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Zenoah Twin 2850 ?

Old 11-26-2016, 06:49 PM
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planman
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Default Zenoah Twin 2850 ?

I have a Zenoah Twin cylinder engine on a plane that I'm trying to figure out what size it is so I can freshen it up. All I can find on it is on the lower part of the jug. It has 2850 on it. I have searched the web with no luck. Can anyone point me in the right direction as to what size it is?
Old 11-26-2016, 07:18 PM
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Truckracer
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There are two common Zenoah twins, the 445 and the GT80. They are the same physical size and differ only in their displacement though they use different cylinders, pistons, etc. The 445 has a plain aluminum intake manifold where the GT80 has a black manifold. The 445 cylinders have no cooling fins on the top of the cylinders where the GT80 has several very small fins in that area. Hope this helps ..... there are other identifying features but those are the main ones.
Old 11-26-2016, 08:15 PM
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The gt80 is 80cc. The 445 is 74cc.
Old 11-27-2016, 09:52 AM
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planman
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That Helps!
Thanks for the Help!
Old 12-04-2016, 09:34 AM
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it may be a tartan twin copy/ most of my experience has been converting the makita 4 cycle for airplane and heli use/ nice thing about the makita robin engine is that it has a oil pump in it .incorporated into the crankshaft with a sump clunk/ so the engine runs great in any position. if inverted however one needs to run a tube from the valve cover to the crankcase port on one side of the engine with a small tee pipe after the crankcase inlet to allow internal pressure to escape .
Old 12-05-2016, 04:44 AM
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planman
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Would the Tartan have Zenoah markings on it?
Old 12-05-2016, 07:05 AM
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if its a clone it may/ tartan was originally made in Italy. however fugitzy corp in china bought them out years ago. and they produce many small 2 cycle and 4 cycle engines for a many different company's worldwide and application.s .

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Old 12-05-2016, 08:55 AM
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How about a photo of the engine so we know what you're dealing with? End the guesswork!

Does the engine have an intake manifold on the top and between a single carb and the two cylinders?
Old 12-05-2016, 09:01 AM
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OK, mystery solved. I have attached a photo of a 445 I recently sold. The mag ignition had been converted to EI so the mag coil is missing. Note the 2850 cast in the base of the one cylinder. Hope this helps.

Go back and reread posts #2 and #3 for more ID info. The 445 is a 74cc engine.

Attached Thumbnails Click image for larger version

Name:	GT445 top view.jpg
Views:	420
Size:	1.06 MB
ID:	2192335  

Last edited by Truckracer; 12-05-2016 at 09:03 AM.
Old 12-05-2016, 11:32 AM
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planman
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I'm sure it's a GT-80 due to it having the Black intake manifold.
Old 12-05-2016, 12:00 PM
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Originally Posted by planman
I'm sure it's a GT-80 due to it having the Black intake manifold.
More significant than the intake manifold would be the cylinder
You said on your first post that the cylinder said 2850. Truckracer confirmed that 2850 was identified with the 445 of 74cc. Is the 2850 cylinder also used for the gt80?
Old 12-05-2016, 12:41 PM
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Good thought. According to the info from Truckracer, the GT-80 will have small cooling fins on the top of the cylinders and the 445 will not. I do have cooling fins on my engine.
Old 12-05-2016, 12:44 PM
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The cylinders could share the same numbers on the cylinder base. If you have the black manifold and the small fins, you have a GT-80.

I have photos of the GT-80 I use to own but the mag coil covers the numbers on the cylinder.

Last edited by Truckracer; 12-05-2016 at 12:48 PM.
Old 12-05-2016, 03:02 PM
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Originally Posted by planman
Good thought. According to the info from Truckracer, the GT-80 will have small cooling fins on the top of the cylinders and the 445 will not. I do have cooling fins on my engine.
Sounds like you are good to go. Nice engine. Zenoah are one of my favorites. Good luck and Merry Christmas to You and Yours.. Sincerely, Richard
Old 12-06-2016, 10:10 AM
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Thank You, and, Merry Christmas to you & yours as well !!
Old 12-13-2016, 04:20 PM
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Just to be positive, does anyone know what the bore size should be on the 445 & the GT80?
The reason I ask is I ordered a rebuild kit and the rings are to large. I have called Horizon and have been searching the web with no luck.

Last edited by planman; 12-13-2016 at 06:17 PM.
Old 12-13-2016, 07:38 PM
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From my old notes:

GT80 Bore = 1.6" or 40.4mm

GT445 Bore = 1.5"

two rings per piston

Zenoah rings are tough! It takes quite a bit to damage them,

Last edited by Truckracer; 12-13-2016 at 07:43 PM.
Old 12-14-2016, 08:22 AM
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Mine has 1 ring per piston, But, the ring for the GT80, part #ZEN8488C41200, that I ordered from Horizon, is to LARGE. Putting the Ring in the cylinder by itself, the ends overlap. I do not have anything small enough to measure inside the cylinder. However, the piston mics approx. 39mm, But, it only has 1 ring.
I would re-use the old rings but one snapped as I was removing them.
Looks like I have opened a can of worms. LOL
.
Old 12-14-2016, 09:33 AM
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How much do the ring ends overlap? If they just overlap by a few thousands, you may have to file the ends to fit. If the overlap is excessive, then you probably have the wrong rings.
Old 12-14-2016, 10:03 AM
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It's at least 100 thousandth
Old 12-14-2016, 10:42 AM
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You may want to get in contact with Ralph Cunningham, the Zenoah expert! He goes by Antique or RC Ignitions on the various forums though he rarely comes to RCU anymore. Do some searches and you'll find his phone # in Williams Arizona. Sorry, I don't have his contact info handy. Call him and you'll get more Zenoah info than you ever wanted to know. He's a little rough around the edges but a darn nice guy at heart.
Old 12-14-2016, 10:53 AM
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You might try Ralph at this #. I'm not sure if it is current though.

928-220-5721
Old 12-15-2016, 07:22 AM
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Thank you Very Much!

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