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RCMK S-520 twin- what do you think

Old 09-27-2010, 07:02 PM
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grant118
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Default RCMK S-520 twin- what do you think

Hi all. I was looking at the RCMK S-520 twin for a large hydro project. I have only found a small amount of information and a few videos. Most of what I have found has been negative. I need the engine gurus on this forum to give me your opinion/experience about this engine... thanks, chris
Old 09-27-2010, 07:17 PM
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Default RE: RCMK S-520 twin- what do you think


I will get in early on this - Keep posts on topic - if it does not relate it will be going. If you have some hostility to share please take it elsewhere

Old 09-27-2010, 08:02 PM
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Default RE: RCMK S-520 twin- what do you think

Thanks JAW. I read down at the bottom of the page and found a "new Evo s-520". It looks like an improved design. So does that make it "safe" to buy? Who has run one of these, what oil mix do you use etc?

best regards,
chris
Old 09-28-2010, 09:01 AM
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Default RE: RCMK S-520 twin- what do you think

The redo of the S520 crank is very new. I belive most of the orginal buyers have either received the replacment parts or have sent the orginal back for conversion. Mr. Park is doing a great job of making things right and we should start to see true life reviews of the new assembly soon.

As far as the oil mix, it would be no different than what you would use now. Everyone has a preference but 8oz to the gallon seems to be the norm.

Leo
Old 09-28-2010, 11:02 AM
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Default RE: RCMK S-520 twin- what do you think

"my momma says life is like a box of rcmks, you never know what your gonna get"
Old 09-29-2010, 09:49 PM
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Default RE: RCMK S-520 twin- what do you think

Thanks Cheezewiz. What improvements were made? If I ran a clutch on this motor would I need to use two water pumps or just 1?
Old 09-29-2010, 11:40 PM
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Default RE: RCMK S-520 twin- what do you think

I can offer some options on the pumps (I will skip the improvements question though as I did not keep up with the S-250).

Running a clutch you have options. If you are just planning on using the clutch to facilitate launching/recovery and will use it minimally during runs then you could get away with no clutch. Just do not idle around too long.

A single walbro pump will likely not flow sufficient water for the cooling needs of twin heads, headers, and flanges. It is not just when at idle you need to consider - but also the flow through the pump when at speed. You would basically be using one fitting to supply all that water and I think you might be restricting the flow a little too much.

Another option (other than twin pumps) might be to use a larger pump or one with twin inputs and twin (or more) outputs. They are around by several manufacturers and are used as fuel pumps on larger jet skis and snow mobiles. Might be an option in place of using a pair of standard fuel/water pumps.
Old 09-30-2010, 07:40 AM
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Default RE: RCMK S-520 twin- what do you think

Since Mat covered you pump queston, here are the "improvements" as posted by Bruce and Mr Parks.

The New version S520 Evo crankshaft is one piece crankshaft. - "New Version S520 Evo"(one body crankshaft).
The center has two grooves for sealing gas just like real 800cc 2cycle twin inline outboard engine.


I wish I had more information for you. You could try giving Bruce a call and discussing the changes with him directly.

Leo


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