dan cata Posted September 7, 2020 Share Posted September 7, 2020 I have never seen something like this... R1200GSA, 130k kms, R/H side upper intake valve seat coming loose. How can it come loose?! There is nothing pulling it towards the chamber... There is no mark left on the piston. So now, what do I do? Do I repair it (how?) or do I replace it? Is it reliable after repairing? The AUDI mechanic I go to says this happens on LPG cars, perhaps the temp is higher in there and such a failure makes more sense, but not on a perfectly running GS engine... Dan. Link to comment
dirtrider Posted September 7, 2020 Share Posted September 7, 2020 15 hours ago, dan cata said: I have never seen something like this... R1200GSA, 130k kms, R/H side upper intake valve seat coming loose. How can it come loose?! There is nothing pulling it towards the chamber... There is no mark left on the piston. So now, what do I do? Do I repair it (how?) or do I replace it? Is it reliable after repairing? The AUDI mechanic I go to says this happens on LPG cars, perhaps the temp is higher in there and such a failure makes more sense, but not on a perfectly running GS engine... Dan. Afternoon Dan I have seen exhaust valve rings come loose in other engines but never in the BMW hexhead, the problem is usually extreme heat related or from a valve welding itself to the seat ring. BMW does offer new valve seat rings but no real procedure on replacing them PROPERLY. Your valve seat ring looks to be in good shape so it doesn't appear to be from valve recession or the valve welding itself to the seat so that pretty well leaves the possibility of either that ring is slightly undersized or the cylinder head ring hole is slightly oversized. In any case, replacing those valve seat rings is a usually a job for a good automotive machine shop with proper tools, know how & they can also precisely measure the press fit to assure that it won't come loose again. In your case it is probably cheaper & more long term reliable to just buy a good used cylinder head. Added: any chance that engine was ridden a long ways with that side cylinder not firing? Those seat rings pretty well stay in place from both a press/shrink fit & by the hot exhaust gas expanding the seat ring more than the surrounding cylinder head. If that engine was run a long time with a non-firing cylinder it is possible that the exhaust ring ran cooler than the cylinder head from the cooler air/fuel flowing out through it. With the valve closed on the valve seat ring that makes a pretty good sized piston when the other side fires. Link to comment
dan cata Posted September 8, 2020 Author Share Posted September 8, 2020 @dirtrider I really like your signature, made me laugh The bike was not ran in one cylinder, the owner reports that he went home from a trip with a perfectly running engine, stopped to open the gate, heard the engine run bad and stopped it. Your assumption makes sense but the timeline does not fit. I will search for a used head, replace the gasket and get it running again. Dan. Link to comment
Alfred02 Posted September 8, 2020 Share Posted September 8, 2020 Let's think about this. The engine ran for 130,000km with no issues. How many hundreds of millions of valve opening/closing would this be??? If anything, natural microscopic carbon deposits would weld the seat even more so into the head. So I am wondering if the owner used some kind of fuel additive in the fuel. Link to comment
dan cata Posted September 10, 2020 Author Share Posted September 10, 2020 I'll ask and report back. Meanwhile, a donor part is on it's way from Holland. Another option would be to machine a new ring, slightly larger in outer diameter. I cannot trust a new OEM ring for staying seated in there. I am thinking that what happened here was a fabrication defect. Can't really see any other reason for this happening. Dan. Link to comment
dirtrider Posted September 10, 2020 Share Posted September 10, 2020 1 hour ago, dan cata said: I'll ask and report back. Meanwhile, a donor part is on it's way from Holland. Another option would be to machine a new ring, slightly larger in outer diameter. I cannot trust a new OEM ring for staying seated in there. I am thinking that what happened here was a fabrication defect. Can't really see any other reason for this happening. Dan. Afternoon Dan I am thinking that what happened here was a fabrication defect. Can't really see any other reason for this happening.-- That would be my guess also but keep in mind that it went many/many/many miles before failure so it couldn't be too far out of specification. On most alloy cylinder heads those valve rings (seats) just drop in with a little push after heating the cylinder head then super cooling the valve ring. When both parts reach the same temperature the cylinder head shrinks & the valve ring expands to they lock together pretty darn tight. Once they lock together tightly nothing can get between the seat ring & the alloy cylinder head casting. What usually happens when they come out is the valve tulips, recedes then, sticks in the seat then pulls the seat ring out (but from the picture that doesn't look like it happened that way on this particular motorcycle) Link to comment
Mark Cross Posted September 12, 2020 Share Posted September 12, 2020 On 9/10/2020 at 1:13 PM, dirtrider said: Afternoon Dan I am thinking that what happened here was a fabrication defect. Can't really see any other reason for this happening.-- That would be my guess also but keep in mind that it went many/many/many miles before failure so it couldn't be too far out of specification. On most alloy cylinder heads those valve rings (seats) just drop in with a little push after heating the cylinder head then super cooling the valve ring. When both parts reach the same temperature the cylinder head shrinks & the valve ring expands to they lock together pretty darn tight. Once they lock together tightly nothing can get between the seat ring & the alloy cylinder head casting. What usually happens when they come out is the valve tulips, recedes then, sticks in the seat then pulls the seat ring out (but from the picture that doesn't look like it happened that way on this particular motorcycle) I have heads if that part doesn't work out for you. cheap, local. Mark Link to comment
dirtrider Posted September 12, 2020 Share Posted September 12, 2020 5 minutes ago, Mark Cross said: I have heads if that part doesn't work out for you. cheap, local. Mark Morning Mark You say local, are you also in Romania? Link to comment
Mark Cross Posted November 3, 2020 Share Posted November 3, 2020 On 9/12/2020 at 5:00 AM, dirtrider said: Morning Mark You say local, are you also in Romania? Hi, Never saw this message before . I am in Northern Cal, 100 miles from San Francisco. Have may R1200 RT motors & parts, retired. On 9/12/2020 at 5:00 AM, dirtrider said: Morning Mark You say local, are you also in Romania? Link to comment
dirtrider Posted November 3, 2020 Share Posted November 3, 2020 On 11/2/2020 at 9:10 PM, Mark Cross said: Hi, Never saw this message before . I am in Northern Cal, 100 miles from San Francisco. Have may R1200 RT motors & parts, retired. Morning Mark You said local & Dan (the Original Poster here) lives in Romania, I was just clarifying that when you said "local" if you lived in, or close, to Romania. Link to comment
Mark Cross Posted November 7, 2020 Share Posted November 7, 2020 I can sell you another working head for a lousy $50 bucks, why bother with this repair? I have hundreds of cheap parts for R1200's form 2005-2009. Mark yankeebeemer@bikerider.com Link to comment
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