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New Scott Spark JR 20" Modifications?

47K views 111 replies 29 participants last post by  thchen 
#1 ·
I just bought my 8 year old daughter a 20" Scott Spark for a good price at a LBS.

It is a really great bike as it is, however, I am interested in lightening it a bit and making it more user friendly without breaking the bank.

I have read the other thread about the 20" Scott build and liked the 2 inch riser handle bars, since the stock ones are real low.

The bike weighs the same as her Huffy 20" or less.

The gearing seems to be low enough for her to go up hills, but I am not sure if she will need that big outer chain ring?

What are some options for riser handle bars, stem, wheels, tires, and possibly shifters?

This bike will be passed on to my 4 year old son, so I do not mind spending money on it, especially replacing parts that wear out.

Thanks
Bill
 

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#82 ·
I use Sinz with Rennen 34t single speed ring. It has deep tooth profile - chain did not jump without any guard. Now there are those narrow/wide rings that may be even better - Wolf tooth components and Race Face just came out. Not sure what they have for 5 bolts. Wolf tooth makes a 30t one, with spacer that fits 104mm middle.

Apparently Rennen comes in 33t as well: Rennen BMX Pentacle Chainring at Danscomp
 
#89 ·
I did a custom wheel build from Universal Cycles a couple months ago. They let you send in your own hubs - including used ones if they are in good shape. I sent in a used rear Sun-Ringle 32h disc hub that was laying around in my garage. Went with the Sun CR18 rims (20" x 1.5" x 32h, 406 ISO), SRAM X.7 front disc hub, Wheelsmith butted (1.7-2.0) spokes and alloy nipples. Total cost: $203. Now I just need time to put everything on my son's Spark 20...
 
#91 ·
Hi guys

i have recently ordered the 2014 Scott spark JR 20 (exactly the same as the previous models it seems) yet more expensive.. although i got 40% discount as my friend works for wheelies.com

my build is geared more towards downhill, so weight isn't so much of an issue in one sense, but is in others, i need my lad to be able to throw it about a bit, and so i really need to keep it under 22 to be satisfied, once the better forks are on.

Bicycle wheel Bicycle tire Bicycle frame Wheel Tire
Bicycle wheel rim Bicycle tire Automotive tire Rim Spoke


I too want to upgrade virtually everything on it to save weight.

options Ive looked into are:

White bros RC80 20" forks with 80mm travel
rear shock????
Kore 20" rims bespoke with HOPE pro 2 hubs
A2Z Rear Disc Brake Mount
A self shortened Ultegra Crankset and upgraded Deore XT Rear Mech with 10 speed XT Cassette

Hydrolic disc brakes probably HOPE or cheaper..

Can i ask if the A2z rear disc mount fits out the box or does it need adjusting? as i don't have the bike here to check as it's not arrived yet? and did anybody sort the shock replacement apart from the OP

cheers guys

ps i'm pretty sure i can get this to fit with a bit of effort

Product Font Bottle cap Suspension part Suspension


if i have to i will make the lower brackets and adjust the top bar width, it WILL go in there, i too will be chewing of the cable stopper
 
#95 ·
That's good news, i will order one today off ebay

i must admit that by the time Ive done the upgrades i probably wont be far off the price of a lil' shredder bike, however, i think every father that enjoys the slopes or any form of riding can take pride and excitement in building his kids bike, as it's maybe something we wish our parents did, although when i was 6 we didn't have anything like this about.

the Rc80's will raise a little on the front, but from what i have seen it's marginal. great ideas on the stem and seat post I will investigate further, i may not put a 10 ring cassette on the back, its just i thought it would be good for normal rides as and when. it looks a bit funny with one on there from pictures Ive seen.
 
#93 ·
The WB fork and Fox shock should make for an excellent suspension package. You may want to re-valve the shock to a low/soft compression tune. As your going for more of a DH set-up, hopefully the fork will also raise the headtube some.
Get an Uno lightweight stem, used carbon bar and a Thompson Elite 26.8mm seatpost. I ended up using a 27.2 Elite on my son's Spark RC. I only had to mill 0.25mm off the seatpost as Thompson's are often undersize, sure enough it was 27.11mm and the seattube on the frame was oversize at 26.85mm. Fit perfect. I also replaced the top cradle with KCNC yokes and Ti bolts to make a nice lightweight post.
 
#96 ·
Hi from the UK

I appreciate it's been a while since anyone posted on this thread but it's been a really useful source of info as I build a decent Scott Spark 20 Junior for my oldest daughter.

I managed to pick up a second hand bike as a starting point and I've been picking up parts for a month or so now. Given the (poor) condition of the starting point, I think everything bar the frame will be replaced.

I've got 2 questions for you all though:

- Has anyone been able to remove the v brake bosses?

- I need to get the lower swing arm off the main triangle so I can check / replace the bearings and get the frame off to the powder coaters but I can't work out how to get the pivot hardware out of the frame.

Removing a thin plastic dust cover on the pivot reveals (on each side of the bike) what looks like two round tubes of metal that have been pressed into the swingarm / main frame connection point. There is a 6mm allen bolt on one side...and this seems to tie these 2 bits of round metal together. Removing this bolt reveals a 10mm allen key style "hole" on the opposite side. Putting an allen key in this and turning either way results in nothing visibly happening.

There doesn't seem to be much of a gap between these metal pieces to allow you to tap them out from opposite sides and I'm a bit stumped.

I can email photos to anyone if that would help.

Scott UK aren't being any help at all. If anyone has a phone number for Scott USA that would be appreciated.

Thanks all
 
#98 ·
Hi Lincoln3

I've slowly been building a Spark Jr20 and I introduced J Tech to that Risse shock after talking to them about various options. J tech reduced the travel on some 24" forks for me so they would work with 20" wheels / the Jr20 frame.

I came across someone else using the Risse shock (Building the Perfect Kids 20" DH / AM Shredder - Pinkbike) and I got in touch with Risse and ended up ordering one. I went with the Astro 5 version to give me a bit more adjustability.

It's not been used in anger yet (nearly finished the build!) but seems decent enough based on a few indoor bounces.

If you'd like more information on the shock, getting one to the UK, or my build, please drop me a PM.

BTW - I sorted out the 2 issues above as well - v brake bosses came out fine after heating them to break down the thread lock, and the main pivot pushes out once you've undone the hex bolt.

smurf
 
#101 ·
my turn to upgrade my DS's scott spark jr 20 !!!
i want to regear it since the 34t / 28 doesn't get him anywhere uphill

thinking about going SS with 34t. I guess i'll have to get sinz expert square taper cranks (140mm) + BB + 34t chainring + chainguide
Any recommendations/specs for these parts ?

Then for the rear:
9sp cassette 11-32 + rear derailleur + shifter (SRAM attack 9sp) ?
Any recommendations/specs for these parts ?

Anything else ?
 
#105 ·
Hello, y'all. I'm reviving this thread and came for some advice. I just picked up this Spark for my son, 7y/o 47in tall. It's a little too big for him, but I'm hoping he gains an inch or two by summer. He wanted a trail bike to take around camping this spring and summer. The previous owner bought the bike after seeing this thread, but found the bike didn't fit his son.

I replaced most of the cables/cable housing, got a new derailleur and shifter as the original revos were trash and the derailleur cage was bent beyond repair. We decided to go with a simple 1x6 setup. The original flat bar was too wide for my son, so I trimmed about 3/4 inch off each side. Eventually going to get a new stem/bar, but going to take my time finding the right one.

Son's ONLY complaint is the crankset. The arms are way too long, and since we're 1x6 he says the 34t is "too easy" and 42t is "too hard. I'm looking at these 36t eBay 140mm cranks What do you guys think? I'm not worried about weight but finding a good fit for him to take camping this summer.
 

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#106 ·
I wouldn't touch those cranks.

For a 20" bike, look for something at 130mm or less. On our boys' 20" bike we used the Spawn 127mm on a square taper BB with great success.
https://spawncycles.com/spawn-cycles-alloy-cranks-127

@POAH recently found these inexpensive cranks on Alibaba available in 114/127/152/170mm lengths. I think you just need to contact the supplier and tell them the length and quantity you need. You'll need to order a BB to work with the new hollowtech cranks.
Lightweight Hollowtech Cnc Kids Children Direct Mount Crank Arm 114/127/152/170mm Bicycle Parts Chainrings Mtb Crankset - Buy Direct Mount Crank,Children Crankset,Mtb Crankset Product on Alibaba.com
 
#108 ·
@POAH recently found these inexpensive cranks on Alibaba available in 114/127/152/170mm lengths. I think you just need to contact the supplier and tell them the length and quantity you need. You'll need to order a BB to work with the new hollowtech cranks.
Lightweight Hollowtech Cnc Kids Children Direct Mount Crank Arm 114/127/152/170mm Bicycle Parts Chainrings Mtb Crankset - Buy Direct Mount Crank,Children Crankset,Mtb Crankset Product on Alibaba.com

They are the same ones I got. came with a BB though. Work really well on the little ones bike and the middle child.



 
#109 · (Edited)
It's done. My son's Priority Start 20 has 114mm cranks that fit well, so I found these $30 eBay "6061 Forged" 114mm cranks. They appear well made.
Reran cables, tidied up cable housing, new Altus rear der, sis thumb shift, adjusted brake levers out as far as possible for my son's short fingers, shorter stem, riser bar, new seat and pedals. The bike fits him PERFECT for now...until he grows...
Bicycle Bicycles--Equipment and supplies Tire Wheel Bicycle wheel rim
Bicycle Bicycles--Equipment and supplies Wheel Crankset Bicycle handlebar
 
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