Possible Project: Dual Predator 420cc Monster

[Ibnzmonkey]

The Comet 40 does not use a backplate. And you definitely do NOT want to use two CVT's. They'd be constantly fighting each other, as it would be impossible to perfectly sync both engines' RPM at all times.

IMHO- The best idea is the original one. Two engines synched 180* off each other, connected by chain to a single jackshaft. The output of the jackshaft would have a clutch (or CVT for that matter), feeding the axle.

Interesting. You may be correct, for dual CVT's to work correctly, you would need both engines turning the EXACT same RPM with the same loading.

I like the original idea too. I may go with that when the time comes. Now I just need to shop around for good prices on those 420cc engines. I see that the Lifan is rated at 15hp, the Predator at 13. Is the extra 2hp to start off with really worth it?

Mods will be minimal but include.

Uni-filter
Candy Cane header
.350 lift cam
55lb Valve springs
.925" Bored Stock Carb
Governor removal

(all parts from AGK) I think I can get a reliable 20hp from each engine with those installed. I will be removing as much unnecessary parts from the engines as possible to lose weight. Those engines weigh like 65lbs each...

 

[Doc Sprocket]

I don't imagine there's much you can remove aside from the fuel tanks. What did you have in mind?

 

[Ibnzmonkey]

I don't imagine there's much you can remove aside from the fuel tanks. What did you have in mind?

Tanks, muffler, airbox, recoil start cover. Maybe one day several months down the road after conctruction I may buy ARCs billet flywheel with starter teeth.

 

[Doc Sprocket]

You can remove the muffler, but you must replace it with something. Is it gonna weigh less? Do not remove the recoil start cover (shroud). That's an integral part of the cooling system.

 

[Ibnzmonkey]

You can remove the muffler, but you must replace it with something. Is it gonna weigh less? Do not remove the recoil start cover (shroud). That's an integral part of the cooling system.

Muffler will be replaced with a candy cane. I was going to fab a Fan cover plate like so. Both engines will be utilizing E-Start. Or, 1 engine will.

 

[Im-a-Torquey]

hey guys im new here. happened to stumble upon this thread. you know you could have an adapter made to sync two motors that attaches to the output shaft on one motor and to the flywheel shaft on the other. you would need to remove the flywheel from one motor tho but you would have the flywheel on the other and you could attach another coil for the other motor. then you could start both motors very easily.

 

[r_chez_08]

This sounds like a sweet project.
Would the engines not want to be 360* out? So that one engine is on exhaust stroke and the other on compression?
I think the first idea sounds best, you could possibly rig up an automotive starter, but that is extra weight. I think the one starter should be fine if you have the compression strokes out. Or you could link both starter switches to one switch.

This will be awesome! So much torque! However, I would not upgrade valve springs without upgrading flywheel and rod (that would be expensive for these two! Does arc even make a predator 420 rod?)

 

[ArachnidBrosMN]

Good ideas! I see two overall ways that have been discovered to get this done:

1. Make the two engines really "one" engine with two cylinders by direct connecting the shafts (using a jackshaft... or otherwise) and offsetting the strokes by 360 degrees (or whatever). Then, as "one engine", only needing one starter (probably needing beefing-up a bit) and only needing one Torque Converter... and one gas-tank.

2. Keep the two engines independent of each other, and decide when you want them to "mate" while running.... but still use only need one electric starter, and one gas-tank. Two clutches would need to be purchased... a main Torque Converter off the common jackshaft, and another "clutch" (using a belt or other type of clutch)

My vote:
I would rather just BUY a two-cylinder snowmobile engine, with the strokes already synched, and put a TC on it.... than try and sync two engines that come with TWO starters, TWO pull-starts, TWO gas tanks... etc.... IMO: The COOL part here is seeing twin engines (like on the back of a boat) on a go kart. I think it would be fun (as said in earlier posts) to use one engine as a "booster". (almost like Nitrous...lol) Plus, if one engine runs out of gas or worse, dies.... well... you always another engine!

Cant wait to watch the build... no matter HOW you do it!

 

[Ibnzmonkey]

I am excited on starting the build. I am in the middle of a turbo build on my Genesis 3.8. SO when I get all that done and figured out. I will really dig into the "KT 840-R" as I have dubbed it.

hey guys im new here. happened to stumble upon this thread. you know you could have an adapter made to sync two motors that attaches to the output shaft on one motor and to the flywheel shaft on the other. you would need to remove the flywheel from one motor tho but you would have the flywheel on the other and you could attach another coil for the other motor. then you could start both motors very easily.

I have thought of this too. I made a model of such a device in solidworks a few months ago when I was toying around with the idea. The issue I ran into was A) I don't own a CNC lathe and B) sending it out to be manufactured costs $$$$$$$

 

[Im-a-Torquey]

then find a local machine shop to do it. most of the time you can get parts like that built for a good price. and it wont need to be very large just strong, so it would be cheep material wise. if i were you i would have it thread into the flywheel shaft and just slide onto the output of the other. it would stay on once you bolt the motor down, and it would be easy to take the motors off for maintenance or mods..... or a turbo.....
imagine dual 420cc engines running as one with a single turbo..... yeah....

 

[Doc Sprocket]

I can't see "threading on" working out well. If this route is taken, it's better to have the bore tapered and keyway cut to match the shaft.

Also- with only one flywheel shared between both engines, you create two potential problems-

1) Hard starting- ask anyone who has run a mower engine without the blade, or who runs a very light flywheel. You are effectively running at half the flywheel mass.

2) Where are you getting the ignition for the flywheel-less side? No flywheel= no magnet=no spark. You can't just tap into the coil on the other side- spark will be too weak if split between two plugs, AND if engines are 180* out of phase, then ignition timing will not work on one engine. If engines are NOT 180* out of phase, GOOD LUCK starting them either by hand or with 1 starter.

I still prefer original plan. K.I.S.S.

 

[Im-a-Torquey]

Why would it not work out is my question? it will work far better than using is with a key, because i just thought that if you made it like a bolt so it would hold the flywheel on so no flywheel removal. then where would be no reason not to, and it would be simple. just take the stock bolt out and thread in the spacer, bolt the second motor down while sliding the shaft into the adapter and your done. problem solved.

Oh and the hard start is only when its cold but once it is running it will rev 2x as fast. good observations tho, thank you for your input. it is what inspired my new idea.

 

[Doc Sprocket]

if you made it like a bolt so it would hold the flywheel on so no flywheel removal.

That's not AS bad- I though you meant to delete the flywheel and just thread the shaft adapter on. Still, I worry about the threads bearing the engine's torque- something they're not designed to do. But at least this keep a very necessary 'wheel.

 

[Im-a-Torquey]

i agree and that was my original idea. but i think my new one would be better, and i think it will be ok, but i don't know for sure cause i haven't tried it. tho i am considering doing so on my magic carpet go kart (aka: ptv [personal tracked vehicle]) project. that would be sweet to have that much torque with something that has tracks. especially if it has a shift able transmission. would be a blast in the mud!

 

[Doc Sprocket]

Hmmm... I would think that a twin-engined tracked vehicle would warrant having the engines seperate- one driving each side. This would allow skid-steer. I guess the laternate option would be to have the engines tied together, and then use an open differential to allow the skid- steer. I think I'd rather the seperate engines, though. With the engines tied together, you can use only braking to steer. With seperate engines, you could use a combination of throttle AND brake to steer. Thoughts?

 

[Im-a-Torquey]

Agreed, yes you could. how ever it would not be as precise of turning and you not be putting the max power to both tracks due to running them on there own track. so i think i would run the engines together and use a diff.... tho i could be wrong about putting power to the ground. also if i run them as one it will be easier to turbocharge... yeah, it would be a 13hp twin cylinder basically.

 

[pgreen491]

just thought I would throw this pic up

 

[Ibnzmonkey]

Update!

I bought this Probe chassis for $100 a few weeks ago.

 

[ZnsaneRyder]

I would recommend for simplicity, for each engine to have its own clutch, to reduce complication and not have to worry about sync.

You could have both clutches each with it's own chain going to the same jackshaft or axle......

OR....

What I would do if this was my kart, is to have each engine drive it's own dedicated rear wheel so you get the sharp turning (steering) benefits of a dead axle (or differential), and the grip & power of a live axle. Also 2X clutches + 2X chains for 2X strength, and not have mechanical stress of different speeds of drivetrain trying to work together. That way if one engine/clutch (or rear wheel) is going a bit harder than the other, it won't make as much difference.

 

[souperman000]

What I would do if this was my kart, is to have each engine drive it's own dedicated rear wheel so you get the sharp turning (steering) benefits of a dead axle (or differential), and the grip & power of a live axle. Also 2X clutches + 2X chains for 2X strength, and not have mechanical stress of different speeds of drivetrain trying to work together. That way if one engine/clutch (or rear wheel) is going a bit harder than the other, it won't make as much difference.

2X the strength or 2X the things to break?

Wouldn't you need two pedals to get a dead axle effect with two engines driving a wheel each? If the throttles are synced it would be the same as a live axle.