KT 100 Yamaha engine

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Postby huronflyer » Tue May 20, 2008 8:29 am

That is in the same range of bucks as the
"Hirth" F 36

It comes with redrive and electric start, BTW I think it is only
15 HP approx.

No idea what the weight is, it must be far more than 8 lbs.

That seems very light?

And what RPMs does it operate at?

You can buy new pistons, even engines (185) form "Wildfire.
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Postby 89 CHARLIE » Tue May 20, 2008 9:16 am

huronflyer @ May 20 2008, 08:29 AM wrote:

You can buy new pistons, even engines (185) form "Wildfire.

Any idea what a new 185 would cost? Is there any way to get a parts list and price list from Wildfire?
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Postby Chappy » Wed May 21, 2008 9:50 pm

huronflyer @ May 18 2008, 12:07 PM wrote:
Help me here, the KT100 @ 97 cc
does it compare with the pioneers at 5 HP  each ?
Since it is 88 cc less than the Rotax 185 s...

Is it a quality engine?
How about weight?


Hi Dave,

There's really not much comparison between a Yamaha KT100 and a Pioneer P61 other than displacement.

The 99cc Pioneer used on the Lazair was physically bandsawed from a very expensive chainsaw - that's been out of production now for quite some time and parts are extremely rare. It weighs about 5-6 pounds, and was rated at 6 HP peak at around 7000 rpm (IIRC), although when loaded up with Ultraflight's plastic prop could only muster about 4.5 HP! This forced de-rating of the output produced a fairly long lived engine- by chainsaw standards anyway. When I added re-drives and spun them back up, these engines had their tbo (time between overhaul) reduced to around 100 hours, and total wear out came at about 200.

The 97cc Yamaha has been in production for something like 30 years, and many, many have been made. Factory parts are available, and aftermarket, premium parts abound. The engine weighs a little over 20 pounds, and is rated for something like 15+ HP. It gets that power by turning about twice as fast as the Pioneer, and utilizing a tuned expansion chamber exhaust that drastically narrows the powerband. That type of exhaust has been fitted to the Pioneers, but they just don't have the structural strength to produce much more power than the factory spec. (they fail internally). If you just look at the crankshafts of the two engines, you would plainly see what I mean. The Pioneer part looks like a toy compared to the one in the KT100. To have a decent powerband and lifespan, the Yamaha needs to be detuned to somewhere about 12 HP for typical UL usage. And even so, what with the required re-drive, it's rather heavy.

The Yamaha starts at about $700, but to that you would have to add an exhaust and a (most probably) custom re-drive. The Pioneer would be an e-bay score, where you will be competing against the large scale RC guys shopping for cheap power.

In comparison, in my opinion, the 185 Rotax is just a better choice.

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