2003 Kona Stuff dirt jump rebuild

[arseface]

I've had a 2003 Kona stuff from new. End of year sale for £500, then another 20% off with staff discount... £400 bargain! That was about 8 weeks of my part-timer wages.

It was my first 'real' bike, and until a few weeks ago, my only 'real' bike. A few weeks ago I got a modern enduro rig to take over the MTB business, leaving me finally able to rebuild the Kona into a dedicated dirt jumper.

Circa 2006, completely stock bike, down at the Forest of Dean. My buddy's Stuff behind has some ridiculous 200 mm Hope M4 brakes. For some summers we shredded trails and jumps.

Circa 2008, throwing some savage moves. Panaracer Fire DH 2.4" tyres. Low speed, high drag.

From various bike shops' spares bins over the next couple of years I got hold of some Tektro Auriga hydraulic brakes, upped the front rotor to 180 mm, and put on a full SRAM X7 2x8 drivetrain.

Then I took a long break from biking. Not really sure why, guess it was mostly not having a car for a while then just forgetting biking was even a thing.

Fast forward to 2021 when I remembered biking is indeed a thing, and I got back into MTB albeit on a budget.

The Kona had sat in the garage unused but 2021 shortages and the finance officer denying me enough pocket money for a new bike led to the Kona being brought up to modern-ish standards as an all-rounder freeride machine:
- Tubeless conversion with Maxxis DHF and DHR tyres.
- 720 mm chinacarbon bars with 35 mm chinaluminum stem (best upgrade ever!).
- 100 mm dropper post.

Aside from these new changes and the brakes/drivetrain upgrades made in previous years, the rest of the bike is stock. This build saw me through red XC trails all around the country, 2-spot downhill runs at FoD, and some great times at Flyup 417 bike park.

But I just got a modern enduro bike for all that, so the Kona can finally return to its roots and become my dedicated dirt jumper! Here it is at the start of the teardown.

We're on a budget still (the enduro bike was not cheap!) so we're crashing through eBay for parts. Here's a £10 purple 30 tooth chainring, which needed some dremel work to fit the cranks. Could have gone 32T and it probably would have fit fine, but I did maths and 30T looked better for the 13/14T single speed conversion I've been eyeballing. It'll probably melt in the first year but then it'll get replaced with something nicer.

See, maths. It shows 30T up front should give nice ratios for the 13T and 14T rear sprockets included in the single speed conversion. If the numbers look odd it's because I've adjusted for the now-uncommon crank length of the Kona. Noob/Mid/Pro numbers courtesy of forum-trawling for a few minutes.

I've decided on purple as a theme. Might get some purple chainring bolts so this side can be shiny too. Side note - I thought ISIS Drive would be a dead standard 20 years later, but ebikes became a thing and apparently my cheap bottom brackets are no longer cheap.

Gearing and front brake stripped off. 3D printed (temporary) headset spacer replaced with purple. Rear Tektro brake is staying until I can get the original mechanical Shimano BR-M475 back from a buddy, and I'll wrap a long cable round the stem - 2022 goal is learning bar spins. Want mechanical for low maintenance, plus the Tektro is probably 12 years old and very leaky with no parts available.

Part 2 to follow with single speed conversion and new tyres...

 

[coomber]

Nice

What did you have to dremel on a £10 chainring or do you mean the cranks?

Personally, I'd abandon those cranks and buy a cheap set of shimano hollowtech. Because a £10 shimano bottom bracket covers the cost outlay on them, when ISIS bottom brackets are so pricey. And avoid the cheap ISIS ones on eBay mine last about 7 miles.

 

[TorrRides]

Excited for this build and amazed your Kona SDG saddle is still in good shape (mine is cracked and looking rather sad)

I didn’t realise ISIS stuff had got so expensive either!

 

[arseface]

Nice

What did you have to dremel on a £10 chainring or do you mean the cranks?

Personally, I'd abandon those cranks and buy a cheap set of shimano hollowtech. Because a £10 shimano bottom bracket covers the cost outlay on them, when ISIS bottom brackets are so pricey. And avoid the cheap ISIS ones on eBay mine last about 7 miles.

The bit that needed material removing was the inside edge of the chainring just by the screw holes - it clashed with the cranks. A 32T ring would probably have slotted in just perfect (that was the original ring size after all) and given very close drive ratio with 14/15T rear sprockets, but I could only get the single speed conversion kit I wanted in 13/14T.

That's a nice point about the hollowtech cranks, and I'd do that except I want to retain as much of the original Kona parts as reasonably possible. The current BB is getting a bit crunchy and due a replacement at some point, but it's only the second one it's ever had in the bike's life and I'd rather fork out for a 3rd and keep the original parts in this particular case.

 

[coomber]

That's fair enough. I was shocked how much they are now, but if you aren't in a hurry you might be able to score one in the interim for a decent enough price as well

 

[arseface]

Got the tyres, chain and tensioner in the post over the last couple of days and found a few spare minutes to do some more build.

Wheels take a hot shower. Tubeless conversions are messy to change out!

Going to leave the tubeless tape on, it'll be fine. These are the original Sun Ditch Witch rims and are in great condition. I've broken a couple of spokes over the years but no lasting damage.

Gusset single speed kit goes on with the 14T option for now. Torque wrench and everything! Also the Race King tyres. Went with 2.2" width. The jumps I ride can have gravel and loose or wet dirt so didn't want anything too slick. These tyres should be fast rolling but grip enough.

Chain line isn't too bad!

Wheels back in, rear disc rotor back on. Cheap and nasty chain tensioner installed. Of all the things on this build to fail I'd bet on that.

Cheap purple chain. This is 1/8" chain running on 3/32" sprockets, which should help with the slight wonky alignment. Seems to run fine so far but time will tell.

Vaguely straight!

Just need the grips to arrive and I can take this out for a spin!

Visual inspiration...

Future plans are to put the original mechanical brake on with a long enough cable to learn bar spins, and do a fork rebuild. That's going to be nasty, it's been a long long time since that was done. As in never

 

[albash82]

Looks great that. Always loved army(ish) green with purple ano.
My mate has exactly the same frame. He's not hugely into biking, uses it for everything including childseat duties. Versatile beast!

 

[arseface]

Looks great that. Always loved army(ish) green with purple ano.
My mate has exactly the same frame. He's not hugely into biking, uses it for everything including childseat duties. Versatile beast!

Thanks! I had so much fun riding it everywhere, it taught me a lot about riding rough trails and how to cope with terrible brakes. Now when I ride my modern enduro bike it feels like cheating!


Another build update - we're near completion of the build now! Does that exist?

Grips arrived! DMR Deathgrips - flangeless, soft, thin.

Got the original Shimano BR-M475 caliper back from my buddy. Yay to near-zero maintenance!

Purple outer cable, it's become a thing with this build - if it needs replacing, new thing shall be purple. I'll do the same with spokes that snap.

Original Avid lever. They're... crisp. Good pull and no freeplay. Enough cable slack to allow bars to spin once in either direction. Probably will need adjusting.

Looking purple-er. Pretty much done now, just want to rebuild the fork if I can find new seals. The chain skips on the rear sprocket a little under heavy load, I want to blame the shitty chain tensioner. To be investigated.

Time to go re-learn how to jump!

 

[velofrog]

Looking at this pic I wouldn’t be laying the blame of the skipping chain at the door of your chain tensioner, looks like the chain isn’t dropping right down into the teeth and engaging correctly.

 

[arseface]

So I took the bike out for a proper spin and ran into two issues - the brake didn't work very well and the chain skipped a lot more under power than when I was testing it around the house & street...

This is why the brake wasn't working... As soon as the pads got hot they released a whole load of hydraulic oil! I'd pinched the pads from my old leaky Tektro hydraulics so I guess that's how it got in there.

Start of the power stroke - top and bottom of the chain are parallel.

Mid stroke you can see the tensioner has been pulled up. This is because the chain was lifting up off the rear sprocket.

Just as the chain skips over the sprocket, you can see the lower chain run whipping around.

Suspected the cause is the chain not being wrapped around the rear sprocket enough. Attempted to solve by reversing the chain tensioner to push up rather than down, but there is too much slack in the chain for this to work. Taking out a whole link would make it too short, and I can't fit a half-link chain due to the narrow-wide front chainring... Took some time to think this problem over while I sorted out the brake.

In the meantime I had my buddy's Stuff frame to prepare for his build. The BB shell was stuck solid and grips, punches, and PlusGas encouragement weren't working. Made a tool out of a spare alu bar.

AAAAALLLLLLLL the torque! And it worked

These were the old pads. The old rotor also had about 5 mm side to side movement from where it got banged up in storage. Time to replace!

eBay's finest rotor and a set of Uberbike Race Matrix pads (love them!). Not worried about rotor failure as I won't be doing much stupid stuff on this bike.

That said, confidence in the rotor is not high. It only had about 3 mm of side to side wibble though, so better than my old one! Easily trued out.

Both the new pads and the new rotor are thicker than normal, to the point where they physically couldn't fit into the caliper even with it fully adjusted out. Couple of shims to space out the fixed pad side worked though!

You'd never know it was bodged.

More purpler.

The eventual solution to the chain tension issue - change the 30T to a 32T chainring! It's very nearly a Magic combo, and has solved the chain skipping.

Refitted the Ring of Fire bash guard (got to keep things OG!), and now we have a working brake and drivetrain!

Hope to hit up the local skatepark this weekend