FNR Gearbox fab/weld/install

[Oldguy1951]

The following pictures show how I added a FNR gearbox to my Predator 212cc and 30 series torque converter. A custom engine/gearbox bracket needs to be made so the engine and gearbox are the proper distance apart for the belt being used and both engine and gearbox shafts have to be perfectly true to each other. This bracket then lines up with the go-kart engine bracket so it can slide back and forth for chain tension.

One more picture showing spacing from a more overhead view.

 

[ezcome-ezgo]

Slick

 

[ThePugLord]

Would be nice to have one for a 420 made , here’s my set up for my 212

 

[Oldguy1951]

Here's one I did with a Stage1 420. Was a little worried if the gearbox would handle the power, but my Grandson and I thrashed it hard all summer and it held up great.

Another shot all painted up and installed!

Would be nice to have one for a 420 made , here’s my set up for my 212

Very nice work! Looks like a great setup!

 

[ThePugLord]

Another shot all painted up and installed!

What’s your sprocket set up and what’s your top speed ?

 

[Oldguy1951]

What’s your sprocket set up and what’s your top speed ?

I am currently running a 10t on the gearbox and 70t on the axle. I have tweaked the governor linkage so I can get 4300rpm. With this setup, my top speed is 33mph (more than fast enough for the tight wooded trails I ride on) and the low end power is unstoppable (I can spin the rear tires going up the steepest hill). I had a 13t on the gearbox which gave 40mph but hardly ever got going that fast and the lower gearing is easier on the belt (went all summer long on the same belt (genuine Comet) and it still looks good.
Gary

 

[Kristopherjh83]

Here's one I did with a Stage1 420. Was a little worried if the gearbox would handle the power, but my Grandson and I thrashed it hard all summer and it held up great.

Glad to see the gearbox holds up to the hp. I was worried about that myself is why I haven’t bought it. Was considering going the way of Polaris or atv engine with reverse

 

[Oldguy1951]

I have also considered an ATV engine with reverse, but most of them have shaft drive and I don't want to go that route. The FNR gearbox is holding up well so I am going to stick with it for now (I do have a complete spare that I can throw on in less than an hour if need be).

 

[Kristopherjh83]

I have also considered an ATV engine with reverse, but most of them have shaft drive and I don't want to go that route. The FNR gearbox is holding up well so I am going to stick with it for now (I do have a complete spare that I can throw on in less than an hour if need be).

Interested in selling it? And I agree on the shaft drive. From what I’ve gathered so far is that really only late 90’s early 2000’s model Polaris 4wheelers have gearbox set up for cvt. The other ones are like you have as far as readily available. I heard peerless made one and then there’s the impossible to find comet brand. My manco deuce has the one made by comex (from Italy). Can’t find nothing about obtaining a replacement so I was thinking to switch out what I got currently for a live axle. It’s already hell to turn around but having reverse would help tremendously

 

[Oldguy1951]

Thanks but no. I hate being down waiting for parts so I keep a spare of everything in stock (drives my wife nuts)!

 

[Kristopherjh83]

Haha. Man I know that’s right. My wife stays on me too.

Thanks but no. I hate being down waiting for parts so I keep a spare of everything in stock (drives my wife nuts)

 

[Oldguy1951]

Ok, I was asked how my F/N/R Gearbox was holding up behind a Stage1 420. Ran it hard all summer long with no problems! There is a mod I do to the 40 series driven that is one of the keys to my success. The shaft coming out of the gearbox is approximately .795 in diameter before it is stepped down to .625. I bore out the backside of the driven .001 over the large step for a depth of .295. This accomplishes 3 things. 1: It allows the driven to utilize the greater strength of the .795 diameter. 2: It allows the driven to locate closer to the gearbox which reduces the side pull of the belt on the shaft and bearings. 3: It allows the driven to slide on far enough to allow some thread engagement for the outside retaining nut (I also drill/tap the end of the shaft for a 1/4" grade 8 bolt to ensure the nut stays on. The second thing for success is how you drive. I took my gearbox apart to see how it was made and was pleased to see the component's for forward are quite robust! The reverse uses drive clogs that mesh when the one forward gear slides off the other forward gear and engages a reverse gear. This is still decently strong, but not as strong as forward. Because of this, I always used gentle throttle movements in reverse. I also decided to NEVER slam from forward to reverse at full throttle to "rock" out of a stuck situation (I never needed to anyhow with the Mudlite XL tires). If forward motion in mud was not happening, I would shift into reverse and gently try to back out. Failing that, I would just jump out and use either the front or back winch to get out. Better a little mud on the shoes than a broken gearbox. One more thing, since the key in the 5/8 bore 40 series driven is broached in (see picture), you will need to extend the keyway on the gearbox shaft through the thread area (see picture). Nut still threads on just fine!