Full Suspension 29er with front drive

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FFV8

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Oct 29, 2013
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Spring Valley NV
I knocked this together just in time for the race at the Grange on the 18th



With a 48cc pocket bike engine & a CVT drive.



Made a sprocket to put behind the brake rotor in the front



It rides nice. Never notice the weight on the front end. Still need to tune the CVT a little, but it was solid all day at the track.
 
Dan

Dan

Staff
May 25, 2008
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Awesome FFV!

Is that a CVT? Really like how it looks balanced. How is the handling?
 
Last edited:
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FFV8

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Oct 29, 2013
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Spring Valley NV
Thanks Dan, it did come together fairly well.

It is well balanced, and it handles great. You never notice the added mass on the forks, and the two wheel drive effect helps in the soft stuff.

The CVT works well. They can be tuned, which helps. Overall gearing with the CVT @ 1:1 is 17.5:1

I rode the bike for about 5 minutes, then loaded it on the truck for the race at the Grange the next day. I broke the engine in on the track, a few practice laps & some carb adjustment. Then it was two 6 lap heats & and 8 lap main. It was running stronger after all of that.

I built it to make the 6 mile run to work. It does that well.

Here is a better shot of the chain line, it is close but works well:



and here is the adapter sprocket I made to fit behind the brake rotor:



B
 
Dan

Dan

Staff
May 25, 2008
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Moosylvania
1:1 is 17.5:1!? that is awesome! Must scream and climb telephone poles!

I am not kidding, I have spent and or used over $20K and my best effort is 7.5 to 15:1.


Really, really dig the sprocket adapter. CNC or manually made? I need to learn how to make sprockets. Well, is on the ever growing list. LOL, the more I learn, the more I learn what I need to know..... Ya know?
 
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FFV8

New Member
Oct 29, 2013
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Spring Valley NV
That sprocket was industrial Surplus that was modified.

It had a 10:1 taper bore that started @ 20mm The sprockets were high quality,made from 4340 & induction hardened on the teeth. And totally useless without further machine work.

I used manual machines to finish that part - the CNC's are all busy making money. The bolt pattern was just dialed X-Y from center with a little trig.

Here is the back side:



The CVT has the usual 2.4:1 reduction to .90:1 overdrive range. It feeds a 5:1 gear box that the sprocket is mounted on. With a 12-42 sprocket set, I get a 17.5:1 drive through the gears & chain.

So at launch I start out at 42:1 overall, but the CVT up shifts at about 5600 rpm, and the top end ratio is 15.75:1

I need to tune the CVT a little more, and get it to shift about 6200 rpm, where the powerband is better on the 48cc engine.

.
 
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FFV8

New Member
Oct 29, 2013
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Spring Valley NV
Just a quick update.

I pulled the variator apart on the CVT, because it was up shifting very early. The pocket bike guys all say to pull one of the 4 rollers to raise the shift rpm.

I was surprised to see that there were 6 rollers! No wonder it was shifting so early. With 3 rollers installed, it is a whole new bike.

Twist & go on the throttle, no need to pedal a launch now. Hills that meant pedaling no longer exist. Stays right on the power band now.
 
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FFV8

New Member
Oct 29, 2013
551
16
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Spring Valley NV
Dan said:
Cool FFV8

Any pictures of the operation?
Click to expand...
Not much to look at really. same as a belt change, pull the outside variator flange & remove the belt. Then pull the inner off the shaft... and chase 6 rollers all over the floor.

Took about 10 minutes, including chasing down the rollers.

.
 
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