How To

The Hack Mechanic Fixes A Flat

I have to admit something. Just between you and me, I’m not very good at wrenching on bikes. I’ve never done my own valve adjustments. Carburetors are little boxes of black magic to me. Part of the reason I got my Honda PC800 is because it was designed to be an extremely low maintenance bike, and with only one exception it has been. I can do simple stuff like add lights and change my own oil just fine, but beyond that I tend to call a shop rather than dive into things myself, because in many cases I simply don’t know what I’m doing.

Particularly since I tend to ride older bikes – my PC800 is the newest bike I’ve ever owned, and it’s 18 years old – this can get me, and particularly my wallet, into trouble. I bought my last pair of tires (Metzeler ME880, if you’re curious – one of the few tires that fit my bike) at The Shop That Shall Not Be Named. Let’s call them Voldemort Garage so I don’t get sued (please be kind, J.K. Rowling). A week or two later, my rear tire sprung a slow leak. The valve stem had started to pop out of the rim. I brought it back, and they fixed it – and insisted on charging me for it, even though an improper previous installation caused the problem, since my old tire never leaked. A few weeks after that, I was out cruising western Massachusetts with my now-wife on the back, and THAT valve sprung a leak. I was lucky to save the resulting tankslapper, not dump the bike or my wife, and pull over to the side of the road where we spent the next two hours waiting for a tow. I took it to Central Mass Powersports who replaced the valve stem, and the tire which, in their opinion, had been ruined from many miles of low pressure. My back tire never leaked again.

Flat tire on I-89
Our story begins here…

On my recent SaddleSore 1,000 shakedown, it was my front tire’s turn to go flat. After my darling, wonderful wife, who I’m still very much sucking up to, hooked up the trailer and drove 60 miles to come rescue me, I tracked down the cause to – surprise, surprise – the valve stem, which had been installed by Voldemort Garage. As a great philosopher once said, “How hard could it be?” I’m a hack mechanic, but even I, under the watchful eye of my professional auto tech friend, managed to use his shop’s equipment to swap tires and install four valve stems, none of which ever leaked.

I don’t have a tire machine at home. But RWT‘s Kate Murphy owns half of one, and offered to help me swap tires myself rather than have a shop do it. She pointed out that you can buy tires online for much less than shop prices, plus you don’t have to pay the mounting and balancing fee. As it turns out my tire is actually fine. The air leak is much faster than last time, which means I didn’t ride on it after it started leaking and cause excessive wear to the tire. But I still needed to replace the leaky valve stem. No worries, said Kate. They have a zillion spare valve stems, and we didn’t even need to fully remove the tire to replace it. Great, so I’ll just load the bike on the trailer and take the wife’s car over to deal with it…

Subaru BRZ manual transmission
Today’s most effective automotive anti-theft device.

…except my wife can’t drive my car. It’s not she can’t drive a stick, but that the motion of shifting my Subaru BRZ causes her pain. Being stranded at home with her kids and no wheels is bad. How was I going to get the bike there? Just remove the front wheel and bring it alone, said Kate.

I autocrossed seriously for several years. I used to swap all four of my street wheels for wheels with sticky R-compound tires, race all day, then swap back to my street wheels and drive home. I’m not NASCAR fast, but I can swap all four wheels myself in about 10 minutes given the proper tools. But I had never removed a motorcycle wheel myself before. I can’t even get my PC800 up on its center stand by myself. But wait, I no longer live alone. I just need someone to give the bike an extra push from the front, and it’s there. So I did. But the bike sits on the stand and the front wheel, not the rear. Throw some weight on the back, suggested Kate. So I put the old warped brake rotors from my wife’s Ford Flex in the trunk. They’re heavy, but not heavy enough. After looking around the garage, I grabbed one of my snow wheels/tires from my BRZ, placed it on the back seat, and BAM, the bike rotated on its center stand onto the back wheel, lifting the front a few inches off the ground. With a bungee cord to hold the wheel to my top trunk, I was ready to pull the wheel.

Honda PC800 hoverbike conversion
My Honda PC800 hoverbike conversion.

First I had to pull the calipers. Having done many brake jobs on cars, this part was familiar to me. I needed a cheater pipe on the bolts and was afraid of breaking my Allen wrench, but with the extra help they popped and came off with no problem. A single Phillips head screw held the speedometer cable on – easy enough. I had to figure out exactly what direction to tap the axle out with a hammer, but I did, and with just a little jiggling the wheel dropped out. (Thank goodness I don’t have an earlier PC800, with almost a full fairing around the wheel.)

I packed all the bolts and little pieces that came out of the axle into a small box to save for later, and then I was ready to take the front wheel away. It even fits in my BRZ’s trunk without folding down the back seat.

Wheel in trunk
A Subaru BRZ trunk may be small, but unlike a Miata it’ll fit a motorcycle wheel.

After work I drove to Will’s place, the other half-owner of Kate’s half-owned tire machine. We fired up the air compressor, pulled the valve out of the stem, and then Kate broke the bead on one side of the tire right next to the stem. This, it turned out, was all we needed to do to gain access to the stem. The rest of the tire machine served as a table but little more for the rest of the project, since we had no need to dismount the tire any further than that. From there it was a simple matter to remove the old stem (which Kate confirmed was shot), then pull the new one through the hole in the rim.

Valve stem replacement
Dirt on her hands, AND nail polish!

Rather than a stem with a 90 degree bend, we used a short, straight one. That’s what CMP did on my rear wheel, and it’s worked fine ever since, so we decided to keep it simple. And simple it was – pull the valve through the rim until it locked into place. Insert the valve. Add air to pop the bead back on and inflate to 33psi, the PC800’s recommended pressure. Done! I couldn’t believe how quick and easy it was. I spent more time geeking out with Will about Miatas than Kate and I spent fixing my flat. All I had to do now was go home and let it sit overnight to see if it lost any pressure. It didn’t!

“Installation is the opposite of removal.” This sentence is every repair manual’s cop-out for not documenting the reassembly of something it just told you how to disassemble. As a professional technical writer, this irks me. In the case of reinstalling the front wheel on my bike, it was almost correct. Almost. After reinstalling the bearing caps and tapping the axle back through the forks and wheel with a hammer (Jeremy Clarkson’s favorite tool), I discovered that the holes on the non-bolt end of the axle are there so that you can stick something through them to keep the axle from rotating as you tighten the bolt. Lacking a special tool for this, I used a punch and a cheater pipe, then torqued the axle bolt down to Really Friggin Tight (that’s a technical term). The brake caliper pistons needed to be squeezed in a little bit to go around the rotors, but that’s no big deal – I’ve done it a billion times before on my cars. The speedometer gear wasn’t lined up quite right to reattach the cable, so I had to loosen the axle, rotate it, and retighten it. No big deal. All of the parts I removed went back on the bike, with nothing left over. I rolled the bike off the center stand with an inflated front tire.

Kate didn’t trust the pressure gauge on the tire machine, so I finished inflating the tire to the recommended 33psi. (It was 25psi before.) I geared up and took a quick trip around the block. Something in the front didn’t feel quite right, so I pulled over to check all the bolts. That was when I realized that I’d forgotten to tighten the bolts at the bottom of the forks that further clamp the axle in. Oops. I gently rode home, did that, and tried again. It felt pretty good, and I got more and more confident in my repair with each mile I rode. I think I’m back in business – and, thanks to Kate, without spending a dime.

Diving into new territory for my wrenching skills and emerging unscathed has given me more confidence to do more work on my own bikes in the future. This is a very good thing considering the new project I’ve just taken on…

1 Comment

  1. Axle bolts, pinch bolts and caliper bolts have +very+ specific torque specifications — look them up and have at them all with a torque wrench. But, and always when reinstalling a front wheel, loosen your pinch bolts and axle bolts (leave your caliper bolts torqued to spec) and do a few divey stops in your garage — let the bike roll a couple inches, jam on the front brake so the front end dives. This will help align everything up front (your fork tubes can twist in the triples) so that you don’t get any undue wear on your bearings. And keep a close eye on that tire pressure!! 🙂

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