+ Reply to Thread
Page 2 of 3 FirstFirst 1 2 3 LastLast
Results 11 to 20 of 25

Thread: yamaha 450 makes no power

  1. #11
    Any chance you can put your old engine back on the dyno to verify? If you are running the same type engine as before it should read the same.
    Break it down to the basics.
    Fuel? what kind? Fresh? egt/o2 read correctly throughout the pulls?
    Spark? strong or weak? locked or timing curve? sparking at right time?
    Compression? compare cranking compression to factory specs. How much is the leakdown? should be well under 10% even for a used engine. A good warm engine should be ~4-8%
    Daryl

  2. #12
    Member
    Join Date
    May 2008
    Location
    Deakin,VIC,Australia
    Posts
    88
    Like Kirk said, you shouldn't assume that the used engine is assembled correctly. If everything else has checked out as identical to your previous setups, I'd be looking at cam timings. 1 or 2 teeth out on the sprockets and the thing can still run. I vaguely recall that that might have been one of the differences between the first gen YZ vs WR 400's and that you could move one of the cams on the WR a tooth for a more YZ like power delivery?

    Turns out my memory isn't too bad! Here, I found it:
    h t t p : / / motoman393. thumpertalk. com/ tech/ yztime. html

    Anyways, my point is to check that all the valves are opening and closing when they are supposed to. And just because it runs, doesn't mean that they are correct.

  3. #13
    Originally posted by dazz:
    Like Kirk said, you shouldn't assume that the used engine is assembled correctly.

    Even the big boys make mistakes. Late-90's and early 2000's Volkswagen 2.0L N/A AVG engines were often assembled at the factory with the piston rings installed upside-down, which gives a little higher oil consumption (tapered sealing rings) but compression is fine. Lots of bulletins out there that VW says up to 1.0 litre of oil consumption per 1000 miles driven is considered 'normal'.... but they also replaced a lot of piston / ring sets under warranty for people who complained.

    That being said, make sure your measuring equipment and bolt on stuff is working like you think it is.

    If you're sure it is, then tear in.
    _______________________________________

    Northwestern Formula Racing Alum
    Head Engineer, Frame/Suspension 2006-2009

    My '73 Saab 99 Road Race Build

  4. #14
    Senior Member
    Join Date
    Oct 2003
    Location
    Airports, A320\'s, 737\'s
    Posts
    310
    You're obviously missing the stickers on the side, those are worth about 5 hp each
    "Man, I need to practice more!" - Kenny Wallace
    "Try not to have a good time... this is supposed to be educational." - Charles M Schulz
    -OptimumG 2005-2006
    -Turner Motorsports 2008-2009
    -Black Swan Racing 2010 & 2011 Team and Driver's Champions
    -HPD Race Engineer 2011-2014
    -Currently Freelance Data/Race Engineer

  5. #15
    Personally I've never been too hot on leakdown tests, typically you get the same results you have listed, which goes as far as telling you "the valves seem to hold air, and the crankcase leaks air."

    Much better to do at least a cranking compression test, that will point you in the right direction as far as cam timing. Again popping the cam cover off and checking the timing marks is a must. Also you can check the condition of the rings by adding a few drops of motor oil to the cylinder: if the cranking compression goes up noticeably, your rings are worn.

    I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."
    Dr. Adam Witthauer
    Iowa State University 2002-2013 alum

    Mad Scientist, Gonzo Racewerks Unincorporated, Intl.

  6. #16
    Originally posted by Adambomb:
    Personally I've never been too hot on leakdown tests, typically you get the same results you have listed, which goes as far as telling you "the valves seem to hold air, and the crankcase leaks air."

    Much better to do at least a cranking compression test, that will point you in the right direction as far as cam timing. Again popping the cam cover off and checking the timing marks is a must. Also you can check the condition of the rings by adding a few drops of motor oil to the cylinder: if the cranking compression goes up noticeably, your rings are worn.

    I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."
    Actually we could not even get him to do that. So Steve and I went and got a compression tester and tested it ourselves when he was not working on it. God that semester sucked so bad.
    ______________________
    Iowa State Univeristy FSAE Alumni
    http://www.sae.stuorg.iastate.edu/?page_id=144


  7. #17
    Member
    Join Date
    May 2008
    Location
    Deakin,VIC,Australia
    Posts
    88
    Originally posted by Adambomb:
    "snip"
    I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."
    Just be a little careful doing this, for example, our KTM's have an auto de-comp that bumps the exhaust valve to bleed off some of the compression. (leaving enough for it to still start - sometimes...) KTM did this to allow them to use a much smaller battery and starter motor on their bikes. We did a cranking compression test and promptly pulled the head off to see what was wrong - nothing. We also tried disabling the auto de-comp only to find that the little starter motor isn't up to the job of cranking without the help of the de-comp.

    I've just had a look at a parts fiche for the 06 WR450 and can see a similar system on the exhaust cam as is used on the KTM, so keep that in mind. There's also the possibility that the de-comp weight is jammed and the auto de-comp is not retracting once the engine starts?

  8. #18
    Originally posted by dazz:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
    "snip"
    I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."
    Just be a little careful doing this, for example, our KTM's have an auto de-comp that bumps the exhaust valve to bleed off some of the compression. (leaving enough for it to still start - sometimes...) KTM did this to allow them to use a much smaller battery and starter motor on their bikes. We did a cranking compression test and promptly pulled the head off to see what was wrong - nothing. We also tried disabling the auto de-comp only to find that the little starter motor isn't up to the job of cranking without the help of the de-comp.

    I've just had a look at a parts fiche for the 06 WR450 and can see a similar system on the exhaust cam as is used on the KTM, so keep that in mind. There's also the possibility that the de-comp weight is jammed and the auto de-comp is not retracting once the engine starts? </div></BLOCKQUOTE>

    It does have a de-compression system and we checked with a local builder before checking the engine. A later rebuild of the engine confirmed the issues with the engine.
    ______________________
    Iowa State Univeristy FSAE Alumni
    http://www.sae.stuorg.iastate.edu/?page_id=144


  9. #19
    Hey guys I was wondering if anyone had a cad model of a yamaha wr450. We're trying to get away from tearing the engine out of last years car to get measurements, so any help would be great.

  10. #20
    Senior Member
    Join Date
    Oct 2009
    Location
    San Antonio, TX
    Posts
    467
    Hey VTMotorsportsTuner, any updates on what you figured out with the weak engine? The Momentum article about your 2012 effort states that the engine was taken to 500+ cc. I'll assume that it made more power after a rebuild, but I've seen my team make 35hp to the sprocket after it was decided that building it to 511cc was the way to go. Volumetric efficiency is a perfectly suitable replacement for displacement.
    -----------------------------------
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

+ Reply to Thread
Page 2 of 3 FirstFirst 1 2 3 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts