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Old 01-01-2013, 01:32 PM   #16
shearboy2004 OP
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Quote:
Originally Posted by supershaft View Post
Wow! I thought only '81 to '84 valves did that! No, not really since I am always pointing out that ALL the models do this sometimes.

Having done well over 100 airhead valve jobs myself, I totally agree with robtg and want to add another danger from what I have seen. If that cooked seat doesn't drop out, a new hard valve is likely to hammer the seat in and you end up with the same problem only different.

In my experience, the intake valves can last a long time. The intake seats can last forever.

This is a perfect example of why I always recommend doing a leak down if an idle issue persists. It's very often a leaking valve in my experience. Usually the intake but . . . . Just last year I leaked down my '92 and both exhaust were leaking at 101,000 miles. The valves' and seats' looked perfect but my exhaust guides were done. I didn't even measure the stems because I new I was going to 45* exhausts anyway. You really should do the same thing shearboy2004. Sticking with 30* valves doesn't work most of the time. It's hard to explain but trust me.


Mate thanks for the input , I was waiting for you to turn up ,
In the pm's we exchanged you told me this was probably the problem and were right !
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Old 01-01-2013, 01:38 PM   #17
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Quote:
Originally Posted by shearboy2004 View Post
Mate thanks for the input , I was waiting for you to turn up ,
In the pm's we exchanged you told me this was probably the problem and were right !
I might write more but when it comes to valve jobs and airhead tranny repair, robtg has a LOT more experience than I do! Lots of other stuff as well but I try!
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Old 01-01-2013, 01:39 PM   #18
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Quote:
Originally Posted by Donkey Hotey View Post
I think too many of you guys are too eager to just start pulling valve guides and seats. The bike I had the problem with was also a 1988. I don't know about other years and problems but, I can tell you from my own experience inspecting those valves and seats that those 1988 valves were absolute crap. They managed to do all that damage with almost no evidence on the valve seat.

Yes, the seat had worn a little but--as I posted--lapping compound was all it took to reveal a decent-width sealing ring all the way around; not too wide, not too narrow.

Bottom line: if you're of the mind to rebuild the heads, go for it. Now is as good a time as any. If you're a little short on cash and don't want to drop a grand right now, you can always carefully inspect the seats and put some new valves in there. If it gets you another 10-20K miles, you might be at a place where you want to go through the whole engine anyway.

There is certainly a bit of a cash flow problem at the moment and a complete rebuild is somewhere down the line but I'm also thinking of a rather large dirt ride this year so the brain is fighting with itself right now ! The correct thing to do is as Supershaft suggests but couldn't afford it right now.
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Old 01-01-2013, 01:46 PM   #19
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If you can'tr afford it you can't afford it but keep your fingers crossed! Dropped seats can tear up EVERYTHING!!!!

supershaft screwed with this post 01-01-2013 at 02:08 PM
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Old 01-01-2013, 01:54 PM   #20
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Quote:
Originally Posted by Donkey Hotey View Post
I think too many of you guys are too eager to just start pulling valve guides and seats..
If the guides are anything like this '89 model had, it would be plain stupid to leave them in.

Mouse over the image to see the slop: http://largiader.com/articles/valves/
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Old 01-01-2013, 02:18 PM   #21
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This reminds me of some goings on when I was working in aviation. My boss and I just delivered a set of Travel Air speed wings to a guy. There in his hanger was one beat up Travel Air fuselage. The thing about it was that the paperwork proved it had been a highly sought after D4D before it became a crop duster and was worked and ground looped into the state it was in. The customer was trying to talk my boss into splicing a longeron ONE more time and my boss was saying sorry but that fuselage is done. But look at all the repairs that have already been done to it, the owner said. One more won't hurt. The old barn stormers did this sort of repair all the time. That's when I spoke up and said, yes, but they were flying their own repairs. It's OK to kill yourself but if we do it that's another matter!
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Old 01-01-2013, 02:26 PM   #22
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Quote:
Originally Posted by AntonLargiader View Post
If the guides are anything like this '89 model had, it would be plain stupid to leave them in.

Mouse over the image to see the slop: http://largiader.com/articles/valves/
Yep I have seen that before , the valves will be out today and I'll check the guides .I will also take the heads down to a small engineering shop here locally and see what they think. They do a lot of work on British and German stuff especially old shit .
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Old 01-01-2013, 03:55 PM   #23
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Valves out and there ain't going to be any short cuts for me ! The guides are fucked ! Flopping around like a Nevada lady of the night !

So guides, seats and valve and should replace springs too .

Fuckityfuckfuck
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Old 01-01-2013, 04:06 PM   #24
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You may not have to replace seats; they are generally not a problem. Valves and guides, and recut the seats to match. You may want to go with 45deg valves instead of the 30deg that were stock. You can usually recut the existing seats for that.

But the guy who does the work should be the final judge of that.
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Old 01-01-2013, 04:09 PM   #25
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It's only money. You'll make more.
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Old 01-01-2013, 04:28 PM   #26
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Old 01-01-2013, 04:33 PM   #27
supershaft
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I didn't replace my exhaust seats with 101,000 miles on them when I did (robtg did!) my valve job but I didn't have hammered valves either. From my experience I would not use those seats and I bet robtg wouldn't either. It helps a lot to have some good experience replacing those seats! The seat boss walls AND floors are often warped and require cutting. The proper interference fit helps! Chances are you will be way better off going to 45* valves. Robtg uses GOOD guides. They do differ. Sunnen honed to fit is the best way to go, not pre-sized like BMW guides. Reamed guides? Compared to a Sunnen hone a ream is like using a chisel. I have seen the heads torn up getting them out too. There is no need for it! Good luck!

I just saw the photos. You pulled those valves in the NICK of time!!!!
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Old 01-01-2013, 05:27 PM   #28
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I just saw the photos. You pulled those valves in the NICK of time!!!!
Yeah I don't think that will buff out even with "Mothers"
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Old 01-02-2013, 10:55 AM   #29
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Still have the BMW emissions plumbing installed?

Bob will do the head right the first time...even dual plug them if you want..the only thing he doesn't do are replacing the exhaust threads..go to Hanson's in Medford for that fix.
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Old 01-02-2013, 11:49 AM   #30
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Still have the BMW emissions plumbing installed?
It was still there when I got it but I removed it fairly quickly .

I would love to use ADVers for the work but shipping and such would be a pain , I will be popping down to Acme my local engineers to see what they can do for me later today and to get some idea of the cost , it may have to go on the backburner for a while . A recent divorce has left me kinda strapped for cash right now .
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