1. Some members were not receiving emails sent from XJbikes.com. For example: "Forgot your password?" function to reset your password would not send email to some members. I believe this has been resolved now. Please use "Contact Us" form (see page footer link) if you still have email issues. SnoSheriff

    Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

how to check compression off bike

Discussion in 'XJ Technical Chat' started by moellear, Jan 29, 2011.

  1. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    found a motor for a cheap price on CL. before I run down to see if its worth buying, I wanted to get some input. the motor is not on the frame so its not hooked up to the electrical harness. by the pictures, it seems that wiring is attached (possibly the starter)

    [​IMG][​IMG]

    I apologize in advance but its not clear to me how to get the motor to crank without the starter button on the handlebars. yesss, I've never gave it much thought and now its biting me in the butt. just a newbie here with a current weird compression problem I stumbled upon with my current bike.

    what would I need? : obviously a pressure gauge, and some way to get juice to the motor. would jumper cables work from my car battery to 'em wires on the motor? keep in mind, I'm in a dorm at school so I don't have a garage on hand, until I go back home which wont be for another month unfortunately. any help please? i'm afraid the seller has no mechanical advice and just wants everything (frame, motor, extra parts) gone, while I want to get this before someone else does :D
     
  2. snowwy66

    snowwy66 Member

    Messages:
    892
    Likes Received:
    2
    Trophy Points:
    16
    Location:
    Salt Lake City, Utah
    all you need is a fully charged car battery and jumper cables. hook up the positive to the starter terminal. negative to ground. and another person to hold the motor still cuz it might jump around.

    compression gauge and plug socket if the plugs are in th motor.
     
  3. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    so as long as there is the starter which looks like this [​IMG]

    and wiring is hooked up to that? then put the positive on it and negative on ground, it should connect to spin the motor? okay sounds feasible. its hard to tell from the pics on CL whether or not the starter is even there.

    BTW: a car battery isn't too much juice is it?
     
  4. Maxim-X

    Maxim-X Well-Known Member

    Messages:
    1,696
    Likes Received:
    76
    Trophy Points:
    48
    Location:
    London Ontario Canada
    If you do try the jumper cable method, make sure that where the carbs are attached (don't see them in picture) is clean of any crud so that it doesn't get sucked into the motor. If the PO has had it sitting for a while you never know what has gotten in there.
    Plus clean around the plugs before you remove them so that any accumulated crud doesn't fall in when you pull them.
     
  5. schooter

    schooter Active Member

    Messages:
    3,048
    Likes Received:
    2
    Trophy Points:
    38
    Location:
    Elkton, Michigan (its in the thumb)
    and remember that just from gauge error and user error, that numbers may not be correct, but it's consistancy you're looking for in an inline 4
     
  6. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    ok thanks so far. hoping to find a consistancy above 130 on all four. what I've gathered though is that if the starter is not on the motor, I wouldn't be able to check compression. the amount of juice from a car battery is not too much though is it?
     
  7. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    i think i see the holes the starter bolts go in :(
    you could use a leak down tester but then you need a compressor :(
    if it's cheap enough, just get it and cross your fingers
     
  8. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    $75
     
  9. wizard

    wizard Active Member

    Messages:
    5,282
    Likes Received:
    26
    Trophy Points:
    38
    Location:
    DEVON ENGLAND
    75 smacks would be cheep for a boat anchor, go fetch.
     
  10. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    Correct. The starter needs to be attached to the motor. You can use a car battery for this, you won't cook anything you're just spinning the starter for a few seconds.

    Or you could use a fully charged motorcycle battery, like the one in your bike?

    Schooter is correct, consistency (less than 10% variation between cylinders) is what you want. So as long as none of them are more than 13-15lbs different, you're good. Even a perfectly good, "normal" motor will vary a couple, maybe 3-4 pounds between cylinders, that's OK.

    I generally run two or three separate sets of tests; do one test on all four, write down my numbers and go back and do it again. Definitely repeat if you get a wonky reading; remove and reattach the gauge, etc., to be sure it wasn't false.
     
  11. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    well I plan to use jumper cables since my motorcycle battery is back home. If there is no starter attached, but boxed up with extra parts, would you recommend installing it in his garage? is it difficult?

    I feel for $75 its a bargain and wouldn't want this to slip outta my hands.

    I'm startin to wonder why everything is dissasembled off the frame... but $75 includes everything apparently (frame, motor, and extra parts) 8)
     
  12. wizard

    wizard Active Member

    Messages:
    5,282
    Likes Received:
    26
    Trophy Points:
    38
    Location:
    DEVON ENGLAND
    The s/motor is just 2 bolts, 10mm socket.
     
  13. snowwy66

    snowwy66 Member

    Messages:
    892
    Likes Received:
    2
    Trophy Points:
    16
    Location:
    Salt Lake City, Utah
    doesn't matter how many amps are in the battery

    what matters is that there's enough amps. the starter motor only pulls what it needs. the battery doesn't push.

    imagine hooking up a car radio directly to the battery. the battery doesn't push into the radio causing it to blow up. instead the radio pulls what it needs to turn on.
     
  14. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    I suspect everything is disassembled because he's selling off his spares; didn't you see the other XJ in the background?

    Wiz is right, the starter just "plugs into" to the engine case and is held down by two bolts.

    Car battery will be fine.

    I would definitely talk to the guy before going there to be sure he has a starter and realizes what you're planning on doing. Some more of the story might pop out.

    Y'know, it's kind of funny how various sellers-to-be react when you tell them you plan to do a compression test when you come to look at a bike; or that you need to come back and do one before you'll say yes or no. Quite often, the reaction will give away their "agenda."
     
  15. Polock

    Polock Well-Known Member

    Messages:
    9,751
    Likes Received:
    2,097
    Trophy Points:
    113
    Location:
    Beaver Falls, PA
    i don't think you want to run a starter on there without a cam chain tensioner
     
  16. JeffK

    JeffK Well-Known Member

    Messages:
    1,208
    Likes Received:
    81
    Trophy Points:
    48
    Location:
    Just North of Annapolis MD
    not trying to hijack the thread but....
    "Y'know, it's kind of funny how various sellers-to-be react when you tell them you plan to do a compression test when you come to look at a bike; or that you need to come back and do one before you'll say yes or no. Quite often, the reaction will give away their "agenda.""

    someone's been to this rodeo a few times, that's obvious!

    jeff
     
  17. TIMEtoRIDE

    TIMEtoRIDE Active Member

    Messages:
    4,686
    Likes Received:
    11
    Trophy Points:
    38
    Location:
    Clermont FL near Orlando
    You could see a low reading on one CYL and it could still be a good motor with a tight valve.
     
  18. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    D' oh! And here we were all worried about the starter.

    Good point, Mr. P; WTF is the cam chain tensioner?

    I'm beginning to suspect that this "motor" is more like a "big piece of motor" or "most of a motor."

    Danger, Will Robinson, danger...
     
  19. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    okay so if the cam chain tensioner is in a box with other parts too I can put that on pretty easily too correct? how much tension do you put once its on?
     
  20. Maxim-X

    Maxim-X Well-Known Member

    Messages:
    1,696
    Likes Received:
    76
    Trophy Points:
    48
    Location:
    London Ontario Canada
    There was a thread here a while back that showed how to adjust a cam chain tensioner, but forget where I read it......anyone :?:
    Also, if he has stripped so many parts off the motor has he done anything else to it, like taking the top end off and then just bolting it all back together :?:
    You need to ask this guy lots of questions before investing any time and money in this venture :idea:
    He could have done much like you and tore everything down, then when he realized he was in over his head just reassembled everthing to put it up for sale like Fitz is alluding to 8O
    Buyer Beware, Caveat Emptor or some Greek S**T!
     
  21. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    As for tensioning the cam chain, you would lock the tensioner in a retracted position, reinstall it and then release it and re-tighten, just like the normal camchain tensioning procedure.

    The bigger question is why is it off?

    And like Max-X says, what else has he had apart that may not have been reassembled correctly?
     
  22. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    okay well i'm off to take a look and find out some history. If he can't give me any explanations, I'll turn it down. Or else I'll offer $50 for motor and extra parts. I plan to visit some buddies in that area today so it won't be a complete waste of my time :)
     
  23. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    You should be able to tell by careful examination how far apart the motor's been.
     
  24. RickCoMatic

    RickCoMatic Well-Known Member

    Messages:
    13,843
    Likes Received:
    66
    Trophy Points:
    48
    Location:
    Massachusetts, Billerica
    Don't take good money and buy somebody's problems.

    Why bother fooling around with a "Mystery Machine".
    If you can't get a straight story about what you are going to spend money on; forget about it.

    Buy a whole Bike and fix-up what needs to be done to make it go.
    Don't look at every deal with rose colored glasses on.

    Some situations are best avoided.
    Don't spend money for parts to assemble and then read a Post about a guy who finds a running bike he found for next to nothing.
     
  25. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    Rick, he's only looking for a motor; but this is looking less and less favorable as the possibility of compression testing it diminishes.
     
  26. streetmaster

    streetmaster Member

    Messages:
    228
    Likes Received:
    0
    Trophy Points:
    16
    What would it hurt to do the compresson test, and replace the rings if need be, cant be that much to it, what gives. :idea:
     
  27. RickCoMatic

    RickCoMatic Well-Known Member

    Messages:
    13,843
    Likes Received:
    66
    Trophy Points:
    48
    Location:
    Massachusetts, Billerica
    Instead of buying a $50.00 Engine that's going to need, ... (Let's just say 15 Hours of work) ... plus $200.00 in Parts, ... (If you're worth $10.00 an Hr.) ... your INVESTMENT is:

    $400.00 If you don't lose time having to work-around something seized or broken.

    $400.00 is a Low Ball. Rings and Gasket Sets are going to cost a duce. You may need more than that.

    ++++++

    $400.00

    EBay - Used - Runner

    http://cgi.ebay.com/ebaymotors/82-YAMAH ... ccessories
     
  28. wizard

    wizard Active Member

    Messages:
    5,282
    Likes Received:
    26
    Trophy Points:
    38
    Location:
    DEVON ENGLAND
    You must have better 'mincers' than me, I keep looking at the picture on the left & I see a cam chain tensioner.

    Rick is right, you must do a comp' test & if it fails (for whatever reason) rings, valves, head gasket, leave it, parts + labour just not worth the effort.
     
  29. snowwy66

    snowwy66 Member

    Messages:
    892
    Likes Received:
    2
    Trophy Points:
    16
    Location:
    Salt Lake City, Utah
    there's the idea of cheap and a good deal.

    then there's the idea of cheap and NOT a good deal.
     
  30. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    a.) wiz gets the award. there is a cam chain tensioner.

    b.) I realize all this "effort" and "time" involved. But you guys just wait til I put a list together of EVERYTHING ELSE I got. My car is loaded with 4 full boxes nearly everything else a frame can handle. Had my car (pontiac sunfire) been larger, I would have been able to take the entire frame. The guy knew I was getting a bargain but just wanted to see it go towards better use.

    So what if the engine isn't much good? I can salvage all covers, polish 'em up in an hours work and get some $ outta that. Plus, with all the extra parts that I won't even be needing such as another front and rear fender, these parts can help another XJer here on the site. I gotta admit, I'm taking a risk with the engine since I couldn't test it without a starter...but somebody (not the PO) has done work on it. For example, there was an extra rubber valve cover gasket (valued at 20-30 bucks right there) and the rubber boots used to hold the cover I found after going through all the stuff.

    Did I get screwed? NO ($70 for the engine and 4 boxes of misc parts, minus the tires and frame) Did I get a lot of other misc parts with no intention? YES I'll get a list of what I got together by the end of the day hopefully. Lets just say I give a member on here the front forks for $30 shipped, I already almost got half my $ back...
     
  31. bigfitz52

    bigfitz52 Well-Known Member Premium Member

    Messages:
    21,283
    Likes Received:
    419
    Trophy Points:
    83
    Location:
    Rural SE Michigan 60 miles N of Motown
    Sounds like if the motor turns out OK it's going to be a BONUS.

    Good strike!
     
  32. moellear

    moellear Member

    Messages:
    858
    Likes Received:
    4
    Trophy Points:
    18
    Location:
    Lima, Ohio
    so even if the engine fails on me.. was the following a good deal?

    rear tire well, rear fender/taillight, yamaha grab bar, front fender, air box leading to carbs, plastic battery box, chain box with chain, rear brake pedal, shaft drive boot cover, ignition cover, rubber tank mounts, chrome air box side covers, front forks, fork emblem, rear axle, front axle, handlebar, front rotor, rear drum brake with nice pads, ignition switch, centerstand, foot rests, starter solenoid, flasher relays/all other relays, front brake sensor, TCI regulator, side emblem grommets, front brake pads and cylinder, spare rubber valve cover gasket in decent shape

    these items, along with 653 cc YICS engine which is fairly clean and sitting in the trunk of my car was all for $70. *fingers crossed* the compression in the engine is great, then I know I scored a great deal :D ! i'll find out once I bring her home and put my starter on it.

    if you want something, send a PM. I don't have to sell any of this (it can sit in the barn for all I care) but I may consider giving parts if you just pay shipping. I'd start another post in the sell/trade forum but I just want some opinions on my CL find...
     
  33. wizard

    wizard Active Member

    Messages:
    5,282
    Likes Received:
    26
    Trophy Points:
    38
    Location:
    DEVON ENGLAND
    a.) wiz gets the award. there is a cam chain tensioner.
     

Share This Page