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Old 04-01-2012, 07:58 AM   #1
helion42 OP
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R75/5 question about the engine -

First question.
The bike's been sitting for about 20 years, in a garage. Oil was clean when I drained it, and it turned over alright, but it is very stiff to pump the kick-starter (with the plugs out even).

I'm yet to do a compression test, but what would make it so stiff? It's in neutral, no spark plugs, carbs are off...
What should the compression test read? Bike/engine has 8,923 miles on it.


Second question.
The first owner last registered the bike in 1979, but maintained it various times in the 80's. He had "some guys" working on it around 1990 to get it running, then abandoned it. These "guys" got a little overexcited with the rebuild, and I found red sealant on:
oil pan-to-block (not supposed to be there),
block-to-cylinder bores (is ok according to snowbum if I'm deciphering his bloody website proper)
head gasket (not supposed to be there), none on the valve cover gasket (good thing)

I'm concerned about the head gasket having sealant, should I take this as an indicator that they were trying to remedy a warped head or cause one? Header pipes are blued a bit, which I thought meant the bike might've ran hot at some point, but my pops says that color is pretty normal. I'm hoping that they were just ignorant, and the bike didn't run on whatever they did for very long
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Old 04-01-2012, 09:00 AM   #2
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Take it apart and see.
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Old 04-01-2012, 09:55 AM   #3
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A boxer motor sitting that long is prone to corrosion damage in the bores. I'd pull it apart to verify that possibility.

I'd also be inclined to tear it down to check on possible damage done by the last "fixers".



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Old 04-01-2012, 10:24 AM   #4
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I'd wonder about "the guys" skills also. Did you put any Marvel Mystery Oil in the cylinders to get things lubed up? How stiff is it if you push it in gear with the plugs out?
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Old 04-01-2012, 11:02 AM   #5
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I wouldn't attach much concern about what you call stiff when using kick starter. Do you know what one is like that does run?

The red sealant might be a problem. Start by taking off the oil pan and tell us what it is exactly. Sounds like some kind of RTV. You say this stuff was applied in 1990? Would be RTV is my guess. I think it should all be removed at this point and you get to check the condition of pistons and cylinders while at it. Since it's all gonna come apart get all the correct gaskets and push rod seals. /5es also have shims on the basses of the cylinders.
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Old 04-01-2012, 11:38 AM   #6
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It turns over like everything's fine, but it's stiff like I have to stand on the damn thing at certain points in the rotation. The rings were not stuck in the bores, I just put like a teaspoon of regular old oil in the plug holes.

I replaced the pan gasket, and it appeared to be something like RTV. In gear with the plugs out, I can push it alright. I have the rear end off at the moment, but the last time I tried, it rolled with a good kick o the hooves. Everything on the bike appears in superb shape, I peeked in the plug holes as best I could, saw no pitting.

What will I need besides gaskets? no stretch bolts apparently.
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Old 04-01-2012, 12:01 PM   #7
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To take the heads and cylinders off you will only need gaskets. Head gaskets (2), cylinder shims (at least two) and pushrod seals (4). You might need valve cover gaskets so might as well get them now anyway. None of this stuff has much miles on it but it is old anyway and it won't take to removal and replacing very well. Since the object is to inspect the cylinders and pistons they should be seperated, you will need some way to compress the rings to get them back together. Various methods exist to do this with out a proper ring tool, I always use a ring tool. I don't see any reason why you will be taking the rings off the pistons but you should be warned the rings are very stiff, they are down right fragile. They do not like to be bent and you need to not break any of them. They break easily if messed with too much.

Try to keep everything in order and replace parts in the same place they were removed from.

They object is to just get this bike running? If you are going to all this much trouble I'd rebuild the carbs or at least clean them out. Check carefully for needed parts in there.

I forget who suggested this has to come apart before starting. I guess I could look at the rest of this thread but it doesn't mater, maybe. Why do we think it needs to come apart? I normally just pour some gas in and with a fresh battery I crank away. Oh, I remember, 20 years storage, we are worried about water damage after that long a time. So my question now is, where was this bike stored for 20 years? Outside, Barn, Under Porch, or next to Out House? Maybe in a dry Basement?
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Old 04-01-2012, 12:28 PM   #8
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Have you taken a peak at the cylinder bores through the sparkplug holes?
Using a penlight or similar, can't see very much but probably enough to satisfy the question of corrosion in the bores, or none.

edit: oh, saw this now
Quote:
Originally Posted by helion42
I peeked in the plug holes as best I could, saw no pitting.
If you're turning the engine over with the kicker it should spin without too much effort till the cam lobes start lifting the valve assemblies. The valve springs offer fair resistance.

hope that helps.
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Old 04-01-2012, 12:50 PM   #9
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compression test

as you may know it's best to do a compression test (assuming the valves are adjusted) after the bike is warmed up, with the throttle plates wide open and the carburetor slide lifted so there are no intake obstructions.
alternatively one can remove the carburetors from the cylinder head spigots. This will give the highest psi and a relatively common baseline for talking compression numbers.

Also, a more informative check is the leak down test ( http://en.wikipedia.org/wiki/Leak-down_tester ).
A decent leak down tester is good to have and not terribly expensive.
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Old 04-01-2012, 07:40 PM   #10
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Quote:
Originally Posted by Renner View Post
as you may know it's best to do a compression test (assuming the valves are adjusted) after the bike is warmed up, with the throttle plates wide open and the carburetor slide lifted so there are no intake obstructions.
alternatively one can remove the carburetors from the cylinder head spigots. This will give the highest psi and a relatively common baseline for talking compression numbers..
Yeah was planning to do that, what numbers should I be looking for?

Quote:
Originally Posted by disston View Post
To take the heads and cylinders off you will only need gaskets. Head gaskets (2), cylinder shims (at least two) and pushrod seals (4). You might need valve cover gaskets so might as well get them now anyway. None of this stuff has much miles on it but it is old anyway and it won't take to removal and replacing very well. Since the object is to inspect the cylinders and pistons they should be seperated, you will need some way to compress the rings to get them back together. Various methods exist to do this with out a proper ring tool, I always use a ring tool. I don't see any reason why you will be taking the rings off the pistons but you should be warned the rings are very stiff, they are down right fragile. They do not like to be bent and you need to not break any of them. They break easily if messed with too much.

Try to keep everything in order and replace parts in the same place they were removed from.

They object is to just get this bike running? If you are going to all this much trouble I'd rebuild the carbs or at least clean them out. Check carefully for needed parts in there.

I forget who suggested this has to come apart before starting. I guess I could look at the rest of this thread but it doesn't mater, maybe. Why do we think it needs to come apart? I normally just pour some gas in and with a fresh battery I crank away. Oh, I remember, 20 years storage, we are worried about water damage after that long a time. So my question now is, where was this bike stored for 20 years? Outside, Barn, Under Porch, or next to Out House? Maybe in a dry Basement?
I already have a few of the gaskets needed, I suppose I would only need to order the cylinder base gaskets and shims then.

As for getting the bike running, that's the main goal with the rebuild. I haven't started a formal rebuild thread yet, will do that this summer when I have time probably. I have already stripped the bike most the way down, re-painted parts of the frame, cleaned and rebuilt the carbs, rebuilt the petcocks, cleaned/scrubbed all the aluminum and chrome, checked wiring, and planned out any parts that I'm yet to order like tires and tank sealant. Worrying about actual running status is the current issue to tackle before I put the battery in and actually try and run it in the current shape.

The mechanic nearby may let me borrow a compression gauge, and possibly a borescope, so that's something I'll be able to do this next weekend.

To answer your question, the bike was stored in a -fortunately watertight, but not temp or humidity-controlled- shed since the mid-eighties, and last worked on and ran around 1990. Conditions in Utah are pretty dry in the summer, and frozen in winter, so most exposed rubber parts are dry and cracked a bit. Owner (original owner, mind you) said it was running rough, and he abandoned it then. The bike was kept dry, only accumulated filth and rust pitting. When I drained the fluids, I visually checked them thoroughly, and there was no sign whatsoever of contamination in any of them. Brake shoes, spark plugs and tires look never used, oils were all extremely clean, no varnish in oil pan. Only problem is that the gas tank has fairly bad rust inside, but nothing that can't be stripped and resealed (planning on gas-and-nails strip, or myriatic acid unless otherwise suggested).

I've worked on cars extensively (rebuilt a 1990 BMW e30), bikes and scooters a little, but this is the first bike I've gotten intimate with - and what a marvelous one to start on.
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Old 04-01-2012, 09:56 PM   #11
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Quote:
Originally Posted by helion42 View Post
It turns over like everything's fine, but it's stiff like I have to stand on the damn thing at certain points in the rotation.
My R75/5 is the same way, I found it lot easier to put it on the center stand in 4th gear and spin the rear wheel (with the plugs out) to check the rotation. I have no idea how long mine went without running but I changed all the fluids, put in a new battery, set the timing and the valves and started it up. So far it's running pretty good, I'm sure the carb rebuild really helps me here.
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Old 04-02-2012, 06:58 AM   #12
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I wouldn't bother with a compression or leak down test at this stage of the game. On a long sitting motor they are going to be low no matter what. At your stage of the rebuild/teardown the readings aren't going to mean much.

If you are finding abnormal things ( gasket goo RTV where it shouldn't be ) then I'd take the heads off. You'll need a ring compressor to get the pistons back on and a torque wrench to get the torque right but that's all you'd need other than standard tools. If you think you've got warped heads, then you could put them on a piece of plate glass and see if they are true.

I can't remember what colour the RTV was, but many coat gaskets including head gaskets with High Tack gasket spray, which is red in colour. If that's what you are seeing on the edges of the head gaskets then I wouldn't worry about it.
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Old 04-02-2012, 07:53 AM   #13
helion42 OP
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I'll probably do one just so I can know more about the health of the engine, but I get your point. Still would like to know the comp #s?
It is red goop, leaking out the sides. def looks like RTV.

Are you folks sure I'll have to pull the cylinder bases? Snobum's article said that it is ok to use sealant on that connection, although I couldn't discern what type or how much.


vvv Disston - Not really leaking lol, it just squeezed out the sides like a gob of RTV would when you mate the surfaces. I have replacement head gaskets *somewhere*, and can easily replace those once I get ahold of an exhaust wrench. What I'm mainly wondering is if I'll have to pull the cylinder base (jug?)

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Old 04-02-2012, 08:33 AM   #14
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You say the red goo is leaking? Is now leaking? It is still liquid? If it is RTV it should have been dry twenty years ago. Do you know what Blue Glue looks like? That's RTV. The Blue one is more common. If these guys put RTV on the head gaskets twenty years ago they were idiots who did not know what they were doing. But why did they take the heads off to do this? That has got me stumped.

If the heads are sealed with any kind of sealant I think you should take it apart. If the sealant is only on the valve covers then clean them up and fire that baby up.
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Old 04-02-2012, 11:39 AM   #15
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from: http://www.bmwscotter.org/procedures/compression_testing/compression_testing.htm
"Each cylinder should measure between 110-160 psi with both cylinders within 10 psi of each other. "

I think my R75/5 was reading 145 both sides last time I checked, after its recent top end job with standard 9.0:1 pistons.
Yours might be low now and come up a bit as it's ridden.

If you run the bike as-is it may do pretty well and return good fun.
If you dive in I'll wager you'll find the cylinder bores tapered beyond spec, requiring over-bore and new pistons in addition to head rebuilding and while you're in there replace the big end shell bearings.
At least that's what I did when I dove in to get rid of the pesky, occasional puffs of oil smoke.

the /5 runs great now. Über-reliable and one of my favorites.
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