Heads Up Warning...Gearheads Please Read

[BruceHarrisJr]

For those that perform their own maintenance in general and valve clearance inspections/adjustments in particular please read on. I'd like to share with the membership my recent experience while inspecting/measuring my LT's valve clearances.
This past Sunday afternoon I was performing a routine 12,000 service. I had checked all valve clearances and was in the process of reinstalling the valve cover. The valve cover is secured to the cylinder head with eleven screws. The first ten screwed right in with no problems/issue. The eleventh and final screw (over cylinder #4 and on the bottom) stripped the internal threads of the camshaft bearing cap. MAJOR problem when that occurred. On Monday morning I went to a local machine shop hoping to have new threads cut into the camshaft bearing cap-machinist says he thinks it doubtful and respectfully declines my request. I called Carolina BMW/Greensboro to inquire about purchasing a new camshaft bearing cap-looong pause by parts person-"That'll be $1,500.00 Mr. Harris, you need to purchase a new cylinder head" Holy smoke I sez to myself. I then called Chicago BMW and relayed my problem and was given the same answer. It seems that when our beloved motors are built the head and camshafts are 'line bored' making the camshaft bearing caps unique to each individual engine.
Fellow member and LT owner Joey Fletcher of Durham, NC (God bless him!) works in an ultra high tech machine shop and is now in possession of one DOA camshaft bearing cap. He is going to try and work some magic on it and return it to me tomorrow. Joey and I discussed that to the best of our collective memory no one on this board has experienced a failure like this thus far. Bottom line: be double dang sure that when installing the eleven valve cover screws that none of them are cross threaded in the least!!

I will post a followup, hopefully by Saturday on the results of Joey's efforts. If the results fail I have no way to prove/document to BMW that I wasn't the culprit. At the moment I'm not blaming anyone or thing just truly amazed that something that should be done every 12,000 miles has the potential for disaster to one's check book. $1500 parts plus perhaps $500 labor for removal and installation of old/new head.

Oh happy days I B seeking u out...

[surfran]

Wow, sorry to hear your misfortune Bruce. I hope you can get it fixed without having to get a new one. I was thinking of doing the valve checks, but think I'll pass now. The dealer I was at the other day was of the opinion that the valve checks as often as recommended was overkill.

[nplenzick]

Couldn't you install a helicoil or a timesert?

[petepeterson]

That was my question,, good ol heli-coil............Regards Pete

[JPSpen]

Have the machine shop just fill the hole with weld.
And then just re-drill and thread it... Shouldn't be a problem for a good machine shop. When I rebuilt the head on my Jag, It required welding and re-machining because of corrosion in the water jacket holes. Machine shops do this kind of thing all the time...

John.

[dshealey]

For those that perform their own maintenance in general and valve clearance inspections/adjustments in particular please read on. I'd like to share with the membership my recent experience while inspecting/measuring my LT's valve clearances.
This past Sunday afternoon I was performing a routine 12,000 service. I had checked all valve clearances and was in the process of reinstalling the valve cover. The valve cover is secured to the cylinder head with eleven screws. The first ten screwed right in with no problems/issue. The eleventh and final screw (over cylinder #4 and on the bottom) stripped the internal threads of the camshaft bearing cap. MAJOR problem when that occurred. On Monday morning I went to a local machine shop hoping to have new threads cut into the camshaft bearing cap-machinist says he thinks it doubtful and respectfully declines my request. I called Carolina BMW/Greensboro to inquire about purchasing a new camshaft bearing cap-looong pause by parts person-"That'll be $1,500.00 Mr. Harris, you need to purchase a new cylinder head" Holy smoke I sez to myself. I then called Chicago BMW and relayed my problem and was given the same answer. It seems that when our beloved motors are built the head and camshafts are 'line bored' making the camshaft bearing caps unique to each individual engine.
Fellow member and LT owner Joey Fletcher of Durham, NC (God bless him!) works in an ultra high tech machine shop and is now in possession of one DOA camshaft bearing cap. He is going to try and work some magic on it and return it to me tomorrow. Joey and I discussed that to the best of our collective memory no one on this board has experienced a failure like this thus far. Bottom line: be double dang sure that when installing the eleven valve cover screws that none of them are cross threaded in the least!!

I will post a followup, hopefully by Saturday on the results of Joey's efforts. If the results fail I have no way to prove/document to BMW that I wasn't the culprit. At the moment I'm not blaming anyone or thing just truly amazed that something that should be done every 12,000 miles has the potential for disaster to one's check book. $1500 parts plus perhaps $500 labor for removal and installation of old/new head.

Oh happy days I B seeking u out...

You are not the first to strip these out! Some have done it by not using a torque wrench, or torqueing to 10 ft. lbs instead of 10 Nm.

All have fixed it by using Heli-Coil inserts, so it is not as bad as it seems. Find anyone who understands how to put in Heli-Coils (It is M6 X 1.0 pitch)

All overhead Cam engines that I know of are line bored, and you cannot switch, or replace caps on any of them. I know one person who swapped two caps on a car engine once, it ran about 10 minutes. cost him a new head. (No, was not me :D )

[dshealey]

Have the machine shop just fill the hole with weld.
And then just re-drill and thread it... Shouldn't be a problem for a good machine shop. When I rebuilt the head on my Jag, It required welding and re-machining because of corrosion in the water jacket holes. Machine shops do this kind of thing all the time...

John.

Welding on a cam bearing cap would most likely warp it too much to be useable. These bearing surfaces and their alignment are critical.

[tarheel_rider]

Not good :(
Hope this doesn't jeopardize your RAT plans.
Let me know if there is anything I can do to help.

[tmgs]

"That'll be $1,500.00 Mr. Harris, you need to purchase a new cylinder head" Holy smoke I sez to myself. I then called Chicago BMW and relayed my problem and was given the same answer. It seems that when our beloved motors are built the head and camshafts are 'line bored' making the camshaft bearing caps unique to each individual engine.
Fellow member and LT owner Joey Fletcher of Durham, NC (God bless him!) works in an ultra high tech machine shop

Yup that is common with about any overhead camshaft setup, even one that uses inserts, and never mix up or change the position of the caps!
Heck building V-8 engines we would line bore the camshaft holes and crank journal's, the dodge 4cy 2.2 engine were known to warp the heads so bad you could not straighten them out enough for them to run the cams again, I've seen a few less experienced shops have the head milled put it together and ruin the cams shaft anyhow (they didn't realize the head would need to be straightened instead of just milled!)

It seems that the journal cap is too small to Heli coil the threads then, Joey Must work in a high tech shop to be able to handle that repair and assure the journal will not be affected without needing the head to line bore the cam shaft journals again, which would turn into a major welding and line boring job.

Good on Joey, hope everything works out real good for you bruce!~
I love a good machinist! I call em miracle workers <grin>

Tom

[tmgs]

Have the machine shop just fill the hole with weld.
And then just re-drill and thread it... Shouldn't be a problem for a good machine shop. When I rebuilt the head on my Jag, It required welding and re-machining because of corrosion in the water jacket holes. Machine shops do this kind of thing all the time...

John.

Then all the journals on the head and caps would need welded and line bored to the correct size.
You would need a VERY VERY experienced welder then have the surfaces Hardened then tested for hardness to be sure the cams would not wipe the welded surface away.
(welding aluminum is a art)
Let alone trying to weld a surface that is actually a bearing surface! remember there is no bearing insert, the head and the caps are the bearings for the cam shafts.

It would be darn near impossible and would definitly be cost prohibitive.

[JPSpen]

I Stand Corrected. Didn't realize it was that critical a part...



John

[tmgs]

I Stand Corrected. Didn't realize it was that critical a part...



John

Not corrected just informed better, welding the hole to re-drill and tap would create heat and distort the cap creating the need to line bore, which would mean doing them all and the head to make sure the line bore job, keeps the correct tolerances for the camshaft

[Joey]

Just sent Bruce on his way with a repaired cam cap. I used a 6x1 heli-coil

What I saw that could have caused this problem was a large amount of anti seize inside the cam cap which could have helped push the threads out. ( from the factory). This is a new bike.

These cam caps are cast alum. not billet. I would try to make a new one from billet material and hand fit it.......Bet I could! No way I would try to weld it

Any ways Mr Bruce should be able to be on his way to getting that good looking Blonde back together.

Good luck on the waltz around Texas

Joey

[tmgs]

Just sent Bruce on his way with a repaired cam cap. I used a 6x1 heli-coil

What I saw that could have caused this problem was a large amount of anti seize inside the cam cap which could have helped push the threads out. ( from the factory). This is a new bike.

These cam caps are cast alum. not billet. I would try to make a new one from billet material and hand fit it.......Bet I could!

Any ways Mr Bruce should be able to be on his way to getting that good looking Blonde back together.

Good luck on the waltz around Texas

Joey


cool beans, I just assumed it was too narrow for a heli coil when I first read the post, and a master machinist could hand fit one they made from scratch I'm sure , the best fitting drive gear bearing on a HD I ever had done was by a old machinist in Iowa, who hand sized the forth gear bearing and race. the guy was good, darn good! Took him ten minutes to walk from one side of the room to the other,
You knew he could do the work though!

Tom

[tmgs]

These cam caps are cast alum. not billet. I would try to make a new one from billet material and hand fit it.......Bet I could! No way I would try to weld it

Joey


joey, I'm wondering, if having one out of billet would cayuse problems, mainly because would it not change shape at a different rate than the sand cast head causing incorrect clearences at different temps

I mean billet won't expand and contract at the same rate as cast will it

[dshealey]

joey, I'm wondering, if having one out of billet would cayuse problems, mainly because would it not change shape at a different rate than the sand cast head causing incorrect clearences at different temps

I mean billet won't expand and contract at the same rate as cast will it

There is very little difference in thermal expansion between any aluminum alloy, cast or wrought. So slight it would not make a difference.

The real issue though is that a different material for the caps would gain little to nothing. The only problem we have ever had with them is stripping, normally because of incorrect torquing, but in this case maybe something wrong from the factory? Cam bearings have not been an issue.

ALWAYS USE A TORQUE WRENCH FOR THESE!
They are borderline on torque, so ANY over-torquing can result in problems. Same with the three screws in the oil filter cover plate!

Some of the cam bearings that have been stripped were because the person inadvertently used 10 Ft. Lbs instead of the required 10 Nm, which is actually 13.5 Nm.. So you can see, it does not take very much additional torque to strip them!

So far though, ALL have been repaired with Heli-coils.

[tmgs]

There is very little difference in thermal expansion between any aluminum alloy, cast or wrought. So slight it would not make a difference.

I didn't know that, and even if it did, how much difference it would actually make , hundreds of thousands wouldn't impact it much thousands would

[dshealey]

I didn't know that, and even if it did, how much difference it would actually make , hundreds of thousands wouldn't impact it much thousands would

Aluminum and it's alloys vary from 11.7-13.7 X 10-6 per deg. F.

That means a 2" wide part would expand 0.00468" from 0 to 200 deg. F. on the low end, to 0.00548" on the high end. That is a 0.0008" difference.

The bearing caps are bolted tightly to the head though, so all is pretty much locked together, and there would likely be barely measurable variations in bearing bore/location.

[Joey]

I can tell you this.. with out a doubt Bruce Harris is a fanatic about every aspect of his motocycle

valve cover is 9 newtons

cam caps are 10 newtons

to me...that is finger tight...LOL

He has a newton torque wrench, a inch pound torque wrench and a foot pound torque wrench

Bruce checks the air pressure in his tires ......every time he rides reguardless


That is how he can get 20k + out of a set of Bridgestones

[niel_petersen]

I wouldn't weld on the head for fear of distorting it. Aluminum weld isn't very strong material anyway - not as strong as the head casting very likely.

The best fix would be to helicoil the threads - as deep as possible without drilling any deeper than the present tapped hole. Helicoils require less metal removal than any other thread fix. Be very careful of maintaining perpendicularity.

Although I've never seen the cam bearing assembly, the reason they are line bored is to be absolutely certain there are no tripping edges catching the hydrodynamic oil flow around the cam journals. And I mean edge heights in the in the microns.

Consider the direction of cam rotation. Polish a very fine small ramp (less than 1/16 inch long) where the journal surfaces enter the cap to prevent the journal lube from being scraped off. That's what causes journal bearings to fail prematurely. You should be able to do it in a few minutes.

Unfortunately, you can't get to the area where the cam journal enters the head, as that is also a potential misalignment trip point. Chill the head and cap w ice ( and heat the cam with a heat gun) immediately before assembly to help the cap align itself to the cam journal.

That's the best I would suggest if the alternate is to replace the entire head. Journal bearings are a very sensitive subtle science.

[tmgs]

I can tell you this.. with out a doubt Bruce Harris is a fanatic about every aspect of his motocycle

valve cover is 9 newtons

cam caps are 10 newtons

to me...that is finger tight...LOL

He has a newton torque wrench, a inch pound torque wrench and a foot pound torque wrench

Bruce checks the air pressure in his tires ......every time he rides reguardless


That is how he can get 20k + out of a set of Bridgestones


No he gets 20k out of a set because he spends as much time riding on the sides of the tires as he does the bottom <g>.

one thing I noticed since I moved up here from FL. we do seem to get more miles out of the tires, but when they are wore out there is much less side tread depth <grin>

[tmgs]

Aluminum and it's alloys vary from 11.7-13.7 X 10-6 per deg. F.

That means a 2" wide part would expand 0.00468" from 0 to 200 deg. F. on the low end, to 0.00548" on the high end. That is a 0.0008" difference.

The bearing caps are bolted tightly to the head though, so all is pretty much locked together, and there would likely be barely measurable variations in bearing bore/location.

Sweet information David!

Tom

[charlieg]

Some of the cam bearings that have been stripped were because the person inadvertently used 10 Ft. Lbs instead of the required 10 Nm, which is actually 13.5 Nm.. So you can see, it does not take very much additional torque to strip them!

So far though, ALL have been repaired with Heli-coils.[/QUOTE]

Yes indeed, I am one of those persons. Stripped out two on my 05' before I realized WTF I was doing. Heli-coil repair worked fine, have about 7000mi. on since that brain fade.

[Rayo]

Have the machine shop just fill the hole with weld.
And then just re-drill and thread it...
John.
Problem with this fix is distlortion to the cap causing the cam problems. Line boring is very common procedure in auto engines for crankshaft, and again if a cap is replaced you have to line bore again.

[dshealey]

Problem with this fix is distlortion to the cap causing the cam problems. Line boring is very common procedure in auto engines for crankshaft, and again if a cap is replaced you have to line bore again.

I have had two in line 6 cyl heads line bored for cams, and it is not cheap! Takes a GOOD shop to do it right. Also, the process is to machine a little off the head surface where the caps sit, also a little off the bottoms of the caps, then everything is bored back to stock diameter. This does have the affect of lowering the cams in the head slightly, and that results in small cam timing differences (retards valve timing), even if new sprockets and chains are installed.

ADDED: If this is done in addition to milling the head, the retardation is even higher. Anything that moves the cams closer to the crankshaft retards valve timing, and there are no adjustments to bring the timing back. Head gasket shims can be used, but these are not always easily available, and can make a blown head gasket more likely if used.

My BMW 525i has dual over head cams, but the cams are mounted in replaceable "cam boxes" that are bolted to flat surfaces on the head. These could be shimmed easily to bring valve timing back to design spec.