Why you should not neglect your valves.

93468 Views 101 Replies 53 Participants Last post by Kawasakian, 9 mo ago

elr658

Discussion Starter · Apr 5, 2007

Several people have been PMing me for advice on mechanical dilemmas which have stumped their local mechanics. On several occasions, they were ultimately resolved by a valve adjustment. This explains why. Now, it doesn't matter what kind of machine it is. Ironhead Sportster, CBX or EX500 the theory is the same. This assumes you have a nodding familiarity with a four stroke, internal combustion engine.

Valves 101.

What is the importance of a proper valve adjustment?

A valve is designed to have a certain amount of clearance specified by the vehicle manufacturer. This specification is determined by the type of actuation system, but it won't be zero. Insufficient valve lash causes many problems, among them valve burning and loss of compression. Valves burn because insufficient lash holds them slightly open. They don't have the opportunity to transfer their heat to the cooler mass of the cylinder head. The heated exhaust gases erode the heads of the exhaust valves causing compression loss. The damage is permanent.

Valve lash will never increase. Valve seats pound into the surrounding cylinder head by the normal operation of the valves. This means valve lash closes up, until the lash goes to zero. Effectively, the valves stay open.

Before this happens, the machine becomes hard to start. This also causes problems which are masked as carburetion problems.

These problems are avoided by setting the valves to the loose side of the factory tolerance. The folks who make motorcycles know way more about making them than I do, the intervals they specify are decided by testing.

See less See more

1 - 20 of 102 Posts

napanock

· #2 · Aug 22, 2007

Just wanted to thank you for this thread. I got so **** frustrated with my zx1000, I went out and picked up a dl1000k7. Now I can take the time to work on the ninja.

The bike sat for 5 years with a busted starter chain. After I acquired it, replaced the chain, all fluids, lined the tank with Por 15 and had the carbs cleaned and synced at a dealer. Compression is fine, "failed" the leak down test, dealer said 2 and 3 were tight? The original owner put in a stage 2 jet kit, modified cams and yosh 4-1. The bike was always difficult to start cold.

I'm assuming carbon buildup may be adding to the valve issues and may hinder a proper valve adjustment. Worst case scenario, the head gets rebuilt, However there is a product from Kano labs called "Kreen", the propaganda states; "Guaranteed to improve your engines performance. When added to Either the gas or oil, of your engine, Kreen dissolves the carbon deposit
buildups and varnishing to Improve Compression · Increase Gas Mileage
Reduce Downtime · Restore Power By thoroughly cleaning the rings, valve, and fuel injectors" the directions say pour one ounce into each cylinder, reinstall plugs, rotate engine a few times and let sit overnight. Then simply start it up and blow out the carbon. Since I have the DL1000 it sure sounds tempting to try!

ELR658, Is a valve adjustment on a motor with 23,000 miles sufficient? or should I just pull the head and have it done somewhere? And do you know a good place in the northeast for this kind of work?

See less See more

elr658

Discussion Starter · #3 · Aug 23, 2007

Seafoam is my snake oil of choice. Adjust valves to loose side of tolerance. Administer a careful beating for 500 miles. Recheck. With 23K, I'd try that first.

Mercury

· #4 · Aug 23, 2007

just to make sure when somebody says loose side of tolerance if the tolerance was .08mm to .13mm you would set it to .13 ??

on my atv i dont see how the distance gets smaller - i would think wear and such would make the gap larger ?

Kenny

elr658

Discussion Starter · #5 · Aug 23, 2007

The valve seats pound into the aluminium head. The lash closes. It NEVER EVER (if you do it right) increases.

That would be correct in your example, Merc. The "extra" clearance is to remove the ring of carbon on the valve face which impedes sealing. It is also why I recommend a recheck after 500 miles. A lot of people can bring a bike back from the dead. Mine's running good 15 years later.

Mercury

· #6 · Aug 23, 2007

so just to get this right... When the rocker arm is not touching the valve - the valve is open? That does not make sense to me

ill have to get a book

kenny

napanock

· #7 · Aug 23, 2007

Dontcha just love that Seafoam

elr658 said:
Seafoam is my snake oil of choice. Adjust valves to loose side of tolerance. Administer a careful beating for 500 miles. Recheck. With 23K, I'd try that first.

Megga Dittos ELR! Thanks to this forum, I now buy it by the case and it has improved things but I think your spot on with the adjust, beat, and recheck. Now i need to just find the time. Thanks again

LordGT

· #8 · Aug 23, 2007

Mercury said:
so just to get this right... When the rocker arm is not touching the valve - the valve is open? That does not make sense to me

ill have to get a book

kenny

I have an old 72 VW Bug. My mechanic, named Kenny, is a VW mechanic for 25 years, and those are his specialty. Not as many around anymore. BUT!! they are Aircooled and they do Require Valve Adjustments fairly often. I've heard him talk about Valve adjustments quite often, since I hang around there a lot.

My point is and I'm not an expert on Valves either, but he is always looking for Tight Valves when someone brings an Old VW in for a tune up or engine problems. He is never looking for a loose one, always a tight one that he needs to loosen up. He says there should be some noise in the Valve train, when it gets quiet, you should start to worry. Means they are getting tight and need adjustment. It just seems backwards to us unknowing types, but I guess that is the way it works.

So he seems to agree with Dr. House...:smile:

See less See more

elr658

Discussion Starter · #9 · Aug 24, 2007

Because your VDubber is right, your majesty.

LordGT

· #10 · Aug 24, 2007

elr658 said:
Because your VDubber is right, your majesty.

Yes, he explained it all to me yesterday. Now I understand..:smile:

inamaze

· #11 · Sep 5, 2007

Yep,

My first bike, and EX500 sat for over a year while the previous owner messed with it... mostly wiring but a lot of attempted starts.
I got it and of course thought carbs... cleaned those out and thrashed the starter for another few months trying everything to get it started.

Going with the advice "most carb problems are fixed with valve work", pulled the head and found several valves that wouldn't close due to carbon buildup (miles on the road and a couple of boneheads trying to start it for months).

Valves aren't perfect by any means, but cleaned them up and it runs about 90%. Not looking for a race bike just something to learn on so 90% is about perfect for now. I would have saved TONS of time if I had inspected the valves after obvious carb work didn't solve the problem.

Alizard

· #12 · Jan 21, 2008

elr658 said:
Valve lash will never increase. Valve seats pound into the surrounding cylinder head by the normal operation of the valves. This means valve lash closes up, until the lash goes to zero.

There is one case where valve clearance will increase (sad to say, I know from first hand experience). If your valve oil seals are leaking, oil will run down through the valves and gunk up the valve seats. Over time, this crud builds up and it will actually cause the clearance to increase because the valve doesn't close fully. On mine, I saw a valve walk from .003" to .005" over time. When I took the head off, I rotated the cam and scrubbed the crud off with a scotchbrite pad and the clearance went back to .003". Of course, the head still needed to be overhauled, but I was lucky I didn't burn the heck out of the valve because as pointed out above, when valves don't close up tight they run WAY TOO HOT from gas blowby and loss of heat transfer to the head.

So, if you do see a valve clearance wandering up......:icon_frow

See less See more

elr658

Discussion Starter · #13 · Jan 22, 2008

My daily rider CB750F has a bit over 40K on its second motor. It smokes like a train. Carbon NEVER happens there, because it's at redline constantly.:biggrin:

Mercury, the valve is closed when the rocker arm isn't touching for your info.

billtuti

· #14 · Feb 1, 2008

Yeah, Valve.

for someone like me who doesnt understand what you guys are talking about, may this link will help:

Howstuffworks "How Camshafts Work"

THRILLA

· #15 · Feb 11, 2008

on vw it is usualy the #3 exhaust valve that burns. you can hear them as they crawl by with no power.

Roofgunner

· #16 · Feb 29, 2008

My experience with a KZ900 with more than 100,000 miles, when it came to valve adjustments was that after about 70,000 miles all I had to do was to check the valves and they didn't need shims. Most valve adjustment occurs in the engines early days. Alot of people think that since the engine runs quiet, the valves are OK. Wrong, they could be doing the silent burn.

Roofgunner

· #17 · Feb 29, 2008

One more thing I forgot. On the KZ400's (1976, etc) Kawasaki put out a service bulletin regarding surging at idle on these bikes. I have a feeling it also effects others such as the 650 and 900. If the valves are not correctly adjusted the motor will surge at idle. The bulletin had us increase the valve clearance slightly on the 400's to stop the surging and it worked.

Bicycle Lee

· #18 · Apr 28, 2008

So this is my first post on this board and it is due to my troubles with my 78 KZ1000 police bike.
From what everyone is telling me, the valves are a safe place to start trying to rectify low compression. the manual is on it's way in the mail, but I figured with the tutorials I have found online I can at least see what I can see about the valve clearances.
One question: I checked compression on all four cylinders and they all hovered around 55-60 psi. I thought this was a bit strange because I assumed they would all be different. Does this strike anyone else as peculiar? Someone on kzrider.com said this may be due to a bad head gasket, but I wanted a second opinion.
Thanks in advance.

OKC_Kent

· #19 · Apr 28, 2008

Bicycle Lee,

Did you do the compression test holding the throttle wide open? Common mistake, try it again.

Bicycle Lee

· #20 · Apr 28, 2008

well, I didn't yesterday but I just pulled out all the plugs and removed the carbs and tried again. #1 was 50 psi, and the rest were 60 psi. Granted, this is testing a cold engine (since the **** thing won't start!) but I can't imagine the compression being only 1/3 of the recommended psi just cuz it's cold. Maybe I'm ASSuming....

I checked valve clearances and here's what I got by cylinder:
#1. INTAKE- .102mm
Exhaust - .102mm
#2. IN - .102mm
EX - .102mm
#3. IN - .051mm
EX - .102mm
#4. IN - .076mm
EX - .102mm

so these are all within the specs I have seen for my model/year. What now? Head gasket? Piston rings?
If not THESE, then what after that?

See less See more

1 - 20 of 102 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.