating temp was reached and rode it for fifteen to twenty minutes. Immediately after shutdown (well, give time to remove the seat, tank, etc.) clearances were rechecked. It appears valve clearance increased by .002" to .0025" on intake, slightly less on exhaust. I thank you for the information, and retract my statement that clearances decrease with heat.

Jmenon: ignore what I said about clearances decreasing with heat. I was wrong, wrong, wrong. It is possible that you have them set to where they are quiet when cold, and noisy when hot.

In case neither of you look at this thread again I'm starting a new thread with the same information.


DRam

RE: Valve noise when hot
 

Thanks guys.. I think your are right. I will check the intake valve lash.. I am almost certain this is it as the bike sounds perfect when cool.

I also but Castrol GTX 10-40 and I don't like how the motor runs on this or shifts.. There honda bike oil seems better..

I will let you guys know how it goes..

Thanks

RE: Valve noise when hot
 

Thanks DRam for checking this up. I was a little unsure regarding the exhaust valves.