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Thread: 1999 R1100RT runs bad, need advice.

  1. #16
    Registered User bcusack's Avatar
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    Hi All, It?s been a few weeks since I posted up any progress here, personal and work commitments have kept me away from the bike. Anyway, today I was able to get back at it and still thinking I was chasing an ignition problem I found the bike would run as well on one cylinder as it did with both at low rpms with the right plug wire removed. It did seem to smooth out and run well with no load above 3000 rpm with both plug wires in. Still seeing a clear difference in the spark I continued to chase the weak spark theory. I picked up a spark gap tester and was happy to find the right spark was much weaker than the left although it did seem to change in intensity on either side. As a final conclusive test and knowing this bike has, I believe, a wasted spark system, I switched the plug wires at the coil expecting to see the side that ran the bike switch from the left to the right, it did not and still found It could start and run with only the left side plug wire in (and the weaker spark) and not vice versa.

    As I thought the above was odd I did a compression test and the left cylinder was above spec at 175 lbs. and very little compression maybe 20 lbs., on the right. Actually feeling good about this I figured I would find maybe the valves were to tight and held open but when I pulled the valve cover all seemed to be in order and operated normally. The valve clearance was good with all four valves closed. I assume if there is carbon built up on the valves I would see a difference in the gap with the valves closed. So I'm perplexed again and I suppose the next move should be a leak down test. Is there any normal reason I would see what I'm seeing? Any advice? Thanks in advance.

  2. #17
    Registered User m_stock10506's Avatar
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    Still waiting for a solution!

    I ran out of ideas. I replaced the Hall Sensor with a new one from Beemer Boneyard and my problem - similar to yours bcusack - my problem persists. After three weeks of chasing possible solutions I have run out of tools and skills. I had my RT picked up by my dealer and they will hopefully get to it this week. I'll report back when I get "the call."
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

  3. #18
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by bcusack View Post
    Hi All, It?s been a few weeks since I posted up any progress here, personal and work commitments have kept me away from the bike. Anyway, today I was able to get back at it and still thinking I was chasing an ignition problem I found the bike would run as well on one cylinder as it did with both at low rpms with the right plug wire removed. It did seem to smooth out and run well with no load above 3000 rpm with both plug wires in. Still seeing a clear difference in the spark I continued to chase the weak spark theory. I picked up a spark gap tester and was happy to find the right spark was much weaker than the left although it did seem to change in intensity on either side. As a final conclusive test and knowing this bike has, I believe, a wasted spark system, I switched the plug wires at the coil expecting to see the side that ran the bike switch from the left to the right, it did not and still found It could start and run with only the left side plug wire in (and the weaker spark) and not vice versa.

    As I thought the above was odd I did a compression test and the left cylinder was above spec at 175 lbs. and very little compression maybe 20 lbs., on the right. Actually feeling good about this I figured I would find maybe the valves were to tight and held open but when I pulled the valve cover all seemed to be in order and operated normally. The valve clearance was good with all four valves closed. I assume if there is carbon built up on the valves I would see a difference in the gap with the valves closed. So I'm perplexed again and I suppose the next move should be a leak down test. Is there any normal reason I would see what I'm seeing? Any advice? Thanks in advance.
    I've read in other threads that a spec of carbon can hold a valve open, causing this. I think it was posted by Paul Glaves. Others with more experience will have to comment.

    Quote Originally Posted by m_stock10506 View Post
    I ran out of ideas. I replaced the Hall Sensor with a new one from Beemer Boneyard and my problem - similar to yours bcusack - my problem persists. After three weeks of chasing possible solutions I have run out of tools and skills. I had my RT picked up by my dealer and they will hopefully get to it this week. I'll report back when I get "the call."
    The way your HES looked it seemed like you'd found the problem. Did you reset the Motronic by disconnecting the battery or fuse 5 after replacing the HES? Will be interested in hearing what the dealer comes up with.

  4. #19
    NC Piedmont Rider ncstephen's Avatar
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    Updates?????
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  5. #20
    . AntonLargiader's Avatar
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    Quote Originally Posted by bcusack View Post
    As I thought the above was odd I did a compression test and the left cylinder was above spec at 175 lbs. and very little compression maybe 20 lbs., on the right.
    You probably have a burnt valve, but it could be a holed piston. If you remove the exhaust header, you can see the edges of the exhaust valves and might be able to see a problem.
    Anton Largiader 72724
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  6. #21
    RD'nNH&AZ rdhudson's Avatar
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    Canister vent lines?

    First of all I bought an R1100R only 1000 miles ago. I posted here with ride-ability somewhat like these two. Several things were wrong with my bike but one has risen to the top in my mind. The vent lines were reversed prior to my ownership. When the solenoid opened the canister to throttle bodies vent line, overly rich gas/air entered the TB's and the bike ran like cr@p. After a few cycles of this the catalyst was fouled, the bike would not run well even when the solenoid was closed (is the fuel tank overfill vent open to air so the mixture was leaned when the solenoid is closed?). Reversing the lines (the ex MaxBMW tech new enough to check this and several posters here suggested unplugging the wires to the solenoid to prevent it opening) fixed part of the problem. I deleted the canister, routed the vent lines to air and plugged the vent inlets in the TB's This reversing is so easy to check it should be a part of any run-ability suggestion. I don't advocate the canister-ectomy but mine was fouled. Others have told me theirs fell off! Be kind I'm new.
    2002 F650GS, 1998 R1100R 75th anniversary edition, 1983 R80RT (just sold), 1959 R60 (in restoration), Honda CT90
    If you must make a mistake, make a new one each time.

  7. #22
    Registered User bcusack's Avatar
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    Thanks for the response Anton, you hit it right on the head, burned valve with a half by quarter inch piece missing along the edge. I lucked out as there is no damage to the piston and the valve seat is clean and the other exhaust and the intake valves look good. Looks like it got sucked out clean if it did come apart in one piece. When a valve ?burns? does it cause a piece to break off or does it slowly eat away at the same point making it bigger as it goes? I know on some old car motors I?ve seen with bad valves the valve is chewed all around the edge. This was just one section like someone bit it off. Waiting on a valve and I hope to get it together soon.

    For those playing along at home I wanted to do a leak down test but I had no easy availability of a true leak down tester. I knew the head had to come off but I wanted to try to better determine what was up before I dug into it. I fashioned some fittings onto the hose off my compression tester and fed compressed air into the cylinder and at TDC I could feel air coming out the muffler, that was pretty conclusive and I took it apart.

    Now, why? I?m open to anyone?s theory. I was still bothered by the clearly weak spark to the same cylinder. While the motor was still together I did replace the coil with a known good one and remember the old coil did test good on a stress test they did at a local bike shop. I now have a good clean snappy spark on both sides of the coil tested through the plugs with the gap tester I picked up. Obviously something is different between the stress test and how it performed in my bike. I was thinking (hoping) maybe the valves were somehow held open a bit with some carbon build up and I did try the sea foam fed through the throttle body trick with no improvement in compression. So, could the bad spark be related to the burned valve? Other than the HES sensor being replaced a few years ago, the bike is well maintained and never any other problems in the 62k miles on it. I do not wail on it (maybe I should). Its ridden often and it rarely get started unless I put down 100 miles or more. Opinions?

  8. #23
    . AntonLargiader's Avatar
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    Quote Originally Posted by bcusack View Post
    When a valve ?burns? does it cause a piece to break off or does it slowly eat away at the same point making it bigger as it goes?
    A channel opens up between the valve and the seat (could be debris, but the root cause is usually a poorly ground seat with insufficient contact) and the hot exhaust gases erode the metal. The seat can usually be saved; you just have to recut it properly (and do the others at the same time).
    Anton Largiader 72724
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  9. #24
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by AntonLargiader View Post
    A channel opens up between the valve and the seat (could be debris, but the root cause is usually a poorly ground seat with insufficient contact) and the hot exhaust gases erode the metal. The seat can usually be saved; you just have to recut it properly (and do the others at the same time).
    When you recut the valve seats, do you have to do both heads at the same time to keep them balanced?

  10. #25
    . AntonLargiader's Avatar
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    No, but both heads have worn seats. The other one just hasn't gone yet.
    Anton Largiader 72724
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  11. #26
    Registered User bcusack's Avatar
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    Any opinion of the weak spark on the same side being the cause?

  12. #27
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by bcusack View Post
    Any opinion of the weak spark on the same side being the cause?
    Maybe delayed combustion or misfire with the mixture still burning as the valve open ?

  13. #28
    . AntonLargiader's Avatar
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    Quote Originally Posted by bcusack View Post
    Any opinion of the weak spark on the same side being the cause?
    Not from me.
    Anton Largiader 72724
    largiader.com bmwra.org

  14. #29
    Registered User m_stock10506's Avatar
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    R1100RT Runs bad - mine too - similar problem

    Stopped at the shop today. They pulled the head on my R1100RT - same symptoms as the OP. No compression on one side; there was a 1/4 inch chip missing from one of the Input valves. I'm glad I did all of the fuel supply maintenance - it was due anyway at 105k miles. And clearly my HES was in poor condition and could have stranded me in wet weather, even though it wasn't the cause of this engine failure.

    We'll get together in the next day or so to decide on the scope of the repair work. Might just go for a top end overhaul at this point.
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

  15. #30
    Registered User m_stock10506's Avatar
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    My R1100RT came home yesterday! What's been the end of your tale of woe bcusack?

    It was a chip missing in one of the exhaust valves, not an intake valve. The shop installed a new exhaust valve along with four new seals and a head gasket. Two of the seats were lapped to make to valve/seat mate complete. The engine is running great; very strong pull and smooth (now). I was a little upset that they did all this head work and didn't do a TB synch when they were done. TBs were way off from my efforts to figure out what was wrong before it was discovered that there was a loss of compression on one side. Took me about 15 minutes with a Harmonizer when I got the bike home to fix the throttle cables and BBSs.
    Michael Stock, Trinity, NC
    R1100RT, R100, R60/6

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