For My Grandson, new builder here

5-7HEAVEN

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When installing the roller/spindle into the bearings, sandpaper the spindle about 20 seconds.
This will change it from a press-fit to a slip-fit.

Then, when installing the bearings into the drive housing, do the same sandpaper reaming on the drive housing.
This will also change the outer bearings from press-fit to slip-fit.

This will save you a LOT of headaches, when changing engine bells, bearings or friction rollers/spindles.

Ask me how I know this, lol.:)
 

Sidewinder Jerry

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Any community bike shops nearby? These will sometimes have smaller 24" wheel MTB's for sale. MTBs are preferred over cruisers because the frames are "V" shaped and will mount up a CG mid engine bike motor more securely.

Note that the sprockets are the weak point of the CG engines, as they bolt to the rear wheel's spokes and if the wheel on the bike is less than perfectly true and spoke tensioned, the engine's power can loosen or break them. You want a bike with good, straight alloy rims. Tight evenly tensioned and stainless steel material spokes.

If it were my child I'd be looking at a drop shipped 70 cc Honda clone engine pit/dirt bike with 10"~14" wheels because you'll end up spending nearly as much on repairs and upkeep on the motorized bicycle.

I totally agree with you on getting a small pocket bike. After reading back and seeing the child is 9, under a 100 lbs and under 5' tall it's going to take a small frame bike that even a 2 stroke might not be able to fit into. This child's balancing skills are still developing and the Staton rear rack mount kits make the bike right side heavier and out of center balanced.
 

mark20

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any chance you have considered getting a minibike for him?

around 450$ shipped, reliable, simple, and lots of fun!


here's one even cheaper! 379$ at waleworld

however, depending on your neighbors and local PD, might not be the best idea for around the block.
 
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Sidewinder Jerry

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any chance you have considered getting a minibike for him?

around 450$ shipped, reliable, simple, and lots of fun!

however, depending on your neighbors and local PD, might not be the best idea for around the block.
Though I wouldn't advise riding on the public streets. There's lots of places one can take a child to ride a mini-bike/pocket bike. Also the kid doesn't have to worry about pedaling the bike any either.

After reading back through this due to clutching a 2 stroke isn't a good idea, the Staton rear rack mount kits are out. Friction mounts front or back are out for numerous reasons. It'd probably be best to wait at least until he is 12 before considering a motorized bicycle for off road use or private road use.
 

LewieBike

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The thing about the pitbike, is it has a large replacement parts source, wear items like the sparkplugs, tires/tubes, chains, sprockets, and brake shoes are all really cheap and readily available.

The tech is proven and there's none of the HT engine skanky stuff like making sure the magneto rotor isn't on backwards, wobbly pinion gears and having to grease the primary gears every 300 miles, These bikes have decent suspension and drum brakes which are easy to maintain. The wheels are far stronger than a bicycle's. The little horizontal Honda clone engines are near bulletproof, 4 stroke, easy kickstarting.
DSC00012.JPG
I have a Coolster 125cc engine in my Honda C50 with over 18K on it, no oil burning, gets over 100 mpg, pushes the little step-through at over 50 mph.
 

Sidewinder Jerry

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I want to build a bike for my 9 year old grandson. I have years of experience working on motorcycles, have tools and a place to work.

But I KNOW NOTHING !!!!

I think I want to go with a 2 stroke. His dad will have enough sense to put pre-mix in it. And he isn't a big kid, so lighter is better.

He isn't a big guy so I need to go with a smaller frame if possible. What is the critical dimensions to look for when I choose the bike? Is a mountain bike the best starting point?

I want to make this bike as simple as possible so my thoughts right now are to use a double cable brake to use the front and rear brake together and there will be just a throttle, brake, and clutch for him to deal with. I also plan to eliminate the derailleurs and make it a single speed bike.

Is this a good plan?

I want this bike to be as simple and reliable as possible. Top speed is not a factor at all. I would prefer it only go about 30mph.

Can y'all give me some advice about what kind of bike to look for and some help on engine choice. Remember I'm going for simple, reliable, easy to maintain.

I want to do this as cheap as I can, but it is for my grandson, so I want to give him a nice bike that will last awhile. Is it possible to do what I want to accomplish on a 500 to 600 dollar budget?

Bike will be ridden just around the neighborhood, daytime use only.

I would appreciate all the help y'all can give me.

Alex

j_alexfleury@yahoo.com
After giving this some thought don't build your grandson a motorized bicycle. Get him a mini-bike/pocket bike. Here's my reasons for telling you this, he's too small, to inexperienced, limited riding terrain and you're an inexperienced builder.

What I advise is building you a motorized bicycle. That way when he gets bigger and more experienced, you'll know exactly what will work best for him.
 

5-7HEAVEN

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One of my first motorized bikes was a 20" Dahon folding bike.

I put a 1.35hp Subaru engine(4-stroke) on it, with friction drive.

Top speed was 27mph on a long stretch on a slight decline.

It was a perfect starter bike.
 

Sidewinder Jerry

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One of my first motorized bikes was a 20" Dahon folding bike.

I put a 1.35hp Subaru engine(4-stroke) on it, with friction drive.

Top speed was 27mph on a long stretch on a slight decline.

It was a perfect starter bike.
You do realise this is a 9 year old kid under 5' tall and less than 100 lbs whose going to have a limited riding terrain with an inexperienced builder who is the grandfather? Why do you keep trying to push a friction drive on them?
 
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mark20

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how about getting him one of these?

quiet, legal, and most of all, enjoyable for a 9-year-old. (i mean, i would of KILLED for one of these when i was 9)

worst case when he grows out of it, you can both swap in a 60v LIPO battery and controller and let er eat!
 

Sidewinder Jerry

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Maybe when he's around 12 or so you might want to consider a 49cc 2 or 4 stroke with a pull start and a centrifugal clutch that's a mid frame mount as a motorized bicycle build.
 
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