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Up close and personal with the MT80

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Up close and personal with the MT80

Old 02-18-2010, 07:22 PM
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Hughes500E
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Default Up close and personal with the MT80

I picked up a used MT80 from a fellow modeler and ordered the new crank that has been balanced with the "new" process for MT and a new cylinder with port changes! I must say Tomy and Jack (MT Engines USA) were great in helping me get into the new parts so much so I'm thinking about purchasing the MT70 twin next [8D] Customer support is important to me.

So, for *****s and giggles I thought I'd show off the MT80. There's not a lot of information out there on them!

In taking the engine apart I used the double nut trick on the prop adapter. It worked well and I'm happy to report there was some medium thread lock compound on it. The hub is keyed (which I like) and I used the parts included to remove the hub with little effort. I was again quite happy to see Japanese bearings in there [8D]

Here are some pictures!
I'll continue with the tear down and make more comments !




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Old 02-18-2010, 11:05 PM
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Default RE: Up close and personal with the MT80

Looks good, I haven't run mine yet I've been playing with 1/2a stuff, But I'll run it soon.
Old 02-19-2010, 08:27 AM
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Default RE: Up close and personal with the MT80

The photos in the background are neat too!!!!
Old 02-19-2010, 05:28 PM
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Default RE: Up close and personal with the MT80

subscribed.
Old 02-19-2010, 10:20 PM
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Default RE: Up close and personal with the MT80

Here are a few pictures of the top end. You can see with the changes in the porting alone that Tomy is trying hard to make this a solid performing engine. It's quite easy to see which is the new and which is the old design! I'm not sure if the original owner of this engine went inside and cleaned things up some but there is visible effort of attempted port chamfering. I'll probably spend a little more time on the new one but only because I'm a bit anal and I'm in no rush.

Perhaps someone with more experience than myself would like to comment on the exact differences and benefits of the change!





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Old 02-19-2010, 10:22 PM
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Hughes500E
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Default RE: Up close and personal with the MT80

That's strange, I guess we're suppose to see the same picture twice for some reason wooops!
Old 02-19-2010, 10:36 PM
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Default RE: Up close and personal with the MT80

The crankcase cleaned up nice, both halves mate well with 4 alignment pins. The crankshaft itself has two large improvements, the balancing and increased lubrication on the conrod viewed in the picture below.

All threads look good with adequate machining visible throughout!


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Old 02-20-2010, 07:01 AM
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Default RE: Up close and personal with the MT80

Looks like the tungsten balance insert is smaller in the new crank web.
The top centering pins could be placed better. The way it is now, the gasket will easily break at the pin locations. A bit of extra flange material would be nice.
Old 02-20-2010, 07:08 AM
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Default RE: Up close and personal with the MT80

New one has bigger transfers and a simpler boost port. Transfers are better angled too. The previous arrangement is not something I've seen before. The old piston is Yamaha RD style with the 2 slots - maybe that's how it got that way on the old engine?
Exhaust might be a bit narrower - can't see tho'.
Piston looks a lot sturdier and the pin is height-centred more like other 2-stroke pistons.

The original system looks a bit, um, strange!

Thanks for posting this thread Hughes500E
Old 02-20-2010, 03:50 PM
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Default RE: Up close and personal with the MT80

Now that I have bared Tomy's bum to the world and his efforts are visible, I'd like to see someone else do the same and see how it goes [:-]

Anyone with a DL 50 or 55........ hmmmm, don't think there are too many more economical manufacturers in the 80cc range to particpate!
Old 02-20-2010, 03:56 PM
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Default RE: Up close and personal with the MT80

I was not meaning to be negatively critical. You did ask for opinions about the changes and that's what I did.

PE Reivers is very experienced and his comment about the locating pins is valid.


Doesn't stop it being a great engine and I honestly appreciate you posting the pics [8D]


Oh and the new one looks good!
Old 02-20-2010, 09:27 PM
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Default RE: Up close and personal with the MT80

I actually quite liked your comments, not sure why you think I didn't !

I have the bottom end back together. The machining on the new crank couldn't be a better fit on the bearings. I had to freeze the crank and heat the bearings to get it together, very happy with that fit! With the aluminum case and the removal of the bearings I opted to use a product from Loctite to "glue" the bearings back in. This is apparently quite normal and used by anal engine builders I hear! Hey, we want it to perform and last!
I did make my own gasket and I use a crankcase sealant so I'm not worried about that. Again I'm not sure if the original owner was as anal as myself but there was crankcase sealant on the gasket when I took it apart. I do agree though, a bit more room in that area would be nice but it did go together without concern.


The piston and piston rings used on the MT80 now are quite nice with an expected longer life span and better performance.
The piston to head clearance (squish) has decreased which will increase power but the piston rings themselves now have what I believe to be a "custom" design. There is now a cut round groove on the top of the ring that seats in the alignment pin to stop ring crawling and to allow for a tighter ring end gap. I believe this is used by Frank Bowman's rings as well, maybe they are Frank's rings?

I am quite excited about running this engine, Tomy is showing signs of an artisan. I think he's being to modest, maybe he will explain some of his changes to us!

I'm not an expert here!


PS
the rings are just sitting on the piston in an effort to show the detail. They are not positioned in line with the pins at all.
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Old 02-21-2010, 07:33 AM
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pe reivers
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Default RE: Up close and personal with the MT80

The engine looks very good.
Can you post a pic of the fit of the reed cage in the rear case? A tight fit is very beneficial to avoid fuel puddling.
Old 02-21-2010, 10:21 AM
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Default RE: Up close and personal with the MT80

Hi Pe,
I should have done that prior to reassembling; when I get back from our first large flying event of the 2010 season I will see what I can do to show it!
Old 02-21-2010, 11:17 AM
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Default RE: Up close and personal with the MT80

I lost my turn to shower first [>:]

Here's some pictures of the assembly.
1st picture shows the taper that the reeds fit into, 2nd pic of course shows them ready to go in!
Since it's apart now I'm going to file the reeds back a bit so the edges don't crack!

Cylinder is ready to go on as well. It didn't take me very long to clean up the chamfering at all.


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Old 02-21-2010, 03:11 PM
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Default RE: Up close and personal with the MT80

In the 58, I filled in the casting cavities you can see in pic 2 with epoxy glue + glass balloons. I also filled in the space between the housing (pic one) and the aluminum rear cover using a milled insert. Epoxy putty would do as well. This mod very much improved throttle response, so I wondered if Tomy has done some extra design work in that area.
Old 02-21-2010, 05:21 PM
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Default RE: Up close and personal with the MT80

I can see the casting cavities but I'm not understanding how you stuffed the rest of the unit!
I think I remember seeing your efforts on the "other" forum. Could you help me try to understand better?

Thanks
Old 02-22-2010, 07:48 AM
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Default RE: Up close and personal with the MT80

I made an alu block that filled the back cover cutout. Then milled a new cutout that very closely fitted the reed valve assembly. The same can be done by fitting the reed block to the rear crankcase first, and then use gas resistant putty to fill all spaces. That also serves to increase the crankcase compression ratio, which shifts the torque curve to higher rpm somewhat.
Old 02-22-2010, 09:53 AM
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Default RE: Up close and personal with the MT80

So ultimately the cut out in the rear crankcase needs to be closed up tighter around the reeds. Could a guy mill an insert with a flange; the flange would push the carb and reeds out an 1/8 of an inch or so?

Tomy could sell it as a perormance upgrade [8D]
Old 02-22-2010, 01:08 PM
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Default RE: Up close and personal with the MT80

That would be counterproductive, and increase the crankcase volume again. Looking from the inside to the back, the opening slit should be as narrow as possible, without loosing reed lift.
Tomy can machine it, but since the sides are tapered, that would substantially increase CNC milling time, more so because a small diameter mill is needed for the small corner radii. A price increase would be the result.
Will post pics of a more pricey 58.
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Old 02-22-2010, 02:30 PM
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Default RE: Up close and personal with the MT80

A slightly fatter gasket on the standard piece could cover the cavities. Suitably stuck down one side or made of a rigid material like PTFE.
Old 02-22-2010, 02:47 PM
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Default RE: Up close and personal with the MT80

The new transfers looks like porting jobs I have one on chainsaw engines.

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