ProMod jackshaft on 212 Predator?

[Dave.]

I just saw the "jackshaft vs. 6.5 engine" thread and now I'm wondering if I did the wrong thing.

I just picked up a 212 Predator to replace the 2.5 Greyhound on the Sensation. The mini's gears are 12/60 and it has no almost no pickup or ability to get up a grade without a running start.

I thought about a jackshaft, but didn't see any way to mount it on the Sensation frame without some welding (and that's another big expense.) So I bought the bigger engine.

Now while looking a the ProMod engine mount, I see they have some kind of bolt-on-the-engine jackshaft kit. Would that have worked on the 2.5 and be a better solution for the kids (oldest is 11)? Of course it's for me, too :wink:

And related--now that I -have- the 212 in the box on the garage floor and HF told me I'd pay a 20% restocking fee to return it...should I be looking at a jackshaft solution anyway? Would that ProMod kit fit the 212 Predator? In the frame?

How the heck do you guys figure this out ahead of time? Draw it all up in CAD?

I'm not planning to mod the engine, by the way.

 

[JamnJM]

Jackshaft Ratio Calculator

go-kart racing Gear Ratio Calculator

 

[Dave.]

Yep, thanks, I've seen the ratio calculators from other threads. I'm wondering more about the the application of a jackshaft: why put one on?

Also maybe someone knows if the ProMod engine-mounted jackshaft plate will fit on the 212 Predator inside the Sensation MB-6A frame...and should I even be considering this (that's the first question). I really can't tell much from the small pictures on the ProMod site, and there is little in the way of dimensions for the products.

What advantage would I have with a jackshaft on smaller engine vs. larger engine with or without a jackshaft? Does it all come down to flexibility of gear ratios? Or is there more to it, like torque curves are different for a jackshaft, vs. a single gear pair with a chain, etc. Does the engine have some kind of an advantage with a jackshaft?

 

[rmm727]

Jackshafts allow for a lot of things to happen.

You can use them to change your gear ratio to something you couldn't get with just the clutch and rear wheel sprocket. This is good for lower gearing to keep your clutch from slipping alot if you ride in rougher terrain. Also lets you use a smaller rear wheel sprocket so its not always in the ground when leaning to the left.

They allow for shorter chain lengths

They allow you to run the chain on the right side of the rear wheel.

 

[rmm727]

12/60 gearing with a Predator wouldn't be a bad combination. You might want a little lower ratio if you ride in a yard all the time. If its a road, you'll be fine. I guess the Predator with a ProMod jackshaft on a DB is insane from what I've read on here. Your top speed would be lower though.

 

[Dave.]

Jackshafts allow for a lot of things to happen.

You can use them to change your gear ratio to something you couldn't get with just the clutch and rear wheel sprocket. This is good for lower gearing to keep your clutch from slipping alot if you ride in rougher terrain. Also lets you use a smaller rear wheel sprocket so its not always in the ground when leaning to the left.

They allow for shorter chain lengths

They allow you to run the chain on the right side of the rear wheel.

That's what I was looking for, thanks! The gearing for rougher terrain with less clutch slippage and smaller rear sprocket is good info. I had not thought of that.

 

[Dave.]

12/60 gearing with a Predator wouldn't be a bad combination. You might want a little lower ratio if you ride in a yard all the time. If its a road, you'll be fine. I guess the Predator with a ProMod jackshaft on a DB is insane from what I've read on here. Your top speed would be lower though.

I think the kids will be mostly in the yard and on a path I made in the woods. I'm not letting them out on the street. The 2.5hp Greyhound could not move me up the inclines very well with the 12/60. Plus from a stop, even on cement, it was a dud.

I need to get a new clutch anyway, but I don't see any 3/4 shaft 11 tooth clutches, so I guess I will stick with 1:5 for now.