Valve clearance increased – OLD Bull Trailriders

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September 1, 2009 at 11:10 am #97091

Paul
Member

Time to check the valves.
OK so the exhaust valves are the same and stable – good.
The inlets though, one is the same as always, .09mm but the other one has been slowly decreasing, until now, now it has increased.
The readings for this valve clearance have been; .09 then .08 then .075 and now it is .09 again!
How can this happen?

I checked it 3 times, turned the engine over between each reading, same every time.
The engine is stone cold (hasn’t been run since Saturday).

I have been using valve saver in the fuel but I dont think that has anything to do with it.

What’s the reason?
Is it some tiny crud between the valve and seat?

Should I be concerned?

September 1, 2009 at 11:44 am #150827

Bruce Curtis
Member

Hey Beemer I have seen this before (i dare say quite a few of us old Bustards have) usually means you have wear or hard facing has come adrift on a component of your valve gear. In old CB750/4s it maeant high rpm oil starvation, amd the same as the big yamaha singles.

To coin a phrase, yes I would be investigating, at least checking with some BMW people to see if it is normal.

BC

September 1, 2009 at 11:47 am #150828

Paul
Member

I think I found an explanation at Yahoo;

“Valve clearance in single overhead cam engines using rocker arms and pushrod type engines will increase becaue of wear at the rocker arms, usually the pivot point. There is some valve seat recession, but that amount is less than wear in the rest of the system. “

The Beemer has assist rockers in between the cam and the bucket, so like it says above, wear on the rocker arm will increase the clearance more than valve recession will decrease it.

Does that seem right?

Does to me.

Anyway they are still well within spec so I will just put it back together and log the measurements as usual.

September 1, 2009 at 11:57 am #150832

Bruce Curtis
Member

Yes Rocker arms traditionally wear, how many Ks on your bike so far Mr Beemer?
probably normal, but usually the valves recess growth takes it up.

BC

September 1, 2009 at 12:02 pm #150842

Paul
Member

5200K’s and 113 hours.
The service intervals and everything all work on engine hrs.

Acording to the book I should have done a full engine overhaul including replace the crank shaft at 70hrs!
But thats for full-on competition use.

September 1, 2009 at 9:42 pm #150843

Greg
Member

I think I would record all the measurements like you have and do another 20 hrs on it and measure it again, in the mean time I would be carefully opening the oil filter when changing the oil having a look for chrome, or hard faced material. The filter should filter from the outside in, you will find it normally down in the joint of the paper. You can also drain the oil across a mirror which will show up brass etc

I wouldn’t be worried, just alert to it I think

TB

September 1, 2009 at 11:12 pm #150850

Bruce Curtis
Member

T/B have you ever heard that harmonic distortion can lead to this sort of wear, as i was told many years ago that kawasaki had made a gross mistake on the old GPZ900r (the first “ninja”) and engineered the primary harmonic period at around 3500rpm, which was 110kph on standard gearing, and this led to abnormal valve train wear?

BC

September 1, 2009 at 11:20 pm #150861

Anonymous

Harmonic distrotion is a problem in a number of fields so I don’t see why it wouldn’t have an effect on engine wear also under the right conditions.

Interesting to see this beemer. I need to check my valves soon so this is a helpful read. My bike has 7000Km’s on it now and probably 150 hours and I’ve never once checked the valves :dry:

September 1, 2009 at 11:42 pm #150867

Trent
Member

Why not moto?

Beemer what feelers are you using because the ones that I bought from bolton don’t let you get that accurate. IIRC there’s a 0.05, 0.06, 0.1, 0.15 , 0.2 and then a whole bunch of useless ones

September 1, 2009 at 11:49 pm #150862

Greg
Member

Mr Blue wrote:

Quote:

T/B have you ever heard that harmonic distortion can lead to this sort of wear, as i was told many years ago that kawasaki had made a gross mistake on the old GPZ900r (the first “ninja”) and engineered the primary harmonic period at around 3500rpm, which was 110kph on standard gearing, and this led to abnormal valve train wear?

BC

At one RPM Blue it can be an issue with some engines, pump and stationary running engine can suffer that’s why we do so much testing for ours but a dirt bike the whole rpm range is used (that’s why the motocool and all cooling systems are a compromise) and never sits the same so I wouldn’t think its an issue

TB

September 1, 2009 at 11:53 pm #150873

Anonymous

Austblue wrote:

Quote:

Why not moto?

It’s not a valve destroying Honda :laugh:

Jokes aside, I have been slack with with it and I’ll be amazed if it doesn’t need a shim or two.

September 2, 2009 at 12:24 am #150874

Bruce Curtis
Member

That’s why it was such an issue on roadbikes doing big kays as generally you sit on the highway at a fairly constant speed, and 110kph is the speed most coppers will turn a blind eye to.
my Isuzu V6 suffers a nasty little period at around 2200 rpm which is around 80 kph in 5th response is doughy and the engine is dull, but get over 2500 again and it comes back into it’s own, although it also could be amapping issue as well as they use avery agricultural ECU.

Wikeds’ beemer if used on firetrails could spend time at constant rpms as i know that’s one of the advantages some of the big4T riders tell me they have over 2Ts the ability to cruise on transport sections.

BC

September 2, 2009 at 1:02 am #150876

Paul
Member

Thanks guys, I will see how it is in another 20 hrs and have a close look at the oil & filter tonight when I change them.

Blue; I have several feeler guages, I think a couple of them are Moore & Wright, Sheffield England ones I got from Dad from when he worked at McPhersons.
Can have a look tonight if you want.
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