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  1. #1

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    Exclamation How many rpms can a sho engine realy take!

    After observing the forum for a while and following several engine failures it is my opinion that WITH stock internal engine parts if you want to avoid major engine failures you should consider keeping you max engine rpms to 8400 and boost 12-14 psi or less. If you want to go above these limits than you should consider upgrading your rods, pistons, valve springs and retainers, head bolts, head gasket, and main engine crank cap bolts also. Yamaha builds very good engines but they can only take so much. I hate to see these forum post of giant holes in the engine block. I know the cost to repair these engine failures is a major expense ($5000-$7000). Please take time to think about what can happen if you push these motor to the limit. Tommy Jordan


  2. #2

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    Good subject Tommy.

    Why is it then Motec has a rpm limit of 8650rpms and Vipec of 8800rpms?

  3. #3
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    The Motec base maps I think have a RPM limit of 8400 or 8300 one of the 2.


    (For some reason I can't add anymore to this thread evrytime I hit the reply or reply with quote I get a blank page that does not let me do anything so I will add it here on my edit)

    Motec's base maps from their web site have a RPM limit of 8400, my original base map states an rpm limit of 8300. The base maps with higher rpm limits must have been "modified" base maps. I am sure motecpete will be able to answer this so I will ask him in the thread I am running in the Motec section.

    The higher you push these motors the higher the risk of breaking things.

    My issue was that I do big wave jumping and ride like a maniac out in the surf so I was seeing big over revs.

    If your limiter is set high and you are running high boost then expect high over revs, easily into the 9000 region.
    I am not prepared to stuff my motor for my style of riding so have my motec set to 7800 which keeps my over revs under 8300 and I am now running stock boost wheel.
    I usally documented over revs at full throtle around 500 to 600 higher than my limiter.

    Some of these reflashes have limiters around 8800 or more so over revs will easily be in mid 9000's.

    If you want top end speed then go for it but you are risking lots of things pushing these limits without internal upgrades.

    Whats a safe limit, who really knows for sure, the higher the more risk. Also riding style plays into it as well if you ride like Grandpa on pure flat water then the stresses at high rpm/boost are going to be less than someone riding in the rough stuff/wave riding at the same rpm/boost.

    On a side note, I have documented some boost levels from varoius wheels and the stock wheel actually provides more boost upto 7000rpm than many of the 13-15 pd wheels. In some cases it had 2 pd more at 6800-7000 rpm than the higher rated wheels.

    These higher rated wheels left the stock wheel for dead once the rps get over 7500 so are better for top end speed but for guys riding in the rough or wave jumping where you really want to keep your rpms under 8000 for long term reliability then IMHO the stock wheel is still good.

    Good topic Tommy.

  4. #4
    fx160's Avatar
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    Quote Originally Posted by coldspace View Post
    The Motec base maps I think have a RPM limit of 8400 or 8300 one of the 2.
    the one i have the base map limit is 8550 even though the limit is actually set at 8650

  5. #5
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    Quote Originally Posted by 2fast4u View Post
    After observing the forum for a while and following several engine failures it is my opinion that WITH stock internal engine parts if you want to avoid major engine failures you should consider keeping you max engine rpms to 8400 and boost 12-14 psi or less. If you want to go above these limits than you should consider upgrading your rods, pistons, valve springs and retainers, head bolts, head gasket, and main engine crank cap bolts also. Yamaha builds very good engines but they can only take so much. I hate to see these forum post of giant holes in the engine block. I know the cost to repair these engine failures is a major expense ($5000-$7000). Please take time to think about what can happen if you push these motor to the limit. Tommy Jordan


    Sorry Couldn't help myself.....

  6. #6
    fx160's Avatar
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    Quote Originally Posted by Gunna View Post
    Good subject Tommy.

    Why is it then Motec has a rpm limit of 8650rpms and Vipec of 8800rpms?
    isn't the vipec recomended as part of a race package not a stand alone rec addition?

  7. #7

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    Talking

    Quote Originally Posted by Gunna View Post
    Good subject Tommy.

    Why is it then Motec has a rpm limit of 8650rpms and Vipec of 8800rpms?
    Just because Motec,Vipec, or R&D reflash have there RPM limiters set high does NOT by any mean imply these engines are safe to those RPMS at all. It is MY opinion that with out aftermarket engine parts the engine is in danger of self distruction at these higher RPMS over 8400 and more than 12-14 psi of boost. All I am trying to do is make everyone informed of the dangers they can encounter when there engine is used at higher than safe RPMS . Tommy Jordan

  8. #8

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    Quote Originally Posted by 2fast4u View Post
    Just because Motec,Vipec, or R&D reflash have there RPM limiters set high does NOT by any mean imply these engines are safe to those RPMS at all. It is MY opinion that with out aftermarket engine parts the engine is in danger of self distruction at these higher RPMS over 8400 and more than 12-14 psi of boost. All I am trying to do is make everyone informed of the dangers they can encounter when there engine is used at higher than safe RPMS . Tommy Jordan
    From what I have seen 8500 is safe for stock, with springs you can do 9200 with an 16lbs wheel. The springs are the weak point in these engines at higher rpms.

  9. #9
    SHOBiz's Avatar
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    Quote Originally Posted by 556SBR View Post
    From what I have seen 8500 is safe for stock, with springs you can do 9200 with an 16lbs wheel. The springs are the weak point in these engines at higher rpms.

    Then the collets, or the SC shaft or the SC bearings or the stock rods or the stock valves or etc...

  10. #10

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    Quote Originally Posted by 556SBR View Post
    From what I have seen 8500 is safe for stock, with springs you can do 9200 with an 16lbs wheel. The springs are the weak point in these engines at higher rpms.
    If you think 9200 rpms with aftermarket springs is ok then Why are we seeing these post of guys with massive holes in there engine block from broken connecting rods? Like I said in my earlier post that this was MY opinion on just how much rpms and boost is safe to run on a oem sho engine. Tommy Jordan

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