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"checking cylinder compression" transistions to no start

Discussion in 'XJ Technical Chat' started by moellear, May 18, 2011.

  1. moellear

    moellear Member

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    after completely installing new rings across the board, a new piston, upper engine rebuild, and rebuilt carbs I can't even get the d*mn thing to start today. purchased new throttle shaft seals, cleaned and passed clunk test, carbs were syncronized running on monday and I got to ColorTune it as well the same day. took it for a ride and this is a video of a popping sound after riding it with poor top-end acceleration (couldn't even get above 4.5k rpm or 50 mph)

    video audio sound after carb sync and colortune

    in the video does it sound like the motor is LUGGING? you have to give the video time to load up

    today it refuses to even FIRE!!!?!? WTH?

    I'm getting really upset right now. $600 rebuilt and this is the result... about time to just get rid of the bike and find myself a reliable 3 grand bike that was made in the 2000's,,, its upsetting :(
     
  2. SecaMaverick

    SecaMaverick Active Member

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    Sorry moellear,
    I feel your pain. Last year I rebuilt the top end, pretty much duplicating all your listed efforts. After break-in, mine wouldn't get much over 55-60 mph and had nothing left to give. And this thing had been a screamer for the 9 years before.

    Last night I figured out what I did: both camshafts were 1 tooth retarded. :oops:

    Maybe you did the same thing. It made mine run rich, and consistently fouled the plugs. Voila, it wouldn't start every couple days until I cleaned the plugs. (I figured it was the new rings not yet seated).

    I was POSITIVE I had put it together right, but evidently something jumped last year during assembly without me realizing it. So I fixed it last night after driving it for 1100 miles that way. She purrs like a kitten now.

    Check your three timing marks just to be sure.
     
  3. moellear

    moellear Member

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    Thanks SecaMaverik. I'm almost hesistant to say I did the same thing. on the initial startup over spring break a month ago, my father helped me get things started. it was rough at first and sounded horrible (like a squealing) around the chain area. think i may as well break the valve cover apart and be sure the timing marks are exact.

    put the crank at TDC and check timing marks? i guess that's all to be sure the motor is not one tooth retarded lol
     
  4. pirok

    pirok Member

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    Hmm! Maybe I have misunderstood you, but to do the check, you have to get the camshaft cover off:
    1. set the timing marks on crankshaft to T.
    2. check the camshaft alignment mark to see if the dot is aligned to the smal arrow on the upper camshaft bearing shell.
    (with no slack on the front side of the camchain)
    Then it's OK.

    Calm down, I think you are pretty close.
     
  5. moellear

    moellear Member

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    its pretty difficult to do when its your birthday (feelin old at 24.. just one year closer to 25) and you'd like to ride as a celebration. anyhow, the bike did fire up after giving way too much ether. checked the plugs and they're fouled . SecaMaverick has given me hope to fix this since his problem coincided with my current situation. hoping for the best

    valve cover off already and triple checking the timing marks
     
  6. moellear

    moellear Member

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    are these the dots you are talking about? looks like the exhaust cam is worse off than the intake. are both of the cams suppose to align exactly with the small arrow? looks like I'm off 1 to 2 teeth. thanks pirok for your assistance. hopefully it turns easier hence a better firing start on the motor *fingers crossed*

    [​IMG]

    [​IMG]
     
  7. pirok

    pirok Member

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    You got it! allign all the marks and you are on the road before you know it.
    BTW Happy Birthday, 25 Ohh it's going worse he he
     
  8. moellear

    moellear Member

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    do both holes align exactly with the corresponding arrows? its being a PITA but i'll keep trying
     
  9. pirok

    pirok Member

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    A good guess: + - 1 mm
    AND keep the front of the camchain tight when you measure.
     
  10. moellear

    moellear Member

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    got it! thank you so much pirok. it is such a relief to have somebody know what I am doing. I'm gonna take a snapshot just for my own assurance and proof my upper engine rebuild is completed correctly. always learning something everyday!

    valve cover going back on as I speak and hopefully I don't have as much backfiring and better starting issues

    many thanks also to bigfitz52 and SecaMaverick for assisting on an issue I was hesistant to say I did correctly the first time
     
  11. moellear

    moellear Member

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    okay got the bike fired up and went for a birthday ride. however, the popping still prevalent while the idle is very nice

    i know I'm suppose to keep the rpms down since the rings are still being seated but I could not get the throttle beyond 5k when I know it should easily zip to redline.

    what is a common problem with carbs that has surging gas problems? its like the fuel flow cuts in and out...
     
  12. iwingameover

    iwingameover Active Member

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    It's possible your spark is cutting out and not the fuel. You said the plugs were fouled?

    I had a similar problem a year ago. Ended up my TCI was cutting out. Verified by replacing with another I had in a box and some other tests I did from a thread here http://www.xjbikes.com/Forums/viewtopic/t=27318.html
     
  13. tskaz

    tskaz Active Member

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    TCI, coils, kill switch, kill switch wiring, loose fuse connection,battery, ignition switch, the list is lengthy but not hard to go through.

    I'm with gameover, sounds like an ignition issue. What you are probably hearing as "popping" is more likely backfiring caused by gas not getting burnt in the cylinder, then passing into the exhaust where it heats up and explodes, causing the noise.

    I had this problem until I found the source - mine was caused by a loose kill switch connector inside the headlight.
     
  14. SQLGuy

    SQLGuy Well-Known Member

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    How was the compression test, after all?

    My "other" bike had an annoying popping problem (which got worse as it warmed up), as well as low power, and inability to maintain idle. The cause was bent intake valves - 3 mildly, but one quite badly, to the point that the affected cylinder wouldn't do more than 30 PSI on a compression test.
     
  15. moellear

    moellear Member

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    i was told to wait til rings get seated ~ at least 200-300 miles. however, I'm gonna do a test anyways tomorrow morning to be sure compression is not significantly low.

    the fuel combustion popping makes sense but I don't understand the low power band not being able to get over 5k rpm. its got me concerned. would it have anything to do with the carbs?

    here's a better video i took after the birthday ride this afternoon. its a signifcant pop that I don't know if you fellas have better experience trying to get rid of. could I eliminate it down to one or two cylinders just by hearing?

    Web Page Name
     
  16. Rickinduncan

    Rickinduncan Member

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    The popping doesn't sound like it's a steady miss. Why not pull the wire on each plug until the popping goes away. That would at least tell you which cylinder is making the noise.
     
  17. tskaz

    tskaz Active Member

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    Sounds like a v-twin at times. Missing but not constantly. Cylinder check by pulling wires one at a time might help.
     
  18. tskaz

    tskaz Active Member

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    Darn! Looks like my Canadian neighbor got there before I did! LOL

    Still a spark issue me thinks, just not one I've had the (dis)pleasure of coming across before. At least not like that.
     
  19. moellear

    moellear Member

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    sorry for confusion but what does this mean? keep the wire attached to the plug and just have it snug to be sure all connections aren't shorted or phyiscally remove each one and see how it acts running with just 3 cylinders?

    remember, i'm just a newbie on motorcycles so simple tasks may seem redundant to ask about but I'm learning as I go

    *EDIT* nevermind, i think I answered my own question. thanks guys' I'll check into soon
     
  20. tskaz

    tskaz Active Member

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    He means, while it's running, pull the plug wire OFF the plug, one cylinder at a time. Popping goes away and you have your bad cylinder/sparkplug/carb. It'll take out 3/4ths of the work to find the problem.
     
  21. moellear

    moellear Member

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    by the looks of these plugs, i'm concerned 2&3 aren't firing. which is weird because if I hold the plug to ground it shows spark (1 on left, 4 on right)

    [​IMG]
     
  22. iwingameover

    iwingameover Active Member

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    Actually, it looks more to me like 2 & 3 are firing and close to a nice mix. I see some paperbag brown on #3 and #2 has a bit but is also black. Can't see the full insulator in the pictures. 1 & 4 are either oil or fuel fouled and very rich if they're running.
     
  23. moellear

    moellear Member

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    is it worth getting a new set of plugs for some more trial and error? i don't know enough about plugs to verify if I can see change... like 1&4 are very sooty; could they change enough if I tweaked the mixture screws enough to a paper brown color? i realize I still got more syncing and ColorTuning once I get the d*mn thing fired up again. these bikes are so cold-blooded (around mid 50's this morning...)
     
  24. iwingameover

    iwingameover Active Member

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    I would get new plugs and start there. They're not much money and can be had easily. Autoparts stores stock them. Make sure you gap them correctly.

    It may fix your problem until 1 & 4 turn black like that again.

    Also, search here and online for plug chop pictures. There's plenty of pictures here and peoples opinions on how they look and what was done to fix them.
     
  25. KrS14

    KrS14 Active Member

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    I'd bet your getting your pop off 1 or 4. When my plugs got fouled like that, they would spark down the fouling to the casing, NOT across the air gap, hence no ignition. This will let gas accumulate and pop after a while (every 3 strokes or so)

    I'd throw new plugs in there, and start by taking a turn off the pilots on 1 and 4.

    Are you using choke when you're starting? If so how much?

    I always found my seca would like JUST a touch of choke to get going, if i used full choke it would foul plugs after 5 mins idling or so.

    Just w couple things to keep in your head :)
     
  26. RickCoMatic

    RickCoMatic Well-Known Member

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    I'm with the guys that say 2 & 3 are firing and 1 & 4 are too Rich.

    Measure how deep the Pilot Screws are on 2 & 3 and set 1 & 4 to the same depth.

    Put the 2/3 Clean Plugs in 1/4
    Clean the 1/4 Plugs with Carb Cleaner and stickk them in 2/3

    Get a 4-Pack of New Plugs when you get done Tuning.

    2/3 are close.
    Get 1/4 like those two.

    Pulling Caps off Plugs is a Test for KNOCK. Not Ignition.
    You put a good Plug in the Sparl Plug Cap and Ground the Plug to the Engine and look for Spark.

    Take a White Golf Tee.
    Clip the Point off, flush.
    Put the Tee in the No-2 Pilot Mixture Screw Hole and let is set flat on top of the Screw.
    Mark how deep the Tee is into the Hole.

    Use the Marked Tee as a Guide.
    Put the Marked Tee in No.-1 and adjust the Screw to match the Mark on the Tee.
    Do 4, ... too.
     
  27. moellear

    moellear Member

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    Thanks guys! I'm starting to get somewhere! its getting exciting now after correcting my camshaft timing issue yesterday and now 3 out of 4 are turning to the right mixture. purchased 6 new plugs just for testing purposes this morning.

    started with #4 and turned mixture out with ColorTune another full turn ~ 3.5 turns out. then switched over to #1 and did same thing with only half turn out ~ 3.0 turns out or so. after putting a new plug into #1 and hitting the start button it blipped right up and was purring like a 4 cylinder motor (only very high rpms! since my idle knob was in too far aparently). turned it down, went for a quick ride down the country road, and boy I could tell the difference already! came back and did a plug chop at 55mph: 4krpm. here's the view from 1 to 4 left to right on the luggage rack stand lol:

    [​IMG][​IMG][​IMG][​IMG]

    obviously #4 is still very rich & sooty. keep turning the mixture screw out? i thing the other three are very good IMO. any suggestions? quick note also, I still can't get the rpms over 5k and shouldn't over-do it since I have new rings on all cylinders but that wouldn't have anything to do with it would it? thinkin a carb issue at high rpms
     
  28. SecaMaverick

    SecaMaverick Active Member

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    Hey moellear,
    Glad you found the timing issue as soon as you did!

    You probably don't want to get in too much of a hurry anyway getting the RPMs up until you get some miles on the rings. I went a full 1000 miles before taking it over 50mph, but I understand that's probably conservative.

    As for the #4 plug, I can't tell from the pic if it's just carbon-black or oily black. Is it just carbon?

    As for the compression test you're going to do, my experience was that it WILL be borderline low, especially if you had any cylinders re-bored (as I did). I haven't rechecked since break-in, but mine was mid-90s and is supposed to be 120s (someone else can chime in with exact figures, but it's in the manual). Someone else can disagree with this, but I wasn't too concerned with compression until after break-in.
     
  29. moellear

    moellear Member

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    you know, its always something... now whenever the start button is hit the throttle steadily increases higher and higher with no tension in the cable. what is weird is I physically seen the throttle raise but there's not tension on the cable, almost as if a voodoo is around so I put the screws down phyiscally with a screwdriver and the idle drops to where appropriate yet no tension in cable... now that its running hot i have no problem firing it over, but any ideas on the throttle idle increasing?
     
  30. Rickinduncan

    Rickinduncan Member

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    If a plug is black and sooty - shouldn't you be turning the mixture screw in
     
  31. moellear

    moellear Member

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    honestly, i don't know. nobody else has said anything up until now, maybe I should have done my homework a little better. i'll take all the help I can get.

    problem now is the idle goes screaming when the bike get warmed up and can't turn her down. took the carbs off to check screws, cable, and butterflies. everything seems fine so maybe someone else knows what the problem is?
     
  32. JFStewart

    JFStewart Member

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    Check XJ4Ever and look for the Church of Clean. Len has a description of the rebuild process. You cannot do a partial on these carbs. You may need to start from scratch and go through them again. You need to go through the process step by step. Before doing the carbs, the valves should be adjusted. It is possible that # 4 float is too high or sticking.
     
  33. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    You're still out of sync or have a float level that's not right. It only takes ONE carb to come up off the idle circuit to pull the other three along.

    Once the motor's cooled down, take a few minutes to re-check the valve clearances in case something "bedded in" already and threw you out of spec.

    Then re-check the float levels, using fuel and clear tubing.

    Then re-check your bench sync, and make sure it's done with enough "free length" to the idle screw to be able to turn it down "below" the butterflies being closed. Quite often between bench and vac sync, you run yourself out of adjustment on the main knob.

    Be sure you don't accidentally trap the throttle linkage under the fins on the back of the motor when you reinstall the rack.

    Also ensure you haven't accidentally mixed up the throttle and choke cables.

    It's gonna be something simple.
     
  34. RickCoMatic

    RickCoMatic Well-Known Member

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    The pictures make the 4-Plug look "Oil Fouled"

    If the Pilot Mixture Screw of 4 is "Close" to the others, ... you need to investigate why there is so much Oil present.

    Get Compression Readings.

    Investigate that the Pilot Mixture Screw's associated Parts are all in order.
    Sometimes the O-ring and Flat Washer fall-off and "Flip", ... making it difficult to accurately Meter the Flow of Air & Fuel.

    Make sure the O-ring isn't Split.

    As you are riding, ... have someone follow you and watch your Exhaust.
     
  35. Rickinduncan

    Rickinduncan Member

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    so - the pilot screw ....... turn in to lean and out to enrich?
     
  36. RickCoMatic

    RickCoMatic Well-Known Member

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    Yep. That's it.

    But, ... Quit thinking in terms of TURNS and fractions thereof.

    Once the Pilot Screw is within its Optimum Position, ... where it is Regulating the AIR~FUEL Ratio for Engine Fine Tuning ...

    The TOTAL DISTANCE between too RICH and Too LEAN is well within the Distance of the Thickness of two Nickels.
    Degrees.
    15-Degrees Max.

    Here's what it looks like compared to 1/4 of a Turn:

    [​IMG]
     
  37. moellear

    moellear Member

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    time for an update: this morning I checked valve clearances.. nothing extreme & all shims were good enough. took carbs off and re-synced them using paperclips again. also, checked float levels using clear tube & gas again. all within +/- 1mm so I'm not gonna bother messing with them. throttle linkage is free of any obstacles and slack is present on cable when relaxed. did a running sync with mercury 4-line manometers again and got them balanced. fired up and went for another ride.

    during the ride, the idle is high but not as high as it used to be ~ 2.5 to 3k rpms. also, popping is present but I predict its cause I didn't ColorTune yet so one or two may be lean (from what I've learned on here). on the way back I plug chopped it and here's the results from 1 to 4 left to right:

    [​IMG][​IMG][​IMG][​IMG]

    what confuses me is none of them look lean to me. 1&4 are definitely rich but 2&3 look good to me. other thoughts?

    btw: thanks Rick for all your fine tuning info. once I get the plugs near the coffee brown color then I can definitely use your thoughts hopefully.
     
  38. SQLGuy

    SQLGuy Well-Known Member

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    Still think a compression test would be a good idea...
     
  39. Rickinduncan

    Rickinduncan Member

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    I'm also voting for compression test. Doesn't matter what the readings are ( well, it kinda does) but just so long as they are all close to each other.
     
  40. RickCoMatic

    RickCoMatic Well-Known Member

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    2.5 ~ 3,000 rpm's is NOT Idle.

    You have Main Jet Fuel added to the Intake.

    This is a Sync Problem common for having the No-3 Carb too Open during Sync.
    >Or,...
    You got Air Leaks.

    The Throttles need to be Bench Synced using a Strip of 3X5 card to allow you to set the IDLE using the Mixture Screws.

    Shoot for 1,000 rpm on the Idle and get the Idle below 12-Hundred.
     
  41. pirok

    pirok Member

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    Check: Church of clean

    ...- Check the long, skinny aluminum Main Jet NEEDLE to make sure they are the correct size, and also to make sure that they haven't retracted from their plastic top cap.....if so, carefully push the needle cap back "flush" with the ridge near the bottom of the cap. Also check the very end of the tip for scratches, gouges, or deformation ("mushrooming") of the very bottom, pointed tip...
    (when you dismantle the Diaphragm you will get to the main jet needle)

    Check that the main fuel jets are the same and correct size.

    And now what I have learned the hard/time consuming way:
    ...Please be aware that quite a few----perhaps 60-70%----of "first time" carb cleaning/rebuilding efforts end in frustration and failure, and it's mainly due to NOT doing a thorough enough job of internally cleaning the tiny, miniscule fuel passages within the carb body. Although the air passages within the carb body are (relatively) huge, and thus do not normally accumulate fuel sludge and varnish, the fuel passages---particularly the pilot fuel circuit passages---are tiny beyond belief and even a "speck" of old varnish, grit, crud, etc. will cause problems.......in essence, that restriction becomes an "unintended" fuel metering jet, with very real consequences. This is why you want to get really, really anal in cleaning them. Many times, simply "dipping" or "boiling" the carbs out is NOT sufficient; you have to do all that AND mechanically probe (scour) these passages with tiny, fine wires to loosen such material, and THEN blast it away under pressure with carb cleaner, compressed air, etc...
    (to do it thoroughly is a pain in .., but it pays off)

    All the above quotations from Chacals IN THE CHURCH OF CLEAN

    Unfortunately "really, really anal in cleaning" doesn't match: lets clean in a hurry and get out riding.

    - When the engine purrs like a cat, I'm singin in my helmet and I'm enjoying my ride (fortunately no one can hear the singing part he he)
     
  42. moellear

    moellear Member

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    whats wrong with this fellas? i've turned the pilot mixture screw all the way in (clockwise) to try to remove the richness. ITS STILL RICH?!?

    [​IMG]

    something is telling me my bench-sync with paperclips is still off (for the 2nd time in a row). what else could be a result of this? note: carbs are CLEAN! i understand the church of clean on these carbs and over christmas break I rebuilt them from start. ask Len how much i've spent with him...
     
  43. iwingameover

    iwingameover Active Member

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    Did you check your float levels with the clear tube? Maybe that one is flooding.

    Is it fuel or oil on that plug?
     
  44. moellear

    moellear Member

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    CLEAR TUBE; not flooding

    fuel or oil...i don't know. its dry when it comes out so fuel?
     
  45. moellear

    moellear Member

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    they aren't 8O new rings across all four cylinders and $300 later i get these results from a dry test run.

    #1: 110psi
    #2: 70psi
    #3: 60psi
    #4 110psi

    what the hell? seriously... and #1 & 4 are the ones I'm fighting to reduce the richness
     
  46. SQLGuy

    SQLGuy Well-Known Member

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    Hmm... can't remember whether you are sure about your valve clearances and cam timing. If you're sure, then these don't look good. Given that the rings are new, I'd be checking for bent valves.

    If you have a compressor, one thing you can try is turning the crank to bring each cylinder, one-by-one, to TDC (valves closed), then use the air gun with rubber tip to force air into the spark plug hole and see whether you hear air blowing out the intake port or exhaust. If 2 and 3 are noticeably louder blowing air out (most likely through the intake) then I think you'll be looking at some valve work.

    Hopefully not, but let us know.
     
  47. RickCoMatic

    RickCoMatic Well-Known Member

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    If the Max Compression you are making is 110psi, ... you have troubles.

    Minimum is around 120.

    Do the Compression Test -- Wet.

    See if its Rings or Valves or a Head Gasket.
     
  48. SQLGuy

    SQLGuy Well-Known Member

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    120 minimum on a warm engine at sea level...

    All other things being equal, compression numbers will be lower at higher elevations and on cold engines.
     
  49. Rickinduncan

    Rickinduncan Member

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    This kind of news would turn me to drinking heavily. Do you remember what your compression readings were before you did the re and re? Most of them must have been acceptable otherwise you would have done all 4 cylinders - not just one. There HAS to be a camshaft/ timing error someplace ortherwise it's valves. I'm wondering if your timing error that you've since fixed was enough to bend the valves. - but you would have heard that noise, and no doubt you turned the engine over by hand a few times prior to starting it up. I'm feeling so bad for you I'm almost ready to air freight my 750 out to you for free! ( well, almost)
     
  50. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Read back up the thread. Both cams were out of time, one moreso than the other. The motor was run that way, up to maybe 5K RPM (bike being ridden) before it was discovered.

    A "wet" test is the next step; I also suspect we now have a couple of bent valves.
     

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