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01-14-2006 02:37 AM  13 years ago
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puttputtmaru

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Montreal,Quebec,Cana da

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OS 91 SZ-H
Well I got the new OS 91 SZ-H for my stratus and as usual the head doesn't fit the fan shroud. Guess it is back to modification of the shroud
If any MA guys are reading this when are youy going to make a shroud upgrade that fits the engine that I guess at least half of the people buying the stratus etc are using?
I would gladly pay for it
(yes I know, I could use a YS)
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01-14-2006 03:49 AM  13 years ago
THX1138

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Indianapolis, IN

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I go to the feild for a week...
and a new damn engine comes out! I know the 50 Hyper is kitty PJ's so I wonder how much better the .91 Hyper will be? Is it still pressurized? Most importantly does it run well out of the box?

Lou
Just give me five dudes and two flashbangs...
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01-14-2006 03:55 AM  13 years ago
rdalcanto

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Salt Lake City, UT

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Early reports in the engine forum would suggest that it runs very well out of the box. I ordered mine today after using YS for years, because I want to run 1950 head speed for crisper 3D. Since it is impossible to have the same fuel mixture start to finish using muffler pressure, I'm still getting an OMI regulator, but at least now no boring appears to be necessary....

Rick
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01-14-2006 12:35 PM  13 years ago
Swing_racer

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Singapore

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I've got mine on ebay. 2 days from Hong Kong. well packaging, real good deal. thanks Jason !

have just passed the breakin stage after 20 flighs at rather rich side. It really rocks! Although OS91SZh is not a pump version, it has more power than OS91 Cspec with pump.

kevin
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01-15-2006 04:32 AM  13 years ago
Jerry Sudimick

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Connecticut

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Well I got the new OS 91 SZ-H for my stratus and as usual the head doesn't fit the fan shroud. Guess it is back to modification of the shroud
If any MA guys are reading this when are youy going to make a shroud upgrade that fits the engine that I guess at least half of the people buying the stratus etc are using?
I will be happy to ask the question and get an official answer. However, I know of no immediate plans to make a new shroud because....this is not a new problem and there are solutions that do not involve milling or grinding a head.

Here are your choices.....

1.) Viperhead - which runs extremely well on the new OS91 SZH - requiring no fan shroud modification. Not suggesting you buy one, but if you have one laying around from a Cspec, it's an option. This requires no shroud trimming.

2.)Trim your fan shroud like this photo. This has no adverse cooling consequence. The Fury fan has quite a bit of output. Sometimes we actually stifle this output by fitting the shroud tightly around a cylinder head. This causes cavitation, and actually could reduce cooling. OS reps from Japan were here for a recent SZH test session. They looked at this shroud arrangement on the attending Fury, and agreed this would not be a problem.

This second photo is a photo of the actual model tested during this session. You can see that it is more liberally trimmed and not as tight fitting. This is the one that the OS engineers looked at and observed.

You will have to support the shroud differently on the stratus as compared to this photo of a tempest mechanic set.

3.) And of course, the answer you don't want to hear and already know. Modify the OS cylinder head to fit the shroud. You can choose your preferred tool.

Some Hatori pipe combinations on the Stratus will require header / cylinder head mods as well. The large bottom ridge on the SZ head can interfere with the header. This happens with fwd facing engines such as on the Raptor and Stratus.

Jerry
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01-15-2006 06:30 AM  13 years ago
Bobby Watts

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Orlando, FL

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I modded my fan shroud just like Jerry's and it is nice. The shroud is not even touching the cylinder head... that means no gray gooie stuff on the motor head. Also, there is no cooling problems, so that is not an issue.

Bobby
www.bobbywatts.com
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05-08-2006 02:31 AM  13 years ago
bkervaski

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Birmingham, AL, USA

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The SB18 fits with no mods, right?Team Synergy Factory Specialist / Scorpion / Thunder Power / Byron's Fuels
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05-08-2006 06:36 PM  13 years ago
Jerry Sudimick

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Connecticut

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With the stock SZ head, if you have the older header - on the right, you have to do a little filing. This is due to a large ribbing on the SZ head. Hatori USA has changed the header recently to the style on the left - for clearance on the SZ.

Other than the normal canopy clearance issues, thats all I can think of.

Jerry


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05-08-2006 07:17 PM  13 years ago
patriot21

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Byron,MN

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I am running the os 91 sz withradix 690s... It is running great...
very responsive
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05-09-2006 03:28 AM  13 years ago
Linley

rrApprentice

Rockville Centre - LongIsland, New York

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Fan shroud on Stratus
Jerry, I have mine trimmed to fit over most of the head. Will this be a problem with cooling / Cavitation ?


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05-09-2006 04:19 AM  13 years ago
Jerry Sudimick

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Connecticut

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No, it wont be a problem at all. They've been working like that for years. It's just brought up because cutting it short isn't necessarily a bad thing. OS saw it - and it was tested in Arizona back in December with the cut shroud.

Your setup looks fine - but Im pretty sure the shroud is touching the metal head. You will probably encounter a gray nasty mess and more shiny abrasions on your cylinder head like that.

Jerry
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05-09-2006 09:06 PM  13 years ago
robhurlin

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Pretoria, South Africa

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I have only read good reports of the 91 SZ plain or pumped. I have been flying mine in a Raptor 90 since late December and it is great - consistent, reliable, plenty power and easy to tune.Rob.
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07-27-2006 02:48 AM  13 years ago
CitationX

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Danville, IN

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Fan Shroud Aft Mount w/SZ
I just got to the point of converting my Extreme from YS80 to OS91-SZ and ran into the same problem that I found most guys have had regarding the fan shroud. I saw the pictures that Jerry Sudimick posted in this thread, which looks easy enough to me. At least I don't have the thought of shaving the head down. My only question is how do you support the aft end of the shroud now that the lower portion that contained the threaded stand-offs is now gone?

Thanks for the help...again.
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07-27-2006 03:24 PM  13 years ago
Jerry Sudimick

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Connecticut

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The top is one Bobby Watt's solution. The bottom one is mine.

Jerry
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07-27-2006 04:02 PM  13 years ago
CitationX

rrApprentice

Danville, IN

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Fan Shroud Aft Mount
Thanks guys. That gets me back on track.
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