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Thread: no compression at all either cylinder!

  1. #16
    Registered User jsouth's Avatar
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    Quote Originally Posted by edheiser View Post
    OK, this is the best info so far, thanks!
    You are right, my problem is my little pump and my DIY leak down tester, and I am confused and frustrated! So last night, I got a new leak down tester with 2 gauges, and a 10 gal compressor (I needed a new one anyway since mine quit working). I will try again as soon as I get the correct hose fittings for the hose, I would have thought they came with the new compressor and hose, but no. Of course I gave my old ones away to the scrap guy.
    I am working with one un torn down cylinder since the other is still torn down. Should I reassemble it first, I'd have to use the old head gasket for now, or just test it as is since both cylinders were at no compression.
    Perhaps it is cam timing, that would explain no compression when cranking (valves open at wrong time), I haven't even taken off the front cover yet. Perhaps you can tell me what to look for. This Haynes manual has crappy photos. I also could use a good photo of the cam chain gear (in head) to get it back on correctly.
    That's a possibility. But HOW would cam timing have changed between running one day and wouldn't start the next? (unless the guy who sold it to you was not telling the truth about that.)

  2. #17
    Quote Originally Posted by dieselyoda View Post
    When you did the compression test, was the throttle wide open?
    good catch. My first suspicion as well. And I've made the same mistake on my Oilhead.

    Not the case with my R90s as I just pin the throttle and lock it.

    Not sure if he's answered yet though.

  3. #18

    throttle open

    Quote Originally Posted by RPGR90s View Post
    good catch. My first suspicion as well. And I've made the same mistake on my Oilhead.

    Not the case with my R90s as I just pin the throttle and lock it.

    Not sure if he's answered yet though.
    Yes on full throttle on compression test, choke off too.
    I've since discovered my right intact cylinder was leaking air like mad out the intake side during a proper (10 gal compressor) leak down test. I loosened the adjusters 2 full turns, and it held 100 psi no problem. Is it possible too tight clearances was the problem all along? I have no idea when or how they were adjusted last. I hope TDC on the compression stroke is where I was at. I'll put it back together and try again after I get a new head gasket and tensioner tomorrow.

  4. #19
    Registered User dieselyoda's Avatar
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    Quote Originally Posted by edheiser View Post
    Yes on full throttle on compression test, choke off too.
    I've since discovered my right intact cylinder was leaking air like mad out the intake side during a proper (10 gal compressor) leak down test. I loosened the adjusters 2 full turns, and it held 100 psi no problem. Is it possible too tight clearances was the problem all along? I have no idea when or how they were adjusted last. I hope TDC on the compression stroke is where I was at. I'll put it back together and try again after I get a new head gasket and tensioner tomorrow.
    This one is easy because you only have two cylinders and they are both at TDC at that same time. However, only one is at the top of its compression stroke, both valves closed and the other is on overlap, intake and exhaust slightly open. If your piston was on overlap, both valves should leak like a goalie on a bad day.

    It is possible, likely, that the reason you had to back off the intake valve is because of two reasons, cam timing and the valve stretched.

    I suggest you put the other side back on, even with the old gasket, and adjust your valves and re-do the cylinder leak-down.

    And the journey will continue until you have the right answer. Guessing is expensive in $$ and drilling to the right answers is expensive in time. Your choice.
    1997 R1100RT, 1981 KZ 440 LTD, R80RT, R90/6 sidecar, K1100RS,1983 K100RS (Cafe now)

    “The major civilizing force in the world is not religion, it is sex.”

  5. #20

    I see, I think

    So I had to be at tdc comp stroke on the right cyl if the exhaust valve was not leaking, and the intake was just out of adjustment if the white OT was in the window. If I was on overlap, both would be leaking?
    See, I didn't even know both pistons were at tdc at the same time. Thanks for the clarification.
    Next question, the left cam chain sprocket has 2 arrows pointing towards the outside, where are they suppose to be pointing to indicate what. My manual photos aren't clear enough to see the marks. I left it on the chain and let it rotate on a screwdriver zip tied to the studs, hoping to not lose it's correct position while rotating the engine. I see a gap in the cam end that the sprocket nub on the back fits into. Where should the gap be orientated upon reassembly. It's at 3 o'clock now.
    So if I can see the OT mark and the right valves are closed, that means the right piston is at tdc comp. So I rotated the engine with the rear wheel in 5th normal direction of travel, until the left piston went all the way in and back out. I can't see the OT mark now. So I tried another in and out. Still no OT mark appearing.
    I stopped for the day. I think I'll remove the front cover so I can rotate the engine in neutral with a 17 mm socket, and observe the timing window at the same time unless someone has a better idea.

  6. #21
    MOA #24991 Pauls1150's Avatar
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    re the arrows - When the engine is assembled correctly, those arrows are used for setting the valves, instead of trying to find a mark on the flywheel. Turn the engine over manually (either by the front nut or the rear wheel, using 5th gear) in the normal direction of rotation (to take up any cam chain slack) until the arrow points straight out horizontally, at either the 9:00 o'clock position (left side as viewed from the rear) or the 3:00 o'clock position (right side as viewed from the rear). That will put you on the "flat" of the cam - but you still need to determine if that cylinder is actually at TDC, or at overlap (as explained by d'Yoda). The actual TDC side should have a little "wiggle" if you grab & jiggle both of the rockers, and this side is ready to adjust, while the overlap side will not have wiggle, it should feel tight ... assuming that they are "in the ballpark" to begin with. Set the valves one RCH loose just to be sure they can fully close, turn the engine over 360 degrees, and you should be set to do the other side.

  7. #22
    Registered User K7GLE's Avatar
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    Quote Originally Posted by edheiser View Post
    I didn't even know both pistons were at tdc at the same time.
    Not quite - they're 180 degrees out of synch: When one is at TDC (top of compression stroke, all valves closed) the other is at top of exhaust stroke (exhaust valves open).
    - Glenn
    2000 R1100RT (current)
    1982 R100RT (traded)
    1970 BSA A65T, 1969 Honda CB350, 1967 Honda CB160 all fondly remembered

  8. #23
    MOA #24991 Pauls1150's Avatar
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    My caffeine hasn't kicked in yet ... should my earlier "360" actually be "180 or 540" ?

  9. #24
    Liaison 20774's Avatar
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    In my world, when the pistons are all the way out, that is top dead center. Doesn't matter if it's compression stroke, exhaust stroke, whatever. It's TDC.

    Setting valves are always done at TDC on the compression stroke for the cylinder under investigation. Oilheads should be the same as Airheads...once you've found TDC on the compression stroke for one side, turning the engine/flywheel 360 degrees to the next indication of TDC will be TDC on the compression stroke for the other side.

    I always am a little leery of the idea of finding TDC in the window and checking for which set of valves are loose. It's not necessarily true that one or the other valves will be loose. If the clearance has significantly tightened up, none of the valves will be loose. So, the best way is to watch the valve action to know when the intake stroke is complete and the piston is on the way up to TDC compressing the mixture. Or remove a plug and put your thumb over the hole and feel for the increase in pressure. The next time TDC shows up will be the end of the compression stroke for that cylinder.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  10. #25
    Clarification: the pistons go out at the same time and in at the same time. While it may be semantics they are at TDC - as far toward the head as physically possible - at the same time. But as was stated one cylinder is on the compression stroke with both valves fully closed while the other cylinder is just finishing exhausting the exhaust and beginning the next intake stroke as the piston retreats from its position away from the head.
    Paul Glaves - "Big Bend", Texas U.S.A
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  11. #26
    Registered User rxcrider's Avatar
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    The following information is for the R1100xx, but if memory serves, the same is true for the R1150xx:

    head-right.JPG

    head-left.JPG

  12. #27
    Registered User m_stock10506's Avatar
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    Yes, that is correct for the 1100 motor - I personally can't confirm it is also true for the 1150. I use this method whenever I am checking valve clearances. This method is MUCH easier than using the timing hole and watching for OT. Also I can't stand trying to put that PITA timing hole cover back on and trying not to push it into the flywheel space. There are too many parts in the way and not enough space to work in there.

    The only "correction" to the diagram that I have is in every R1100 bike that I have used this method, the cam chain sprocket did not have an "R" or "L" marking. The sprocket simply has an arrow on it. Rotate the motor until the arrow is horizontal pointing outward and you're there.
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

  13. #28

    Thanks again everyone

    I just got back from the BMW dealer with my cache of new parts including a tube of special sealant "Drei Bond" I speak a little German and told them that means "Three Bond" which is 3 bond found lots of places, just got a blank stare back. Very nice people, took the whole staff to find the right piston for the new 15 mm head tensioner The tech came in and tried to answer my questions about reassembling the valve train. Couldn't remember a lot. The left lower tensioner blade came out with just the outer bolt removed, the diagram shows it secured by a pin and circlip in the center of the engine Either mine was never attached properly, or the diagram is drawn backwards, wouldn't be the first wrong drawing I've seen. Nothing to do but reassemble it that way.
    Thanks rxcrider, nice diagrams of the 1100. I'll try again in the morning.

  14. #29

    no joy yet

    I got the engine reassembled with a new head gasket and updated 15 mm tensioner. I left off the intake and exhaust for now, hooked up the battery, sprayed starter fluid in the intake side, and......nothing, no backfire fart or peep. I did a compression test, none. I did a leak down test, held fine. Has spark.
    I did have a hard time getting the OT to show in the window, it turns evenly until it's almost in the window, then is very hard to turn, and when it moves, it goes way past the OT mark. Hopefully this all will mean something to someone, because I'm not getting it. I'm back to square one.

  15. #30
    Liaison 20774's Avatar
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    Being hard to turn as you approach OT and then shooting past would seem correct. You're building pressure on the compression stroke with both valves closed. Then as you move past OT, the exhaust valve opens allowing the exhausting process to begin. Remove the spark plug and the build up of compression will be gone.

    Sure sounds like you have compression. You provided the fuel. No fire. Sounds like something's wrong with the ignition and/or timing.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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