valve recession

[Air4Life]

What is considered a high rate of valve recession for this engine?

I ask because I am planning on an extended high speed trip and want to check them before I go.  These are my last readings after about 5K miles.  Currently I have 1K since the following.

Adjusted left exhaust valve lash from 0.0077 back to 0.009  

Checked left intake valve lash good at 0.005

Adjusted right exhaust valve lash from 0.00825 back to 0.009  

Checked right intake valve lash good at 0.005

[Bob_Roller]

Iwouldn't be concerned about your findings .

Valve recession was at it's worse on the '81 model year bike .

I had the valves seats and springs replaced at 45,000 miles, the exhaust valve heads were close to being pulled into the exhaust port of the head .

Only real method to find out what you have, is to remove the exhaust system and look at the valve face when it is open .

I think they had the recession issue fixed by the '83 model year bikes .

[nhmaf]

Allowing for possible error in measurement, a change of .001" in 1K miles or more isn't too bad.   I'd keep an eye on it, but go ahead with your trip.   Generally when the valves start to really deform the closure will be 3x-4x that amount in 1K miles.

[georgesgiralt]

Hello !
I , for one, would be concerned by the burnt oily colour of the cylinder head in the left side you show on the picture attached.
This denotes a high play in the valve guide and high temperature gasses passing through it to burn the oil present in the vicinity.
I would began to save money to have the valves and guides exchanged in a very near future.
I was told we had to replace valves in our engines around 80 000 ~ 100 000 km because the valve stem are thinner than on other BMW airhead engines if we do not want a valve to break.  Play in the guides is a fair indication of wear, on the guides and on the valves. At that time you will be able to see the status of the valves seats and if recession is present or not.

[tvrla]

I'm curious how you came up with a measurement like 7.7 thousandths? My thinnest feeler gauge is either one or two thousandths.

Losing more than a thousandth in a thousand miles with as wide a setting as .009" seems like a lot. Were you riding it hard and fast in those thousand miles?

I'm thinking you'd be ok taking it nice and easy, but pushing at high speed doesn't seem like a good idea.

[Bob_Roller]

These measurements  were taken after 5,000 miles of use, it's been 1000 miles since the valve clearance adjustment .

The valve clearance closed up a little over .001 inches in 5,000 miles, not enough to get concerned about .

[Air4Life]

Thanks Bob, you are right on the money about my indications.  

Yes wirespokes, I think even nhmaf read between the lines when he wrote, "Allowing for possible error in measurement". It is true that it is at best an estimation made using comparative drag on the different gauges available to me.

Either way, as Bob noted, it was a difference that represented 5000 miles.  Its been 1000 since that adjustment and before I do any kind of extended 65 mph riding, I thought I'd go back in and check.  

Georgesgiralt: As far as the baked in oil, its been that way since I first opened it up at 24K miles when I first got the bike.  I hope its not serious, and was hoping someone else could offer their opinion.  I now have nearly 41K on it.  

Based on the pictures I'd say that I'm slightly more than halfway through what's left of adjustment for them.  I have to check it to be more comfortable.

Thanks

By the way those pictures are probably at 30K

[Barry]

Just over a thou in 5000 miles is not so bad especially as depending on technique it's easy to have a measurement error of a half a thou. 7.77 thou is curious. If it had been 7.78 I would have said you used a 0.2mm metric feeler.

I don't think there is anything wrong with running slightly wider clearances like 5 and 9 thou.  It gives you a  little more leeway if the exhaust clearance is closing up.  Valve recession will increase at high speed, in fact you can argue it's only ever an issue at high speed so it would be interesting to check them again after your trip to see if you can detect any change.

[georgesgiralt]

Hello !
As your exhaust guide began to worn out, the closing of the clearance could be the valve's stem going thinner due to heat from gasses going in the guide and extended stress and thus going a bit longer.
So the seat could not been the culprit here...
R65 exhaust valves have a hard time as they have thinner stem and the engine is snappier.
As I said before start to spare money for a guide and valve job in a few thousand miles.

[Air4Life]

Barry:  Yep, I kind of got the impression my riding would be taking more from the bike than some others would.  I'd estimate 50 percent of my mileage total to be at 65 mph.

georgesgiralt: Okay, thanks.  I'm saving for a complete overhaul of the entire bike as well as saving for an additional motorcycle.

[tvrla]

That's really confusing. And I still don't quite understand the statements of a thousand miles and five thousand. It's not very clear what happened when.

Losing a thousandth in five thousand miles isn't horrible, especially if it's been ridden hard. I wouldn't call riding at 65mph, riding it hard.

[Air4Life]

Both exhaust valve clearances closed by roughly 0.001 in a span of 5000 miles.  Since that last check I now have an additional 1000 miles.  I thought before I take it on a 2000 mile drive, I'd check it once more - mostly because its all 65 mph running.

[tvrla]

Should have waited two more miles to snap the pic! :-)

Ok, I'm trackin witcha now!

[nhmaf]

The exhaust side of the cylinder heads pretty much always get a kind of "bronzed" look from the higher heat around the exhaust valve area, but I also agree that the very dark brown circles in your pics seem worse than several I have seen.   I also suspect maybe the valve guides are a bit worn, but I wouldn't consider it a hazard or cancel your trip at this stage.   They will need to be addressed eventually though.

[Air4Life]

I don't know how pertinent the following judgement of mine is, other than my internal desire for optimism in this situation; but both the left and right sides appear equally "bronzed".

Again, the above pictures are at roughly 30 K.  I have to snap a current picture later.  Maybe its worse. Maybe its gotten better.