1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Discussion Nitrous Oxide

Discussion in 'The Pub' started by Frankster, Jun 3, 2021.

  1. Big Balls

    Big Balls Active Member

    Messages:
    41
    Likes Received:
    32
    Trophy Points:
    188
    Joined:
    May 16, 2021
    Gender:
    Male
    Occupation:
    Bum
    Location:
    Manawatu/Wanganui. New Zealand
    My Bike:
    1991 ZXR250, 2018 Hayabusa
    back in the 80s they used a method called the squish method on 2 strokes when they were raced. Solder was placed down the spark plug hole, piston up to TDC, remove solder and measure the squashed solder to give clearance piston to cylinder head. Too small, no racing.
     
    • Like Like x 1
  2. jmw76

    jmw76 Well-Known Member

    Messages:
    1,151
    Likes Received:
    585
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    Yep solder wire works really well. I have used this on numerous occasions.
    It is a good way to confirm what you have before pulling an engine apart.
    It takes a bit of skill to feed the solder down the plug hole and manoeuvre the solder wire into the right location.
     
  3. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
    It takes a bit of skill to feed the solder down the plug hole and maneuver the solder wire into the right location

    It would be almost impossible on the ZXR heads with their deep recess for the spark plugs. I'm going to pull the head off anyway (to deck the barrels), so I might as well do the plasticine method. It'll be a good experience for me. I did the solder squish test on the 2-stroke motor in the Nostalgia drag bike...it was 6mm, so that explains why it was running poorly.
     
    • Like Like x 1
  4. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

    Messages:
    3,225
    Likes Received:
    1,415
    Trophy Points:
    918
    Joined:
    Oct 1, 2013
    Gender:
    Male
    Location:
    Narrabeen, NSW Australia
    My Bike:
    Yamaha FZR250 3LN1
    I wondered what the issue was that and if you got it resolved
     
  5. jmw76

    jmw76 Well-Known Member

    Messages:
    1,151
    Likes Received:
    585
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    It is not as difficult as you might think. It works fine on GSXR engines and the plugs are in fairly deep on those.
     
  6. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
    I might have a crack at doing the solder test before I pull the head off.
     
  7. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
    @ruckusman the bigger issue was the (nostalgia) bike's instability. It was shaking from front to back (chain was smashing against the frame and chain guard) and the head was shaking just to complete the picture. The project is parked until further notice as there are zero chances to race a nostalgia bike at the moment.
     
  8. jmw76

    jmw76 Well-Known Member

    Messages:
    1,151
    Likes Received:
    585
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    @Frankster choose some solder wire that is a little bigger than your expected squish clearance.
    You need to feed it down the plug hole and angle it over towards the main squish area of the combustion chamber.
    Make sure you are on the compression stroke for that cylinder with the piston just a bit before TDC. maybe 10mm down. This helps direct the solder into the right area. Carefully wind the engine past TDC. You will feel a little resistance as the solder gets compressed. Pull the solder out carefully and measure the thickness. That should be your current squish dimension. Subtracting your compressed head gasket away from this tells you how far below the deck you pistons sit.
    On older engines, you may get a little piston rock which can complicate things. 2 bits of solder either side of the piston might give a better reading.
    Some people just like to run zero deck height, leaving only the gasket thickness for clearance. Sometimes this works ok, but depends on your gasket. Single thickness metal shim gaskets will not provide enough clearance.
     
    • Nice Work Nice Work x 1
  9. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
  10. thebeefsalad

    thebeefsalad Well-Known Member

    Messages:
    490
    Likes Received:
    301
    Trophy Points:
    273
    Joined:
    Feb 28, 2015
    Gender:
    Male
    Location:
    San Antonio, Texas USA
    I use soft solder (i.e. high lead content) to check squish (2t and 4t) and synthetic clay to check valve/piston clearance. Hadn't considered plasticine for piston/valve but I might change to that as it's less likely to deform.
     
  11. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
    Lift the head again and cut the plasticine to see what your valve to piston clearance is.

    It's 3.98mm. Does that sound right?

    IMG_2127.JPG Squish.jpg
     
  12. jmw76

    jmw76 Well-Known Member

    Messages:
    1,151
    Likes Received:
    585
    Trophy Points:
    498
    Joined:
    Mar 12, 2017
    Gender:
    Male
    Location:
    Melbourne, Australia
    My Bike:
    Honda cbr250rr mc22 road + 1 track, Honda RC 162 tribute bike, Honda Spada Vt250, Honda CBR900RR
    @Frankster did you wind the engine through a full cycle? If yes, then that value should be the your valve to piston clearance. Looking at the images you have posted, you need to measure the minimum clearance value. This is likely to be at the extremities of the valve area. Using the same method, maybe with a bit more plasticine, you should also be able to get the minimum piston to head clearance (squish) also.
    My recommendations for intake clearance > 1.2mm & exhaust > 1.0mm. Others might say you can run less, but you will need really good valve springs and avoid over revving.
     
    • Agree Agree x 1
  13. gregt

    gregt Well-Known Member Premium Member

    Messages:
    320
    Likes Received:
    292
    Trophy Points:
    273
    Joined:
    Mar 26, 2016
    Gender:
    Male
    Location:
    Hororata NZ
    My Bike:
    many and varied
    That sounds about right for dead stock. Take a couple of cuts at different angles - you've got enough coverage for a good explore.

    JMW has his figures wrong, Those figures are for quite large valves - and you should run larger clearance on the exhaust side as that's the one most likely to be tagged by the piston.
    With very light and small valves as here, I've already said you can come as close as .030in without risk.
    There's a major weight difference between bucket and shim - and the lever type cam followers used on his GSXR engine.
    It's apples vs oranges.
     
    • Informative Informative x 1
  14. inchoate

    inchoate Well-Known Member

    Messages:
    103
    Likes Received:
    86
    Trophy Points:
    228
    Joined:
    May 2, 2021
    Gender:
    Male
    Occupation:
    Technician
    Location:
    Philadelphia USA
    My Bike:
    1988 MC19
    Just curious, with these small displacement, high rpm motors does rod stretch become an issue?
     
    • Like Like x 1
  15. gregt

    gregt Well-Known Member Premium Member

    Messages:
    320
    Likes Received:
    292
    Trophy Points:
    273
    Joined:
    Mar 26, 2016
    Gender:
    Male
    Location:
    Hororata NZ
    My Bike:
    many and varied
    Not in my experience.
     
    • Like Like x 1
  16. Gen

    Gen Well-Known Member

    Messages:
    324
    Likes Received:
    330
    Trophy Points:
    273
    Joined:
    Aug 16, 2014
    Gender:
    Male
    Location:
    50 K's from South Australia, in NSW
    My Bike:
    blown CBR250r
    • Like Like x 1
  17. thebeefsalad

    thebeefsalad Well-Known Member

    Messages:
    490
    Likes Received:
    301
    Trophy Points:
    273
    Joined:
    Feb 28, 2015
    Gender:
    Male
    Location:
    San Antonio, Texas USA
    • Agree Agree x 1
  18. Gen

    Gen Well-Known Member

    Messages:
    324
    Likes Received:
    330
    Trophy Points:
    273
    Joined:
    Aug 16, 2014
    Gender:
    Male
    Location:
    50 K's from South Australia, in NSW
    My Bike:
    blown CBR250r
    Every time I hear a "new" 250/4 buzzing around town @ redline I think of this article , it's easy to get sucked in by the manufacture's claims of the era regarding redlines, inaccurate tach readings & peak HP, but how many of you have pulled a head & found valve sized "shiney" circles of carbon free valve cutouts on the tops of all 4 pistons ?
     
    • Like Like x 3
  19. thebeefsalad

    thebeefsalad Well-Known Member

    Messages:
    490
    Likes Received:
    301
    Trophy Points:
    273
    Joined:
    Feb 28, 2015
    Gender:
    Male
    Location:
    San Antonio, Texas USA
    sample size of 2. no such (bad) luck!
     
  20. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

    Messages:
    3,980
    Likes Received:
    2,208
    Trophy Points:
    923
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Occupation:
    Gardener
    Location:
    Tasmania
    Home Page:
    My Bike:
    Spada, VT250F & ZX2R
    That CBR250 article is interesting. I wonder if spinning an engine that fast without a head on it would make the rods stretch more since there's nothing (resistance) for the piston to push against. Even with the readings they got at 18,000rpm (23.5 thou) it's only stretching half a millimeter. So, as long as I allow for a small amount of rod stretch, then that should be okay.

    @gregt thanks for your post. I'll make a few cuts and report back with the figures. I did the squish test on all the cylinders, so I'll sample each one and note the results.
     
    Last edited: Jun 9, 2021

Share This Page