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Old 02-11-2020, 06:36 PM
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Default Engine for Buggy Project

Been doing some research on engines to use for a planned project, and I'm looking for something with around 40 horsepower. Obviously a quad/dirt bike engine would work, but to retain mechanical simplicity I'm thinking something with a CVT/torque converter. Next thought would be snowmobile, but I live in an area where snowmobiles are quite uncommon. So I'm thinking a built Predator engine. I know people build up those Predator 670cc engines to 60 horsepower and beyond, but they are quite large and overpowered for what I'm looking for. So that brings me to the Predator 420cc or any equivalent clone. They sell staged kits for these engines just like the 212cc, but can you build these 420s to 40 horsepower?

I'm thinking governor removal, billet rod/flywheel, exhaust header, Mikuni carb, timing key, and valve springs. Any of you guys have built 420s pushing around 40 horsepower? I would imagine that if you can build a 670cc to 60 horsepower you could build a 420cc to 40 horsepower, right? Thanks in advance.

EDIT: I've decided on the Predator 670cc after doing some looking. Anybody know how many RPMs these engines turn without a governor (and with upgraded springs, rods, flywheel, etc)?
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Old 02-11-2020, 09:07 PM
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A lot of machine would would need to be done. In your other thread, I posted a link for Duromax engines. The 440 will take any Predator 420 mods. Plus with the discount code I sent there, for the rest of Feburary you'll get the 440 for less than a Predator 420. Red Beard's Garage was able to push out 30hp and about 40lb/ft of torque out of a heavily modded 440 Duromax. $1000 alone in mods and had the head milled down for more compression. I'm sure you could get close to 40hp.

Here's a sled for sale in Jersey https://cnj.craigslist.org/snw/d/man...071405676.html. If it's a 440 fan, it'll be about 47hp. If it's a 500 (might be a Fuji 488), it'll be about 56hp. If it were watercooled and not a fan, numbers would be 65hp on the 440 and 72hp on the 500. I have a carb tuning chart for temperature and elevation.
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Old 02-11-2020, 10:35 PM
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Just watched that Red Beard video, very impressed with the output of that Duromax. I was hesitant to trust the Duromax simply because I really wasn't familiar with them but they seem to do the job. As for the snowmobile, guess i should've checked Craigslist before making this post lol. I'll take that carb tuning chart if you got it. Thanks.
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Old 02-11-2020, 11:00 PM
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Hope this helps!
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Old 02-12-2020, 06:52 AM
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Thanks again Kartorbust.

Although I'm still wondering if anyone on this forum has any horsepower ratings of their own for a built Predator 420 just for curiosity's sake. If Red Beard's Garage can get 30 out of a Duromax 440 I'm sure you could do the same for a Predator, it's only a 20cc difference. NR Racing sells a kit they claim can take a GX390 to "35+ horsepower", and a 420/440 to "40+ horsepower", but I'm sure how accurate that is. Here's the kit if you want to see for yourself: http://www.nrracing.com/product-p/stage4kit390.htm
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Old 02-12-2020, 09:52 AM
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Far as I remember, no one on here has modified a Predator 420 to that extent. Grant (KartFab) modified a Gx390 extensively. But members on here? Not that I can recall. Would have to look at many build threads to see. YouTube is pretty much where it more "commonly" happens.
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Old 02-12-2020, 04:39 PM
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While looking at engines I came across a buggy built by a company called Protodie Powersports which is almost exactly what I plan on building, everything from dimensions, weight, and Predator engine powered. They call it the Protolite FXT630.


Only difference is that they use a stock Predator 670cc (which I know can be built to 50 horsepower and beyond), so 40 horsepower should be easily attainable with some bolt-ons, Mikuni carb, and billet internals. I think the price point would be similar as well, since less modification would be needed to a 670cc than to a 420cc simply because of the displacement advantage. Now obviously I could just buy the buggy outright but A: what's the fun in that? and B: it's $15,000...so, yeah. I know I can build a buggy for way less than that, even if it's at a, ah, "lower level of craftsmanship".

Of course the snowmobile engine route is always there but if I'm honest I'm sort of adamant on using a Predator engine simply for the reason that there's so much information available online about them and that parts easy to find. That being said, does anyone have any experience with the 670cc engines? Are they worth the money? Anything to look out for? Most importantly, how many RPMs can you get out of them without the governor?
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Old 02-12-2020, 06:14 PM
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Hopefully someone may chime in on the 670 Predator. After what happened to Vasily Custom Builds and the stock throttle sticking on his buggy, going with dual Mikuni carbs would be a good idea.

Sled engines are kind of a niche. You can find some or all parts for a rebuild online. A shop manual for it would be a good idea to have on hand if going down that route. But you will have more of a guarentee of engine longevity vs a heavily modified industrial engine. Just throwing that out there. Last I knew Jody (aka Protodie on Minibuggy.net) was selling Protodie and has halted most sales. He might sell plans for the MXT (also uses the 670 Predator) and not just the SS1000.
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Old 02-13-2020, 11:55 AM
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Found a guy on YouTube who put a built 670 on a lawnmower who was helpful with my questions. He's getting 60 horsepower and 8000 RPM, well above what I would need but I'm not gonna complain about extra power. 8000 RPM with 22" tires and a 7:1 gear ratio is still 75 mph - and that's without accounting for overdrive from the CVT! Mikuni carbs would be the plan, but I don't think the issue Vasily had is a "common" problem with these engines, plus he didn't have a killswitch installed yet.
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Old 02-13-2020, 12:05 PM
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You've sparked my curiosity, what video did you find on the 60hp 670? Was going to say sounds like a mower racer, but every sanctioning body for lawn mower racing does not allow for CVTs.
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Old 02-13-2020, 12:13 PM
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Performance670.com has performance kits for the 670, along with complete engines.

Not cheap, but that's the price of power.

Small sport bike engines are a good place to turn for the range you're looking for.
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Old 02-13-2020, 12:18 PM
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Eh, cheaper than for a 670 than a Briggs. Briggs V-twin billet rods are twice as expensive, since you have to buy them individually vs 670 who sells them in a pair. https://www.performance670.com/sub-c...0-engine-parts

He's already nixed a bike engine and hasn't fully written off a sled engine, however, wants to use an industrial Predator for his project. Which is fine, we can help on this front.
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Old 02-13-2020, 12:20 PM
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It was a custom build. Very clean looking, downright scary to drive I imagine. Here it is:


Cars and Cameras also did a very similar build, albeit a bit rougher looking, but equally insane. Very cool build series with an unfortunate ending.
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Old 02-13-2020, 01:25 PM
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I'm sure they'll rebuild the frame at some point. The fans/subscribers will demand it. Granted some of them wanted that Ducati engine dropped in. If you want more inspiration, look at the Chenowth Mini Mag.
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Old 02-13-2020, 02:55 PM
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Well they originally had the 670 rail, but then moved the engine over to the 670 mower that they flipped. I wish they would do more 670 builds. Right now I'm just waiting on the Vasily video with the 50 horsepower 670 on the IRS buggy.
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