Build report – custom Scott Spark 20 Junior

I’ve been meaning to write up this build for a long time but I’ve never set aside the time to do so. I’ve a couple of days off at the moment so I’ll see if I can get it finished now.

I’ve tried to add in some useful links and details for other mums and dads who are thinking of building a smaller bike….but please get in touch if you have questions. I’ve a spreadsheet of the final build that I’d also be pleased to send on if it’s of interest.

I’d like to add a big thank you to everyone from STW that helped with my questions…this is my first full build and it’s fair to say it took longer, had more challenges, and cost a bit more than I had expected. However, I’ve had loads of “proud dad” moments riding with my daughter, and both her and the bike have created a lot of conversations and memories so far so it was definitely worth it.

Best quote so far… “Daddy…when I’ve done the blue trail without any mistakes…can I do the next hardest one?

On with the write up:

With my oldest daughter getting more confident on her 20″ Isla bike I was keen to take her with me to a few trails. Both kids have spent time on a LOCT seat when they were younger but my oldest was now way too big so hadn’t been out to places like Swinley for some time. I was also hoping this would increase the time I get to ride as well.

I did think of putting a suspension fork on the isla bike, with maybe a few other upgrades (e.g. new tyres) but in the end I decided to keep that standard and use it for use at home and on local cycle path trips.

A bit of online searching turned up a few possible bikes…with the Scott Spark 20 Jr getting some good reviews, both as a stock bike and as a starting point for some interesting custom builds:

http://www.pinkbike.com/news/If-you-cant-buy-it-youve-got-to-build-it-2012.html

Young Rippers Bikes: Harry Barrett’s J-Tech suspension Scott Spark

http://www.pinkbike.com/news/Building-the-perfect-kids-20-DH–AM-shredder.html

OK – keep it coming, just toying with how best to “develop” a Beinn20 myelf 🙂

I’d not built a bike from scratch before, but I’d done quite a few maintenance jobs, so armed with a few tools and the attitude that I could learn what I didn’t know, I decided I’d do a Scott Spark custom build.

The first job was to find a donor bike / frame. After a few weeks searching one turned up on ebay that was poorly described so I got it for a great price.

A friend collected it from the sellers and brought it down a few weeks later when he was heading my way. When I’d got the bike home and checked it over carefully, it was clear it had been “thoroughly enjoyed” but the frame was OK, which was the main thing – I wasn’t expecting much of the original components to be used.

Original build:

1 Original build by Simon Murfin[/url]]null

With the frame sourced, I stepped up the search for decent second hand components and working out what I could reuse from the spares box. This took longer than planned – partly because of work, partly because I was trying to keep the costs down by finding second hand bits that offered good value for money, and partly because decent components for a 20” bike took some finding.

Eventually, I had enough parts to fill a big box….

1.1 Large box of bits by Simon Murfin[/url]

I knew that getting a new rear shock was going to be a challenge before I settled on the bike choice…but after quite a few hours of online searching, a few posts on MTBR, and a few phones calls to J Tech (here in the UK – and who were very helpful – they built the “Harry’s bike” mentioned above) I settled on a custom new rear shock from Risse Racing. As the original was broken, I had to get something, and whilst the new one was expensive, it should offer decent performance and have a pretty good resell value. Risse were helpful on the phone (email’s weren’t responded to though) and a shock was built.

I then spent an afternoon stripping the frame and weighing all of the original components. Spare bolts, washers etc were saved for the “bits box” before the rest went for recycling. The fork was passed on to someone on STW.

Having read quite a few other build threads on STW and MTBR I’d seen that it’s a good idea to run full length outer cables where possible, and I also planned to run a rear disc brake. So I spent a full afternoon filing out all of the cable guides on the frame so they would accept full length cables even after the frame had been powder coated. This was as tedious and painful as it sounds!

2.5 filing out cable guides by Simon Murfin[/url]

This has the making of an excellent thread! 8)

There were a lot of these guides to file out but it was worth it when it came to the final build as the outers just slipped through nicely and I’ve now got full length outers on all cables.

Whilst I was getting the frame ready I sent the rims and hubs off to CycleFast in Halifax. They’d had some good reviews on STW for wheel builds and they wanted a lot less than local places to build the wheels. After weeks of searching I’d managed to find a pair of 32h Alienation Deviant rims on ebay.

These are one of only a handful of 20” rims that come in 32h and are quite light, a decent width, and suitable for disc brakes. I wasn’t sure what hubs to use – cheap and cheerful that will hopefully last a couple of years (and which would be sold on with the rims), or decent hubs that should last longer, and which I move onto future bikes.

After finding a set of new DT Swiss 240s hubs (with a 20mm front) for less than half price on ebay Germany, I went down the “get decent hubs that you move from bike to bike” route. These should last for years with some basic maintenance and give us some future proofing as well as they can be changed to work with nearly all of the current front and rear axle standards.

The wheels came back about a week later. Fitting the rim strip was a bit of a pain .. I found it tough to ensure the valve hole in the rim strip stayed over the same hole in the rim.

3 Fitting rim tape by Simon Murfin[/url]

I then fitted the light weight Intense Racing inner tubes (sourced from the US via a friend) and the Schwalbe Mow Joe 1.85 tyres (ebay UK find).

A spare XT 9 speed cassette was fitted. I now had a light, decent set of wheels ready.

3.1 Wheels finished by Simon Murfin[/url]

For the fashion police, I’ve since replaced the red valve colours 🙂

Getting the frame apart ready for powder coating proved to be a challenge.

After some help on STW and a few new tools, I got the original crankset off, giving me access to the main bushing / pivot. A few more posts on STW and some trial and error I eventually got this out and the frame apart.

2.3 main bearing by Simon Murfin[/url]

All of the bushings, bolts etc were cleaned up and polished as they a bit tatty….

2.4 polishing by Simon Murfin[/url]

Using a home made bearing puller, I got the four original bearings out of the linkage plates.

2.8 home made bearing puller by Simon Murfin[/url]

I ordered replacements from SimplyBearings which came a few days later. The home made bearing puller didn’t work well as a pusher, and after a bit of trial and error (and 2 new bearings that I had to order!) a large J clamp from the tool box and one of the old bearings, worked pretty well as a bearing press.

After lots of time spent trying to persuade my daughter to pick a colour, the frame went off to LSN Coatings (with thanks to Tracey on STW for her help).

The guys weren’t that keen on a mail order job but I assured them they could reuse the packaging and I’d arrange a courier to collect the frame when it was ready. About a week later the frame came back.

The colour was slightly different from the original one my daughter had chosen (which they had called me about before hand) but thankfully my daughter liked the variation better than the original. The sparkle top coat went down very well!

4 Sparkle by Simon Murfin[/url]

I think it looks great and quality of the finish is excellent.

With the frame back from the powder coaters it was time to give it a quick clean to get rid of the dust, and pull together all of the cleaned, polished, and new parts needed to get the frame back together again. You can see the Risse Racing shock in this photo.

4.1 Frame ready to be built by Simon Murfin[/url]

Getting the frame back together was more of a challenge that I expected. Unfortunately, the powder coating had made the tolerances too small so there was loads of stiction.

After wondering what to do…I finally hit on the idea of using a dremel clone, a circle of plastic cut from a margarine tub, and a circle of wet and dry paper, to make my own sanding disc. This allowed me to file the inside and outside edges of each part of the frame to increase the clearance.

This was a tedious, slow job and I also needed to use a needle file on a few edges as well.

5 Filing the frame by Simon Murfin[/url]

After a lot of hours spent sanding, trying to get the frame back together, more sanding, etc etc, I finally got a complete frame with fresh bearings, nicely greased bushes, and a fresh powder coat finish.

6 Frame now built by Simon Murfin[/url]

Of course, it was only later on when I tried to add some air to the rear shock that I realised it was impossible with it in that way round.

So…for what felt like the hundredth time, I took the shock out and swapped it round in the frame.

With the frame together and a seat post fitted I could use my bike stand which was a big help.

I decided to fit the headset next.

The headset is from KCNC – it’s light and has one of the lowest stack heights I could find – something I needed given the fork was a bit longer than the original.

I’d picked up a good quality headset press a while ago on ebay so after looking at a few videos online I set to work.

7 Fitting headset by Simon Murfin[/url]

With a little care and patience this proved to be really straightforward job. The headset press made it really easy to slowly push in the headset cups.

8 Fitting headset 2 by Simon Murfin[/url]

The next job was fitting the fork….which would be another first.

The fork is a modified RST First 24. After a fair bit of time looking online I rang J Tech again and they confirmed they should be able to drop the travel from 60mm to 40mm and do what they could to improve the internals. The travel can be returned by removing a couple of spacers – something I should be able to do at home.

So, I ordered the fork from bike.de and had it sent to J tech. They sent it back to me about a week later. This gives us a decent, fairly light air fork that almost keeps the original geometry and I can move it on to the next bike.

After a LOT of measuring and thinking, I finally settled on a steerer length and tried to cut it down without a guide. After making a mess of the first cut I ordered a guide and waited for it to turn up. The second attempt was much easier.

Next up was fitting the star nut. This was possibly one of the most frustrating jobs. I could not get it to go in straight, no matter what I tried.

So, I ordered the correct tool for the job (again) and when that arrived it took all of 30 seconds.

9 Fitting star fangled nut by Simon Murfin[/url]

Fueled with enthusiasm, and beer, I finally got the fork installed, the stem fitted, and the front wheel in.

10 Fork fitted by Simon Murfin[/url]

More due to luck than judgement, there was just enough clearance for the fork!

10.1 Just enough clearance by Simon Murfin[/url]

Next up was the bar. I’ve used a spare Easton monkeylite SL bar with a little bit cut off the ends.

The guide used on the fork steerer worked a treat on the bar as well so this was a quick and easy job.

11 Getting bar ready by Simon Murfin[/url]

Grips are the thin foam grips from poshbikes. These were about £9, weigh very little, and are thin enough for little hands. I cut off a tiny bit from each one with a very sharp knife.

Shifters and grips by Simon Murfin[/url]

With the bar fitted I could add brakes.

I started adding an old set of Avid 7’s brakes but it turned out that the pistons has seized in one of the calipers so I ended up using a set of SLX brakes from bike.de (much cheaper than in the UK). Swapping them was a pain as I needed to disconnect the hose (again) and pull it out of the frame….and then fit the new brakes….and then shorten another hose etc.

13 Fitting cables2 by Simon Murfin[/url]

The rear brake hose was secured to the frame with a MPart boss bolt and cable guide, and a v small cable tie. I needed to drill out the cable guide to make a small hole for the cable tie after the brake hose was found to keep popping out of the cable guide.

I also needed to fit an A2Z rear brake adapter as the frame doesn’t have the right tabs.

15 Rear brake adapter by Simon Murfin[/url]

This bolts onto the frame but I found I needed to add in some home sourced spacers to stop the bolts flexing the flat plate when they were tightened up. This has been great in use with no issues to date.

Rotors are from KCNC – some of the lightest on the market and great value if you shop around.

Skewers are Mt Zoom MTB Ti – these have been fine with a very light rider.

I also used the same cable guide for the front brake hose as I’ve used on my bikes (from A2Z)

14 Front brake cable holder by Simon Murfin[/url]

More tomorrow!

What a great project! Bookmarked.

Fantastic keep them coming it looks brilliant, you’ve got a very lucky daughter

The original rear brake boss bolts were a pain to remove. After a bit of time on google I learnt that heating them up helps break down the thread lock, so after a few minutes with a hot air gun, they were out.

Original frame before the build:

2.1 brake bosses by Simon Murfin[/url]

brake bosses by Simon Murfin[/url]

The photos below show the new bolts I’ve used to fill in the empty holes in the frame (and the fork), and how I’ve secured the rear brake hose.

brake bosses bolt by Simon Murfin[/url]

bolt and cable holder for rear brake hose by Simon Murfin[/url]

One of the things that I’d expected when I started the build was that not everything will run smoothly. What I hadn’t really expected though was the degree to which parts needed to be modified or adjusted with washers, spacers etc.

The rear brake adapter is a good example. After fitting the A2Z rear frame adapter, routing the rear brake hose, fitting the caliper etc, I couldn’t get the pads to bite the disc properly. After a fair bit of time trying to work out what was wrong, it was clear that the rear brake adapter (the piece you swap over when you change rotor sizes) wasn’t quite allowing the caliper to sit in the right place.

So began another stint with the needle files as I carefully removed a tiny amount of metal from the right place on the adapter to allow the caliper to sit down by 1 – 2mm.

16 Rear brake adapter (2) by Simon Murfin[/url]

The caliper was just touching the top edge of the adapter, preventing it from sitting low enough. I think this is due to the way that the A2Z adapter is working with the other parts as I’ve never had this issue before on other bikes.

After some careful work, several re-assemblies, and a few cone washers, it all slotted together really well with spot on alignment.

Next up was the transmission.

After a lot of research I settled on a set of Thorn 110/74 PCD Triple Solo Alloy Cranks (140mm arms) with Middleburn 34T and 24T rings. I also got a Shimano BB.

These were sourced from SJS Cycles – a really helpful bunch for projects like this.

I liked the cranks as not only did they fit the frame, were a good length for the rider, but though a combination of spacers and rings you can run any combination of 1,2,3 rings and / or a bash guard at the front.

I settled on a 2×9 build as whilst 1×9 might be ok I wasn’t sure if the gearing would be low enough for the hills on some of my regular routes.

After a few miles on the bike, it’s clear 1×9 is fine for 90%+ of the time, and the only time it’s been really handy to have the extra range is for my daughter to get some quick help when she’s forgotten to change down the cassette in time for a hill and I can tell her to “press the left button” which immediately gives her low enough gearing to get up most hills.

The BB and cranks, rings and spacers were fitted easily. The rear mech also bolted to the frame easily.

The front mech was less straightforward – the one I’d bought on ebay didn’t slide low enough on the frame to fit the tiny rings…so I did some more research and bought another on ebay. And then another. I finally had a decent front mech that worked with the frame and rings.

With a SRAM chain and a tip from someone else to use an old coat hanger to help pull the chain together to help join the ends, I now had a basic transmission.

fitting the chain by Simon Murfin[/url]

Thoroughly enjoyable thread Simon

Next were the shifters. I picked up a set of 9 speed X9 triggers from ebay at a great price. I run X0 on a couple of my bikes and I love the shift action and they are easy to work on…so I figured I’d stick with what I know.

These were fitted to the bars in no time, and after buying some cable outer and inners in bulk I made a start on adding the cables. Youtube videos were really helpful for this….but it took me a while and a few goes to get the cable routing on the frame just right.

I was now very grateful for taking the time to file out all of the cable guides on the frame as I could re-thread the outers through the guides several times until I got just the right routing and lengths sorted out.

new cable routing3 by Simon Murfin[/url]

IMG_1084 by Simon Murfin[/url]

When I’d got the routing right, it was then an easy job to thread the inners through, hook up the ends in the triggers and the mechs and everything ready for setting up the gearing.

Having watched a few youtube videos, I was ready to set up the gearing, but no matter what I tried I couldn’t get the full use of the 2×9 gearing.

Even with the adjusters all the way in / out the rear mech wasn’t moving the full range needed.

So, with a spare X9 rear mech in the spares box, I swapped the mech to see if there was something wrong with the mech. There wasn’t.

I packed everything away and had a A Think.

This thread might give the impression that this was a quick build but in reality it took place over weeks as I researched a stage, waited for the right tools to turn up, ordered a replacement part (3 front mechs for example), did other things for a while etc.

After a fair bit of time online….it turns out that certain models of X9 rear mechs don’t have a thick enough mounting plate to work with bikes that have thin dropouts. So, with a fairly thick washer fitted, I had a much better range of motion.

washer between rear mech and frame2 by Simon Murfin[/url]

It still wasn’t perfect, with a little rubbing on the front mech, so I used the adjusters so the smallest cog on the cassette wasn’t available and that was as good as I could get it. I think with such a short distance between the cassette and the cranks, the chain is running at too great an angle at the extremes to be accommodated by the front mech and give a perfectly smooth chain run. By not allowing use of the smallest cog on the cassette things improved enough for me to be happy with the shift and chain line.

For a seat and seat post, I’d read in another Scott Spark 20 Jr build thread that a Kokua seat and seat post work well. These can be bought from Like a Bike for about £20 (for both).

I needed a seat post shim, and the seat post isn’t very long, but they weigh 172g, saving 108g from the originals. The seat angle can’t be adjusted but the seat tube angle on a Scott Spark is the same as the balance bike so it works well.

So….here’s a photo of progress at this stage.

build almost complete by Simon Murfin[/url]

The seat post and saddle were great to start with but I quickly needed a longer seat post. As my daughter grew and with the seat post getting too short, she was sitting too low on the bike, compressing the rear shock more when going uphill. This exaggerated the slightly taller front end height, making uphill sections a challenge.

I found a Thomson elite post on ebay with the unusual size of 26.8mm so I fitted that and the original saddle and that’s really helped to get the saddle height right and improve the handling.

I’ll add the final installment tomorrow.

That is a lovely little thing.

what did they do to the internals? I’ve found the fork to be pretty good as is although it does need a lower leg service fairly regularly as it only uses grease. The OE stuff isn’t particularly great.

@poah. I can’t remember to be honest and it wouldn’t have been much. I just asked them to have a look and see what they could do when they had them apart.

They’ve been a decent fork in use and you can set them up quite soft for a lighter rider. I’ve not stripped for a service yet as we’ve been on dry rides only and they haven’t had loads of use. Thanks for the heads up though.

So, after months of elapsed time and plenty of hours spent on the build, it was time for the finishing touches and a final front to back bolt check.

After some more help on STW I asked Gil (gil@thecycleshed.co.uk) to make up a custom set of decals.

These were tricky to fit – only because it’s tricky to do a fully symmetrical job – the decals themselves were great.

After plenty of checking and measuring I made a start……

IMG_0069 by Simon Murfin[/url]

I thought these looked great and added a nice finishing touch.

I then applied loads of heli tape to anything that looked like it would be hitting the ground lots – most of the frame, sides of the fork legs etc. That should hopefully mean it still looks good after both girls have grown out of the bike.

Pedals were finally chosen (AEST CNC, Ti Axle) and bought via ebay.

These are nice and small for little feet, really light and offer some decent pins for keeping feet on the pedals but they do scratch legs that aren’t paying attention!

That’s a thing of beauty!
One small comment (please don’t be offended), the curve that the rear mech cable goes through at the back of the shock looks a bit tight. That’s all I’ve got 😉

Thanks for the comments gents. No offence will be taken – I’m a complete novice at this compared to many on here!

I may well have improved the cable routing in the final configuration…we’ll see.

So, with the pedals on, decals on, the heli tape on…it was time for a final bolt check and a couple of photos before it got mucky!

Since these photos have been taken, and my daughter has grown in confidence a bit (and grown in size), so I’ve swapped the seat post for a taller Thomson as mentioned above and the proportions look a little better as a result.

IMG_0073 by Simon Murfin[/url]

IMG_0082 by Simon Murfin[/url]

IMG_0077 by Simon Murfin[/url]

IMG_0080 by Simon Murfin[/url]

This is the current spec and I’ll add a weight comparison list at a later date…as some changes saved a lot more than others. I took just over 2kg off the original weight in the end. The plan is to move most of the parts to other bikes as the kids grow.

Cockpit

Bar – Easton MonkeyLite SL (spares box)
Grips – Poshbikes nitrile (poshbikes)
Headset – KCNC KR3 (bike.de)
Spacers – Carbon spacers (from ebay)
Stem – KCNC Flyride 50mm (bike.de)

Suspension

Fork – RST First Air 24″ fork (modified to reduce travel from 60 – 40mm) (bike.de with work by J Tech)
M Parts black boss bolts for forks (ebay)
Rear shock – Risse Racing Astro 5 (Risse racing)
New bearings in linkage plates (simplybeardings)
Bushes were cleaned and polished at home

Transmission

Crankset – Thorn 110/74 PCD Triple Solo Alloy Crankset – Silver – 140mm, with Middleburn 34T and 24T rings (SJS Cycles)
BB – Shimano UN55 68mm x 113mm (SJS Cycles)
Front shifter – X9, 3 speed (ebay)
Rear shifter – X9, 9 speed (ebay)
Rear mech – X9, medium cage (ebay)
Front mech – XT top pull, 31.8mm clamp (ebay)
Cables – Shimano SP41 & inner (??)
Chain – SRAM hollow pin (bike.de)
Cable crimps (ebay)

Brakes

Brakes – SLX (bike.de)
Adapters – A2Z disk brake adapter and parts from spares box (??)
Front rotor – KCNC 160mm (smallest I can use with the fork) (pinkbike or ebay)
Rear rotor – KCNC 140mm (pinkbike or ebay)
M:Parts M10 black cable holder & boss bolts (ebay)
A2Z front brake hose holder (Edinburgh Bike shop via ebay)

Wheels

Front hub – DT Swiss 240s 20mm with QR adapter (ebay)
Rear hub – DT Swiss 240s (ebay)
Rims – Alienation Deviant 32h (ebay)
Rim tape – Alienation rim tape (??)
Skewers – Mt Zoom MTB Ti (XC Racer)
Cassette – XT 11 – 34 (spares box)
Tyres – Schwalbe Mow Joe 20 x 1.85 folding (ebay, with some 20 x 2.0 folding in the spares box after another ebay success)
Inner tubes – Intense racing lightweight tubes (JR Racing from USA)

Seat

Seat – Original Scott (was Kokua (from like a bike))
Post – Thomson elite – 26.8 x 410mm (was Kokua with seat post shim) (ebay)
Seat QR – KCNC light weight (bike.de)

Other:

Pedals – AEST CNC, Ti Axle (ebay)
Decals – From gil@thecycleshed.co.uk
Helitape – From D T Automotives Limited
Powder coating – LSN

A big thank you to everyone from STW that provided advice and to my wife for her patience whilst I built a bike in the kitchen 🙂

Very nice, Do you know the weight?

It was 10.37kg (original weight was about 12.5kg ) as measured on a Feedback digital scale with the Kokua seat post and saddle.

It will be a bit higher now with the longer Thomson post. I might try it with a 1×9 gearing and a bashguard which would lose a little weight.

Biggest sources of weight loss were:

Cockpit – 59% reduction (the new bar is a third of the weight of the original)
Brakes – 34% reduction
Wheels – 27% (most of which is from the tyres and tubes (both more than 50% less in weight than the originals)

So, swapping the bar, tyres and tubes would deliver most of the weight savings. The rest is harder, and more expensive, to save – as with all builds I guess.

Great build! Brave doing your first full build with a child awaiting for the results – no pressure 😉

So, honestly, what do you reckon it cost you? Obviously these sort of builds are really about the bottom line (they always end up costing more than you thought they would!), but it’d still be interesting to know.

I see someone else already picked up on the front mech cable housing, so I won’t mention that. Those foam grips look a bit fat to me. Are they comfy in use? Soft squidgy grips can be comfy for small hands for short periods, but get more tiring over longer rides (IME). ODI Ruffians have always been my skinny grip of choice for the kids, but I discovered Uberbike do some nice lookalikes (in fun colours) which I just got a few sets of (in suitably garish child-pleasing combinations):
http://www.uberbikecomponents.com/view-product/Uberbike-Skinny-Logo-Lock-On-Grips-Grip-Builder

Magnificent. All you need to do now is get the receipts fired into space and the laptop with the spreadsheet on buried in the earths core and you’ll be laughing.

lewis has Ergon slims on his bike. those uberbike ones were too hard and thick for his hands