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    Re: Re-engine Buggy with a (modified) Predator 670
    #41
    Senior Member darwinpayne2000's Avatar
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    . . . and it's September.

    We sent camping on Labor Day and took the minibuggy with us. My daughter rode it most of the time. No issues, but we ended up swapping vehicles on one of the longer rides. The exhaust noise was a little too loud for her and she wanted a break from the noise.

    The issue is the forward exhaust pipe. It's not as noisy as the exhaust on my old engine, but the forward exhaust port is only a foot or so from your head. I think that's the issue. With that in mind, I think I will go with Plan A and replace the exhaust system with a muffler that exhausts out the back.

    Now for the carburetor and a new intake manifold adapter. Performance 670 sells an adapter plate for making your own intake adapter. It looked like it would save me some work, so I ordered one. Unfortunately, the intake port holes in the plate don't line up with the intake manifold. I don't know what they're thinking. It's back to Plan A for the intake adapter as well.

    As a further note, Performance 670 is now selling a 40 amp alternator kit that bolts onto the non-PTO side of the crankshaft. The kit provides an adapter to extend the crankshaft and a pulley to drive the alternator. Forty amps is a lot of juice, but my goal is to keep this project on a budget and an alternator kit is a little pricey. Again, I'm going with Plan A and I bought a pair of LED lights from Harbor Freight to replace my standard lights.
    Last edited by darwinpayne2000; 09-12-2019 at 12:15 PM.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #42
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    For $289 for the alternator bracket is a bit steep. However it looks like it's for a standard GM Delco 10si or 12si alternator, so you could have more than 40amps if you need like upwards of 100amps. Trying to find the pulley adapter to fit on the flywheel side is usually the most expe sive adapter, usually that runs for like $110 or so.

    How satisfied are you with the 670 vs the Briggs Vanny 479cc?
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    Re: Re-engine Buggy with a (modified) Predator 670
    #43
    Senior Member darwinpayne2000's Avatar
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    The stock Predator 670 is roughly comparable to the modified Briggs. The Briggs has more horsepower (thanks to a new camshaft and a Mikuni carburetor), but the Predator has more torque. With the modifications, the Briggs engine probably cost twice as much as the Predator, so the Predator wins the bang-for-the-buck competition. With some fairly cheap upgrades, I'm hoping the Predator will leave the Vanguard engine in the dust.

    My only real disappointment with the Predator is the anemic stator. I might have chosen a Lifan engine with an 18 amp stator if I had known that. It's not a huge deal, since I can substitute LED lights, but it's just another indicator that the engine was built to be as cheap as possible.
    Last edited by darwinpayne2000; 09-16-2019 at 02:53 AM.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #44
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    The CDI or whatever they use for the ignition, seems to be another weak point on the 670. I do like they have options now for mods. But the Vanny just seems to hold up better with mods.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #45
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    Quote Originally Posted by JagerDanger View Post
    For $289 for the alternator bracket is a bit steep. However it looks like it's for a standard GM Delco 10si or 12si alternator, so you could have more than 40amps if you need like upwards of 100amps. Trying to find the pulley adapter to fit on the flywheel side is usually the most expe sive adapter, usually that runs for like $110 or so.

    How satisfied are you with the 670 vs the Briggs Vanny 479cc?
    Don't think it's a GM SI alt, looks more like the one off a kubota. It's a smaller package and the output (depending on who you ask) matches.
    https://www.dbelectrical.com/product...E&gclsrc=aw.ds
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    Re: Re-engine Buggy with a (modified) Predator 670
    #46
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    I guess the kicker is the 10si one wire has the external cooling fan. They said one wire on the kit and GM came to mind first. Oh well, long as it does its job.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #47
    Senior Member darwinpayne2000's Avatar
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    Yeah, I saw a 35 amp 1 wire mini alternator on Ebay. It was relatively cheap. I kicked around the idea of making my own PTO for driving the alternator, then decided that it violated my "don't spend a ton of money" goal for this project. I want to see what I can get for the least amount of money. As JagerDanger is suggesting, if you're gonna spend a ton of money building up an engine, you might was well start with a Vanguard. After you spend the money for the carbs, the camshaft, the rocker arms, pistons, etc, the difference in price between a Predator and a Vanguard is almost in the round-off.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #48
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    Quote Originally Posted by darwinpayne2000 View Post
    Yeah, I saw a 35 amp 1 wire mini alternator on Ebay. It was relatively cheap. I kicked around the idea of making my own PTO for driving the alternator, then decided that it violated my "don't spend a ton of money" goal for this project. I want to see what I can get for the least amount of money. As JagerDanger is suggesting, if you're gonna spend a ton of money building up an engine, you might was well start with a Vanguard. After you spend the money for the carbs, the camshaft, the rocker arms, pistons, etc, the difference in price between a Predator and a Vanguard is almost in the round-off.
    Exactly. I've been watching people modify the Vanguard for extreme use, Factory Expiemental Single and Twin lawn tractor racing and the blocks just hold up better. Just from an initial cost standpoint, you can get a V-twin vanguard used for a couple hundred to a few hundred dollars, vs about $800 for a brand new 670. Right there, you can spend $600 savings on the Vanguard for billet connecting rods, billet flywheel, stiffer valve springs.

    Sorry to have derailed this thread a bit, just making an observation for any future readers that stumble upon this build.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #49
    Senior Member darwinpayne2000's Avatar
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    No, the goal of this thread is to look at the Predator, but also to discuss the Briggs, Honda, etc so people can decide which engine will work for their application.

    Speaking of . . .

    Predator 670 offers a Mikuni carburetor kit for $350 or just the adapter for $59.50. As I mentioned earlier, the carburetor is a 34mm Mikuni flat-slide. The flat-slide is a good choice and when they say that it has better throttle response than the round slide, they aren't kidding. I have one on a Polaris 400 and the thing takes off like a Cheetah.

    However, . . .

    I have a Keihin 39mm flat slide carb sitting on the shelf. I had it on my Polaris 400 with a performance pipe but I decided that it wasn't a good fit. Carburetor tuning is a black art and tuning an oversized carb is even harder. I put the stock carb back on the ATV with the performance pipe and that gave me everything I wanted.

    My Polaris 500 has a 40mm carburetor, so there is some precedent for using the 39mm over the 34mm. It's not necessarily a good precedent because the Polaris engine is a 4-valve performance engine, but this project is all about testing and finding out what works, so Plan A will be the Keihin.

    Now, for the intake manifold. I made the intake manifold for my Vanguard/Mikuni combo so I figured that making a simple intake adapter for the Predator would be easy. Well, . . . maybe not so easy. Mating a single venturi carburetor to a two-barrel intake manifold wasn't as easy as I thought. You really need to machine an adapter out of a chunk of aluminum, like the Performance 670 guys did. I played around with some tubing and finally MacGuyver'ed a solution together.

    I'm ready to put it all together, but a big windstorm decided to kick up this evening. The buggy is parked outside and moving it into the garage is more hassle than it's worth, so I'll tackle it tomorrow. During the rainstorm.

    Here are a couple of pictures of the adapter.
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    Re: Re-engine Buggy with a (modified) Predator 670
    #50
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    Obviously there is no replacement for displacement. How modified was the Briggs before you decided to jump for a 670? Would the hassle be worth it to just to synchronize 2 carburetors, instead of trying to make a single carb work on a two cylinder?

    My dad just gave me a similar Briggs Vtwin from a Cub Cadet lawn tractor of his with just over 700 hours on it. It needs a new electric clutch and those are $350. So he's giving me the engine from it. So I'm in the front seat of seeing if it'll be worth refreshing this engine and installing billet rods, hone the cylinders (thinking having it punched and sleeved for 0.020 over) and run it until it blows apart. So I'll be watching this closely and asking a metric ton of questions.
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