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Thread: HKS700 engine

  1. #1
    New Member William's Avatar
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    HKS700 engine

    Does anyone have any knowledge/experience of this engine?

    I know it had problems a few years ago. I'm thinking of buying a Merlin SSDR and installing instead of the usual 582

    Cheers William


  2. #2
    Co-Pilot Randombloke's Avatar
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    It's a free air cooled engine. You might have to figure out cowlings to facilitate this.

    It's not as powerful as the 582, but comes close. Very top end of the RPM band is for 3 minutes at a time only.

    You'd need to check who provides spares. It used to be Conair but they've closed.

    It was used in the AX2000 and Robin at P&M is knowledgeable about them.

    Stick to the TBO unless you're an expert.

    It requires a working battery for the ignition to function.
    Steve U.
    PG, HG & microlights
    "Weekend bimbler, day to day car driver & genuinely undeserving Southern oik who has never done anything of any worth"


  3. #3
    Co-Pilot Martin Watson's Avatar
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    I've enough experience with both the HKS and the 582 to know you should stick with the 582
    Martin
    BMAA 5370
    Fixed wing instruction, examinations and revalidations in Norfolk.


  4. #4
    New Member William's Avatar
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    Quote Originally Posted by Martin Watson View Post
    I've enough experience with both the HKS and the 582 to know you should stick with the 582
    Thanks, problem with the 582 for the Merlin SSDR is that the (wing) tanks only hold <40 litres usable so very limited range - ? probably less than two hours with reasonable margin. Merlin is otherwise a capable and fast aircraft for more than local bimbleing.


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    Wannabe Pilot john murphy's Avatar
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    Hi William

    From my personal experience of owning and flying the Merlin I would disagree with the limited range. My fuel burn has been in the range of 11 litres per hour. This is recorded by filling both tanks and on return refiling so no doggy gauges involved.

    You also need to remember that your flying speeds are that much faster, I cruise at between 85 & 90 mph with about 4500 - 5000 rpm. I have the oil injected 582 and use a lot less oil that if using premix.

    Your best bet is to contact Graham Smith of Sprite Aviation theimporter and all round guru regarding the Merlin.
    The choice of engine for the Merlin in the UK SSDR categoryis down to weight and I am afraid the HKS 700E is way to heavy unless yourflying weight is below 70kg.
    It also cost a lot more.

    The empty weight of my Merlin is 186kg and I think this isthe lightest of the Mk. 2 currently flying in the UK.
    I don’t think there is a 4 stroke that can beat the power toweight of a 582 in the Merlin.
    An alternative to Rotax could be the Hirth engines at 50 –70 hp, but as I say speak to Graham heis very knowledgeable and always willing to help.
    Regards

    John

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  7. #6
    New Member William's Avatar
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    Quote Originally Posted by john murphy View Post
    Hi William

    From my personal experience of owning and flying the Merlin I would disagree with the limited range. My fuel burn has been in the range of 11 litres per hour. This is recorded by filling both tanks and on return refiling so no doggy gauges involved.

    You also need to remember that your flying speeds are that much faster, I cruise at between 85 & 90 mph with about 4500 - 5000 rpm. I have the oil injected 582 and use a lot less oil that if using premix.

    Your best bet is to contact Graham Smith of Sprite Aviation theimporter and all round guru regarding the Merlin.
    The choice of engine for the Merlin in the UK SSDR categoryis down to weight and I am afraid the HKS 700E is way to heavy unless yourflying weight is below 70kg.
    It also cost a lot more.

    The empty weight of my Merlin is 186kg and I think this isthe lightest of the Mk. 2 currently flying in the UK.
    I don’t think there is a 4 stroke that can beat the power toweight of a 582 in the Merlin.
    An alternative to Rotax could be the Hirth engines at 50 –70 hp, but as I say speak to Graham heis very knowledgeable and always willing to help.
    Regards

    John
    Very grateful for your helpful reply John. I think that will settle it for me, I have been in touch with Graham but not discussed engines with him. I will go down to Kent and see him in the New Year. Did they sort out the exhaust noise issue on the mark 2?


  8. #7
    FLYBYNIGHT
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    Take the advice to stay with a 582. Wasn't there someone bemoaning the HKS 700 in a big way?


  9. #8
    Co-Pilot Randombloke's Avatar
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    Quote Originally Posted by Martin Watson View Post
    I've enough experience with both the HKS and the 582 to know you should stick with the 582

    The HKS does have some useful traits but your statement is impossible to contradict, especially when that 582 is already installed and tried.


    Quote Originally Posted by john murphy View Post
    From my personal experience of owning and flying the Merlin I would disagree with the limited range. My fuel burn has been in the range of 11 litres per hour. This is recorded by filling both tanks and on return refiling so no doggy gauges involved.

    You also need to remember that your flying speeds are that much faster, I cruise at between 85 & 90 mph with about 4500 - 5000 rpm. I have the oil injected 582 and use a lot less oil that if using premix.

    The 15 to 17 litres an hour quoted for 582s is in very, very draggy aircaft like the AX2000 and the X-Air. We're revving the engine to between 5,200 & 5,500rpm for cruise. To get down to cruise at under 5,000rpm is another dimension. For those RPM figures 11 litres an hour sounds very reasonable.


    Quote Originally Posted by john murphy View Post
    Your best bet is to contact Graham Smith of Sprite Aviation theimporter and all round guru regarding the Merlin.

    ...snip...

    I don’t think there is a 4 stroke that can beat the power to weight of a 582 in the Merlin

    Nope, you're right, it's a genuine 64hp as far as we can tell. Four strokes offered for the Merlin are a lot less powerful, round about 33hp AFAIK but Graham can confirm this.


    Quote Originally Posted by FLYBYNIGHT View Post
    Take the advice to stay with a 582. Wasn't there someone bemoaning the HKS 700 in a big way?

    The person bemoaning the HKS in a big way was doing so for other reasons, but we may as well not re-open that can of worms.
    Steve U.
    PG, HG & microlights
    "Weekend bimbler, day to day car driver & genuinely undeserving Southern oik who has never done anything of any worth"


  10. #9
    Wannabe Pilot john murphy's Avatar
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    William

    You are most welcome.

    You will not be disappointed with the Merlin both in performance and customer support.

    Tech Pro do not use the Rotax exhaust and have designed a tail pipe extension that effectively reduces the noise output to an acceptable level.

    John


  11. #10
    FLYBYNIGHT
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    The Merlin 582 is a very capable SSDR that can handle a bimble at 50kts or a high cruise at 100kts.
    I found 5200rpm gave me about 75kts burning about 13lph or 6000rpm gave about 90kts burning 17lph.

    I found I used a lot of rudder to centre the slip ball during power changes, I also wasn't that keen on the brake lever being in a quadrant with the Throttle. These are the only 2 criticisms I have on the Merlin....other than those the machine is a good un.

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