View Full Version : Hatori SB-18 on YS 91?
Greg Alderman
08-02-2006, 10:44 AM
OK, boys and girls...I have given up on every getting my OS 91 SZ Pumped motor to ever run correctly and am putting a YS 90 that I have sitting around back in my back up machine...here is the question...
Does Hatori make a SB-18 header to fit the YS? I wasn't even thinking about it until I went to put the SB-18 on the YS and realized it was only drilled for the OS...
If they do make one...any idea who might have one?
Thanks!
Gary O
08-02-2006, 10:47 AM
The 18 is for OS only as far as I know Greg. Is your OS the one with the OS reg?
Greg Alderman
08-02-2006, 10:52 AM
Ok...I thought so...I might get another OS someday...so I guess it will sit for a while...geez...now I need to go get another muffler before IRCHA!
Yes the OS 91 is the one with the OS regulator and pump...
Gary O
08-02-2006, 11:13 AM
David can probably add to this better than I can but somewhere I read that most of the guys were running the OS reg and pump version with the mid needle closed or maybe just a few clicks open and using the high for the most part to tune. Are you already doing that?
DavidH
08-02-2006, 11:17 AM
I don't have an SZ. I have the CSpec that OMI has sprinkled magic dust on it. It runs great so I don't see a reason to change it out for a another letter in alphabeth. <G>
Jerry Sudimick and couple of others have flown the SZ's with pumps and OS regulator for nearly a year. So they are the ones to ask about the tuning and such on them.
David
Gary O
08-02-2006, 11:24 AM
I agree with you there David. My OMI C-Specs run fantastic. I do have some of the SZ's with the kline and they are definitely stronger but for my ability of flying it's not that important for me.
ClayK
08-02-2006, 11:48 AM
Wasn't the 16 for the YS?
Gary O
08-02-2006, 12:00 PM
The 16 will fit both.
ClayK
08-02-2006, 12:08 PM
hmmm.... so whatcha going to do with that 18 Greg???
Dr.Ben
08-02-2006, 01:47 PM
The answer to this question lies in just how strong a tuned pipe the SB-18 is. If it only exerts a modest tuning effect like a MPII, then you might be able to make it play well with the YS91 in the correct RPM range. If it is a really strongly tuned exhaust, then the SB-18 is going to get along with a YS91 about like any other tuned pipe does, IE LOUSY.
I would like details on exactly how the SZ has been acting up, since folks from OS/Futaba watch these pages and read how the engines are running "in the real world".
Ben Minor
Gary O
08-02-2006, 02:33 PM
I would like to know a little more myself since I'm building another Tempest FAI machine and am using one of these engines in it. I still have to 60M carbs left that James worked his magic on that I could use but I have 3 of the OS Reg SZ's and I want to try one of those.
Greg Alderman
08-02-2006, 04:16 PM
OK...all...Dr. Ben...it runs extremely rough, kicks the tail out, breaks bolts, etc...I attend a crap load of events and have had most of the OS experts try their luck at smoothing it out or at least given me some suggestions to try...I have tried shims from the stock .008 all the way to .032. I have tried needle sttings on the mid from closed to 2 turns open, top end from about 1/2 turn to 2 1/2 turns open....And I just don't buy that it is the "Magnum" fuel I am using...Bottom line is that I just don't have the patience or the time to continue screwing with it...the person that is buying it from me is sure he can get it to smooth out so I am selling it...I have flown YS for years and have always been happy with them...but all though very uncommon for me...I jumped on this “OS SZ” band wagon this past spring and now not really happy with my decision...so I am going back to YS...I knew the 18 might not be the right muffler for the YS...but it is a moot point as it doesn't fit the exhaust flange anyway! :D
Use the SB-16 header, $30.00 at Heliproz. Be very careful not over lean the YS as the exhaust note is a bit different from the SB-16. Power is noticeably more than the SB-16, tuning is tougher.
Take a look at the Nigel Brown IRCHA 2006 demo, he was using the SB-18FH and a YS 91 in his Synergy. I exchanged messages with Nigel and he confirmed that was indeed the combo he was using then.
I flew this combo in my Synergy for about (4) gallons of fuel trying to find the magic tune. I eventually overleaned the motor as it screamed to its death, then did a beautiful emergency auto! :D I found that I had wiped out the ring, piston, and cylinder sleeve in a perfect exhaust port pattern. :WOW
There is definitely a power gain with the SB-18, I just have to figure out how to tune for it properly!!!!
I'm going to try the OS SZ and SZH-PS and see how that goes while I rebuild the YS for another try.