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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › YS91sr converted to YS91sr-3ds
10-13-2010 06:58 PM  8 years agoPost 1
Gernejr

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Miami, Fl

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Well i decide to turn my sr into 3ds . I order the 3ds liner,piston and ring. pulled crank out in the lathe it went so i could bore the fuel port from 11.5 sr to 11.85 -3ds spec. then grinded the crank intake port to 3ds spec which is only .15 mm wider and smooth it where i removed metal from inside crank. DONE , I did install a lightly worked carb from my ported ys . it only had intake thoart rework and polished up. head combustion cambers are same shape and volume so 3ds only has little more cooling area, so im only polishing it. Ive been using sr backing plate on 3ds because i use skeptrum rpm sensor . II nstalling new bearings because i have them from local bearing supplier. 10 bucks for both. total cost 130 bucks with bearings. well that 1gal fuel this weekend .. I dont use my old piston because i had lean run this past weekend and and hurt top ring landing. Old liner going to ver.2 on my still perfecting ys95.6sr. lol. i post pictures of crank later but there not much to see.

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10-13-2010 11:27 PM  8 years agoPost 2
HeliBenj

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Provence, France

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I have installed piston, ring and sleeve from the 3DS into my SR in my last rebuild without changing anything else. I'm only breaking in, but it seems to run fine. Do you think I should be concerned about something?

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10-14-2010 01:09 AM  8 years agoPost 3
Gernejr

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Miami, Fl

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HeliBenj , It Should be fine as long as your doing 4-6 tank breakin . Myself bythe 5-6 tank I'm flying like a stole it. Temps between 175F-185F . I only did the crank as i have a great mini lathe so might as well get as close to 3DS as i can. If you look at a mic .175mm (total .35mm dia) from side more is not much, but it's the little things that make it work.
Broken crank is old , this is what happen after who knows how many flights at 1980HS and how many flights before that ..LOL

Couple pictures of crank not much to look at.

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10-14-2010 01:39 AM  8 years agoPost 4
Pulento

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CHILE

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Crank fuel port is increased both sides equally ? I mean open and close timing is increased ?

Edit: Open timing decreased and close timing increased

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10-14-2010 03:04 AM  8 years agoPost 5
Gernejr

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Miami, Fl

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Pulento , Best i can tell it's equal. Understand it's total .15mm so .075mm from each side. So it's almost nothing . Most of what i did was smooth out the ridge line after boring fuel port/canal . As you can see factory cut line in broken stock crank. After boring ridge was .17mm deeper and did NOT take very much grinding at all.

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10-14-2010 02:20 PM  8 years agoPost 6
Pulento

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CHILE

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Thanks

BTW, when I got my 3DS I think I found the exhaust port on the crankcase a bit bigger than the SR.

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10-14-2010 02:34 PM  8 years agoPost 7
HeliBenj

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Provence, France

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Thanks Gernejr

Pulento, about the exhaust ports I don't know if they are different but I can tell you the 3DS liner in my SR doesn't get blocked at all. Both SR and 3DS liner exhaust ports seem to be the same width.

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10-14-2010 04:26 PM  8 years agoPost 8
Gernejr

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Miami, Fl

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The exhaust port on case are same as the Kasama header is port macth fit annd fit both motor same. Which is what Hatori did to new SB19 header this allowed for peak power at about 150 rpm more on motor.

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10-15-2010 01:23 AM  8 years agoPost 9
Pulento

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CHILE

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BTW. I'm changing bearings on my YS91SR and took a look on the crank. The intake port does have the smoothed edge

My YS91SR is relatively new.

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10-15-2010 02:26 AM  8 years agoPost 10
Gernejr

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Miami, Fl

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all production crank have that machine line , it not going to hurt nithing. Thats the little things motor builders clean up to get every bit extra power. There a lot of those little ridges that could be removed to help fuel flow. = more hp

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10-15-2010 03:02 AM  8 years agoPost 11
Pulento

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CHILE

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I'm not referring to the machining line. I refer to the other port of the crank.

Keep us posted please. I'm planning to convert my SR to 3DS.

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10-16-2010 12:52 AM  8 years agoPost 12
Gernejr

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Miami, Fl

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Ok engine is know as close to 3ds as I can make it without changing head which is only extra cooling. Well just got 2 tank thru it break-in Mid 1.75 Hi 1.5 idle is nice smooth. Temp was about 135F at hover. Sure be broke in tomorrow and tuned for power..

Here's some picture of YS91sr liners from left to right
New 3DS ----1.5 year old SR ------ 6 month

3ds liner has 2 ports opposite the exhaust are wider .
3ds ports are 7.60 W by 5.47 H
SR ports 6.30W by 5.47 H
The bridge between them is 1.35 on both so ports were just widened.
The mid liner and 3ds are exactly the same otherwise.
The SR Liner to far right Has many changes as you can see: ports shapes and sizes exhaust has bevel on bottom.

Now the Piston they are exactly the same period.. including weight.

Quick pic of 3ds piston liner installed at BDC.

Hope this helps anyone that has question about using 3DS parts in SR motor. I will need to have both engine apart to really be sure if any changes have been made to crank case. I hope i don't need to have both engine apart at the same time.

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10-16-2010 10:35 PM  8 years agoPost 13
Gernejr

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Miami, Fl

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It's was beautiful day at the field to bad QuickUK clucth broke in first 1/4 tank. So i just flow my other FBL 3DS 700 ALL day ..
Well ther alway tomorrow LOL

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11-02-2010 07:11 AM  8 years agoPost 14
Kona Chopper

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Kailua-Kona, Hawaii USA

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Good info...
Anyone else installed a YS91 3DS piston/sleeve/ring into a SR motor without changing anything else?



Why buy?? when you can borrow and no return

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11-02-2010 01:35 PM  8 years agoPost 15
Gernejr

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Miami, Fl

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quick updated motor running perfect. power just like my 3ds motor , temp only 160f , super happy with motor.

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11-05-2010 10:11 PM  8 years agoPost 16
jstarks

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Louisiana US

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@gernejr

Do you have a link to, or a model of the mini-lathe that you have?

Thanks,

J.

My 3D = Devistation...Destruction....Discover Card!!!

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11-06-2010 08:08 AM  8 years agoPost 17
Paul Woodcock

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Dubai - United Arab Emirates

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Hi

I have had both open at the same time. The SRS has a slightly smaller cut out on one of the transfer ports..... sorry i can't give more details, or pictures.

Couldn't see any other differences.

Regards
Paul

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11-07-2010 01:30 AM  8 years agoPost 18
Gernejr

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Miami, Fl

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The is new out this year, it Littlemachineshop.com 7x12 lathe for the money it best you can get. now i want there mini milling machine but it will have to wait till next year, Christmas is coming ...

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11-13-2010 07:03 AM  8 years agoPost 19
F3CWNB

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Napier, New Zealand

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Here's some picture of YS91sr liners from left to right
New 3DS ----1.5 year old SR ------ 6 month
Is the RH liner a new SR? It looks like the one in mine... It appears more "advanced" due to the angles at the bottom of the ports...

'Life' is Looking Up!!!

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11-14-2010 01:21 AM  8 years agoPost 20
Gernejr

rrKey Veteran

Miami, Fl

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F3C Yes the liner to far right is lateest SR liner before the new 3DS motor come out. Fun thing is the OLD SR liner is almost excatly like the new 3DS just two ports widen.

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