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Warning to engine rebuilders/overhauls-Important Info about Valve Guides
- Micha
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Warning to engine rebuilders/overhauls-Important Info about Valve Guides
I learned this the hard way, it turns out others did too viewtopic.php?f=7&t=18309.
When I brought my engine heads to the workshop, with all the assemblies shiny new (valves, springs, guides, etc.), I didn't have to ask him to do a good job. He is considered a leading workshop in the field and the whole country works with him. That's why I felt confident when I installed the rebuilt heads on my engine. After about 100 km I got stuck and needed a tow. Back home, lifting the RH engine head, I saw that the intake valve rocker arm was broken: the valve was stuck inside its guide. Oil reached the head and the push rod was full of it. To be on the safe side, I also pulled the LH cover, to find the following pictures. After consulting with the friends here and with Jan in the Netherlands, Salis BMW, I came to the conclusion that nowadays the workshops automatically ream the guides according to the tolerances accepted today, in the age of modern engines, but - it is important to ask them to give an oversize of 0.10 mm and to make sure that the valve stem does have a slight lateral play inside its guide. Mainly in a hot environment, which nowadays due to global climate change, most places on our globe, even in the relatively cold areas, already get there in one period or another, for a few days or weeks.
R51/3 1952
Engine Nr. 529466
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Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
- Micha
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Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
Too late for that and the workshop guy does not remember.
R51/3 1952
Engine Nr. 529466
- jwonder
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Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
Anyway, I bring them to spec and then loosen them up a bit. I forget the exact numbers but I think I went .001” on the intakes and a bit more on the exhaust. Mine run perfect!
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York
Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
Dave
- Rodolfo850
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Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
I just have this kind of fail last Sunday on my way to Distinguished Gentleman's Ride, after less than 20 milles after a full rebuilt of mine R60/2.
While stopping at red light engine start to sound like a type writer machine and stops..
Post mortem autopsia shows a stuck exhaust valve on right cylinder head.
I said it was a lucky strike, found some dirty sludge on oil pan, maybe was some Sodium carbonate that stays inside block after cleaning.
- jwonder
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Re: Warning to engine rebuilders/overhauls-Important Info about Valve Guides
If you are using a rebuilder that your not sure of, ask that they do two things:
1) Use high-quality valve guides! Even if you source them from a known reseller they may still be of lesser quality. I use KPMI guides.
2) Set the clearance appropriately for our needs. i.e. Loosen them up a bit and measure with thin oil.
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York