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Thread: Rebuild problems

  1. #16
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    I just ordered a copper head gasket which should boost it some I was going to reuse metal one being it didn't even have a tank of gas on rebuild but I thought better I'm getting tired of ripping it down lol

  2. #17
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,737
    Couple suggestions. I would ditch the spacer plate and run an 87 or 88 piston. That would ensure less leaks from the base gasket. Also, I would be damn sure I ran a uccr on that motor before you fire to ensure you are running the right octane.
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  3. #18
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    Uccr? Not sure what you mean

  4. #19
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,737
    Uncorrected compression ratio. It’s a test to determine your true compression ratio and tell you what are safe levels of octane to run. You can search the procedure and calculations on the web.
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  5. #20
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    Ok thanks will do

  6. #21
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    No big bore just long rod and 68mm piston and bolt on fmf exhaust boyesen cage and reeds

  7. #22
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    So I installed new rings and gaskets still getting low compression I realized my squish clearance is way to high with this spacer plate but to low without it has anyone had a similar problem and what is the best remedy to use?

  8. #23
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    Quote Originally Posted by dmple1230 View Post
    So I installed new rings and gaskets still getting low compression I realized my squish clearance is way to high with this spacer plate but to low without it has anyone had a similar problem and what is the best remedy to use?
    How low? What's the number?

    Is the head shaved or has the cylinder been decked? Because this makes no sense otherwise. You said the piston hits the head with no spacer at all as I recall.

    Did you measure the squish clearance with the spacer on, or is that what you're figuring since the compression is low?

    You kick it a three or four times with the throttle wide open before reading the compression number? (I have to ask, no offense intended)....Is your compression guage trustworthy? (Mine once had a cracked o-ring at the fitting where it screws into the head and it gave me wonky readings)

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  9. #24
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    Also I'm confused on the 89/85 cylinder part...

    So you got the bike and it had a long rod and an 89 TRX jug on it? Was it running good before you rebuilt it?

    Then, I'm gathering that you put a freshly bored 85 ATC jug and ATC piston on the long rod and bought a spacer plate so it doesn't hit the head because it was hitting, correct? Bent a ring, had 80psi after install, pulled apart and changed ring, and still have low compression? Was the jug bored to the piston? Or was the piston purchased after the bore? Cylinder to piston clearance?

    The only way to be sure what spacer you need at this point is to measure the head and the piston protrusion from the cylinder deck at TDC.

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  10. #25
    Outlaw #24's Avatar
    Outlaw #24 is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    May 2013
    Location
    Iowa
    --
    364
    What was wrong with the 89 cylinder? My suggestion would be to put the 89 back on as it is superior to the 85 and put the 89 piston in it also. This will match the rod length the head dimensions will be back to normal and eliminates the need for the spacer. You say the piston is a 68mm what size is the 89 cylinder because the head may be cut for a smaller dimension or larger dimension depending? sounds to me like you may have to much area when the piston is all the way up to create anymore than 80 psi of compression! By the way if the spacer option is used correctly. this will provide more bottom in each gear and smoothen out the performance of the engine! Just sayin

  11. #26
    Join Date
    Mar 2017
    Location
    Jeffersonville ny
    --
    16
    Yes the cylinder was bored to match piston the 89 head I have would need to be rebored with the spacer plate I have 144 thousandths of squish without the plate the piston will come in contact with the dome I used two different compression testers and kicked over until the needle would not move I am now going with a thicker base gasket and deleting the spacer plate which should give me my correct clearance

  12. #27
    Outlaw #24's Avatar
    Outlaw #24 is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    May 2013
    Location
    Iowa
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    364
    What did you find out?

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