R75/5 Valve adjustment, pushrod and rocker arm question

[Bill Harris]

Local Airhead Tech Day:

http://www.advrider.com/forums/showthread.php?t=859007
http://www.advrider.com/forums/showthread.php?t=839970

--Bill

[khale]

Originally Posted by chollo9

Exhaust valve adjuster was at its limit. Pulled apart to find a burnt exhaust valve and seat, but honestly I expected worse. Heads are currently at bmwrench's for whatever is needed to bring them up to snuff.

Thanks. In the event that I need new seats, do you recommend sending off to bmwrench? He seems to be the go-to airhead machinist in the country.
What can I expect to pay for 4 valves, guides, seats, etc? I'll replace the valves myself, just need a machinist to press the seats in the heads.
Should I be looking to do the whole she-bang as this inmate did?
http://www.advrider.com/forums/showthread.php?t=533058

Is it good practice to replace all the valves, guides and seats at once, since the engine is at 56k miles?

[disston]

Khale,

I've been getting by on a second set of heads but will be right behind you in the cylinder head refurbishing pretty soon. So I'm not an expert.

I believe the exhaust seats are the ones that get replaced. Intakes run cooler and don't have a problem.

I think the rest of the work has to be checked before knowing if it all gets done or just some of it. Has your brother done Airhead valve work before? You seem to trust him. The heads are heated up, very hot, and the old guides driven out and new guides driven in. Then the guides are reamed. Sometimes the intake valves might be reused. But having 4 new valves also sounds nice.

If you are really looking to make some improvements consider adding dual plugging while the heads are being tended to.

[chollo9]

Originally Posted by khale

Thanks. In the event that I need new seats, do you recommend sending off to bmwrench? He seems to be the go-to airhead machinist in the country.
What can I expect to pay for 4 valves, guides, seats, etc? I'll replace the valves myself, just need a machinist to press the seats in the heads.
Should I be looking to do the whole she-bang as this inmate did?
http://www.advrider.com/forums/showthread.php?t=533058

Is it good practice to replace all the valves, guides and seats at once, since the engine is at 56k miles?

bmwrench has an excellent reputation, and is on the east coast.

Dunno the cost yet, it is what it is--e.g., genuine BMW exhaust valves are $150 each.

I'm for replacing what needs replacing.

[chasbmw]

If you are doing the work, replace the exhaust valves and guides as a service item. The valve heads can and do drop, which can be very expensive.

[khale]

Thanks for the help, guys. I really appreciate it. I took off the head last night and here's what I saw. Not as bad as I originally thought. The exhaust and inlet valves are still seating perfectly on their seats. No wiggling or movement on the valves either. No cracks. They just have a lot of carbon build up, which I assume is normal.
Any advice after seeing this? I don't think it would hurt to have fresh valves...

Exhaust valve closed:


Exhaust valve open. Hard to see the seat due to carbon build up on the outskirt. The actual seat where the valve rests itself is clean as a whistle.

[khale]

Can someone provide the laundry list of parts I need in order to perform a full valve job on this bike? Parts numbers would be lovely. Looking on MAX BMW for right now.
Should I go ahead and complete the top end by replacing piston rings as well?
Forgive any ignorance, my first time doing this...
I've sent an email to Bud to see if he's interested in putting new seats on my heads.

[disston]

You let the machinist provide valves, guides and seats. New springs are a nice touch and not terribly expensive. You get what the machinist recommends. There are several choices of after market or OEM valves and guide materials. There are threads and surveys here on AdRdier dot Com that have more than a hundred posts and give well into the neighborhood of 3 dozen opinions on how to do this. Nobody is going to digest this and make any sense out of it. If you want to learn how to do BMW Airhead cylinder head work then I suggest you enroll in a BMW Service School. The tools for this work will run into the tens of thousands of dollars and the school will probably be a hundred thousand dollars. After 30 years of messing up other peoples machines I think you may get a refereral or two from some of the Inmates here.

It is not a list of parts and some pointers off the Web kinda thing. See?

Your part is called the R&R That is Removal and Replacement of the parts. To do this you need a pair of head gaskets, a pair of base gasket/shims and 4 push rod tube rubbers. You generally don't need things like new valve cover gaskets but when taking things apart you check these to make sure they don't need replacing.

To see if you might need rings, take the pistons off the rods, take the rings off the pistons and set them in the cylinders to check the ring gap. If rings are with in spec you can reuse them. The pistons can also be checked by putting into the cylinders with out their rings on and checking the fit with feeler gauges. Also wiggle the pistons inthe cylinders to see how well they fit and note weather the cylinder walls are worn in a taper. If you have trouble deciding if you need cylinder or piston ring work then a machinist can measure these things with accurate tools that most of us don't have.

You must be very careful when removing and replacing piston rings. These are not made to bend and they are easily broken. If you break one ring you will be buying all six too make things right. May in fact be what you need but it's still recommended you don't break the rings. There are special pliers for removing the rings and helping to not break them. I recommend using these tools instead of the finger nails which is usually what we do when we don't have the ring pliers.

You'll also need a suitable ring compressor tool to put the pistons and rings back into the cylinders.

If you are doing this much so far then also get the special triple square driver for removing and replacing the rod bolts and replace the big end rod bearings. These are not terribly expensive and are service type parts for our bikes. They get replaced merely because we are there.

You are going to need a suitable torque wrench for the rod bolts and the cylinder head bolts. The rod bolt toque is in your manual. If you still need it I'll look it up later. The cylinder head bolts are to be tightened to 25 ft/lbs in three stages. Use 25 ft/lbs as the final torque value and disregard any other toque value published anywhere.

[chollo9]

If Bud is doing your heads, I'd let him provide anything head related. The rest is just gaskets and such. As for rings, just check the gaps--if they are well within spec, I wouldn't change them (and you won't have to seat them). If they are outside, or close, then a fresh set would be in order (along with light honing).

My rings were way out, and my pistons are just within tolerance. I decided to let the pistons ride, knowing they will make it at least a year, and go with first over rings, which I will file to get good gaps.

My thinking is that it's so easy to pull the top-end, I don't mind fudging a little. When I'm sending stuff like heads off to have work done, that's different, I'm getting it all done while it's there.

Just my way of thinkin', and the budget has a bunch of other stuff in it this winter too!

(disston replied while I was typing, so . . .)

[disston]

After all the directions earlier I'm looking at the pics of your heads and don't see what the problem is. If the valve is not eroded and the seat is not eroded then why is the adjustment at it's limit?

[disston]

Yes Chollo I'm rather long winded.

[chollo9]

As am I.

But then I stare.

And edit.

Then I appear to be a Man of Few Words.

Ha! If only.

[disston]

Why is his adjustment at the end? If the seat and the valve look good? Is there something we aren't seeing?

[khale]

Originally Posted by disston

Why is his adjustment at the end? If the seat and the valve look good? Is there something we aren't seeing?

This is really what I'm trying to get to the bottom of... After pulling the head, evidence shows the exhaust valve looks completely fine, worthy of 4 or even 5 digits worth of miles. Why would the exhaust rocker arm adjuster screw be at the end?

[khale]

Originally Posted by disston

You let the machinist provide valves, guides and seats...

Appreciate the thoroughness. This all helps me a lot. I guess I should have stated I'm not entirely a novice when it comes to mechanics, but I'm absolutely not on the level of Click/Clack. I own many tools, including a torque wrench.