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  1. #1

    Exclamation Fuel pump pressure on msx 140?

    Ok I just rebuilt the top end on my msx 140.I have two questions.my fuel pressure is 19.5 lbs and my compression is 100 across the board,this seems low to me.will it go up after breakin? And is this fuel pressure normal?is it safe to run it? Any input is very appreciated


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What was the reason for the rebuild?

    What did you replace and do when you did the rebuild?
    Just new piston rings?

    Normally fuel pressure on a Ficht engine is something over 20PSI, maybe 23PSI.

  3. #3
    The reason was it was rebuilt is because that it burnt a hole in center piston between the two rings on exhaust side.is the fuel pressure ok or do I need to change my fuel pump? What about compression numbers?

  4. #4
    Oh also it was the complete topend from sbt.

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by 2000 gtx rfi View Post
    ...it was the complete top end from SBT.
    SBT cylinders too, or just pistons and rings?

    This was a rebuild kit for an MSX 140 engine (1192cc), or a red 1200 engine (1165cc)?

    Compression numbers seem low, even without being broken in yet. Can you check it with another gauge, hopefully one that is known to be accurate?

    I would say that your fuel pressure reading is on the low side. It could be your gauge. Check it again with another gauge, if you can.

  6. #6
    It was the cylinders too.I had to send my cylinders in for resleeving.I will try to get another guage to recheck compression

  7. #7
    Ok just got back from breaking it in and I was dissapointed with it! I was told and have read that this is 65mph ski.I only saw 53-55 tops! What's going on with it?rpms are off too.max was 6350 and I only saw that one time.it would maintain 6100.please help,somethings not right with it

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by 2000 gtx rfi View Post
    Ok just got back from breaking it in and I was disappointed with it!

    I was told and have read that this is 65mph ski. I only saw 53-55 tops!

    What's going on with it?

    rpms are off too. max was 6350 and I only saw that one time. it would maintain 6100.
    What was your break-in procedure?

    What is the cylinder compression now?
    Do you have a second compression gauge to compare readings?

    The MSX speedometer is not highly accurate. On a good day a stock MSX 140 will run just over 60mph, give or take (measured using a GPS). Hot weather will reduce the engine power slightly.

    The maximum sustained RPM is the more useful measure. Properly broken-in the engine should be running around 6700RPM, again plus or minus.

  9. #9
    Been around for years...seen it all Kawi-Guy's Avatar
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    The SBT engines run a little loose, so your compression will be a little lower than normal. If you are not worried about the warranty you can have your head milled down to get some more oomph and compression. ( this will void the SBT warranty but will gain you some speed)
    Have a pro do it please so you are careful.

  10. #10
    2&4strokepolaristech's Avatar
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    that compression is low for a msx 140 engine. In good health they are 120-125psi cold. Are you running stock heads? Did SBT install steel sleeves in the cylinders? What size are the bores? 85mm or 84mm? MSX are 85mm cylinders and are a plated engine.If they sleeved them and installed the 84mm pistons or there 1.0mm over 1200 pistons you will loss compression because the dome profiles are different.The MSX head is very big cc wise and that is why they are light on compression in comparison to the 1200 D.I engines. The MSX cylinder heads pour 57.3cc compared to the 1200 D.I. at 47.5cc (mag and center) and 50.00cc (pto)If you are sure you have 19.5 psi I would seriously look into your fuel pump. The range is 20-30 psi but you will find that 99% are at 22-23 psi cranking or running. Can you give us more information? There could be a couple of things going on here....

    This is some of the "issues" when dealing with a company that is high volume and not brand specific on there repairs/rebuilds.

    JAy

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