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Old 11-03-2010, 05:59 PM   #1
bikecat OP
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Pushrod seals replacement


Had a leak at the pushrod seals, hence their replacement. I thought that my pushrod tubes' seals melted, when I saw a mess of black at the base of one. After removal of the seals and pushrods, it looks like this:





Looks like the PO used silicon to seal bases of the seals, to either forestall leaks or to patch one. Good or bad idea? Necessary?

Here's the heads and pistons:

Left side:





Right side:





Anything I should worry about from what you guys see? I plan to remove the carbon and see if that improves my high fuel consumption, reinstall stainless covers and new seals.
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Old 11-03-2010, 06:12 PM   #2
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everything looks good (heads, clyinders, pistons)


I wouldn't recommend using gasket seal for the pushrod seals... They work fine without it. Granted you use bmw parts, I heard there are some aftermarket ones that tend to crack with hardly any use
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Old 11-03-2010, 06:16 PM   #3
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Thanks.

The seals are from Motobins; eh .. they are BMW, right? Anyone used theirs?
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Old 11-03-2010, 06:22 PM   #4
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Originally Posted by bikecat
Thanks.

The seals are from Motobins; eh .. they are BMW, right? Anyone used theirs?
Yep. I've got seals from Motobins on my bike right now. They're about 5 years old and getting ready for replacement. Worked fine so far.

I don't know if they were BMW parts 5 years ago or now.
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Old 11-03-2010, 06:22 PM   #5
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more than sure they use bmw group parts
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Old 11-03-2010, 06:20 PM   #6
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Do NOT use silicone on the push rod seals. a) They work fine w/out the goop, b) you end up with a mess (as you've found) and 3) how will you ensure that a bit of silicone won't spooge out into the oil galley and subsequently block oil circulation.

There's no need for silicone goop (and make sure you keep the remains of the PO's mistake out of your engine).

As for removing carbon to improve mileage, I don't think you'll see much of a change. Much more inportant is what was your compression before disassembling? Healthy compression plus well tuned carbs will have the biggest impact in a stock motor.

Nice work.
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Old 09-30-2012, 04:25 PM   #7
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Quote:
Originally Posted by fishkens View Post
Do NOT use silicone on the push rod seals. a) They work fine w/out the goop,
Few questions about a push rod seal replacement.

-No Silicone on the push rod seal replacement job at all?

-Can I put back the head without using the H-alignment piece?

-Some owner leave the piston ring and the head and remove the connecting rod instead. What's the reason? I found remove the piston from the housing is easier.

Thank you for the reply,

TT
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Old 11-03-2010, 06:23 PM   #8
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I just did that exact same job on my '78 R100S. It looked as though the PO had goobered silicone on the seals to try (unsuccessfully) to stop the leaks. I would recommend taking the heads apart to check the valve guide clearance, also it will allow you to do a more through job of cleaning them.

I got my parts from Hucky.
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Old 11-03-2010, 07:51 PM   #9
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That's a nice, healthy-looking piston crown, typical of Nikasil bore bikes. Have a good look at the rings for wear and pull the lifters and inspect their faces.
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Old 11-03-2010, 07:53 PM   #10
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Good call on the lifters Bud. At least half of the lifters I've pulled out of my airheads have pitting and damage on the faces, even though the cam journals look perfect. Worth double checking and replacing if necessary.

dc
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Old 11-03-2010, 08:21 PM   #11
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If you have to replace a lifter, soak it overnight (at least) in motor oil. They are cast iron and absorb oil, just as an iron frying pan does. Whether you are replacing them or not, smear the faces with cam assembly lube, or if you don't have this ass'y lube, get some CV Joint grease from the local auto parts store. The first minutes of use for lifers and cam are the most critical in their lives.
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Old 10-04-2012, 12:17 PM   #12
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Originally Posted by bmwrench View Post
If you have to replace a lifter, soak it overnight (at least) in motor oil. They are cast iron and absorb oil, just as an iron frying pan does. Whether you are replacing them or not, smear the faces with cam assembly lube, or if you don't have this ass'y lube, get some CV Joint grease from the local auto parts store. The first minutes of use for lifers and cam are the most critical in their lives.
In a former life when starting an engine with a new cam and/or lifters it was highly recommended to raise the RPM well above idle ASAP as it supposedly would decrease the load on the lifter face and get it spinning to avoid the initial "first minutes" wear for both the lifter and cam lobe.

Preset everything, valve adjustments, ignition timing, fluids etc etc and double check everything. Engine starts and runs, gets oil pressure, no fluids spraying out or other immediate problems then rev it up a bit and hold it. I think we used to try for 2000 rpm for 20 minutes. However a running airhead will not stay cool so a few minutes may have to be good enough.
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Old 11-03-2010, 10:38 PM   #13
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Quote:
Originally Posted by Country Doc
Good call on the lifters Bud. At least half of the lifters I've pulled out of my airheads have pitting and damage on the faces, even though the cam journals look perfect. Worth double checking and replacing if necessary.

dc
I ALWAYS check the lifters when I have a cylinder off. If they are flaked at all, I replace the ones that are. No need to replace the set. I think an old one that hasn't yet flaked is more likely to not flake in the future than a new one. It's already been flake tested! CV grease? I think lithium is fine. I never soak them either. I agree with bmwrench that the first seconds is most critical but our cams and lifters do just fine without pre-soaking them and lithium grease. Cams that need that much special attention say exactly what they need in the instructions. If I was installing a cam in my friends wingless sprint car, I would follow that lumpy mofo's instructions to the T!!. Personally, the best thing I think you can do for the lifters in our bikes is to run motorcycle specific oil in them and not automotive oil but that is for a dreaded oil thread.

Boy have lifters gone UP in price lately!

I think Motobins sells a lot of stuff that isn't BMW from what I can tell. They seem to be like Capital Cycle only different? I would only use push rod tube seals from a BMW dealer myself but I am not down on the dealers like a lot of people are.

The rings look like they have sealed real well from the looks of the piston crowns. I would only clean off the piled up and caked carbon. There is NO need to clean it down to bare metal. If you do, a carbon layer will be back in no time so why do it. DON'T gouge the stuff cleaning it. IMO, the rings won't be worn but the top side of the top ring groove might be. If you clean the heads with the valves out be careful and don't ruin the valve sealing surfaces. Do not wire wheel the valves or the pistons.

Some people put oil on the push rod seals. I install them dry after I clean the mold release from them and have had good luck. My own seals right now don't even weep and they have been in there for nine years and about 65,000 hard miles.
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Old 11-03-2010, 11:29 PM   #14
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Yeah, what's all this shit about buying seals from Motobins?
bikecat, where are you?
There's nothing in your profile that says where you are.
If you are in the USA, WHY would you buy $2.00 seals from England????
Do you own stock in a shipping company or something?
C'mon folks, lets get real here.
Once in a while there's a deal to be had at Motobins, but for fuks sake, let's check a US dealer first, (if you are in the US of course.)
Max's has current prices listed on their catalog.
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Old 11-04-2010, 02:08 AM   #15
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Quote:
Originally Posted by supershaft


The rings look like they have sealed real well from the looks of the piston crowns.
What would it look like if the rings hadn't sealed? Pitted?

I would only clean off the piled up and caked carbon.

What with? Green scouring pads?

IMO, the rings won't be worn but the top side of the top ring groove might be. Anything you can do about that? Is it a critical issue?


Sorry for the hijack Bikecat
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