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Old 05-18-2009, 11:59 PM
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Default How about a Tuned-Up 79cc HF engine?

The little 2.5HP, 79cc OHV engine is getting pretty popular. It's also getting more available. This small engine would be great for minibikes, small go karts, bicycles, and other projects. Especially if you could get a lot of HP for its small size.

Has anyone tried to get more HP from one yet? It's OHV, and designed after the Honda GX clones, and I'm wondering if some GX200 parts may swap. 4HP+ and 6000RPM would be a nice goal. It's not a bad engine, but kinda mild as stock, and some projects, you want a nice small and powerful engine, that's not big and heavy like a 6.5.

I don't have a 2.5 anymore, my brother has it for his bike now. I plan on getting another one.

The carburetor on the 2.5 looks like it may swap for a 6.5 carb, but I'm not sure.
The muffler will swap for a 6.5 muffler.
Also, I'm wondering if 6.5 valve springs may fit in this engine for more RPM.

Do any of you have both the 2.5 and 6.5 engines to see if any parts swap? It would be nice to come up with a small high-revving engine that's fast, light, and 4-stroke with just a simple clutch, for ease of use.

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Old 05-19-2009, 09:57 AM
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Looks like those new Clones designs have set in. 2.5HP won't have much torque to begin with, and modifying may be extremely limited due to parts...

You know where I can purchase one of these engines?
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Old 05-19-2009, 12:06 PM
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http://www.harborfreight.com/cpi/cta...emnumber=97964

Right here of course!
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Old 05-19-2009, 09:12 PM
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i don't know much about the 2.5 but with the 6.5 you can get modified part for them.
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Old 06-03-2009, 06:22 PM
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i imagine it is tunable. how much are you willing to spend? i used to be into model airplanes and cars, the o.s. and other engines available for em could put out 2 and 3 hp at say 21krpm. of course they run on nitro, some off of diesel. don't know if specs are the same though. these engines are .21 c.i.?
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Old 06-04-2009, 07:13 AM
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I'd spend another $50-$100 on the engine at least if there's nice gains to be had. It seems to increase performance just by removing the crappy air filter cover, and the carb looks small, which could be upgraded, so I feel this engine has lots of potential, but it's just being restricted.

The 6.5 is great, but it's too large, bulky, and heavy for some stuff. That's why I'm hoping with some mods, this could have good power, but weigh less.

They are powerful engines. My Bro has a 2.5 on his ride. If an ungoverned stock 2.5 with just a slightly modified air filter setup, can get 38Mph on the flats, pushing this much weight, hauling a toolbox, and a car battery, while pushing a bicycle, than it has potential for more.

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