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98 STX1100 compression

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  • 98 STX1100 compression

    Need some advice on a 98 STX1100.

    It has great top end and pulls 6900 rpm with good throttle response but it starts very poorly (both cold AND warm) and does not idle

    I did a compression check and found my middle cylinder is at 40 while the other 2 cylinders are at 120. The plug with the low compression cylinder looks good (no metal anywhere) and a quick inspection via pen light did not reveal any piston or cylinder scatches (at least the area I could see). The piston wash also looked ok.

    When I contacted a dealer to inquire, they simply mentioned that the entire motor needs to be replaced. This seems a little excessive.

    I'm thinking of just replacing the top end versus the entire motor. I would like your feedback on what criteria should I use to determine whether I choose a SBT standard engine package, SBT cylinder exchange package or just the piston and ring set for my 98 STX1100.

    As mentioned, outside of the hard starting condition, it still has good top end and pulls 6900 rpm.

    Thanks for your feedback.

  • #2
    Re: 98 STX1100 compression

    No one can guess - you need to pull the engine out and tear it down for inspection. Hold the crank in our hand and check each bearing before you OK the reuse of it.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

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    • #3
      Re: 98 STX1100 compression

      ok.....please confirm the following process to get at this compression problem:

      1. Remove engine and determine what caused the problem in the first place. I'm assuming right now a potential lean condition exists so check the carbs, jets, needle etc. Repair or replace.

      2. Check crank/bearing to see if any markings exist or other visible damage. If yes...then replace entire motor.

      3. If crank/bearings appears ok, then remove top end and go with the cylinder exchange to replace cylinders, pistons, rings.

      4. Whether i go with the full engine replacement or just the top end...what other areas with respect to carburation and oil injection should be addressed to ensure the problem does not happen again. (ie. I downloaded the installation guides for the engine..but I'm not sure what to 'check' in the carburation and oil injection systems when replacing the motor).

      When replacing a new engine or cylinders, do you recommend a carb rebuild kit just to be safe? Also..what is your opinion on keeping the oil injection system versus going with pre-mix after the engine is replaced? I am trying to understand the process of replacing my engine or top end...without having the problem appear again.

      Thanks for your advice.

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      • #4
        Re: 98 STX1100 compression

        Yes that is correct. What needs to be doen all depends on what you find, I don't want to go into detail for what-ifs. Let us know what you find.
        SBT Tech Support is here to help with your problems.
        We try to answer each question quickly and accurately.
        Please do not use Private Messaging for Tech Support, use the forums.

        Comment

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