ADVrider

ADVrider (http://www.advrider.com/forums/index.php)
-   Airheads (http://www.advrider.com/forums/forumdisplay.php?f=85)
-   -   R75/5 Valve adjustment, pushrod and rocker arm question (http://www.advrider.com/forums/showthread.php?t=858879)

khale 01-27-2013 05:20 PM

R75/5 Valve adjustment, pushrod and rocker arm question
 
Hey guys,
I just finished up a valve lash job on my r75/5 at 56,600 miles and noticed by left side exhaust push rod wasn't lining up completely straight with the screw end of the rocker arm. Is this normal?

I adjusted the inlet to .10mm (.004 in) and the exhaust to .20mm (.008 in) on both sides. I've read elsewhere that people adjust inlets to .15mm. Is there a poll anywhere on ADV for inlet valve clearance gap on r75/5's?

Left side, looks off?
http://i.imgur.com/5lUc074l.jpg

Right side, looks correct
http://i.imgur.com/jJQTZmrl.jpg

Is this a symptom of a larger problem? I did notice the left side pinging slightly loudly than the right side when I started the bike back up.

This image from Duane seems like the rocker arm/push rod alignment looks correct
http://w6rec.com/duane/bmw/valve/valve6.JPG

disston 01-27-2013 05:58 PM

I don't see a problem with the push rod alignment.

I used .10 mm and .20 mm valve adjustments for a long time. I think my /6 runs better with .15 and .20 which I currently use.

bmwrench 01-27-2013 07:12 PM

The rocker arms can be moved around quite a bit in the cylinder heads you have. They should be set up so that the rocker tip is inboard of the center of the valves tip. This reduces valve guide wear and noise and keeps the rocker from rubbing the valve spring.

khale 01-27-2013 07:34 PM

Quote:

Originally Posted by bmwrench (Post 20590112)
The rocker arms can be moved around quite a bit in the cylinder heads you have. They should be set up so that the rocker tip is inboard of the center of the valves tip. This reduces valve guide wear and noise and keeps the rocker from rubbing the valve spring.

Any tutorials on how to do this? I loosened the rocker arm shaft and attempted to move it to align it better with the push rod with no luck.

khale 01-27-2013 07:39 PM

Quote:

Originally Posted by disston (Post 20589596)
I don't see a problem with the push rod alignment.

It's not so much the pushrod as it's the angle the rocker arm seats on the push rod. Do you see in the first pic how the exhaust rocker arm creates a slight angle rather than a straight line like the exhaust (and inlet) rocker arm to pushrod in image 2?

khale 01-27-2013 07:44 PM

Here's a line drawn on the angle the pushrod to the rocker arm I'm referring to that's concerning me. The ball end of the push rod still sits flush in the socket end of the screw, it's just not perfectly straight like the others.

http://i.imgur.com/vYcWC2Rl.jpg

disston 01-28-2013 12:02 AM

So the left exhaust rocker is rotated around more to get the correct valve lash? All these pics were taken with that particular side at TDC for setting? I see now what it is you are talking about. I don't know that you have a problem. The one thing we are told to watch for is exhaust settings that change a lot or too fast. This can indicate a valve seat that is receding too fast.

So when you set the valve lash was this valve tight? Did it take a lot of adjustment to get the right gap? Has it been a long time since the last valve adjustment?

I think it may be wise to remove the heads and check the valves and seats. Maybe a more knowledgeable inmate can correct me.

Houseoffubar 01-28-2013 12:59 AM

My observation would be the POSSIBILITY of a receding valve, that previous valve adjustments have been compensating for. Notice how screwed out the adjuster is? this causes the rocker to tip much more toward the pushrod, giving the impression the valve is too long. Since it was probably not originally installed too long, it would appear to be receding.
Or.... it's a....never mind I'm not clever enough to come up with something entertaining, sorry!:dunno

khale 01-28-2013 06:28 AM

Quote:

Originally Posted by disston (Post 20591335)

So when you set the valve lash was this valve tight? Did it take a lot of adjustment to get the right gap? Has it been a long time since the last valve adjustment?

I'm probably going to get a few chuckles and reprimanded by you inmates for this one... This was my first valve job I have done by myself on my bike (valve jobs have been done before, just not by me). I didn't realize that valve lash adjusting was a diagnostic tool to see what maybe wrong with the bike, rather than a mechanical procedure that actually effects engine performance. So I didn't record or measure my inlet/exhaust lash gap for either cylinder when I first took off the valve covers, thus not knowing if the gap was too tight for inlet/exhaust. :eek1 What I plan on doing, and correct me if I should do otherwise, is put another 1,000 miles on the bike, pull the valve covers and check the valve lash gap again.
The last valve lash adjustment was around 6k miles ago, or 2+ years. I don't put more than 2-3k a year on this bike.
And before anyone asks, yes, I was at TDC/OT for each cylinder I was checking; the pushrods could be rotated on the side I was adjusting.
I used this guide and Hayne's as a reference:
http://w6rec.com/duane/bmw/valve/index.htm

khale 01-28-2013 07:00 AM

I could also just be overthinking it too much, and it's just the positioning of the exhaust rocker arm in TDC on this cylinder.

disston 01-28-2013 08:55 AM

I'm afraid you would be well advised to not put another thousands miles on her before further investigation. It sometimes takes us a day or so to get up to speed but I see now what I did not see at first concerning the rocker arm. There is no adjustment left or very little. Either one of two things appears to be happening. Either the exhaust seat has eroded or the ehaust valve on the left head has started to wear severely. I would like to further say that you may just be in time to save this engine but this is not something that is just a little over the edge. It appears from here you have something very serious going on.

Here's a web page put up by inmate Anton Largiader that shows some pretty serious valve wear;

http://www.largiader.com/articles/valves/

There are many other pictures around of valves set too deep in the heads but for whatever reason your exhaust valve is set too deep in that head. This makes the tip of this valve set higher and the adjustment gets used up. When these screws are at the end of their adjustment they are already in danger of having a broken valve. The valve could break before you get to this point it is only luck that has kept you running so far.

Do you have the tools to take the heads off? Do you have the tools to take the valves out? Depending on where you live a place to work off the street and indoors will be helpful. Get your wallet out. The heads are going to have to be sent for rebuilding. Where do you live? There may be somebody that we will recommend for this work close to you.

One more word of caution. This work should be done by somebody with experience in Airhead work not your corner machine shop.

I'm sorry for the bad news. Maybe somebody will tell me to shut up and go away but that doesn't change the condition you have there. Sorry.

khale 01-28-2013 09:31 AM

More food for thought: I used a heat gun on my bike when I buttoned it back up and the left side (the side I'm concerned about) is running about 50F hotter than the right side. Does this indicate the exhaust valve of concern is about to crap out? Jetting is stock and the same on both carbs.

disston 01-28-2013 09:55 AM

You mean an Infra Red Thermometer? The temp of the cylinders can be varied by small turns of the mixture screws or other carb variations. I think 50* is a big difference. Big enough to be concerned about. But we have no data relating this to what is happening with your valves. I have one of those thermometers also but they are a relatively newer type of tool for Shade Tree Mechanics like myself.

Do you have a wrench suitable for removing the exhaust flange nuts? The large fined things holding the exhaust headers on. You need the tool for this and you will need a suitable torque wrench for 25 ft/lbs to put the heads back on. Parts for just getting the heads off and back on are going to run ruffly $100. The cylinder head work and parts for that is extra at this point but plan on close to $500 for rebuilding the heads. Sometimes less but I give you the upper limit this time.

The only way to know what is happening with your valves at this point is to take the heads off and if you have a suitable valve spring compressor you can remove the valves. However all the work to do this has to be done by a shop skilled in Airheads head rebuilding so sending the heads out for service is the first or the next step.

Think about this. Everybody else will be home later today and they will give you some other opinions, maybe.

khale 01-28-2013 09:58 AM

Quote:

Originally Posted by disston (Post 20593724)
The only way to know what is happening with your valves at this point is to take the heads off and if you have a suitable valve spring compressor you can remove the valves. However all the work to do this has to be done by a shop skilled in Airheads head rebuilding so sending the heads out for service is the first or the next step.
Think about this. Everybody else will be home later today and they will give you some other opinions, maybe.

Thanks for your help. My brother has a healthy supply of Airhead tools. We are going to investigate the valves tonight as I think that's the first order of business from your advise.

chollo9 01-28-2013 10:30 AM

I recently had the same problem (start with post #38 to avoid annoying jibber-jabber):

http://www.advrider.com/forums/showt...=830576&page=3

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.


Times are GMT -7.   It's 11:00 AM.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014